Energy Metabolism

Question 1

Define anabolic reactions, and give an example

Answer 1

Anabolic reactions: build compounds, uses energy (glucose + glucose → glycogen)

Question 2

Define catabolic reactions and give an example

Answer 2

Catabolic reactions: breakdown compounds, releases energy (protein → amino acids)

Question 3

Define ATP, and describe its 3 major functions in the body.

Answer 3

Adenosine triphosphate: a chemical that is body’s main source of energy. 
Mechanical work (muscular contraction)
Chemical work (biosynthesis)
Transport work (osmosis)

Question 4

Mechanical Work

Answer 4

heart beat, breathing, movement

Question 5

Chemical work

Answer 5

create new enzymes, protein synthesis, etc

Question 6

Active transport

Answer 6

move items across cell membrane and throughout the body

Question 7

Besides ATP, list the other 2 compounds produced in cells after food is completely metabolized.

Answer 7

CO2 and H20

Question 8

Identify where energy metabolism occurs in the cell.

Answer 8

mitochondria

Question 9

Identify the 3 major metabolic pathways through which the macronutrients are converted into energy.

Answer 9

glycolysis, TCA cycle, electron transport chain

Question 10

Breakdown of carbohydrates

Answer 10

glucose → pyruvate via glycolysis; pyruvate → acetyl CoA → TCA cycle → ETC

Question 11

Breakdown of fat

Answer 11

glycerol → pyruvate; fatty acids → acetyl CoA

Question 12

Breakdown of protein

Answer 12

AAs → pyruvate (glucogenic); → acetyl CoA (ketogenic); or straight to TCA cycle

Question 13

Glycolysis

Answer 13

6 carbon glucose becomes two 3 carbon pyruvate molecules (reversible reaction)

Question 14

TCA Cycle

Answer 14

loss of CO2 from pyruvate and it becomes Acetyl CoA (irreversible reaction). The TCA cycle is a series of chemical reactions that cells use to convert the carbons of an acetyl group to CO2 while harvesting energy to produce ATP

Question 15

ETC

Answer 15

Electron Transport Chain: the passage of electrons along a series of electron carriers. As electrons are passed from carrier to the next, small amounts of energy are released

Question 16

Sources of glucose

Answer 16

carbohydrate food sources, body glycogen stores, and endogenous biosynthesis (some amino acids, glycerol → gluconeogenesis)

Question 17

HSL

Answer 17

Hormone Sensitive Lipase: TG in adipose cells catabolized to glycerol plus free fatty acids with hormone-sensitive lipase (HSL). HSL activity increased by glucagon, growth hormone, epinephrine (decreased by insulin)

Question 18

When does fatty acid oxidation work best?

Answer 18

When carbohydrates are available

Question 19

Ketosis

Answer 19

Condition that results from the incomplete oxidation of fatty acids

Question 20

When does ketosis occur

Answer 20

when low CHO intake or insufficient insulin. Acetyl CoA accumulates because fatty acids cannot enter TCA cycle (no glucose for oxaloacetate). Acetyl CoA → ketones

Question 21

Outline the metabolic consequences of consuming an excessive amount of any macronutrient (in excess of the body’s energy/calorie needs).

Answer 21

Body stores little glycogen and lots of fat. No need for TCA cycle, so acetyl CoA accumulates from excess fatty acids, AAs and glucose. Acetyl CoA converted into triglycerides.

Question 22

Lipogenesis

Answer 22

glucose and AAs become fatty acids

Question 23

Symptoms of ketosis

Answer 23

Nausea, Fatigue, Constipation, Low blood pressure, Elevated uric acid, Stale foul taste in mouth, Fetal harm and still birth

Question 24

Describe the fate of each macronutrient during short-term and prolonged fasting (starvation).

Answer 24

0-6 hours: Body uses glycogen and fat stores for energy (glycogenolysis: liver glycogen converted to glucose)
3-5 days: Body breaks down proteins to AAs for glucose (gluconeogenesis)
Starvation: Glucose still needed for some brain cells (from protein), shift to ketosis

Question 25

Metabolism Regulation

Answer 25

Enzymes: availability, phosphorylation status, their presence and rate of activity are critica to chemical reactions in the body
Hormones: glucagon, insulin, epinephrine; low level of insulin promote gluconeogenesis, protein breakdown and lipolysis
Blood glucose concentration
ATP concentration: high ATP concentrations decrease energy-yielding reactions and vice versa
Liver