Chapter 13 - Cell Biology

citric acid cycle

oxidative catabolism of acetate (from glycolysis)

NADH - e.t.c. - O2

For glycolysis, _____ must get electrons into the mitochondria for use by the e.t.c. The mitochondrial oxidative pathways depend on ______

complex - allosteric by several enzymes - phosphorylation regulates some enzymes --- this enables a quick response to extracellular signals

The regulation of glycolysis is ________. How so?

the cytosol

Where does glycolysis occur?

1. Aerobic respiration 2. anaerobic respiration -- happens when O2 is low or absent --- pyruvate reduced in cytosol to regenerate NAD+ --- lactate or ethanol is produced

What kind of mitochondrial oxidative pathways occur in glycolysis due to the dependence on oxygen?

D. triacylglycerol

In what form do plant and animal cells store fat? A. nitroglycerin B. glycogen C. phospholipids D. triacylglycerol E. starch

1. Pathways retrieve energy (some as ATP, most as electron pairs) as molecules are broken down. Electrons then enter mitochondrial e.t.c 2. Enzymes 'slow the burn' -- step wise catabolism to improve energy capture 3. Organic molecules eventually enter citric acid cycle

Describe the basic steps of oxidative catabolism.

mitochondria - pyruvate

During the final step in glycolysis, NADH carries electrons to the ________, where they can be passed into the electron transport chain. _______ enters this place for further oxidation in the citric acid cycle

1. complete oxidation of reduced organic substrates to yield CO2 2. energy retrieved in electron pairs is carried by NADH and FADH2 to e.t.c. 3. some energy captured in substrate-level phosphorylation at step 5 4. INPUT --- acetate carried by Coenzyme A (Acetyl-CoA) and amino acids with amine group removed

Give an overview of the steps of the citric acid cycle.

1. oxidative catabolism of sugars --- glucose (6C) -> 2 pyruvate (3C) 2. energy retrieved in electron pairs is carried by NADH --- NAD+ + 2e- + 2H+ -> NADH + H+ 3. Some energy is captured in substrate-level phsophorylation (ATP synthesis) at two steps. 4. Glucose -> 2 pyruvate + 2 NADH + 2 ATP

Give the "overview" of glycolysis.

Glucose + 2NAD+ + 2ADP + 2Pi --> 2 pyruvate + 2NADH + 2ATP

Give the final equation for glycolysis.

B. pyruvate and NADH

In cells that cannot carry out fermentation, which products derived from glycolysis will accumulate under anaerobic conditions? A. lactate and NAD+ B. pyruvate and NADH C. glucose 6-phosphate and NADH D. glucose and NADH E. pyruvate and NAD+

all of them

In cells, pyruvate can be converted to which of the following? Alanine Glucose oxaloacetate lactate acetyl CoA

A. H2O

In the electron transport chain, the oxygen atoms in O2 become part of which of the following molecules? A. H2O B. glucose C. NADH D. CO2 E. ATP

E. ATP and other activated carriers

Most of the energy released by oxidizing glucose is saved in the high-energy bonds of what molecules? A. H2O and CO2 B. ADP and other activated carriers C. O2 D. GDP and other activated carriers E. ATP and other activated carriers

- the outer mito membrane is crossed using wide channels called porins - the inner mito membrane is crossed using a symporter protein that moves pyruvate and H+ into the matrix

Pyruvate must cross two membranes to get into the matrix at the center of the mitochondria for oxidation in the citric acid cycle. How can it do this?

Glucose --> 2 pyruvate --> 30 ATP +++ 2 NADH (via oxidative phosphorylation) --> 4 or 6 ATP +++ 2 ATP (net gain in glycolysis) TOTAL::: 36 or 38 ATP per glucose (depends on cell type and organism)

What is the energy yield with glycolysis + citric acid cycle + oxidative phosphorylation

D. the electron transport chain

The NADH generated during glycolysis and the citric acid cycle feeds its high-energy electrons to which of the following? A. the citric acid cycle B. H2O C. ADP D. the electron transport chain E. FAD

biosynthesis

The citric acid cycle and glycolysis also provide precursors for __________ of organic molecules

matrix - complexes I and II

The citric acid cycle occurs in the _______ of the mitochondria and feeds electrons straight into _______ and ______ of the e.t.c.

constant

The citric acid cycle requires a ______ supply of NAD+

E. It is passed to an electron transport chain that uses it to generate a proton gradient across the inner mitochondrial membrane

What happens to the energy captured during glycolysis and the citric acid cycle by the activated carriers NADH and FADH2. A. It is passed to an electron transport chain that uses it to oxidize food molecules. B. It is passed to an electron transport chain that uses it to produce oxygen. C. It is passed to ADP to form ATP. D. It is used to drive biosynthetic reactions. E. It is passed to an electron transport chain that uses it to generate a proton gradient across the inner mitochondrial membrane.

NADH is water soluble - found in the cytosol and mitochondrial matrix FADH2 is membrane bound to the inner mitochondrial membrane

What is the difference in properties between NADH and FADH2 in oxidative catabolism

Glucose --> 2 pyruvate + 2 NADH + 2 ATP (net gain via substrate-level phosphorylation) ===== 2 ATP per glucose from glycolysis

What is the energy yield for glycolysis?

allosteric - inhibits - inhibits - stimulates

The regulation of the citric acid cycle is mostly _________. ATP _______, NADH _______, ADP _______.

B. fermentation

Under anaerobic conditions, which metabolic pathway regenerates the supply of NAD+ needed for glycolysis? A. breakdown of amino acids B. fermentation C. breakdown of fats D. citric acid cycle E. formation of acetyl CoA

E. glycolysis, the citric acid cycle, and oxidative phosphorylation

Useful energy is obtained by cells when sugars derived from food are broken down and processed by: A. glycolysis, the citric acid cycle, and gluconeogenesis B. gluconeogenesis, fermentation, and oxidative phosphorylation C. gluconeogenesis, the citric acid cycle, and oxidative phosphorylation D. glycolysis, the Calvin cycle, and oxidative phosphorylation E. glycolysis, the citric acid cycle, and oxidative phosphorylation

1. complete oxidation of reduced organic substrates to yield CO2 2. ATP made (one directly) 3. most energy retrieved from electron pairs is carried by NADH and FADH2 to e.t.c.

What happens in the third step of oxidative catabolism when the organic molecules enter the citric acid cycle?

For every acetate - 12 ATP are made -- Acetate --> 2CO2 + 3NADH + FADH2 + ATP ~~~ each NADH -> 3 ATP ~~~ each FADH2 -> 2 ATP For pyruvate, 3 ATP are made Pyruvate -- >CO2 + NADH + acetyl-CoA TOTAL: 15 ATP with both acetate and pyruvate

What is the energy yield from the citric acid cycle?

B. enzymes involved in gluconeogenesis will use energy to produce glucose

When ATP and food molecules such as fatty acids are abundant, which will occur? A. Enzymes involved in glycolysis will break down glucose to generate pyruvate. B. Enzymes involved in gluconeogenesis will use energy to produce glucose. C. When food and ATP are plentiful, both glycolysis and gluconeogenesis will occur. D. Enzymes involved in glycolysis will operate in the reverse direction, using pyruvate to produce glucose. E. When food molecules are plentiful, neither glycolysis nor gluconeogenesis will occur.

glycogen

When food is plentiful, animals can store glucose as what? A. glycogen or starch B. acetyl CoA C. starch D. glucose 6-phosphate E. glycogen

D. starch

When nutrients are plentiful, plants can store glucose as what? A. fats B. glycogen C. glucose 6-phosphate D. starch E. glycogen and starch

Carbohydrates: glycolysis via pyruvate -- cytosol Fatty acids: Beta-oxidation -- peroxisome and mitochondria

Where does the input of acetate come from during the citric acid cycle?

D. mitochondrion

Where does the oxidative (oxygen-dependent) stage of the breakdown of food molecules occur in a eukaryotic cell? A. cytosol B. endoplasmic reticulum C. golgi apparatus D. mitochondrion

in pyruvate

Where is most of the energy still found after glycolysis?

oxaloacetate, O2, GDP, NAD+

Which molecules are required for the citric acid cycle to fully oxidize the carbons donated by acetyl CoA? oxaloacetate O2 GDP GTP NAD+ ATP

E. oxidative phosphorylation

Which of the following processes generates the largest number of ATP molecules? A. citric acid cycle B. glycolysis C. fermentation D. gluconeogenesis E. oxidative phosphorylation

A. it is inhibited by glucose 6-phosphate and by ATP

Which statement is true of glycogen phosphorylase? A. It is inhibited by glucose 6-phosphate and by ATP. B. It stimulates gluconeogenesis. C. It is activated by glucose 6-phosphate, but inhibited by ATP. D. It is activated by glucose 6-phosphate and by ATP. E. It is inhibited by glucose 6-phosphate, but activated by ATP.

NAD+ and ADP

glycolysis requires a constant supply of ______ and _______

glycolysis

the breakdown of glucose by enzymes (oxidative catabolism), releasing energy and pyruvic acid.