232 Biology MCQs that appeared in MDCAT 2023, arranged unit by unit in syllabus order. Tap “Show answer” under any question for the correct option and a short solution.
1.Which of the following viruses contains single stranded DNA? (MDCAT 2023)
Correct answer: (c) parvovirus
The parvoviruses are the single stranded DNA viruses; the other three carry double stranded DNA.
2.What of the following virus contains single stranded DNA? (UHS MDCAT 2023)
Correct answer: (c) Parvo virus
The parvoviruses are the smallest DNA viruses and their genome is a single strand.
3.How may tail fibrils are attached to the end plate of a bacteriophage? (UHS MDCAT 2023)
Correct answer: (c) 6
Six tail fibres spread from the end plate and hold the phage to the bacterial wall.
4.All viruses are: (SZABMU MDCAT 2023)
Correct answer: (c) Parasites
A virus can multiply only inside a living cell, so every virus is an obligate parasite.
5.The complete, mature and infectious virus particle is known as: (NUMS MDCAT 2023)
Correct answer: (c) Virion
A complete infectious virus particle is a virion.
6.Virus is what type of agent? (UHS MDCAT 2023)
Correct answer: (b) Infectious agent
A virus can do nothing but infect a living cell and multiply in it.
7.Which of the following is transmitted through infected blood and hypothermal syringes? (SZABMU MDCAT 2023)
Correct answer: (a) HIV
HIV travels in blood, so transfusions and shared needles carry it.
8.The provirus of HIV is structurally and chemically made up of? (UHS MDCAT 2023)
Correct answer: (d) dsDNA
Reverse transcriptase copies the viral RNA into double stranded DNA, which is then integrated.
9.What is the end product of glucose by yeast in anaerobic respiration? (UHS MDCAT 2023)
Correct answer: (c) Ethanol and CO2
Yeast ferments glucose to ethanol and carbon dioxide.
10.Each carrier in Electron Transport Chain is first ______ and then ______. (UHS MDCAT 2023)
Correct answer: (d) Reduced, Oxidized
Each carrier takes the electrons from the one before, so it is reduced, then passes them on and is oxidized again.
11.Electron transport chain explains: (UHS MDCAT 2023)
Correct answer: (d) Mechanism of ATP synthesis
The chain pumps protons whose return through ATP synthase makes the ATP.
12.Which of the following is NOT a consequence of anaerobic respiration in humans muscles cells? (UHS MDCAT 2023)
Correct answer: (b) High consumption of energy
Anaerobic respiration yields far less energy, not more; the cramps and pain come from the lactic acid.
13.Which of the following is used in baking? (UHS MDCAT 2023)
Correct answer: (b) Anaerobic respiration
The yeast in dough ferments anaerobically, and the carbon dioxide raises the bread.
14.Which is the major event in electron transport chain? (UHS MDCAT 2023)
Correct answer: (a) ATP synthesis
The chain pumps protons whose return through ATP synthase makes most of the cell’s ATP.
15.Hydrolysis process is a reverse of -------------------- process. (UHS MDCAT 2023)
Correct answer: (b) Condensation
Condensation joins two units with the loss of water; hydrolysis splits them by adding it back.
16.Which bond is the potential source of chemical energy for cellular activities? (SZABMU MDCAT 2023)
Correct answer: (b) C-H
The carbon hydrogen bond is where the energy of a food molecule is stored.
17.Most abundant organic compound in mammalian cells are: (NUMS MDCAT 2023)
Correct answer: (d) Proteins
Proteins are the most abundant organic molecules of an animal cell; water is not organic.
18.Energy is by the breakdown of complex molecules into simpler ones, such reactions are called catabolic reactions (UHS MDCAT 2023)
Correct answer: (a) Released
Catabolism breaks large molecules down and releases the energy held in their bonds.
19.Which property of water enables it to act as temperature stabilizer in living organisms? (SZABMU MDCAT 2023)
Correct answer: (c) High specific heat capacity
Water takes in a great deal of heat for a small rise in temperature, so it steadies the body.
20.Thermal stability of organisms in the environment is because of which characteristic of water? (NUMS MDCAT 2023)
Correct answer: (b) Heat capacity
Water takes in a great deal of heat for a small rise in temperature, so it steadies the body.
21.Which type of bond must be broken for water to vaporize? (UHS MDCAT 2023)
Correct answer: (c) Hydrogen bonds
Vaporizing water means pulling its molecules apart, which breaks the hydrogen bonds between them.
22.___________ forms almost three-fourth of the body by weight (UHS MDCAT 2023)
Correct answer: (a) Water
About three quarters of the mass of the body is water.
23.Upon initial hydrolysis starch yields: (UHS MDCAT 2023)
Correct answer: (a) Maltose
Starch is broken first to maltose and only then to glucose.
24.Which of the following carbohydrates are sweetest among all? (SZABMU MDCAT 2023)
Correct answer: (a) Monosaccharides
The simple sugars taste sweetest, and sweetness falls as the chains grow longer.
25.Chemically, cell wall of fungi is made up of: (SZABMU MDCAT 2023)
Correct answer: (c) Chitin
The fungal wall is chitin, the same polymer as the arthropod skeleton.
26.These carbohydrates are sweetest among all carbohydrates: (NUMS MDCAT 2023)
Correct answer: (a) Monosaccharides
The simple sugars taste the sweetest of all the carbohydrates.
27.Most of the monosaccharides form a ring structure when in solution. For example ribose will form a five cornered ring known as (UHS MDCAT 2023)
Correct answer: (b) Ribofuranose
Ribose closes into a five membered ring, the ribofuranose form.
28.Which statement is true about regarding both starch and cellulose? (UHS MDCAT 2023)
Correct answer: (a) They are both polymers of glucose.
Both are chains of glucose; they differ in the linkage, which is why we can digest only starch.
29.Unique three-dimensional shape of the fully folded polypeptide, constitutes: (UHS MDCAT 2023)
Correct answer: (c) Tertiary structure of protein
The folded shape of a whole polypeptide is its tertiary structure.
30.Proteins are the main ---------- of the cell? (UHS MDCAT 2023)
Correct answer: (b) Functional components
Enzymes, carriers, receptors and antibodies are all proteins, so proteins do the work of the cell.
31.Which of the following proteins acts as carrier of copper in blood plasma? (UHS MDCAT 2023)
Correct answer: (c) Ceruloplasmin
Ceruloplasmin is the copper carrying protein of the plasma.
32.Select an example of fibrous protein: (SZABMU MDCAT 2023)
Correct answer: (b) Collagen
Collagen is a fibrous structural protein of tendon, skin and bone.
33.Which function is NOT performed by proteins? (SZABMU MDCAT 2023)
Correct answer: (d) Providing insulation against heat loss
Insulation against heat loss is the work of fat, not of protein.
34.Based on function, thyroxin can be classified as: (SZABMU MDCAT 2023)
Correct answer: (a) Hormonal protein
Thyroxine carries a message from a gland to its target, so it is classed as a hormonal protein.
35.Which of the following protein establishes the matrix of bone and cartilage? (NUMS MDCAT 2023)
Correct answer: (c) Collagen
Collagen fibres are the framework of the matrix of both bone and cartilage.
36.Three hydrophobic fatty acid tails and a glycerol molecule join to form a: (SZABMU MDCAT 2023)
Correct answer: (c) Triglyceride
Glycerol esterified with three fatty acids is a triglyceride.
37.Which hormone is chemically a steroid? (NUMS MDCAT 2023)
Correct answer: (c) Cortisone
Cortisone is built on the cholesterol ring system, so it is a steroid.
38.C-H bonds in lipids are important: (NUMS MDCAT 2023)
Correct answer: (b) Providing more energy
Fats are rich in carbon hydrogen bonds, so a gram of fat yields about twice the energy of a gram of sugar.
39.DNA stores biological information in discrete units termed as: (UHS MDCAT 2023)
Correct answer: (a) Genes
A gene is the length of DNA that codes for one polypeptide.
40.Cells of different types can be distinguished on the basis of surface: (MDCAT 2023)
Correct answer: (c) glycolipids and glycoproteins
The sugar chains on the outer face of the membrane differ from one cell type to another and act as its markers.
41.Movement of molecules against the concentration gradient is? (UHS MDCAT 2023)
Correct answer: (b) Active transport
Moving a substance against its gradient costs energy, which is what active transport means.
42.Which molecules do not contribute to the formation of biological membranes? (SZABMU MDCAT 2023)
Correct answer: (d) Nucleoproteins
Membranes are built of phospholipids with glycolipids and glycoproteins in them; nucleoproteins belong to the chromosomes.
43.Adenylate cyclase, in the cell membrane acts as: (SZABMU MDCAT 2023)
Correct answer: (c) Enzyme
Adenylate cyclase makes cyclic AMP, so it is an enzyme built into the membrane.
44.Glycogen, lipid droplets form the most important_________of the cell. (SZABMU MDCAT 2023)
Correct answer: (b) Cell inclusions
Stored granules and droplets, with no membrane of their own, are the cell inclusions.
45.According to the fluid mosaic model of cell membrane, which zone is embedded inside? (NUMS MDCAT 2023)
Correct answer: (a) Hydrophobic
The fatty tails of the phospholipids turn inwards, away from the water on both sides.
46.Cell membrane also contains _______ place by active and passive transport: (NUMS MDCAT 2023)
Correct answer: (c) Charged pores
Charged pores through the protein channels let ions cross the bilayer.
47.Biologically, plays key roles in maintaining the integrity of lipid bilayer membranes. (UHS MDCAT 2023)
Correct answer: (b) Hydrophobic
The fatty tails are hydrophobic and turn away from water, which is what holds the bilayer together.
48.Which structure of a prokaryotic cell plays the role of the mitochondrion? (MDCAT 2023)
Correct answer: (d) mesosomes
The respiratory enzymes sit on the mesosome, the infolding of the plasma membrane.
49.The cell wall of a prokaryotic cell is composed of: (MDCAT 2023)
Correct answer: (b) carbohydrates and proteins
Peptidoglycan is a sugar backbone cross-linked by short peptides.
50.A bacterial cell maintains its shape through its: (MDCAT 2023)
Correct answer: (a) cell wall
The rigid peptidoglycan wall is what holds the shape against the turgor inside.
51.Structure formed by invagination of plasma membrane and involved in cell division and DNA replication of prokaryotic cell: (UHS MDCAT 2023)
Correct answer: (b) Mesosomes
A mesosome is an infolding of the bacterial membrane, and the chromosome is anchored to it.
52.Which one is common in both prokaryotic and eukaryotic cells? (UHS MDCAT 2023)
Correct answer: (b) Ribosome
Both kinds of cell make protein on ribosomes, though the ribosomes differ in size.
53.Number of layers present in Gram-negative bacterial cell wall : (UHS MDCAT 2023)
Correct answer: (b) two
A gram negative wall has a thin peptidoglycan layer with an outer membrane over it.
54.The division of cocci in three planes form Sarcina, which is a cube of ------------ Cocci? (UHS MDCAT 2023)
Correct answer: (c) 08
Dividing in three planes gives a packet of eight cells.
55.Nitrifying bacteria are the examples of: (UHS MDCAT 2023)
Correct answer: (b) Chemosynthetic bacteria
Nitrifying bacteria get their energy by oxidizing ammonia and nitrite, so they are chemosynthetic.
56.The unique macro-molecule in the bacterial cell wall is: (SZABMU MDCAT 2023)
Correct answer: (c) Peptidoglycan
Peptidoglycan is found in no other kind of cell.
57.Transfer of genetic material from one bacterium to another through a third party usually bacteriophage is called: (SZABMU MDCAT 2023)
Correct answer: (c) Transduction
Transfer carried by a bacteriophage from one bacterium to another is transduction.
58.All of the following are physical methods to control bacteria except: (SZABMU MDCAT 2023)
Correct answer: (d) Antiseptics
An antiseptic is a chemical; heat and radiation are the physical methods.
59._______ increases the pathogenecity of bacteria: (NUMS MDCAT 2023)
Correct answer: (a) Capsule
The capsule hides the bacterium from the phagocytes and helps it stick to surfaces.
60.The smallest known bacteria belong to the genus: (NUMS MDCAT 2023)
Correct answer: (a) Mycoplasma
Mycoplasmas are the smallest bacteria and have no cell wall.
61.What distinguishes Prokaryotic cell wall from Fungal cell wall? (NUMS MDCAT 2023)
Correct answer: (b) Prokaryotic cell wall contains peptidoglycan
A bacterial wall is peptidoglycan; a fungal one is chitin.
62.Cell wall of prokaryotic cell is composed of: (UHS MDCAT 2023)
Correct answer: (a) Carbohydrates
Peptidoglycan is a carbohydrate backbone cross linked by short peptides.
63.Number of layers of cell wall in Gram positive bacteria is: (UHS MDCAT 2023)
Correct answer: (a) 1
A gram positive wall is one thick layer of peptidoglycan with no outer membrane.
64.Which structure of prokaryotic cell will play the role of mitochondrion? (UHS MDCAT 2023)
Correct answer: (d) Mesosomes
The mesosome carries the respiratory enzymes, which in a eukaryote sit in the mitochondrion.
65.Bacterial cell have ability to maintain its shape through (UHS MDCAT 2023)
Correct answer: (a) Cell wail
The rigid peptidoglycan wall is what holds a bacterium in shape.
66.Cyclosis and amoeboid movements are due to: (MDCAT 2023)
Correct answer: (c) microfilaments
Actin microfilaments slide past one another and drive both streaming and crawling.
67.Proteins and lipids are modified into glycoproteins and glycolipids by which cell organelle? (MDCAT 2023)
Correct answer: (a) Golgi complex
The Golgi apparatus is where the sugar chains are added.
68.Which of the following are single membranous organelles? (UHS MDCAT 2023)
Correct answer: (c) Golgi bodies, Lysosome and ER
Golgi bodies, lysosomes and the endoplasmic reticulum each have a single membrane; a mitochondrion has two.
69.The digestive vacuoles and autophagosomes are also known as? (UHS MDCAT 2023)
Correct answer: (c) Secondary lysosome
A primary lysosome that has fused with a vacuole becomes a secondary lysosome.
70.Which organelles would be more abundant in a secretory cell than non-secretory cells? (SZABMU MDCAT 2023)
Correct answer: (b) Golgi complex
The Golgi complex packages and dispatches secretions, so a secretory cell is full of it.
71.The structure which disappears during cell division is: (SZABMU MDCAT 2023)
Correct answer: (c) Nucleolus
The nucleolus breaks up at prophase and is rebuilt at telophase.
72.The enzyme ATP synthase is located on the membrane of: (SZABMU MDCAT 2023)
Correct answer: (b) Mitochondria
ATP synthase stands in the inner mitochondrial membrane, where the proton gradient drives it.
73.Intracellular digestion of food is done by the organelle: (SZABMU MDCAT 2023)
Correct answer: (b) Lysosome
Lysosomes carry the hydrolytic enzymes that digest what the cell takes in.
74.Which organelles of animal cells are called suicidal bags? (SZABMU MDCAT 2023)
Correct answer: (c) Lysosomes
A lysosome that bursts digests the cell itself, which is why it is called a suicide bag.
75.The organelle which provides neurotransmitters in the nervous pathway is: (SZABMU MDCAT 2023)
Correct answer: (c) Golgi apparatus
The Golgi body packs the transmitter into the vesicles of the synaptic knob.
76.The inner membrane of the mitochondria is folded to form finger like: (SZABMU MDCAT 2023)
Correct answer: (b) Cristae
The inner membrane folds inwards as cristae, which multiply its area.
77.Each centriole is composed of ________ of Microtubules: (NUMS MDCAT 2023)
Correct answer: (c) Nine Triplets
A centriole is a cylinder of nine triplets of microtubules.
78.The folds of Inner Membrane of mitochondria are called: (NUMS MDCAT 2023)
Correct answer: (b) Cristae
The infoldings of the inner mitochondrial membrane are the cristae.
79.Select the one which is NOT a function of Smooth Endoplasmic Reticulum (SER)? (NUMS MDCAT 2023)
Correct answer: (d) Processing of glycoproteins
Glycoproteins are finished in the Golgi body; the smooth reticulum handles lipids and transport.
80._______ are spherical sacs, surrounded by a single membrane and contain hydrolytic enzymes: (NUMS MDCAT 2023)
Correct answer: (c) Lysosomes
That describes the lysosome.
81.Proteins and lipids are modified into Glycoproteins & Glycolipids by which cell organelle? (UHS MDCAT 2023)
Correct answer: (a) Golgi complex
The Golgi complex adds the sugar chains that make glycoproteins and glycolipids.
82.The terminal ends of chromosomes are called: (SZABMU MDCAT 2023)
Correct answer: (d) Telomeres
The ends of a chromosome are capped by telomeres, which keep it from fraying.
83.The pressure receptors that receive deep pressure stimuli in the human body are called: (MDCAT 2023)
Correct answer: (b) Pacinian corpuscles
Pacinian corpuscles lie deep in the skin and respond to heavy pressure and vibration.
84.The pressure receptors that receive deep pressure stimulus in human body are called. (UHS MDCAT 2023)
Correct answer: (b) Pacinian Corpscles
Pacinian corpuscles lie deep in the skin and respond to pressure and vibration.
85.The chemical messengers that transmit an action potential across a synapse are: (MDCAT 2023)
Correct answer: (c) neurotransmitters
The vesicles of the synaptic knob release a neurotransmitter across the cleft.
86.During the resting membrane potential of a neuron: (MDCAT 2023)
Correct answer: (a) the outer surface is positive and the inner surface negative
The sodium-potassium pump and the potassium leak leave the inside about $-70$ mV with respect to the outside.
87.In a typical nerve, the action potential duration is: (MDCAT 2023)
Correct answer: (a) 1 millisecond
Depolarization and repolarization together take about a millisecond.
88.There is no clear difference between dendrites and axons in sensory neurons, except: (UHS MDCAT 2023)
Correct answer: (b) Length
In a sensory neuron both processes look alike, and only their length tells them apart.
89.The neurotransmitter active outside the CNS (Central Nervous System) is: (UHS MDCAT 2023)
Correct answer: (a) Acetylcholine
Acetylcholine works at the neuromuscular junction and in the autonomic ganglia, outside the brain and cord.
90.Which axon would transmit an action potential most rapidly? (SZABMU MDCAT 2023)
Correct answer: (d) 2mm diameter neuron with myelin
Speed rises with the diameter of the fibre and again with myelination, so the thick myelinated axon is fastest.
91.In neurons, the message istransmitted across synapse in the form of chemical messenger called: (SZABMU MDCAT 2023)
Correct answer: (b) Neurotransmitter
The chemical released into the synaptic cleft is the neurotransmitter.
92.Microscopic gap between the two neurons is called: (SZABMU MDCAT 2023)
Correct answer: (b) Synapse
The gap between two neurons is the synapse.
93.In a reflex arc, the cell body of sensory neuron is located in: (SZABMU MDCAT 2023)
Correct answer: (d) Dorsal root ganglion
The cell body of a sensory neuron sits in the dorsal root ganglion, outside the cord.
94.Na+ (sodium ions) are nearly ________ times greater in fluid outside the cell than inside: (NUMS MDCAT 2023)
Correct answer: (a) 10
The sodium pump keeps sodium about ten times more concentrated outside the resting cell.
95.The site of production of neurotransmitters is: (NUMS MDCAT 2023)
Correct answer: (b) Presynaptic neuron
The transmitter is made in the presynaptic neuron and stored in the vesicles of its knobs.
96.Endorphins are produced in: (NUMS MDCAT 2023)
Correct answer: (a) Brain
Endorphins are made in the brain and act as its own painkillers.
97.The junction between two neurons is: (NUMS MDCAT 2023)
Correct answer: (b) Synapse
The junction between two neurons is the synapse.
98.During testing membrane potential condition: (UHS MDCAT 2023)
Correct answer: (a) Outer suite of neuron is more positive
The pump drives sodium out, so the outside of the resting membrane is positive.
99.The chemical Messengers that transmit action potential across the synapse in the form of chemicals are? (UHS MDCAT 2023)
Correct answer: (c) Neurotransmitters
Those chemicals are the neurotransmitters.
100.The middle layer of meninges is: (UHS MDCAT 2023)
Correct answer: (a) Arachnoid mater
The three membranes are the dura outside, the arachnoid between and the pia against the brain.
101.The part of brain which guides smooth and accurate motions and maintains body position is: (UHS MDCAT 2023)
Correct answer: (b) Cerebellum
The cerebellum smooths movement and holds the body in position.
102.Which function is not controlled by hypothalamus? (SZABMU MDCAT 2023)
Correct answer: (d) Storing long time memories
Long-term memory is laid down by the hippocampus, not the hypothalamus.
103.The feelings and emotions of love and hate are controlled by: (SZABMU MDCAT 2023)
Correct answer: (a) Amygdalae
The amygdala of the limbic system handles fear, rage and affection.
104.NAD is an important: (MDCAT 2023)
Correct answer: (b) coenzyme
It is a non-protein carrier of hydrogen that an enzyme needs to work, which is what a coenzyme is.
105.Which enzyme is different from the others? (MDCAT 2023)
Correct answer: (d) lactase
The first three digest protein; lactase splits a sugar.
106.Zinc ion is attached at the active site of the enzyme carboxypeptidase. The zinc ion functions as (UHS MDCAT 2023)
Correct answer: (b) An activator
A metal ion held at the active site and needed for activity is an activator, or cofactor.
107.Enzyme is a natural substance that: (SZABMU MDCAT 2023)
Correct answer: (a) Increases the rate of chemical reaction
An enzyme is a biological catalyst; it speeds the reaction up.
108.The major enzymes involved in transfer of phosphate group from ATP to Glucose is: (UHS MDCAT 2023)
Correct answer: (c) Kinase
An enzyme that moves a phosphate group from ATP to another molecule is a kinase.
109.The active sites of enzymes are composed of: (MDCAT 2023)
Correct answer: (d) a few amino acids
A handful of amino acid side chains, brought together by the folding of the chain, make the active site.
110.Enzymes lower the activation energy by stabilizing the transition state of a metabolic reaction due to? (UHS MDCAT 2023)
Correct answer: (a) Changing conditions within the active site
The chemical surroundings inside the active site hold the transition state and lower the barrier to it.
111.The catalytic activity of an enzyme is restricted to its small portion: (SZABMU MDCAT 2023)
Correct answer: (a) Active site
Only the active site, a small pocket in the molecule, does the catalysis.
112.Enzyme work by lowering the of the reaction they catalyze: (SZABMU MDCAT 2023)
Correct answer: (b) Activation energy
An enzyme offers a path over a lower energy barrier, so more collisions succeed.
113.Which enzyme can work at pH 7 of the medium? (MDCAT 2023)
Correct answer: (b) sucrase
Sucrase works near neutrality; pepsin needs a strong acid and the pancreatic enzymes an alkaline medium.
114.What is the best physiological pH for optimum functioning for most of the cellular enzymes of human? (UHS MDCAT 2023)
Correct answer: (c) 6-8 pH
Most enzymes of the human cell work best near neutrality, about pH 7.
115.The maximum enzymatic activity of trypsin is shown at: (SZABMU MDCAT 2023)
Correct answer: (d) pH 8
Trypsin works in the alkaline intestine, at about pH 8.
116.Most enzyme have an optimum temperature of around: (SZABMU MDCAT 2023)
Correct answer: (b) 40 O C
Most human enzymes are fastest near body temperature, about $40^{\circ}\mathrm{C}$.
117.In terms of enzyme action, maximum temperature refers to a temperature at which: (SZABMU MDCAT 2023)
Correct answer: (a) Enzyme start to denature
Above the maximum temperature the bonds holding the shape give way and the enzyme is denatured.
118.Most enzymes work the best at the following temperature: (NUMS MDCAT 2023)
Correct answer: (b) 40°C
Most human enzymes are fastest near body temperature, about $40^{\circ}\mathrm{C}$.
119.In term of enzyme action, 'maximum temperature' refers to a temperature at which: (NUMS MDCAT 2023)
Correct answer: (a) Enzymes start to denature
Above that temperature the bonds holding the shape give way.
120.Competitive inhibitors are: (MDCAT 2023)
Correct answer: (b) analogous to the substrate
They resemble the substrate closely enough in shape to occupy its active site.
121.Competitive inhibitors compete with? (UHS MDCAT 2023)
Correct answer: (b) Substrate
It resembles the substrate and takes its place in the active site, so the two compete.
122.Non-competitive inhibitor molecules have: (UHS MDCAT 2023)
Correct answer: (b) A quite different structure from the substrate molecule
It bears no resemblance to the substrate and binds elsewhere, at an allosteric site.
123._____ reduces the enzyme activity by blocking the substrate from entering the active site due to similar shapes: (SZABMU MDCAT 2023)
Correct answer: (a) Competitive inhibitors
A competitive inhibitor resembles the substrate closely enough to sit in the active site.
124.Non-competitive inhibitors react with enzymes at: (NUMS MDCAT 2023)
Correct answer: (a) Allosteric site
A non-competitive inhibitor binds at an allosteric site away from the active site.
125._______ reduce the enzymes productivity by blocking the substrate from entering into the active site due to similar shapes: (NUMS MDCAT 2023)
Correct answer: (a) Competitive inhibitors
A competitive inhibitor resembles the substrate and occupies the active site.
126.Competitive inhibitors stop an enzyme from working by: (UHS MDCAT 2023)
Correct answer: (c) Blocking the active site of the enzyme
A competitive inhibitor takes the place of the substrate in the active site.
127.Competitive inhibhnors are ______________? (UHS MDCAT 2023)
Correct answer: (a) Homologous to substrate
A competitive inhibitor is close enough in shape to the substrate to sit in the active site.
128.According to evolutionary studies, prokaryotes may have arisen around: (MDCAT 2023)
Correct answer: (b) 3.5 billion years ago
The oldest fossil bacteria are about 3.5 billion years old.
129.Which of the following types of organs are supposed to have been functional in ancestral species rather than in present day species? (MDCAT 2023)
Correct answer: (a) vestigial organs
A vestigial organ is the reduced remnant of one that worked in an ancestor.
130.For evolutionary process to occur, which of the following is NOT a geographical barrier? (UHS MDCAT 2023)
Correct answer: (d) Atmosphere
The atmosphere is continuous, so it separates no population from another.
131.Among the oldest known fossils comes the: (SZABMU MDCAT 2023)
Correct answer: (a) Prokaryotes
The oldest fossils are of prokaryotes, some three and a half thousand million years old.
132.This theory says that 'mitochondria and chloroplasts are, in effect, ancient bacteria which now live inside the larger cells'? (NUMS MDCAT 2023)
Correct answer: (d) Endosymbiotic theory
The endosymbiotic theory traces mitochondria and chloroplasts to bacteria taken up by an early cell.
133.Which of the following is the main point of Darwinism? (MDCAT 2023)
Correct answer: (b) variation
Natural selection needs heritable variation to act on, and that is the heart of Darwin's argument.
134.The animal species on Galapagos resemble species living on the: (UHS MDCAT 2023)
Correct answer: (d) South American mainland
The Galapagos species are closest to those of South America, from which their ancestors came.
135.He presented the theory of origin of species by means of natural selection: (SZABMU MDCAT 2023)
Correct answer: (d) Darwin
Darwin published On the Origin of Species by Means of Natural Selection.
136.The organs which are similar in function but differ in structure are called: (NUMS MDCAT 2023)
Correct answer: (a) Analogous organs
Organs alike in work but unlike in build are analogous, and they point to convergence.
137.Which of the following type of organs are supposed to be functional in ancestral species rather than in present day species: (UHS MDCAT 2023)
Correct answer: (a) Vestigial organs
A vestigial organ is a reduced remnant of one that worked in the ancestor.
138.What is true about oxytocin? (MDCAT 2023)
Correct answer: (d) it dilates the milk ducts of the mammary glands
Oxytocin contracts the uterus in labour and drives milk out along the ducts.
139.The function of the hyaluronidase enzyme is: (MDCAT 2023)
Correct answer: (a) penetration of the sperm into the ovum
The enzyme of the acrosome digests a path through the coats of the egg.
140.In human females, what is the small, pear-shaped, muscular, distensible, sac-like organ where gestation takes place? (MDCAT 2023)
Correct answer: (a) uterus
The uterus holds and nourishes the embryo through pregnancy.
141.The labour pains to expel the foetus are due to the action of oxytocin on the: (MDCAT 2023)
Correct answer: (b) myometrium
The myometrium is the muscular coat of the uterus, and it is what contracts.
142.Which cells in the human males are responsible for the release of testosterone? (UHS MDCAT 2023)
Correct answer: (d) Leydig cells or interstitial cells
The interstitial, or Leydig, cells between the tubules secrete testosterone.
143.Fertilized ovum is implanted and undergoes further development in the: (UHS MDCAT 2023)
Correct answer: (b) Uterus
The embryo implants in the endometrium of the uterus and develops there.
144.After fertilization, zygote takes________for its journey from fallopian tube to uterus: (SZABMU MDCAT 2023)
Correct answer: (a) 6-7 days
The zygote takes about six or seven days to reach the uterus and implant.
145.The best temperature forspermatogenesis is: (SZABMU MDCAT 2023)
Correct answer: (d) 35 O C
Sperms are made a couple of degrees below core temperature, at about $35^{\circ}\mathrm{C}$.
146.Leydig cells in testes are responsible for: (SZABMU MDCAT 2023)
Correct answer: (a) Testosterone production
The Leydig cells between the tubules secrete testosterone.
147.The hormone responsible for production of sperm cells and male secondary sexual characteristics is: (NUMS MDCAT 2023)
Correct answer: (c) Testosterone
Testosterone from the Leydig cells drives spermatogenesis and the male secondary characters.
148.Leydig cells are responsible for: (NUMS MDCAT 2023)
Correct answer: (a) Testosterone production
The Leydig, or interstitial, cells secrete testosterone.
149.The function of hyaluronidase enzyme is: (UHS MDCAT 2023)
Correct answer: (c) Entrance of the sperm into the fallopian
Hyaluronidase from the acrosome digests a path through the layers round the ovum.
150.The term menopause means: (MDCAT 2023)
Correct answer: (c) stop of ova production
The ovaries stop releasing ova and the cycles come to an end.
151.The production of follicle-stimulating hormone and luteinizing hormone from the pituitary gland of the female is controlled by the: (MDCAT 2023)
Correct answer: (d) hypothalamus
Gonadotrophin releasing hormone from the hypothalamus governs the anterior pituitary.
152.A hormone that plays a major role in social bonding, childbirth, milk ejection and sexual reproduction is: (UHS MDCAT 2023)
Correct answer: (b) Oxytocin
Oxytocin drives the contractions of labour and the let-down of milk.
153.Hormone produced by placenta is: (UHS MDCAT 2023)
Correct answer: (c) Progesterone
The placenta takes over from the corpus luteum and secretes progesterone through the pregnancy.
154.Level of luteinizing hormone (LH) is maximum in blood during which stage of menstrual cycle? (UHS MDCAT 2023)
Correct answer: (c) Ovulation stage
The LH surge comes at ovulation, about the middle of the cycle.
155.In human females, FSH stimulates: (SZABMU MDCAT 2023)
Correct answer: (a) Follicle development
Follicle stimulating hormone ripens the follicle in the ovary.
156.Which hormone induces labour pains? (NUMS MDCAT 2023)
Correct answer: (b) Oxytocin
Oxytocin from the posterior pituitary drives the contractions of labour.
157.The estrogen hormone secretion during the oogenesis is stimulated by: (NUMS MDCAT 2023)
Correct answer: (c) Follicle Stimulating Hormone
Follicle stimulating hormone ripens the follicle, and the growing follicle makes the oestrogen.
158.Which of the following hormones of the pituitary gland regulate the menstrual cycle? (NUMS MDCAT 2023)
Correct answer: (c) Follicle Stimulating Hormone and Luteinizing hormone
FSH and LH from the anterior pituitary drive the ovarian cycle.
159.The labour pains to expel fetus are due to action of oxytocin on: (UHS MDCAT 2023)
Correct answer: (b) Myometrium
Oxytocin acts on the myometrium, the muscular layer of the uterus.
160.What is true about Ozytocin? (UHS MDCAT 2023)
Correct answer: (d) Dilate milk ducts of mammary glands
Oxytocin contracts the muscle round the milk ducts, so the milk is let down.
161.Production of Follicle-stimulating hormone (FSH) and Luteinizing Hormone (LH) from the pituitary gland of female is controlled by: (UHS MDCAT 2023)
Correct answer: (d) Hypothalamus
Gonadotrophin releasing hormone from the hypothalamus sets the pituitary secreting FSH and LH.
162.Major source of transmission of syphilis is: (UHS MDCAT 2023)
Correct answer: (d) Sexual contact
Syphilis is spread by sexual contact with an infected person.
163.Cartilage is a type of which tissue? (MDCAT 2023)
Correct answer: (a) connective tissue
Cells in a matrix they have secreted themselves is the pattern of connective tissue.
164.Human Bone cells contain. ........% of water? (UHS MDCAT 2023)
Correct answer: (a) 20
Bone cells hold about a fifth of their mass as water.
165.Cartilage is more difficult to heal than bone because cartilage: (NUMS MDCAT 2023)
Correct answer: (a) Lacks vascular supply
Cartilage has no blood vessels, so repair materials reach it only by slow diffusion.
166.Irregular striations and involuntary control are related to: (MDCAT 2023)
Correct answer: (a) cardiac muscle cells
Cardiac muscle is striated like skeletal muscle but works without the will, and its striations are less regular.
167.Which feature is absent from cardiac muscles? (NUMS MDCAT 2023)
Correct answer: (b) Multinucleate cells
Cardiac muscle cells have a single nucleus each; it is skeletal muscle that is multinucleate.
168.Smooth muscles are found in all mentioned below except (UHS MDCAT 2023)
Correct answer: (d) Alveoli
The alveolar wall is a single layer of flat cells with no muscle in it.
169.Irregular striations and involuntary control is related to? (UHS MDCAT 2023)
Correct answer: (a) Cardiac muscle cells
Cardiac muscle is faintly striated and beats without conscious control.
170.The cell membrane of a muscle cell is the: (MDCAT 2023)
Correct answer: (b) sarcolemma
Sarcolemma is the name of the plasma membrane of a muscle fibre.
171.Which of the following is a muscle component that act as store for energy? (UHS MDCAT 2023)
Correct answer: (b) Creatine-PO4
Creatine phosphate is the quick store that rebuilds ATP in a working muscle.
172.Which of the following is NOT found in skeletal muscle fibers in human? (UHS MDCAT 2023)
Correct answer: (d) Large amount of hemoglobin
Muscle stores its oxygen on myoglobin; haemoglobin belongs to the red cells of the blood.
173.What is the function of myoglobin? (SZABMU MDCAT 2023)
Correct answer: (a) Store oxygen
Myoglobin holds a reserve of oxygen in the muscle fibre.
174.Sarcoplasmic reticulum of muscle fibers is mainly responsible for: (NUMS MDCAT 2023)
Correct answer: (a) Calcium storage
The sarcoplasmic reticulum holds the calcium and releases it when the impulse arrives.
175.The cell membrane of muscle cell is: (UHS MDCAT 2023)
Correct answer: (b) Sarcolemma
The membrane of a muscle fibre is the sarcolemma.
176.During the sliding filament mechanism, ATP is used for: (MDCAT 2023)
Correct answer: (b) cross bridge breaking
The head attaches and pulls without ATP; hydrolysing ATP is what releases it for the next stroke.
177.The muscle contraction involve the breakdown of cross bridges of active myosin filaments due to the following process: (SZABMU MDCAT 2023)
Correct answer: (c) ATP is hydrolyzed
Splitting ATP on the myosin head is what breaks the cross bridge and cocks it again.
178.Tetany is caused by ________ in blood. (SZABMU MDCAT 2023)
Correct answer: (a) Low Ca++
Too little calcium in the blood leaves the nerves over-excitable and the muscles in spasm.
179.Under activity of parathyroid glands causes a drop in blood of: (NUMS MDCAT 2023)
Correct answer: (d) Ca2+
Parathyroid hormone raises blood calcium, so too little of it lets the calcium fall.
180.During sliding of actin filaments, ATP is used for? (UHS MDCAT 2023)
Correct answer: (a) Cross bridge formation
ATP is split on the myosin head, which cocks it ready to form the cross bridge.
181.Hinge joint is present between which of the following bones? (UHS MDCAT 2023)
Correct answer: (a) Humerus and radio-ulna
The elbow, between the humerus and the radius and ulna, is a hinge joint.
182.A joint in which ends of bones are covered with hyaline cartilage and held together by surrounding tube like capsule of dense fibrous tissue: (SZABMU MDCAT 2023)
Correct answer: (b) Synovial Joint
A synovial joint has cartilage-covered ends within a fibrous capsule lined by synovial membrane.
183.Pubic symphysis and inter vertebral disc are the example of: (NUMS MDCAT 2023)
Correct answer: (c) Cartilaginous joints
Both are cartilaginous joints, allowing a little movement.
184.________ is the inflammation of joints: (SZABMU MDCAT 2023)
Correct answer: (a) Osteoarthritis
Osteoarthritis is inflammation of a joint as its cartilage wears away.
185.A test cross is made to check the genotype of a trait. Which of the following crosses is a test cross? (MDCAT 2023)
Correct answer: (b) unknown $\times$ tt
Crossing with the homozygous recessive lets the unknown's alleles show in the offspring.
186.According to Mendel's law of segregation, one individual out of four in the $F_2$ generation had a phenotype that failed to express in which generation? (MDCAT 2023)
Correct answer: (a) $F_1$
The recessive phenotype is hidden in the $F_1$ and reappears in a quarter of the $F_2$.
187.Only those genes can assort independently whose loci are on: (MDCAT 2023)
Correct answer: (c) non-homologous chromosomes
Genes on different chromosomes are dealt out independently at meiosis; genes on one chromosome tend to travel together.
188.Mode of inheritance in humans can be traced through: (UHS MDCAT 2023)
Correct answer: (c) Pedigree Analysis
Human families cannot be bred to order, so the record of a trait through the generations is what is read.
189.Mendelian inheritance follows which form of dominance relation? (SZABMU MDCAT 2023)
Correct answer: (a) Complete dominance
In each of Mendel’s pairs one allele masked the other completely.
190.When both the alleles of a gene pair are same, the organism is said to be: (NUMS MDCAT 2023)
Correct answer: (c) Homozygous
Two identical alleles make the organism homozygous for that gene.
191.According to Mendel Law of Segregation, the one individual out of four in F2 generation had phenotype that failed to express in generation. (UHS MDCAT 2023)
Correct answer: (a) F1
The recessive phenotype is hidden in the F1 and reappears in a quarter of the F2.
192.Test cross is made to check the genotype of a trait. Which of the following crosses is a test cross? (UHS MDCAT 2023)
Correct answer: (b) Unknown x tt
A test cross is with the homozygous recessive, whose gametes carry nothing to mask the unknown allele.
193.Which one of the following is an X-linked dominant disorder? (MDCAT 2023)
Correct answer: (c) hypophosphataemic rickets
Hypophosphataemic rickets is carried on the X chromosome and shows in the heterozygote; haemophilia and colour blindness are X-linked recessive.
194.To study sex linkages in Drosophila, Morgan mated white eyed males with wild type red eyed females. What will be the phenotype of offspring? (UHS MDCAT 2023)
Correct answer: (a) All red eyed males and females
Red is dominant and the mother gives every offspring a red-bearing X, so all the F1 are red eyed.
195.Which one of the following is X Linked Dominant disorder? (UHS MDCAT 2023)
Correct answer: (c) Hypophosphatemic rickets
Hypophosphataemic rickets is carried on the X chromosome and is dominant.
196.Which of the following traits is transmitted directly from an affected father to only his son? (NUMS MDCAT 2023)
Correct answer: (c) Y-linked
A gene on the Y chromosome goes from father to son and to no daughter.
197.These are the genes which tend to be inherited together and do not assort independently: (SZABMU MDCAT 2023)
Correct answer: (a) Linked genes
Genes on the same chromosome are linked and travel together.
198.The descending aorta bifurcates into two vessels which on further division form the femoral artery that supplies blood to the muscles of the legs. These two vessels are the: (MDCAT 2023)
Correct answer: (b) iliac arteries
The aorta ends by dividing into the two common iliac arteries.
199.Flow of blood in the capillaries is adjusted by? (UHS MDCAT 2023)
Correct answer: (b) Pre-capillary sphincters
A ring of muscle at the mouth of each capillary bed opens or closes it as the tissue needs.
200.Mesenteric veins drain the blood from: (NUMS MDCAT 2023)
Correct answer: (b) Large intestine
The mesenteric veins drain the intestine and join to form the hepatic portal vein.
201.Descending aorta is bifurcated into two vessels which on further division from femoral artery that supply blood to high muscles of legs: (UHS MDCAT 2023)
Correct answer: (b) iliac artery
The descending aorta divides into the two iliac arteries, which become the femoral arteries of the legs.
202.In human heart, the left atrium receives: (SZABMU MDCAT 2023)
Correct answer: (d) The four Pulmonary Veins
Four pulmonary veins bring oxygenated blood from the lungs into the left atrium.
203.The heart chamber from where aorta originates: (NUMS MDCAT 2023)
Correct answer: (a) Left ventricle
The aorta leaves the left ventricle, which drives blood round the whole body.
204.The final destination of lymph is the: (MDCAT 2023)
Correct answer: (c) subclavian vein
The thoracic duct returns lymph to the blood at the subclavian vein.
205.The lymphatic vessels of the body empty the lymph into blood stream at ? (UHS MDCAT 2023)
Correct answer: (c) Subclavian vein
The thoracic duct empties the lymph into the left subclavian vein.
206.Lymphatic system contains all of the following organs / structures except: (SZABMU MDCAT 2023)
Correct answer: (d) Lungs
The lungs belong to the respiratory system; the lymphatic system is vessels, nodes, spleen and thymus.
207.The final destination of lymph is: (UHS MDCAT 2023)
Correct answer: (d) Subclavian vein
The thoracic duct empties the lymph into the subclavian vein.
208.Select the duration of cardiac cycle: (SZABMU MDCAT 2023)
Correct answer: (d) 0.8 sec
A cardiac cycle at seventy-five beats a minute lasts $0.8\,\mathrm{s}$.
209.---------- proteins are produced by WBCs in response to -------- and provide immunity? (UHS MDCAT 2023)
Correct answer: (d) Antibodies, antigen
Lymphocytes make antibodies against a specific antigen.
210.Vaccination is an example of: (SZABMU MDCAT 2023)
Correct answer: (c) Acquired/Artificial active immunity
A vaccine makes the body raise its own antibodies, so the immunity is active and artificially given.
211.Which of the following helps in developing immunity against germs? (SZABMU MDCAT 2023)
Correct answer: (c) Vaccines
A vaccine primes the body to make its own antibodies before the germ arrives.
212.Which may NOT be a mode of action of an antibody? (NUMS MDCAT 2023)
Correct answer: (c) Secretion of cytokines
Antibodies neutralize, precipitate and mark antigens for phagocytes; cytokines come from the cells themselves.
213.The cells which play very important role in developing immunity are: (NUMS MDCAT 2023)
Correct answer: (c) Lymphocytes
The lymphocytes, B cells and T cells, carry the specific immune response.
214.The molecules used to control virus during infection of animal cells are: (UHS MDCAT 2023)
Correct answer: (a) Interferon
An infected cell releases interferon, which warns its neighbours to resist the virus.
215.Smooth muscles are found in all of the following except the: (MDCAT 2023)
Correct answer: (d) alveoli
The alveolar wall is one cell thick, for gas exchange, and carries no muscle.
216.The method of bringing oxygenated air into contact with a gas exchange surface is called: (MDCAT 2023)
Correct answer: (b) ventilation
Ventilation is the movement of the medium over the surface; respiration is what the cells then do with the oxygen.
217.The respiratory surfaces exhibit following characteristic? (UHS MDCAT 2023)
Correct answer: (a) It must be permeable
Gases must pass through it, so it is thin, moist and permeable.
218.The area between the two lungs is called: (SZABMU MDCAT 2023)
Correct answer: (c) Mediastinum
The space between the lungs, holding the heart and great vessels, is the mediastinum.
219.Digested food from intestine is carried to the liver by? (UHS MDCAT 2023)
Correct answer: (c) Hepatic portal vein
The hepatic portal vein carries the absorbed food straight from the gut to the liver.
220.When food reaches stomach, the action of which of the following come to an end due to acidic PH? (UHS MDCAT 2023)
Correct answer: (b) Amylase
Salivary amylase works at a slightly alkaline pH and is destroyed by the acid of the stomach.
221.What is the contribution of hormone cholecystokinin? (SZABMU MDCAT 2023)
Correct answer: (a) Facilitates bile release from gall bladder
Cholecystokinin from the duodenum makes the gall bladder contract and empty its bile.
222.Which of the following is not a component of bile? (SZABMU MDCAT 2023)
Correct answer: (a) Digestive enzymes
Bile emulsifies fat but carries no enzyme of its own.
223.The first chemical digestion of proteins takes place in the: (SZABMU MDCAT 2023)
Correct answer: (c) Stomach
Pepsin of the gastric juice makes the first cut in a protein.
224.Select the hormone which increases the activity of parietal and chief cells: (SZABMU MDCAT 2023)
Correct answer: (c) Gastrin
Gastrin drives the parietal cells to make acid and the chief cells to make pepsinogen.
225.Enzyme trypsinogen is activated by: (SZABMU MDCAT 2023)
Correct answer: (c) Enterokinase
Enterokinase of the intestinal juice converts trypsinogen into trypsin.
226.Emulsification of large fat globules is facilitated by: (SZABMU MDCAT 2023)
Correct answer: (b) Bile salts
Bile salts break the large fat globules into a fine emulsion for the lipase to work on.
227.Pepsinogen is converted into its active form pepsin by: (NUMS MDCAT 2023)
Correct answer: (d) Hydrochloric acid
The hydrochloric acid of the gastric juice strips a length off pepsinogen and leaves active pepsin.
228.Intrinsic factor is secreted by: (NUMS MDCAT 2023)
Correct answer: (c) Stomach
The parietal cells of the stomach make intrinsic factor along with the acid.
229.Digestion of which food component starts from oral cavity? (NUMS MDCAT 2023)
Correct answer: (c) Carbohydrates
Salivary amylase begins to break starch down in the mouth.
230.After the digestion & before absorption the product of the protein is: (UHS MDCAT 2023)
Correct answer: (a) Amino Acid and small polypeptide
Peptidases leave a mixture of amino acids and short peptides for the villi to absorb.
231.Which enzyme is different from others? (UHS MDCAT 2023)
Correct answer: (d) Lactase
Lactase splits a sugar; the other three are protein digesting enzymes.
232.Hormone secreted in bulk due to decreased water content of blood is: (NUMS MDCAT 2023)
Correct answer: (a) Anti-Diuretic Hormone (ADH)
Concentrated blood is sensed by the hypothalamus, which calls for antidiuretic hormone.