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MCAT Biology > Biological Molecules and Enzymes > Flashcards

Biological Molecules and Enzymes Flashcards

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1
Q 
The most common catabolic reaction in the human body is:
A. Dehydration
B. Hydrolysis
C. Condensation
D. Elimination
A

B. Hydrolysis

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2
Q 
A molecule of DNA contains all of the following EXCEPT:
A. deoxyribose sugars
B. polypeptide bonds
C. Phosphodiester bonds
D. nitrogenous bases
A

B. polypeptide bonds

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3
Q 
Which of the following is a carbohydrate polymer that is stored in plants and digestible by animals?
A. Starch
B. Glycogen
C. Cellulose
D. Glucose
A

A. Starch

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4
Q

Metabolism of carbohydrate and fat spares protein tissue. All of the following are true of fats EXCEPT:
A. Fats may be used in cell structure
B. Fats may be used as hormones
C. Fats are a more efficient form of energy storage than proteins
D. Fats are a less efficient form of energy storage than carbohydrates

A

D. Fats are a less efficient form of energy storage than carbohydrates

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5
Q 
Which of the following is found in the RNA but not the DNA of a living cell?
A. Thymine
B. A double helix
C. An additional hydroxyl group
D. Hydrogen bonds
A

C. An additional hydroxyl group

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6
Q

What molecule is a reactant in the breaking of the beta-1,4 glycoside linkages of cellulose and chitin?

A

Water

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7
Q

Which of the following is always true concerning the base composition of DNA?

A

In a molecule of double stranded DNA, the number of adenine residues plus thymine residues equals the ratio of cytosine residues to guanine residues

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8
Q 
All of the following types of lipids can be found in cell membranes except:
A. glycolipids
B. Steroids
C. Prostaglandins
D. Sphigolipids
A

C. Prostaglandins

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9
Q

Types of lipids

A

1) Fatty acids (Linolenic acid)
2) Triacylglycerols (Triglyceride)
3) Phospholipids (Phosphatidylcholine)
4) Galactocerebroside
5) Sphingolipids (Sphingosine)
6) Steroids (Cholesterol)
7) Terpenes (Vitamin A1)
8) Waxes (Palmityl palmitate)

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10
Q

6 Factors contributing to Tertiary Structure

A
  1. Covalent Disulfide bonds between two cystine amino acids on different parts of the chain
  2. Electrostatic (ionic) interactions mostly between acidic and basic side chains
  3. Hydrogen bonds
  4. Van der Waals forces
  5. Hydrophobic side chains pushed away from water (toward center of protein)
  6. R group of proline causes kinks
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11
Q 
Denaturing agents:
Urea:
Salt or change in pH:
Mercaptoethanol:
Organic solvents:
Heat:
A 
Urea: Hydrogen bonds
Salt or change in pH: electrostatic bonds
Mercaptoethanol: Disulfide bonds
Organic solvents: Hydrophobic forces
Heat: All forces
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12
Q

Excessive amounts of nitrogen are found in the urine of an individual who has experienced a period of extended fasting. This is most likely due to:

A

B. breakdown of body proteins.

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13
Q

Proline is not technically an alpha-amino acid. Due to the ring structure of proline, it cannot conform to the geometry of the alpha-helix and creates a bend in the polypeptide chain. This phenomenon assists in the creation of what level of protein structure?

A

C. Tertiary

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14
Q

Enzymes are required by all living things because enzymes:

A

Properly orient reactants and lower activation energy.

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15
Q

All of the following must change the rate of an enzyme catalyzed reaction EXCEPT:

A

Decreasing the concentration of substrate

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16
Q

Since an increase in temperature increases the reaction rate, why isn’t the elevation of temperature a method normally used to accelerate enzyme-catalyzed reactions?

A

Heat changes the configuration of the proteins

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17
Q

The partial double bond character of a peptide bond has its greatest effect in which level of structure of an enzyme

A

Secondary

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18
Q 
Which of the following nutrients has the greatest heat of combustion?
A. Carbohydrate
B. Protein
C. Saturated fat
D. Unsaturated fat
A

C. Saturated fat

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19
Q

Oxidoreductases

A

Catalyze the transfer of electrons or hydrogen ions

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20
Q

Transferases

A

Catalyze reactions in which groups are transferred from one location to another

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21
Q

Hydrolases

A

Regulate hydrolysis reactions

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22
Q

Lyases

A

Catalyze reactions in which functional groups are added to double bonds or, conversely double bonds are formed via the removal of functional groups

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23
Q

Isomerases

A

Catalyze the transfer of groups within a molecules, with the effect of producing isomers

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24
Q

Ligases

A

Catalyze condensation reactions coupled with the hydrolysis of high energy molecules

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25
Q

DNA methylation

A

Involves the addition of an extra methyl group to particular cytosine nucleotides. Methylation causes DNA to be wound more tightly. Methylated sections are inaccessible to cellular machinery and cannot be transcribed, so the expression of genes in these sections is reduced.

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26
Q

Stop codons

A

UAA
UGA
UAG

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27
Q 
VLDL is produced by which of the following organs?
A. The intestines
B. The liver
C. Adipocytes
D. Muscle
A

B. The liver

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28
Q 
Which of the following organs CANNOT use fatty acids as an energy source?
A. The liver
B. Muscle
C. The brain
D. The kidney
A

C. The brain

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29
Q

Which of the following blotting techniques is (are) used for nucleic acids?
I. Southern
II. Northern
III. Western

A

B. I and II only

30
Q

In thin layer chromatography, polar compounds will:

A

Rise more slowly through the silica gel than nonpolar compounds

31
Q

Extraction is an effective method for separating compounds that can be treated with an acid or base and made to differ in:

A

C. water solubility

32
Q

Steps of an action potential

A
  1. Membrane is at rest. Voltage gated sodium and potassium channels are closed.
  2. Voltage gated sodium channels open and the cell depolarizes.
  3. Voltage gated potassium channels open as sodium channels begin to inactivate
  4. Voltage gated sodium channels are inactivated. Open potassium channels repolarize the membrane
  5. Voltage gated potassium channels close and the membrane equilibrates to its resting potential.
33
Q

White matter

A

Areas of nervous system that are composed of myelinated axons of neurons.

34
Q

Grey matter

A

Bundles of cell bodies of neurons

35
Q

Action of parasympathetic neurons:

A
  • Have an inhibitory effect on the heart

- Excitatory effect on the digestive system

36
Q

Pons

A

Coordinates communication between the motor cortex and cerebellum, facilitating the transfer of motor commands.

37
Q

White matter in the brain and spinal cord appears white because:

A

It contains large amounts of myelinated axons.

38
Q

If an acetylcholinesterase inhibitor were administered into a cholinergic synapse, what would happen to the activity of the postsynaptic neuron?

A

D. It would increase, because acetylcholine would be degraded more slowly than normal

39
Q

Which of the following activities is controlled by the cerebellum?
A. Involuntary breathing movements
B. Fine muscular movements during a dance routine
C. Contraction of the thigh muscles during the knee-jerk reflex
D. Absorption of nutrients across the microvilli of the small intestine

A

B. Fine muscular movements during a dance routine.

40
Q

Rhodopsin

A

Pigment in rod cells, made of protein bound to a prosthetic group called retinal, which is derived from vitamin A

41
Q

Bipolar cells in the visual system

A

Receive signals from their associated photoreceptors. Depending on the type of glutamate receptor, a given bipolar cell may be inhibited or excited by changes in the amount of glutamate released by photoreceptors.
-Bipolar cell either inhibited or excited, depending on glutamate receptors

42
Q

As light enters the eye, what is the correct order of the layers through which it passes before being converted into an electrical signal?

A

B. Cornea–Aqueous humor–lens–vitreous humor–retina

43
Q

Exocrine glands

A

Release enzymes to the external environment through ducts

44
Q

Endocrine glands

A

Release hormones directly into bloodstream

45
Q

3 Types of hormones

A
  1. Peptide hormones
  2. Steroid hormones
  3. Tyrosine derivatives
46
Q

Peptide hormones

A
  1. The anterior pituitary hormones: FSH, LH, ACTH, HGH, TSH, and prolactin
  2. The posterior pituitary hormones: ADH and oxytocin
  3. Parathyroid hormone (PTH)
  4. Pancreatic hormones: glucagon and insulin
  5. Thyroid C cell hormone: calcitonin
47
Q

Steroid hormones

A
  1. The glucocorticoids and mineral corticoids of the adrenal cortex: cortisol and aldosterone
  2. Gonadal hormones: estrogen, progesterone, testosterone (estrogen and progesterone are also produced by the placenta)
48
Q

Tyrosine derivatives thyroid hormones

A

T3 (Triiodothyronine)

T4 (Thyroxine)

49
Q

Catecholamines formed in the adrenal medulla

A

Epinephrine and norepinephrine

50
Q

ADH role

A

Regulation of plasma volume by stimulating receptors on cells of the kidneys’ collecting ducts to facilitate reabsorption of water

51
Q 
Most steroid hormones regulate enzymatic activity at the level of:
A. replication
B. Transcription
C. Translation
D. The reaction
A

B. Transcription

52
Q 
All of the following act as second messengers for hormones EXCEPT:
A. cyclic AMP
B. calmodulin
C. acetylcholine
D. cyclic GMP
A

C. Acetylcholine

53
Q

Which of the following side effects might be experienced by a patient who is administered a dose of thyroxine?
A. An increase in endogenous TSH production
B. A decrease in endogenous TSH production
C. An increase in endogenous thyroxine production
D. A decrease in endogenous parathyroid hormone production

A

B. A decrease in endogenous TSH production

54
Q

The exocrine portion of the pancreas releases:

A

Digestive enzymes through a duct.

55
Q

Anterior pituitary releases 6 major hormones

A
  1. Thyroid-stimulating hormone (TSH)
  2. Adrenocorticotropin (ACTH)
  3. Follicle-stimulating hormone (FSH)
  4. Luteinizing hormone (LH)
  5. Human growth hormone (HGH)
  6. Prolactin
56
Q

Hormones:

HALF PiT

A 
H: Human growth hormone
A: Adrenocorticotropin
L: Luteinizing hormone
F: Follicle-stimulating hormone
P: prolactin
i: ignore
T: Thyroid stimulating hormone
57
Q

Calcitonin

A

“Tones down calcium”: moves calcium to the bones for resorption

58
Q

Ectoderm

A

Epidermis of skin, nervous system, sense organs

59
Q

Mesoderm

A

Skeleton, muscles, blood vessels, heart, blood, gonads, kidneys, dermis of skin

60
Q

Endoderm

A

Lining of digestive and respiratory tracts, liver, pancreas, thymus, thyroid

61
Q

Carbon dioxide is carried by the blood in 3 forms

A
  1. dissolved in solution
  2. as bicarbonate ion
  3. in carbamino compounds
62
Q

Haldane effect

A

Facilitates the transfer of carbon dioxide from the blood to the lungs, and from the tissues to the blood

63
Q

Plasma

A

Contains the matrix of the blood, which includes water, ions, urea, ammonia, proteins, and other organic and inorganic compounds

64
Q

Albumins

A

Transport fatty acids and steroids

65
Q

Serum

A

Plasma from which the clotting protein fibrinogen has been removed

66
Q

Hematocrit

A

Percentage by volume of red blood cells.

67
Q

Four methods by which materials cross capillary walls:

A
  1. Pinocytosis
  2. Diffusion or transport through capillary cell membranes
  3. Movement through pores in the cells called fenestrations
  4. Movement through the spaces between the cells.
68
Q

Two main methods used by the body to regulate blood pressure

A

1) Baroreflex (involving quick nervous system control)

2) Renin-angiotensin-aldosterone system (involving hormonal control): through regulation of plasma volume

69
Q

The atrioventricular node:

A

Delays the contraction of the ventricles in the heart

70
Q 
Which of the following is responsible for the spread of the cardiac action potential from one cardiac muscle cell to the next?
A. Gap junctions
B. Desmosomes
C. Tight junctions
D. Acetylcholine
A

A. Gap junctions

71
Q

Hypovolemic shock is most likely to occur during:

A

Arterial bleeding

72
Q

In a healthy individual, the highest blood pressure would most likely be found in:

A

A. The aorta

MCAT Biology (9 decks)

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