MIDTERM 1 Flashcards Preview

LS7A > MIDTERM 1 > Flashcards

Flashcards in MIDTERM 1 Deck (22):
1

Which of the following molecules is held together by nonpolar covalent bonds?
NH3, CH4, KCl

CH4

2

Which of the following molecules is held together by polar covalent bonds?
NH3, CH4, KCl

NH3

3

Phospholipase is an enzyme that cleaves the phosphate head group off a phospholipid molecule. The plasma membrane is not, however, permeable to the enzyme. Imagine a cell where phospholipid A is present in the layer of phospholipids facing the exterior of the cell, and phospholipid B is present in the layer of phospholipids facing the interior of the cell. After adding phospholipase to the medium in which the cell is growing, what would you expect to find in the fluid surrounding the cell?

The phosphate head group from phospholipid A only

4

Which one of the following molecules would MOST likely require a transport protein to cross the plasma membrane of a red blood cell?
CO2, C6H12O6, O2, H2O

C2H12O6

5

Why does a phospholipid on the cytoplasmic side of the cell membrane rarely flip to the extracellular side if both environments are polar?

The two sides have different functions and thus the phospholipid would not function properly.

The cytoplasmic phospholipid is too big to pass through the membrane.

The polar head group cannot pass through the nonpolar interior.

The cholesterol does not allow lipids to move.

The polar head group cannot pass through the nonpolar interior.

6

In the figure below, the cell is _____ to the solution. If the membrane is permeable to water, but not to solutes, net movement of water will be _____ the cell

Inside cell: 285mM
Solution: 500mM

Hypotonic; out of

7

Which of the following examples is considered catabolism?
A. hydrolysis of glycogen (a glucose polymer) during activity
B. synthesis of new DNA copies prior to cell division
C. fat cells growing bigger during times of ample nutrition
D. use of fat (triglyceride) stores as a cellular energy source
E. a person losing weight on a calorie restriction diet

A, D, E

8

Which of the following reactions would you predict could be coupled to ATP synthesis from ADP + Pi?
A. creatine phosphate + H2O → creatine + Pi, ΔG – 10.3 kcal/mol
B. glutamic acid + NH3 → glutamine, ΔG + 3.4 kcal/mol
C. glucose 6-phosphate + H2O → glucose + Pi, ΔG – 3.3 kcal/mol
D. glucose 1-phosphate + H2O → glucose + Pi, ΔG – 5.0 kcal/mol
E. phosphoenolpyruvate + H2O → pyruvate + Pi, ΔG – 14.8 kcal/mol

A, E
delta G < -7.3 kcal/mol

9

When carbohydrates are oxidized, the C–H bonds of the carbohydrate become C=O bonds of carbon dioxide. Oxidation is defined as a loss of electrons, but carbon does not become positively charged in the process. Why then is this considered oxidation?

A. The shared electrons in C–O bonds spend less time close to the carbon nucleus than the shared electrons in C–H bonds.
B. C=O bonds in CO2 are double bonds, and C–H bonds are single bonds.
C. Electrons in the C=O bonds are higher energy than the electrons in the C–H bonds.
D. The phosphate groups of ATP are ionized, and carbons donate those electrons.

A

10

Which of the following is/are TRUE regarding redox reactions?
A. If a molecule accepts electrons, it has been reduced.
B. Oxidizing agents accept electrons.
C. Reducing agents accept H atoms.
D. Redox reactions may involve the transfer of hydrogen ions (H+).
E. A molecule that has gained H atoms is said to be reduced.
F. Oxidizing agents accept H+ ions.

A, B, E

11

Which pair of atoms form a stronger bond? The one with high potential energy or the one with lower potential energy?

Lower potential energy

12

Which of these bonds/ interactions has the highest potential energy?
Covalent, Ionic, Hydrogen bonds, van der Waals' forces

van der Waals' forces (weakest bond)

13

Rank the following molecules in order of least permeable to most permeable: oxygen, Na+ ion, urea, glucose

Na+ ion, glucose, urea, oxygen

14

Water travels into a piece of lettuce: the plant cells are ____ compared to the surrounding solution.
Hypertonic, Hypotonic, Isotonic

Hypertonic

15

Based on the diagram, the concentration of K+ ions should be:
Higher, Lower, The same... inside the cell as outside

Higher

16

If the Na+/glucose co-transporter stopped working, the concentration of glucose inside the cell would most likely ____

Decrease

17

You add a toxin that prevents the Na+/K+ pump from hydrolyzing ATP. As a result, the rate of glucose leaving the cells and entering the blood will eventually ____

Decrease

18

Which of the following statements are TRUE about catabolic and anabolic reactions?
1. In anabolic reactions chemical bonds are only formed and in
catabolic reactions chemical bonds are only broken.
2. In anabolic reactions the products have higher potential
energy than reactants; in catabolic reactions the products
have lower potential energy than the reactants.
3. In anabolic reactions the products have lower entropy than
the reactants; in catabolic reactions the products have higher
entropy than the reactants.

2 and 3

19

Is the process of diffusion exergonic or endergonic?

exergonic

20

Which of the following is the most precise general
description of the role of enzymes in catalyzing
biochemical reactions?
A. Enzymes provide the necessary activation energy to overcome the transition state.
B. Enzymes stabilize the transition state by decreasing
its free energy.
C. Enzymes cut hard to break bonds allowing the
reaction to proceed.
D. Enzymes increase the ΔG of the reactions making
them proceed rapidly.
E. Enzymes decrease the ΔG of the reactions making
them proceed rapidly.

B

21

Based on the diagram below, how would
you compare the potential energies of
AH2
, NADH, and BH2
?

AH2 > NADH > BH2

22

Reducing NAD+
to NADH is an
________ process.

Endergonic, Exergonic

Endergonic