L2 Carb Catabolism

Question 1

Energy Transfer

Answer 1

1. in presence of O2, cells can break down 1 mole of glucose into CO2, water, 686 kcal
2. Large fraction of energy is lost as heat
3. Other energy is transferred to ATP

Question 2

Metabolsim

Answer 2

all the chemical reactions involving in maintaining life

Question 3

Catabolism

Answer 3

breakdown
occurs when the body needs energy

Question 4

Anabolism

Answer 4

Synthesis
occurs when the body has enough energy

Question 5

ATP

Answer 5

known as energy currency
energy is released from ATP in presence of water and ATPase

sole function is to transfer energy from molecules storing energy to energy requiring processes

Question 6

Hydrolysis

Answer 6

energy being released from ATP

Catabolic process in which energy is released when chemical bonds are broken in presence of water

1 ATP = removal of terminal phosphate, release of 7kcal

Question 7

Stored ATP

Answer 7

quantity is extremely limited
almost all activities powered by ATP must be generated instantly through catabolism

Question 8

1 Calorie

Answer 8

= 1,000 calories
= 1 kcal

Question 9

How are calories measured in food?

Answer 9

Food in placed in bomb calorimeter
heat is produced, which is equivalent to total energy value that food has

Question 10

How are calories burned by the body measured?

Answer 10

human calorimeter (direct)
cold water at constant rate removes heat, temperature difference represents heat production

can also measure via O2 uptake (indirect)

Question 11

Enzyme

Answer 11

suffix is ASE
specific protein catalyst that accelerates forward and reverse rates of chemical reactions without being consumed or changed in reaction

enzymes are reused

Question 12

Substrate

Answer 12

any substance acted upon by an enzyme

Question 13

Conenzyme

Answer 13

nonprotein substance that facilitates enzyme action by assisting in binding the substrate with its specific enzyme

much less specific than enzymes
Examples: B vitamins

Question 14

Condensation

Answer 14

anabolic process in which energy is used and a molecule of water is formed

Question 15

Reduction

Answer 15

involves a gain of electrons

Question 16

Oxidation

Answer 16

involves loss of electrons

Question 17

Redox reaction

Answer 17

oxidation or reduction reaction

Question 18

Common oxidized form/reduced forms

Answer 18

NAD+ (oxidized)
NADH + H (reduced)

O2 (oxidized)
H2O (reduced)

Question 19

Glycolysis summary

Answer 19

1. always anaerobic
2. Only catabolizes monosaccharides
3. Convert one 6 carbon molecule into 3 carbon molecules (glucose to pyruvate)
4. All reactions occur in cytoplasm

Question 20

Net gain of Glycolysis

Answer 20

2 ATPs are USED

Net gain: 2 ATP , 2 NADH, 2 pyruvates

Question 21

Pros of GLycolysis

Answer 21

1. replenishes ATP more rapidly than oxidative pathway
2. Plays major role in fueling sports that require max energy production for 30-120s
3. Only means of ATP production in RBCs

Question 22

Which skeletal muscle fiber type has the highest concentration of glycolytic enzymes?

Answer 22

Type 2

Question 23

Cons of Glycolysis

Answer 23

inefficient in terms of total ATP made vs how much energy is in 1 glucose

Question 24

Beginning of glycolysis

Answer 24

ATP molecules are used

1st Step: ATP donates phosphate to glucose to make glucose-6-phosphate

This reaction traps glucose inside most cells b/c phosphorylated molecules can’t cross cell membranes

Question 25

What cells can allow phosphorylated glucose molecules to pass through their membrane?

Answer 25

LIVER (and kidney) contain an enzyme which removes phosphate, allowing glucose to leave the cell

Question 26

Later Steps in Glycolysis

Answer 26

4 Hs are removed from glucose, reduce 2 molecules of NAD Remember that there are irreversible steps in glycolysis

Question 27

Phosphofructokinase (PFK)

Answer 27

KEY regulatory enzyme for glycolysis -Activity of PFK is sensitive to energy status of cell -When cell has enough energy/ATP/citrate, PFK's activity is inhibited -When cell's energy level is low (high AMP/ADP inside cell), PFK's activity is increased

Question 28

Aerobic Conditions after glycolysis

Answer 28

In the presence of O2, pyruvate enters the Krebs cycle where it is broken down into smaller fragments and CO2

Question 29

Anaerobic Conditions after glycolysis

Answer 29

Pyruvic acid is converted in lactic acid by LDH 2 H are transferred from NADH + H to pyruvic acid, making lactic acid lactic acid becomes a storage site for H+

Question 30

When does pyruvic acid get converted to lactic acid?

Answer 30

Whenever a cell's energy demands eexceeds either its O2 supply or rate of O2 utilization

Question 31

Examples of when pyruvic acid is converted to lactic acid

Answer 31

skeletal muscle cells when cells are contracting at a fast rate RBC continually form lactic acid because they do not have mitochondria Ischemia--downstream cells become hypoxic

Question 32

Lactic acid dehydrogenase

Answer 32

LDH catalyzes pyruvic acid to/from lactic acid

Question 33

Which cell types have the greatest concentration of LDH?

Answer 33

RBCs, heart, skeletal muscle, liver kidney due to each unique metabolic requirements

Question 34

LDH and the heart

Answer 34

in case of a thrombus, all downstream cells by hypoxic and can die so heart cells begin to upregulate the production of LDH in attempt to continue producing ATP to allow for contraction LDH leakage is present after MI, peaks 48-72 hours after

Question 35

What must be present for glycolysis to continue?

Answer 35

NAD has to accept hydrogen for glycolysis to continue

Question 36

What happens to lactic acid after it is formed?

Answer 36

1. Converted by aerobic respiration to CO2 and water 2. Some lactic acid goes through the Cori Cycle

Question 37

Lactic Acid and Cori Cycle

Answer 37

1. Lactate in blood goes to the liver 2. In the liver, LDH converts lactate to pyruvate 3. Liver converts pyruvate to glucose-6-phosphate 4. G6P can be used to make glycogen or broken down to glucose

Question 38

Purpose of Cori Cycle

Answer 38

removes lactate from the blood path for gluconeogenesis

Question 39

Lactic ACID vs lactate

Answer 39

Lactic acid is an acid, meaning it can release a proton. When it releases H+, it joins with a positive cation to form acid salt (like sodium lactate, which is not charged)

Question 40

Lactic Acid Key points

Answer 40

1. Likely is not what causes the burn felt during intense exercise, because it is very quickly turned into lactate. 2. Acidosis is likely not responsible for muscle fatigue

Question 41

Acidosis during exercise

Answer 41

an increase in H+ causes acidosis during exercise lactate production is the CONSEQUENCE not the CAUSE of acidosis Lactate production helps to slow down acidosis; it coincides with acidosis

Question 42

Muscle fatigue and lactic acid

Answer 42

individuals who are unable to accumulate lactic acid fatigue more rapidly lactic acid has been shown to have beneficial effects on performance

Question 43

Pyruvate breakdown (aerobic)

Answer 43

Has to be broken down into acetyl-CoA before entering the krebs cycle enters the mitochondria and undergoes this: Pyruvate + CoA +NAD+ --> Acetyl CoA + CO2 + NADH + H (this is for one pyruvate, glucose contains 2, so multiply everything by 2 for 1 glucose molecule)

Question 44

Acetyl Coenzyme A

Answer 44

Entry point for all metabolic fuels to enter Krebs cycle Derived from B5 vitamin Function: transfer 2-carbon acetyl groups from one molecule to another

Question 45

Where do acetyl groups come from?

Answer 45

pyruvic acid breakdown of fatty acids, some AA

Question 46

Krebs Cycle net production

Answer 46

For 1 acetyl CoA: 1 ATP, 3 NADH, 3 H+, 1 FADH2

Question 47

Krebs Cycle Overview

Answer 47

1. Operates only under aerobic conditions, O2 is not used directly 2. Occur entirely in the mitochondrial matrix 3. Operates only under aerobic conditions

Question 48

Oxidative Phosphorylation

Answer 48

produces energy when H combines with O2 to form water, ultimately used to make ATP

Question 49

Where does hydrogen come from that is used in oxidative phosphorylation?

Answer 49

From the reduced coenzymes NADH and FADH2 in the Krebs Cycle

Question 50

Net production of Oxidative Phosphorylation

Answer 50

O2 + NADH + H+ --> H2O + NAD+ + 53 kcal

Question 51

Proteins that mediate Oxidative Phosphorylation

Answer 51

Embedded within the inner mitochondrial membrane Two groups: Cytochromes and ATP Synthase

Question 52

Cytochromes

Answer 52

mediate transfer of H+ to O2 called the electron transport chain

Question 53

ATP Synthase

Answer 53

couple the energy that is released as electrons move from cytochrome to cytochrome to form ATP

Question 54

How is ATP produced in the electron transport chain?

Answer 54

1. Electrons are passed down the chain, small amounts of energy is released 2. Energy is then used to pump H+ ions from mitochondrial matrix to cytosolic side of inner mitochondrial membrane, forming H+ gradient 3. H+ gradient passes through ATP synthase channel, forms energy

Question 55

ATP Formation in ETC

Answer 55

3 ATP = from each NADH that goes through the ETC 2 ATP. = from each FADH2 that goes through the ETC, enters further along vs NADH

Question 56

Why do we get either 4 or 6 ATP from the coenzymes generated in glycolysis?

Answer 56

1. In glycolysis, H+ bound to conensymes are transferred to a carrier that can cross the mitochondrial wall 2. H+ are then transferred to NAD+ or FAD+ 3. FAD+ produces less ATP vs NAD+, depends on the type of cell

Question 57

Why don't we make 98 ATP from the breakdown of 1 glucose?

Answer 57

686 kcal is broken down 1 glucose, but we only produce 38 ATP and not ATP remaining 61% of energy lost is released as heat