Chapter 5 - Essentials of Metabolism

Question 1

PCr produces ATP for how long?

Answer 1

~10 seconds

and if this exercise intensity is sustained, then the energy system has to switch to continue producing ATP to the cells that need it

Question 2

what is the substrate of glycolysis?

Answer 2

Glucose

Question 3

enzyme

Answer 3

a substance that acts as a catalyst to bring about a specific biochemical reaction

Question 4

isoenzyme

Answer 4

A group of enzymes that catalyze the same reaction but have different enzyme forms and catalytic efficiencies

It is thought that isozymes exist to maximize biological capacity

Question 5

phosphocreatine

Answer 5

Phosphocreatine, sometimes referred to as creatine phosphate (abbreviated to PCr or PC) is a high-energy phosphagen capable of donating its phosphate to ADP and, as a result, resynthesizes ATP

Kinase is the enzyme that triggers this interaction between phosphocreatine and ATP molecules

Creatinine is also a product of the reaction.

burns out quickly because the body only stores a small amount of creatine phosphate

Only supplies energy for up to 10 seconds

Question 6

how much phosphocreatine (PCr) can be stored in human muscle at once?

Answer 6

Storage of PCr in human muscle is limited to 80 mM/kg dry mass (120g total, less in vegetarian and vegan individuals)

During aerobic recovery, PCr can also be resynthesized in the mitochondrial intermembrane space by the mitochondrial isoform of creatine kinase

Question 7

what enzyme catalyzes phosphocreatine ATP synthesis?

Answer 7

creatine kinase (CK)

when the body begins to run low on creatine phosphate (and high in adenosine diphosphate), it triggers the chemical action of phosphocreatine molecules donating their phosphate group back to ADP, making it ATP once again

Question 8

what sports utilize the ATP-PC system?

Answer 8

1. 40 meter sprinters
2. olympic weightlifters
3. golf
4. 100 meter sprinters

Question 9

what are the two primary reactions in the ATP-PC system?

Answer 9

1. creatine kinase reaction (uses CP to turn ADP into ATP)
2. myokinase reaction (uses 2 ADP molecules to create ATP and AMP. When AMP accumulates, that serves as a signal to start up the glycolitic pathway)

Question 10

glycolysis

primarily an anaerobic pathway

Answer 10

The anaerobic metabolic pathway that converts glucose into pyruvate

products are 2 pyruvate, 2 ATP, and 2 NADH

literally means the cutting of sugars

occurs in the cytoplasm of the cell

Question 11

resynthesize

Answer 11

To combine or produce something again

Question 12

pyruvate

Answer 12

a 3-carbon acid that is naturally produced during glycolysis

a key intermediate in various metabolic pathways such as gluconeogenesis, fermentation, cellular respiration, fatty acid synthesis

An important molecule present at the intersection of multiple biochemical pathways

Question 13

glucose vs glycogen

Answer 13

Glycogen is essentially glucose molecules bonded together to make a larger storage molecule

Glycogen must first be broken down to release its glucose molecules by a process known as glycogenolysis, catalyzed by the enzyme glycogen phosphorylase.

Question 14

different GLUT receptors

Answer 14

GLUT 1-4

depends on what type of organ the glycolysis is occuring in

Question 15

protein

GLUT-4

Answer 15

An insulin-regulated glucose transporter found primarily in adipose, skeletal, and cardiac tissue

responsible for insulin-regulated glucose uptake into fat and muscle cells

Question 16

glycogenolysis

Answer 16

conversion of glycogen back into glucose, which is then ready to undergo glycolysis to produce ATP

the hormone glucagon (from the liver) stimulates this reaction

the hormone adrenaline controls this process

The process is under the regulation of two key enzymes: phosphorylase kinase and glycogen phosphorylase

Question 17

glycogen phosphorylase

Answer 17

Enzyme responsible for the breakdown of glycogen into glucose monomers

Question 18

G-1-P

Answer 18

Glucose-1-phosphate

The first step in glycogen phosphorylase is to break down glycogen into G-1-P

Question 19

G-6-P

Answer 19

glucose-6-phosphate

The result of the glycogen phosphorylase reaction is G-1-P, which is then converted to G-6-P and available for glycolytic breakdown to release energy

Question 20

glycolytic breakdown

Answer 20

The breakdown of glucose by enzymes, releasing energy and pyruvic acid (3-carbon molecule intermediate)

Question 21

AMP

adenosine mononphosphate

Answer 21

consists of the phosphate group, the pentose sugar ribose, and the nucleobase adenine

AMP is used as a dietary supplement to boost immune activity, and is also used as a substitute sweetener to aid in the maintenance of a low-calorie diet

Question 22

adrenaline (epinepherine)

*catecholamine hormone

Answer 22

A hormone involved in regulating visceral functions, normally produced both by the adrenal glands and by a small number of neurons in the medulla oblongata; also known as epinephrine

In both the liver and muscles, which store glycogen, the process of glycogenolysis is controlled by the hormone adrenaline

Question 23

how is adrenaline (epinepherine) involved in exercise

Answer 23

Adrenaline is released during exercise and is transported in the circulation to the muscle and liver, where it binds to its receptor on the cell membrane.

When adrenaline is bound to its receptor, glycogen breakdown is initiated

Question 24

adrenal medulla

Answer 24

Inner part of an adrenal gland that controls hormones that initiate the flight or fight response

Question 25

# Glycolytic Pathway Step 1

Answer 25

Turn glucose (transported into the cell cytoplasm by GLUT4) into glucose-6-phosphate (G-6-P) Consists of adding a phosphate group to the 6 carbon of the glucose monomer ## Footnote Enzyme responsible? hexokinase

Question 26

# Glycolytic Pathway Step 2

Answer 26

G-6-P is further catalyzed into fructose-6-phosphate (F-6-P) ## Footnote Enzyme responsible? Phosphohexose isomerase

Question 27

# Glycolytic Pathway Step 3

Answer 27

F-6-P gets converted into Fructose-1,6 diphosphate (Bisphosphate ) | Enzyme Responsible? phosphofructokinase-1 ## Footnote Bisphospate means that the 2 phosphate groups are not attached to carbons that neighbor each other. Here, they are attached to the 1 and 6 carbons, making this a bisphosphate

Question 28

# Glycolytic Pathway Step 4

Answer 28

F-1,6-P is then broken down into two three-carbon compounds: 1. dihydroxyacetone phosphate (DHAP) 2. glyceraldehyde 3-phosphate (Ga3P) ## Footnote Enzyme Responsible? Aldolase

Question 29

# glycolytic pathway Step 5

Answer 29

glyceraldehyde 3-phosphate is converted to 1,3,diphosphoglycerate (bisphosphoglycerate), during which nicotinamide adenine dinucleotide (NADH) is formed from nicotinamide adenine dinucleotide (NAD) ## Footnote Enzyme Responsible? Glyceraldehyde 3 - phosphate dehydrogenase

Question 30

# glycolytic pathway Step 6

Answer 30

1,3,diphosphoglycerate is subsequently converted to 3-phosphoglycerate (a phosphate is broken off), and that phosphate turns an ADP into an ATP ## Footnote Enzyme Responsible? Phosphogycerate kinase

Question 31

# glycolytic pathway Step 7

Answer 31

3-phosphoglycerate is then converted to 2-phosphoglycerate (because the phosphate is moved from the 3-carbon to the 2-carbon) ## Footnote Enzyme Responsible? Phosphoglycerate mutase

Question 32

# Glycolytic Pathway Step 8

Answer 32

2-phosphoglycerate and then phosphoenolpyruvate (or PEP) ## Footnote Enzyme Responsible? Enolase

Question 33

# Glycolytic Pathway Step 9

Answer 33

The final stage of glycolysis is the production of pyruvate and another ATP from PEP A point to consider is that glycolysis results in a net production of two ATP molecules, a relatively small amount when understanding how much ATP can be produced from aerobic metabolism | The fate of pyruvate depends on anaerobic/aerobic cell conditions ## Footnote Enzyme Responsible? Pyruvate Kinase

Question 34

# Glycolytic Pathway Step 10

Answer 34

The cell is either in an *anaerobic or aerobic* condition at this stage If **anaerobic**, the floating NADHs unload their hydrides onto the pyruvates, turning them into lactic acid (lactate dehydrogenase). LA is highly acidic, which drops the PH of the blood (metabolic acidosis). This happens when oxygen isn't making it to the tissues If **aerobic**, the pyruvate will undergo the link reaction and enter the Krebs Cycle

Question 35

How does dihydroxyacetone phosphate (DHAP) get converted into the aldehyde glyceraldehyde 3-phosphate (Ga3P)?

Answer 35

The enzyme triose-P-isomerase that isomerizes DHAP into GA3P

Question 36

phosphorylation

Answer 36

the attachment of a phosphate group to a molecule or an ion Its inverse is called dephosphorylation

Question 37

kinase

Answer 37

an enzyme that catalyzes the transfer of a phosphate group from ATP to a specified molecule

Question 38

monocarboxylate transporters

Answer 38

Various proteins that act as carriers for lactate, pyruvate, and ketone bodies across the plasma membrane of a cell

Question 39

lactate shuttling

Answer 39

is best contextualized when considering energy metabolism in fast and slow twitch fibers during exercise During high-intensity exercise, near VO2 max lactate produced by fast-twitch, glycolytic muscle fibers will be transported out of the fiber and taken up by a neighboring slow-twitch, oxidative muscle fibers, where it is oxidized to pyruvate and used in the tricarboxylic acid cycle (TCA), also known as Krebs cycle

Question 40

Acetyl coenzyme A (acetyl CoA)

Answer 40

A molecule involved in protein, carbohydrate and lipid metabolism. Its main function is to deliver the acetyl group to the citric acid cycle (krebs) to be oxidized for energy production of ATP | beta oxidation converts lipids into CoA ## Footnote Enzyme Responsible? pyruvate dehydrogenase (PDH)

Question 41

link reaction

Answer 41

chemical reaction that links the glycolitic pathways to the oxidative pathway under aerobic conditions, this reaction catabolizes pyruvate into acetyl CoA

Question 42

mitochondrion

Answer 42

An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur; has a double membrane, the inner part being folded inwards to form layers called cristae ## Footnote **a higher concentration of mitochondria in a cells means greater aerobic capacity/fitness**

Question 43

Krebs Cycle (TCA) | produces 3 NADH and 1 FADH2

Answer 43

after the link reaction occurs (transforming pyruvate from glycolysis into acetyl CoA), the krebs cycle catabolizes acetyl CoA into 3 NADH and 1 FADH2 11 total ATP produced Each NADH will eventually produce **three** ATP molecules and FADH₂ will produce **two** ATP molecules in the main energy pathway in the mitochondria called the electron transport chain (ETC) **BIG PICTURE**: extract high-energy electrons from acetate in the form of acetyl COA and transfer them to FADH2 and NADH | occurs in the mitochondria ## Footnote acetyl CoA that is used in the TCA can be supplied from the breakdown of carbohydrate or fat

Question 44

metabolic integration

Answer 44

The coordination between the metabolites of carbohydrates, lipids and proteins, and how the fuels are regulated for energy production

Question 45

Energy Metabolism of High-Performance Athletes

Answer 45

100-meter sprinters will have a high proportion of **fast-twitch glycolytic muscle fibers (type II)** that can produce high forces but fatigue quickly The elite endurance performers, on the other hand, have a higher proportion of **slow-twitch oxidative fibers (type I)** endowed with the molecular machinery to metabolize carbohydrates and fats effectively due to their dense capillary supply and high mitochondrial mass

Question 46

metabolism

Answer 46

the process of generating kinetic energy from sources of potential energy

Question 47

2 types of energy in the body

Answer 47

1. kinetic 2. potential

Question 48

3 names for 1st step in the oxidative system

Answer 48

1. krebs cycle 2. citric acid cycle 3. TCA cycle (tricarboxylic acid cycle)

Question 49

what are the 3 forms of energy in the body?

Answer 49

electrical, chemical, and mechanical

Question 50

law of conservation of energy

Answer 50

energy can neither be created nor destroyed ## Footnote because the body is a closed system, it abides by this rule

Question 51

joule

Answer 51

the standard international (SI) unit for energy ## Footnote we can easily convert kcals to kilojoules by multiplying the kcal by 4.184

Question 52

adenosine triphosphate (ATP)

Answer 52

The basic structure of ATP consists of a base (adenine) attached to a sugar (ribose) and three phosphate molecules ## Footnote Although ATP is the main energy source in cells, it exists in short supply. In muscle, this is approximately 25 mM/kg of dry mass (40–50 g total). In terms of powering muscle contraction during exercise, this only provides enough energy for 2–4 seconds of work

Question 53

hydrolysis

Answer 53

breakage of a chemical bond in a molecule i.e., the hydrolysis of a phosphate group from an ATP to release energy

Question 54

exergonic

Answer 54

energy-releasing

Question 55

when AMP accumulation occurs, what does that signal in the body?

Answer 55

to switch from the ATP-PC system to the glycolytic system

Question 56

what are the three energy systems the human body uses?

Answer 56

1. ATP-PC (uses stored 40-50g of ATP) 2. anaerobic glycolysis (uses stored glucose) **link reaction 3. oxidative system (Krebs cycle and then ETC) (uses acetyl CoA)

Question 57

creatine concentration in the muslces based on nutrition status

Answer 57

Question 58

lactate

Answer 58

Lactic acid production occurs in muscle cells and red blood cells, but it can come from any tissue in the body. It's most commonly associated with muscles during exercise, **when the body needs to produce energy faster than it can supply oxygen.** ## Footnote highly acidic (low PH), which increases the acidity of the blood and creates lactic acidosis in the blood

Question 59

the 2 steps of the oxidative system

Answer 59

1. TCA/Krebs Cycle (1st step that produces 2. electron transport chain (extracts electrons from

Question 60

oxidative system

Answer 60

comes after the glycolitic system, where pyruvate is converted into CoA and is run through the 1) Krebs AND THEN the 2) ETC to produce more ATP ## Footnote energy system for low-intensity exercise

Question 61

under what conditions is pyruvate converted into CoA in the oxidative pathway?

Answer 61

under aerobic conditions ## Footnote If anaerobic, pyruvate is reduced to lactate

Question 62

what compound is the input to the krebs cycle

Answer 62

Acetyl-coenzyme A

Question 63

electron transport chain (ETC)

Answer 63

the last stage of the oxidative system NADH and FADH2 enter a sequence of reactions, involving protein channels in the inner mitochondrial membrane that extract their high-energy electrons and give them to oxygen (creating H20 as a byproduct) ## Footnote takes place across the mitochondrial matrix (folds in membrane called cristae)