Chapter 2 - Cell Chemistry and Bioenergetics

Percentage of CHON in an organism’s weight

A. 95.5%

B. 96%

C. 96.5%

96.5%

It is a crucial property of any bond, measured by the amount of energy that must be supplied to break the bonds. (expressed in kJ/mol or kcal/mol)

Bond strength

What are the four noncovalent attractions that help bring molecules together in cells?

Ionic bonds

hydrogen bonds

Van der Waals forces

hydrophobic forces

Acids, especially weak acids, will give up their protons more readily if the concentration of H3O+ in the solution is (high, low).

Low

Many biologically important molecules contain this functional group in weak bases

Amino (NH2) group

Its presence maintains the neutrality of the cell interior and keeps the cell environment relatively constant under a variety of conditions

Buffers

The four major families of small organic molecules

1. sugar

2. fatty acids

3. nucleotides

4. amino acids

T OR F.

Small organic molecules are more abundant than the organic macromolecules

False

These are less abundant, accounting for only about one-tenth of the total mass of the organic matter in the cell.

Principal building blocks from which a cell is constructed

Macromolecules

Three functions of proteins in cells

1. As catalysts (enzymes)

2. Structural components

3. Molecular motors

The reaction by which each polymer grows by the addition of a monomer onto the end of a growing chain

Condensation reaction

Enzyme-catalyzed reactions are connected in series, so that the product of one reaction becomes the _____ for the next reaction

Substrate

Another term for anabolic pathway

Biosynthetic pathway

Biological order is made possibly be the release of ____ from cells

Heat energy

Second law of thermodynamics

The degree of disorder always increases in the universe or any isolated system

T OR F.

Higher disorder = higher entropy

True

What does the first law of thermodynamics say?

Energy can be converted from one form to another, but it cannot be created or destroyed

The first law of thermodynamics tells us that the total amount of energy must always be the same

True

Cells obtain energy from the _____ of organic molecules

A. oxidation

B. hydrolysis

C. condensation

Oxidation

Reduction reaction has (lower, higher) CH bonds and (gains, loses) electrons.

Oxidation reaction has (lower, higher) CH bonds and (gains, loses) electrons.

• Reduction - Higher CH bonds; gain of electrons

• Oxidation - Lower CH bonds; loss of electrons

Each enzyme binds tightly to a substrate and greatly (a) increases (b) decreases the activation energy

(B) decreases

T OR F.

Activation energy is always negative

False

Activation energy is always positive, but the total energy change for the energetically favorable reaction is negative

T OR F.

An enzyme can speed up a reaction, but it cannot change its direction.

True

An enzyme cannot change the equilibrium point for a reaction. Since it lowers the activation energy for the reaction (Y-X), it also lowers the activation energy for the reaction (X-Y) by EXACTLY the same amount

Molecules are also in constant translational motion, which causes them to explore the space inside the cell through _____

A. translational motion

B. collisions

C. diffusion

Diffusion

T OR F.

The stronger the binding of the enzyme and substrate, the faster their rate of dissociation

False

Slower rate of dissociation

It is a measure of the spontaneity of a reaction

Free energy change (delta G)

T OR F.

A negative delta G means higher disorder and energetically unfavorable reaction

False

Energetically favorable

T OR F.

The concentration of reactants influences the free-energy change of a reaction, as well as its direction

True

For example, a reversible reaction Y ←→ X , a large excess of Y over X will tend to drive the reaction in the direction of Y → X. Thus, as the ratio of Y to X increases, the delta G becomes more negative for the transition Y → X

A measure for comparing the relative energies of different types of reactions

A. Free energy change

B. Standard free energy change

Standard free-energy change

Formula of delta G (free energy change) when standard free-energy change is given

R

T

delta G0

ln

[X], [Y]

delta G = delta G0 + RT ln [X] / [Y]

RT = 2.58 J/mole

X and Y = concentrations of reactants, mol/L

---

Formula for equilibrium constant, K

K = [X] / [Y]

Another term for activated carriers

A. Coenzymes

B. Cofactors

C. Ions

Coenzymes

The formation of an activated carrier is coupled to an _____ reaction

Energetically favorable

Spontaneous

Inside the cell, the ratio of NAD+ to NADH is kept (high, low) whereas the ratio of NADP+ to NADPH is kept (high, low).

High

Low

Activated form of coenzyme A

Acetyl CoA

Hydrolysis reaction (spontaneous) is coupled by ____ reaction for ATP hydrolysis

Condensation

Net gain of one round of glycolysis

• 2 3C pyruvate

• -2 ATP +4 ATP = +2 ATP

• 2 NADH

During anaerobic conditions, the pyruvate and NADH from glycolysis stay in the ____

Cytosol

Fermentation will take place.

Why does fermentation require a higher glucose input than a normal oxidation process?

During anaerobic conditions, the cells cannot utilize oxygen to produce ATP. Since glycolysis has less ATP gain, the cell will need more glucose input to compensate the ATP it needs

What two steps in glycolysis that create high-energy phosphate linkage directly from Pi? This accounts for the net yield of 2 ATP and 2 NADH.

A. Glucose to G6P; G6P to F6P

B. DHAP to G3P; G3P to 1,3 BPG

C. G3P to 1,3 BPG; 1,3 BPG to 3-PG

• Step 6 - G3P to 1,3 BPG

• Step 7 - 1,3 BPG to 3-PG

Both plants and animals store food molecules through fats. But for short-term reserves, what reservoirs are they using?

Starch for plants

Glycogen for animals

Sugars and fats are both degraded to ____ in mitochondria for citric acid cycle

Acetyl CoA

Sugar → pyruvate → acetyl CoA, CO2, NADH

Fats → fatty acyl CoA → acetyl CoA, FADH2, NADH

The TCA accounts for about what fraction of the total oxidation of carbon compounds in most cells?

2/3

The TCA cycle does not use gaseous O2; instead, it uses oxygen atoms from ____

Water (H2O)

Net result of Krebs Cycle

• 3 NADH

• 1 FADH2

• 1 GTP

• 2 CO2

Site of:

Glycolysis

Krebs Cycle

ETC

Cytosol

Mitochondrial matrix

Inner mitochondrial membane

The total complete oxidation of a glucose molecule to water and carbon dioxide produces how many ATP molecules?

30 ATP

What are the 9 essential amino acids?

PVT TIM HALL

phenyalanine

valine

threonine

tryptophan

isoleucine

methionine

histidine

leucine

lysine