Which observation is better explained by induced fit than by the lock and key model?
Correct answer D. Some enzymes can act on a small group of structurally similar substrates
Subject / 1,067 questions
MDCAT Biology MCQs
Page 26 of MDCAT Biology multiple-choice questions with answers. Tap an option to check yourself.
Page 26 of 54
- Biological Molecules 74
- Coordination and Control 72
- Biology Diagnostic 70
- Cell Structure and Function 67
- Biotechnology 65
- Reproduction 58
- Bioenergetics 55
- Circulation 50
- Inheritance 48
- Digestion 45
- Immunity 45
- Support and Movement 45
- Acellular Life (Viruses) 45
- Homeostasis 45
- Respiration and Gaseous Exchange 45
- Evolution 45
- Enzymes 45
- Cell Cycle 41
- Chromosome and DNA 40
- Biology Introduction 38
- Ecosystem 27
Enzyme specificity is mainly due to ____.
Correct answer D. the unique three-dimensional shape of the active site
Amylase hydrolyses starch but not cellulose, although both are polymers of glucose. This shows that enzymes are ____.
Correct answer D. specific for particular bonds and substrates
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Enzymes working inside human cells usually show their highest activity at around ____.
Correct answer C. 37 °C
Below the optimum temperature, the rate of an enzyme reaction increases with temperature because ____.
Correct answer D. molecules gain kinetic energy and collide more often
What happens to an enzyme heated well above its optimum temperature?
Correct answer A. Its hydrogen and ionic bonds break and the active site loses its shape
Enzymes kept at near-freezing temperatures ____.
Correct answer C. are inactive but regain activity when warmed
For many enzyme-controlled reactions below the optimum, the rate roughly ____ for every 10 °C rise in temperature.
Correct answer B. doubles
Which enzyme works best in the strongly acidic conditions of the stomach?
Correct answer D. Pepsin
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Trypsin acts in the small intestine, where its optimum pH is ____.
Correct answer A. slightly alkaline, about 8
A change in pH reduces enzyme activity mainly because it ____.
Correct answer B. alters the ionic charges of amino acids in the active site
If substrate is in excess and other conditions are constant, increasing enzyme concentration will ____.
Correct answer D. increase the rate in proportion
As substrate concentration increases at fixed enzyme concentration, the rate eventually levels off because ____.
Correct answer D. all active sites become occupied
Which condition is typical of the later stage of AIDS?
Correct answer D. Pneumocystis pneumonia and Kaposi's sarcoma
A few weeks after HIV infection, many people first show ____.
Correct answer D. a short flu-like illness with fever and swollen lymph nodes
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Zidovudine (AZT), used to treat HIV infection, acts by inhibiting ____.
Correct answer C. reverse transcriptase
Antibiotics are ineffective against viral infections because viruses ____.
Correct answer A. lack the cell walls, ribosomes and enzymes that antibiotics target
Poliovirus enters the body mainly through contaminated food and water and may damage ____.
Correct answer B. motor neurons of the spinal cord
Swelling of the parotid salivary glands is the characteristic sign of which viral disease?
Correct answer A. Mumps
Hepatitis B virus is most commonly transmitted through ____.
Correct answer C. infected blood and sexual contact