Unit 2 Chapter 9: Cell Respiration + Photosynthesis

Question 1

What is the first step in a metabolic pathway

Answer 1

almost always a multisubunit enzyme negatively regulated by cooperative allostery

Question 2

How are metabolic pathways regulated

Answer 2

negative feedback loops/feedback inhibition

Question 3

What is phosphorylation

Answer 3

the addition of a phosphate group to a substrate

-exergonic because ADP and phosphate group have much less pot. E than they did in ATP

Question 4

What is an activated substrate

Answer 4

• phosphorylated compound

- contain a phosphate group and have high free E

Question 5

What drives the formation of ATP

Answer 5

redox reactions

Question 6

What is NADH

Answer 6

an electron carrier that readily donates electrons to other molecules
-has reducing power

Question 7

What is the change in free energy that occurs during glucose oxidation used for

Answer 7

synthesizing ATP from ADP and a phosphate group

Question 8

What is the structure of ATP

Answer 8

3 phosphate groups (high pot.E), adenine and ribose

Question 9

What is glycolysis

Answer 9

• occurs in the cytosol
• exergonic
• the breakdown of glucose into 2, 3-C pyruvates (occurs twice); 2 ATP made from ADP and 1 NAD+ is reduced to form NADH

steps:
1. starts by using 2 ATP(which are reduced to ADP), glucose phosphorylated to form glucose-6-phosphate by hexokinase, then phosphohexoisomerase rearranges it to become fructose-6-phosphate, a second phosphate is added to form fructose-1,6,biphosphate (catalyzed by phosphofructokinase), then G3P is made

2. 2 NAD+ are reduced to NADH, 4 ATP produced (net=2) (phosphate group transferred from phosphorylated substrate to ADP which oxidizes it into ATP), 2 pyruvates are produced

Question 10

What is pyruvate oxidation

Answer 10

• in eukaryotes occurs in pyruvate dehydrogenase in mitochondrial matrix
• pyruvate form acetyl coA by reacting with CoA (coenzymeA), one of the carbons from the pyruvate is oxidized to form CO2and one more NADH is made (from NAD+)

Question 11

What is the citric acid cycle

Answer 11

• occurs in mitochondrial matrix (in eukaryotes), acetyl coA is oxidized into 2 molecs of CO2, 1 more ATP and 3 NADH are made, 1 FAD is reduced to form FADH2
• cycles twice for each glucose

Question 12

What is the ETC

Answer 12

• electron transport chain
• occurs in inner mitochondrial membrane
• electrons from NADH and FADH2 move through a series of proteins, doing work to release H+ and create a proton gradient
• flow of protons back across the membrane through ATP synthase = prod. of ATP from ADP and phosphate group (oxidative phosphorylation)
• molecules pass from protein with lower electroneg. to one with higher electroneg. via redox rns
• potential energy decreases with every rxn
• NADH donates electrons to complex 1, FADH2 donates them to complex 2
• at complex 3 electrons are passed from coenzyme Q to cytochrome c
• Q also carries a proton across the membrane

Question 13

What is the diff. between cellular resp and fermentation

Answer 13

cell resp:

• aerobic
• complete ox.
• waste=H2O and CO2
• 29 ATP made(net)

ferment:

• anaerobic
• incomplete ox
• waste=org. compounds
• 2 ATP made(net)

Question 14

What is the general rule of thumb about oxidation

Answer 14

it decreases the number of C-H bonds

Question 15

What is substrate level phosphorylation

Answer 15

enzyme-catalyzed reactions that result in ATP production (energy comes from phosphorylated substrate)

Question 16

How does feedback inhibition regulate glycolysis

Answer 16

-phosphofructokinase has 2 binding spots for ATP, one at the active site and one at the regulatory site, if ATP levels are high then the enzyme will bind to both; when it binds to the regulatory site the enzyme changes shape which lowers the reaction rate at the active site. Therefore ATP acts like an allosteric regulator in this case.

Question 17

What happens to pyruvate oxidation when there is a lot of ATP

Answer 17

it is shut down (when pyruvate dehydrogenase become phosphorylated and changes shape)
-phosphorylation increases when there is a lot of acetly coA and NADH

Question 18

What happens to pyruvate oxidation when there are high amounts of NAD+,CoA

Answer 18

these indicate low ATP, so it speeds up pyruvate ox.

Question 19

Pyruvate ox is run by positive or negative control?

Answer 19

both (high amounts inhibit, low amounts stimulate)

Question 20

What is energy produced from pyruvate ox. used for

Answer 20

production of NADH

Question 21

How is the citric acid cycle regulated

Answer 21

• speeds up when low ATP
• slows when high ATP
• enzyme that converts acetyl coA to citrate is shut down when ATP binds to it
• NADH binds to another enzymes active site later (inhibition) (1st dehydrogenase)
• even later, ATP binds to an allosteric regulatory site

Question 22

What is energy produced from citric acid cycle used for

Answer 22

production of NADH, FADH2, ATP/GTP

Question 23

For each molecule of glucose what does the the cell produce from gylcolysis, pryruvate ox and citric cylce

Answer 23

6 CO2, 10NADH, 2 FADH2, 4 ATP

Question 24

What is the final electron acceptor in the ETC and what does it produce

Answer 24

oxygen, produces H2O

Question 25

Why does hexokinase add a phosphate group to glucose to make glucose-6-phosphate

Answer 25

• adds a neg. charge which traps it in the cell

- remove more glucose from cytoplasm to allow more to enter

Question 26

Why does phosphohexoisomerase rearrange glucose-6-phosphate to make fructose-6phosphate

Answer 26

to create symmetry in the 6-C sugar to prepare for break up into two 3-C pyruvates

Question 27

Does the citric acid cycle directly require oxygen

Answer 27

not directly, but the amount of NADH generated can only be oxidized with O2 so yes it needs to be present

Question 28

What is chemiosmosis

Answer 28

the production of ATP via a proton gradient

Question 29

Can ATP be produced without the ETC

Answer 29

yes, it really only depends on the flow of protons back into the membrane

Question 30

How many protons make 1 ATP

Answer 30

about 3

Question 31

How is the ETC regulated

Answer 31

by H+ gradient, low gradient = faster electron transport

Question 32

What is fermentation

Answer 32

• anaerobic resp
• occurs when no oxygen is present
• regenerates NAD+ from stockpiles of NADH
• NAD+ used for glycolysis
• pyruvate accepts electrons from NADH

Question 33

Difference between lactic acid and ethanol fermentatin

Answer 33

lactic: pyruvate accepts electrons directly from NADH and makes lactate
ethanol: pyruvate is converted to acetylaldehyde and 2CO2 are produced; acetylaldehyde accepts electrons from NADH, makes ethanol

Question 34

Can pyruvate ox, , the citric acid cycle and ETC occur without oxygen

Answer 34

yes, many bacterial and archaeal species rely on electron acceptors other than O2 and donors other than glucose

Question 35

What happens if there aren’t enough food molecules in the body to be broken down

Answer 35

stored carbs used first, then fats, then proteins

Question 36

Where are carbs, fats, proteins used in catabolic pathways

Answer 36

carbs: sugars into glucose and then glycolysis
fats: glycerol into G3P in glycolysis+fatty acids into Acetyl CoA in citric
proteins: amino acids into pyruvate, acetyl CoA into citric

Question 37

Where are glucose, glycolysis, pyruvate, acetyl coA and products from citric cycle used in anabolic pathways

Answer 37

glucose; glycogen of starch

glycolysis: pathway for synthesis of RNA and DNA
pyruvate: lactate used to make glucose

acetyl CoA into fatty acids into phospholipids and fats

products from citric acid: substrates for amino acid synthesis