L1-Principles/Design Of Metabolism

Question 1

LO10- list two major goals of metabolism

Answer 1

• to extract energy and reducing power from the environment

- to synthesize building blocks needed to make more complex polymeric macromolecules

Question 2

LO10- what type of pathways achieve each major goal of metabolism? Give examples of each.

Answer 2

Catabolic- degradation
Oxidative examples
- glycolysis
-fatty acid oxidation
Non oxidative examples
-glycogenolysis
-hydrolysis of triglycerides to fatty acids

Anabolic- synthesis

• glycogen synthesis
• fatty acid synthesis

Question 3

LO1- how are metabolic pathways arranged and why? How are they controlled?

Answer 3

• chemical pathways arranged in distinct sequences that are regulated, coordinated and interconnected to maintain homeostasis
• pathways are distinct so they can occur independently/prevent futile cycling
• pathways have regulatory steps/enzymes
• pathways all use building blocks, ATP, electron carriers, reducers, and acyl carriers

Question 4

LO2-skeletal muscle structure vs function (white/red fibers) + its metabolic capacities

Answer 4

F(x): intermittent mechanical work; white muscle fibers contract rapidly and are short acting while red muscle fibers are slow contracting and longer lasting

• white: limited aerobic oxidation due to low mitochondria content, so they use glycogen (early in exertion) and glucose breakdown with lactate formation (short acting)
• red: higher oxidative capacity due to high mitochondria content (slow contracting and longer lasting)

Question 5

LO2: heart function + its metabolic capacities

Answer 5

Continuously contracting muscle->high oxidative capacity due to highest density of mitochondria (1/2 of heart volume=mitochondria and it has negligible energy reserves)

Mainly uses fatty acids (to help supply be continuous) but can also use glucose, lactate, and ketone bodies

Question 6

LO2: liver function + its metabolic capacities (including list of processes it is involved in)

Answer 6

F(x)s: biosynthesis and detoxification, so lots of mitochondria and microsomes (can itself use glucose, fatty acids and amino acids)

Involved in: glucose homeostasis
glucose storage (as glycogen)
gluconeogenesis
urea synthesis
ketone synthesis
lipoprotein assembly (fatty acids)
coordination of fuel homeostasis (b/c it processes glucose and fats)

Question 7

LO2: brain/nerve function + its metabolic capacities

Answer 7

F(x): electrochemical signaling
-high energy demands (O2 and ATP) to maintain membrane potentials for signaling

High glycolytic and oxidative capacity (more mitochondria than kidney or liver, second highest only to heart/skeletal muscle)

• major fuel is glucose (~60% of our total glucose utilization at rest) but can convert to using ketones during starvation (can’t oxidize fatty acids however)
• like heart, cannot store energy so supply of O2 (~20% of total oxygen consumed at rest) and glucose must be continuous

Question 8

LO2: adipose tissue function + its metabolic capacities

Answer 8

F(x): storage, mobilization, synthesis of triglycerides (regulated by fasting/feeding hormone signals)

Adipocyte structure allows efficient storage of fuel in form of lipids (fats, excess carbs, excess proteins can all be stored in small amount of space)

Question 9

LO2- kidney function + its metabolic capacities

Answer 9

F(x): fluid homeostasis (high rate of active transport), osmotic work, acid and base balance, excretion of waste, ammonia synthesis, gluconeogenesis (second to liver; 10% during overnight fast, up to 40% during starvation)

Similar levels of mitochondria as brain/nervous system, can use fatty acids, lactate and ketones as fuels

Question 10

LO2: RBCS + their metabolic capacities

Answer 10

F(x): exchange O2 and C02, make 2,3-bisphosphoglycerate (BPG) to regulate O2 affinity to hemoglobin
-constitute 1/2 of blood volume and >99% of blood cells, so primary pathway in energy metabolism of blood

Mature RBCs have no mitochondria- get all energy from anaerobic glycolysis (no oxidative metabolism)

Question 11

LO2- GI tract function + its metabolic capacities

Answer 11

Absorbs and transports nutrients

Contains specific enzymes and transporters

Uses glutamine/glutamate for its own energy (transport/to replace rapid turn-over of epithelial cell lining)

Question 12

LO2: skeletal muscle function (at rest vs. during starvation) + its metabolic capacities

Answer 12

Skeletal muscle can use glucose, fatty acids, and ketone bodies, but at rest it uses fatty acids

Skeletal muscle stores about 3/4 of the total glycogen in humans, but it can’t be released from the cell for use by other tissues (except in starvation, when muscle protein can be degraded for use)

Question 13

LO2: creative phosphate role in skeletal muscle function

Answer 13

Short term energy reserve- can generate ATP without metabolism of fuels (exhausted quickly in exertion)

Question 14

LO8: list the caloric value of the three major metabolic fuels

Answer 14

Kcal/gram (1000 calories=1 Calorie=1 kcal)

Carbs: 4
Proteins: 4
Fat: 9
For comparison- EtOH: 7

Question 15

LO9: Name four metabolites at major branch points in metabolism

Answer 15

Glucose-6-phosphate
Pyruvate
Acetyl-CoA
Glutamate

Question 16

LO7: Name the circulating fuels and their key tissue intermediates

Answer 16

Carbs: glycogenglucose-6-phosphatepyruvate
Circulating forms: glucose, lactate

Proteinsamino acids (circulating form)

Fats: triglyceridestriglycerides or fatty acidsacetyl-Co-Aketones or ATP
Circulating forms: triglycerides, fatty acids, ketones

Question 17

LO6: List the three major stages of energy extraction (and where they occur-LO4)

Answer 17

Stage I: Degradation of macromolecules into smaller building blocks (no useful energy gained

Stage 2: Building blocks converted to common intermediates (small amount of energy extracted)

Stage 3: Terminal oxidation of acetyl-CoA to CO2 and H2O, O2 is required (most of energy extracted here)

Question 18

LO4: List the major metabolic processes that occur in the cell and what subcellular compartments they occur in: cytosol

Answer 18

Glycolysis
Pentose phosphate pathway
Fatty acid synthesis
Nucleotide synthesis
Protein synthesis

Question 19

LO4: List the major metabolic processes that occur in the cell and what subcellular compartments they occur in: mitochondria

Answer 19

TCA cycle
Oxidative phosphorylation
B-oxidation of fatty acids
Ketogenesis
Ketone oxidation

Question 20

LO4: List the major metabolic processes that occur in the cell and what subcellular compartments they occur in: cytoslic and mitochondrial enzymes used

Answer 20

Gluconeogenesis
Urea synthesis
Steroid hormone synthesis

Question 21

LO4: List the major metabolic processes that occur in the cell and what subcellular compartments they occur in: smooth ER

Answer 21

Triglyceride synthesis
Phospholipid synthesis
Glycolipid synthesis
Cholesterol synthesis
Hydroxylation reactions
Detoxification reactions

Question 22

LO3: Outline the major metabolic transitions and why some transitions aren’t permitted

Answer 22

*Evolutionary design: for when starvation was our greatest metabolic challenge

Fatty acids, ketones, acetyl-CoA: can be converted only into energy (purpose=storage, can’t be used to maintain blood glucose levels)

Glycogen/glucose: can be used for energy, converted into FAs etc via lipogensis or into proteins etc via synthesis of non-essential amino acids

Proteins/amino acids: can be used for energy, converted into FAs etc via ketogenesis, or into glucose etc via gluconeogenesis

Question 23

LO5: Describe the roles of ATP, NADH, NADPH, NAD+, NADP+, FAD and acetyl-CoA in metabolism integration

Answer 23

ATP: universal source of chemical energy generated by catabolic pathways and used in energy-requiring anabolic pathways
NADH: reduced form of NAD+
NADPH: supplies reducing power for biosynthetic rxns
NAD+: major carrier of electrons in oxidation rxns
NADP+: oxidized form of NADPH
-other major carrier of electrons in oxidation reactions
Acetyl-CoA: (coenzyme A), universal carrier of acyl groups, intermediate of pathways