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4 Clinical Physiology > L2 Carb Catabolism > Flashcards

L2 Carb Catabolism Flashcards

1
Q

Energy Transfer

A
  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
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2
Q

Metabolsim

A

all the chemical reactions involving in maintaining life

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3
Q

Catabolism

A

breakdown
occurs when the body needs energy

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4
Q

Anabolism

A

Synthesis
occurs when the body has enough energy

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5
Q

ATP

A

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

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6
Q

Hydrolysis

A

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

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7
Q

Stored ATP

A

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

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8
Q

1 Calorie

A

= 1,000 calories
= 1 kcal

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9
Q

How are calories measured in food?

A

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

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10
Q

How are calories burned by the body measured?

A

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

can also measure via O2 uptake (indirect)

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11
Q

Enzyme

A

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

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12
Q

Substrate

A

any substance acted upon by an enzyme

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13
Q

Conenzyme

A

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

much less specific than enzymes
Examples: B vitamins

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14
Q

Condensation

A

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

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15
Q

Reduction

A

involves a gain of electrons

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16
Q

Oxidation

A

involves loss of electrons

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17
Q

Redox reaction

A

oxidation or reduction reaction

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18
Q

Common oxidized form/reduced forms

A

NAD+ (oxidized)
NADH + H (reduced)

O2 (oxidized)
H2O (reduced)

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19
Q

Glycolysis summary

A
  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
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20
Q

Net gain of Glycolysis

A

2 ATPs are USED

Net gain: 2 ATP , 2 NADH, 2 pyruvates

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21
Q

Pros of GLycolysis

A
  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
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22
Q

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

A

Type 2

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23
Q

Cons of Glycolysis

A

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

24
Q

Beginning of glycolysis

A

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

25
Q

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

A

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

26
Q

Later Steps in Glycolysis

A

4 Hs are removed from glucose, reduce 2 molecules of NAD

Remember that there are irreversible steps in glycolysis

27
Q

Phosphofructokinase (PFK)

A

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

28
Q

Aerobic Conditions after glycolysis

A

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

29
Q

Anaerobic Conditions after glycolysis

A

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+

30
Q

When does pyruvic acid get converted to lactic acid?

A

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

31
Q

Examples of when pyruvic acid is converted to lactic acid

A

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

32
Q

Lactic acid dehydrogenase

A

LDH catalyzes pyruvic acid to/from lactic acid

33
Q

Which cell types have the greatest concentration of LDH?

A

RBCs, heart, skeletal muscle, liver kidney

due to each unique metabolic requirements

34
Q

LDH and the heart

A

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

35
Q

What must be present for glycolysis to continue?

A

NAD

has to accept hydrogen for glycolysis to continue

36
Q

What happens to lactic acid after it is formed?

A
  1. Converted by aerobic respiration to CO2 and water
  2. Some lactic acid goes through the Cori Cycle
37
Q

Lactic Acid and Cori Cycle

A
  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
38
Q

Purpose of Cori Cycle

A

removes lactate from the blood
path for gluconeogenesis

39
Q

Lactic ACID vs lactate

A

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)

40
Q

Lactic Acid Key points

A
  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
41
Q

Acidosis during exercise

A

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

42
Q

Muscle fatigue and lactic acid

A

individuals who are unable to accumulate lactic acid fatigue more rapidly

lactic acid has been shown to have beneficial effects on performance

43
Q

Pyruvate breakdown (aerobic)

A

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)

44
Q

Acetyl Coenzyme A

A

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

45
Q

Where do acetyl groups come from?

A

pyruvic acid
breakdown of fatty acids, some AA

46
Q

Krebs Cycle net production

A

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

47
Q

Krebs Cycle Overview

A
  1. Operates only under aerobic conditions, O2 is not used directly
  2. Occur entirely in the mitochondrial matrix
  3. Operates only under aerobic conditions
48
Q

Oxidative Phosphorylation

A

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

49
Q

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

A

From the reduced coenzymes NADH and FADH2 in the Krebs Cycle

50
Q

Net production of Oxidative Phosphorylation

A

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

51
Q

Proteins that mediate Oxidative Phosphorylation

A

Embedded within the inner mitochondrial membrane

Two groups: Cytochromes and ATP Synthase

52
Q

Cytochromes

A

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

53
Q

ATP Synthase

A

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

54
Q

How is ATP produced in the electron transport chain?

A
  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
55
Q

ATP Formation in ETC

A

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

56
Q

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

A
  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
57
Q

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

A

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

4 Clinical Physiology (9 decks)

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