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BIO NMDCAT

1895 questions found

Subcategories

📁 ACELLULAR LIFR 20 📁 AIDS and HIV Infection 50 📁 and nerve impulse Reflexes and reflex arc 0 📁 Arthritis 0 📁 axon 0 📁 BIOENERGETICS 0 📁 Biological Importance of Water 95 📁 BIOLOGICAL MOLECULES 126 📁 Biotechnology 0 📁 Biotechnology and Health Care 0 📁 Blood Vessels 0 📁 Brain 25 📁 Carbohydrates 100 📁 Cardiac cycle and phases of Heartbeat 0 📁 cell body 0 📁 cell membrane 70 📁 CELL STRUCTURE & FUNCTION 100 📁 Chromosomes 76 📁 Circulation 0 📁 Concept of Evolution 50 📁 Conjugated molecules 100 📁 COORDINATION & CONTROL NERVOUS & CHEMICAL COORDINATION 0 📁 Cytoplasmic Organelles 75 📁 Darwinism 50 📁 dendrites 0 📁 DIVERSITY AMONG ANTMALS (THE KTNGDOM ANIMALIA) 0 📁 ENZYMES 108 📁 EVOLUTION 0 📁 Factors that Affect the Rate of Enzyme Reactions 60 📁 Form and Function in Plants 0 📁 Gene linkage and crossing over 0 📁 Homeostasis (kidney specifically) 0 📁 Homeostasis Mainly Kidney Portion nmdcat etea 0 📁 Human Heart 0 📁 Human Reproductive system 0 📁 Human Reproductive system-Menstrual cycle 0 📁 Human skeleton 40 📁 INHERITANCE 0 📁 Inhibitors 40 📁 Joints 0 📁 Lamarckism 50 📁 Lipids 45 📁 lmmunity 0 📁 Lymphatic system 0 📁 Mendel's laws of Inheritance 0 📁 Menstrual cycle 0 📁 Mode of Enzyme Action 60 📁 Muscle contraction 0 📁 Muscles 70 📁 myelin sheath 0 📁 Neurons 41 📁 PROKARYOTES (KTNGDOM MONERA) 0 📁 Prokaryotic and Eukaryotic cell 0 📁 Proteins 95 📁 Receptors 40 📁 REPRODUCTION 0 📁 Respiration 15 📁 Respiratory system 0 📁 Ribonucleic acid (RNA) 100 📁 Sexually transmitted diseases 50 📁 Skeletal muscles 0 📁 Specific Defense Mechanism 0 📁 Structure of DNA 98 📁 SUPPORT & MOVEMENT 0 📁 Viruses 46 📁 X-linked Recessive inheritance 0

Practice Questions

In an experiment, an enzyme shows maximum activity at pH 8.0 and greatly reduced activity at pH 5.0. The most appropriate explanation is

A. The substrate is absent at pH 5.0
B. Catalytic amino acid residues become improperly ionized at pH 5.0 ✓
C. Enzyme concentration decreases automatically
D. The enzyme changes into another protein

Changes in pH alter the ionization of amino acid side chains, affecting substrate binding and catalytic function.

nmdcat.online BIO NMDCAT
Jul 11, 2026

An increase in enzyme concentration fails to increase reaction rate when

A. The enzyme becomes inactive
B. Substrate concentration is insufficient to occupy additional active sites ✓
C. Temperature is optimum
D. pH is optimum

Additional enzyme molecules remain unused if substrate molecules are limiting.

nmdcat.online BIO NMDCAT
Jul 11, 2026

During enzyme activity, the formation of enzyme-substrate complexes depends directly upon

A. Frequency of effective molecular collisions ✓
B. Molecular weight of the enzyme
C. Number of peptide bonds
D. Product concentration only

Successful collisions between enzyme and substrate are essential for enzyme-substrate complex formation.

nmdcat.online BIO NMDCAT
Jul 11, 2026

The characteristic feature of denatured enzymes is

A. Increased catalytic efficiency
B. Altered three-dimensional structure with loss of active site shape ✓
C. Increased substrate specificity
D. Increased peptide bond formation

Denaturation changes the tertiary structure, destroying the active site's ability to bind substrate effectively.

nmdcat.online BIO NMDCAT
Jul 11, 2026

During substrate saturation, increasing enzyme concentration results in

A. Increased reaction rate because additional active sites become available ✓
B. No change in reaction rate
C. Complete enzyme inhibition
D. Product degradation

With abundant substrate, adding more enzyme provides more catalytic sites, increasing the overall rate.

nmdcat.online BIO NMDCAT
Jul 11, 2026

Regarding enzyme action, optimum temperature and optimum pH are both important because they

A. Determine the molecular formula of enzymes
B. Maintain the proper conformation of the active site ✓
C. Increase substrate synthesis
D. Reduce enzyme concentration

Appropriate temperature and pH preserve the enzyme's three-dimensional structure necessary for catalysis.

nmdcat.online BIO NMDCAT
Jul 11, 2026

In a controlled experiment, all factors remain constant except temperature. A decline in reaction rate above 50°C indicates

A. Increased substrate concentration
B. Thermal denaturation of the enzyme ✓
C. Increased enzyme synthesis
D. Product activation

High temperatures disrupt the weak bonds stabilizing enzyme structure, reducing catalytic activity.

nmdcat.online BIO NMDCAT
Jul 11, 2026

During enzyme assays, substrate concentration is considered the limiting factor whenever

A. Active sites remain unoccupied because substrate molecules are insufficient ✓
B. All active sites are permanently occupied
C. Enzyme molecules are denatured
D. Product concentration becomes zero

When substrate is limiting, many enzyme molecules remain free, preventing the reaction from reaching its maximum rate.

nmdcat.online BIO NMDCAT
Jul 11, 2026

The optimum conditions for enzyme action represent the combination of

A. Maximum enzyme concentration only
B. Temperature and pH producing the highest catalytic activity ✓
C. Highest product concentration only
D. Lowest activation energy without substrate

Each enzyme has a characteristic optimum temperature and pH where its catalytic efficiency is greatest because its active site has the proper conformation and ionization state.

nmdcat.online BIO NMDCAT
Jul 11, 2026

An enzyme obtained from thermophilic bacteria generally exhibits maximum activity at

A. Lower temperatures than human enzymes
B. Higher temperatures than human enzymes ✓
C. Freezing temperatures
D. Only room temperature

Thermophilic enzymes are structurally adapted to function efficiently at temperatures that would denature most ordinary enzymes.

nmdcat.online BIO NMDCAT
Jul 11, 2026

During the effect of pH on enzyme activity, alteration of ionic charges mainly interferes with

A. Peptide bond formation
B. Enzyme-substrate binding and catalysis ✓
C. DNA replication
D. ATP synthesis only

The ionization state of amino acid residues determines substrate binding and catalytic efficiency. Changes in pH alter these charges.

nmdcat.online BIO NMDCAT
Jul 11, 2026

In a reaction mixture containing excess substrate, doubling enzyme concentration mainly increases

A. Activation energy
B. Number of active sites available for catalysis ✓
C. Product inhibition
D. Enzyme denaturation

More enzyme molecules provide more active sites, allowing more substrate molecules to be converted into product per unit time.

nmdcat.online BIO NMDCAT
Jul 11, 2026

During an enzyme assay, maintaining constant temperature and pH primarily ensures

A. Constant enzyme molecular weight
B. Reliable comparison of reaction rates ✓
C. Permanent substrate activation
D. Increased product concentration

Temperature and pH strongly influence enzyme activity. Keeping them constant allows the effect of the experimental variable to be measured accurately.

nmdcat.online BIO NMDCAT
Jul 11, 2026

A decrease in substrate concentration after prolonged reaction causes the reaction rate to decline because

A. Active sites become permanently damaged
B. Fewer substrate molecules collide with enzyme molecules ✓
C. The enzyme loses its amino acid sequence
D. Product molecules destroy enzymes

As substrate becomes depleted, enzyme-substrate complex formation decreases, reducing the overall reaction rate.

nmdcat.online BIO NMDCAT
Jul 11, 2026

During an experiment, cooling an enzyme solution from 37°C to 5°C decreases the reaction rate mainly because

A. The enzyme is permanently denatured
B. Molecular motion and collision frequency decrease ✓
C. The substrate is chemically destroyed
D. The active site changes permanently

Low temperature slows the movement of enzyme and substrate molecules, reducing effective collisions. The effect is generally reversible.

nmdcat.online BIO NMDCAT
Jul 11, 2026

Regarding enzyme activity, reversible loss of catalytic efficiency is most commonly associated with

A. Low temperature exposure ✓
B. Very high temperature exposure
C. Extreme acidic conditions causing denaturation
D. Hydrolysis of peptide bonds

Low temperatures slow molecular motion without permanently altering enzyme structure. Normal activity usually returns when the temperature is restored to the optimum value.

nmdcat.online BIO NMDCAT
Jul 11, 2026

The catalytic efficiency of an enzyme decreases rapidly after exposure to very high temperature because

A. Peptide bonds are hydrolyzed immediately
B. The tertiary structure maintaining the active site is disrupted ✓
C. ATP production stops
D. The substrate becomes insoluble

Heat primarily disrupts weak interactions such as hydrogen bonds, altering the shape of the active site and reducing enzyme activity.

nmdcat.online BIO NMDCAT
Jul 11, 2026

Regarding pH, enzymes exhibit maximum activity only within a limited range because

A. Every enzyme has identical amino acid composition
B. Proper ionization of catalytic residues is maintained only near the optimum pH ✓
C. Substrate concentration is highest at optimum pH
D. Enzyme concentration increases automatically

Correct protonation of amino acid side chains is essential for substrate binding and catalysis. Extreme pH alters these charges.

nmdcat.online BIO NMDCAT
Jul 11, 2026

During digestion in the human stomach, pepsin remains highly active because

A. Gastric juice maintains an acidic environment near its optimum pH ✓
B. Pepsin functions best in alkaline medium
C. Pepsin is unaffected by pH changes
D. Hydrochloric acid increases enzyme concentration

Pepsin functions optimally around pH 2 due to the highly acidic conditions of the stomach.

nmdcat.online BIO NMDCAT
Jul 11, 2026
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