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.