Metabolism Physiology

Question 1

What is the definition of metabolism?

Answer 1

The total collection of chemical reactions that occur in the body or in a living organism

Includes both catabolism and anabolism

Question 2

What is catabolism

Answer 2

Breaking molecules down

Question 3

What is anabolism

Answer 3

Reaction that makes bigger molecules out of smaller molecules (synthesis reaction)

Question 4

During and after a meal you _______nutrients from the gut

Answer 4

Absorb

This is absorptive state

GI tract with nutrients +are entering blood + lymph

Typical meal takes 4 hours to absorb

Question 5

Between meals you ______ absorb nutrients from the gut

Answer 5

Don’t

This is the postabsorptive state

GI tract without nutrients

Energy must come from body’s energy stores

During the night u r in postabsorptive state (not eating)

Question 6

Carbohydrates in the absorptive state

Answer 6

Carbs are entering the blood from gut as monosaccharides (mostly glucose) which go to the liver via the hepatic portal vein

Some glucose is taken up by the liver glucose that isn’t taken up by liver is used as energy (cells use to make ATP)

Question 7

What is the main energy source for cells during absorptive state?

Answer 7

Glucose

Question 8

What are uses of glucose in absorptive state?

Answer 8

Used as energy

Can be stored as glycogen

**above the liver takes up glucose and stored it as glycogen

Question 9

Why is it important to maintain high enough glucose blood levels?

Answer 9

The nervous system (the brain) won’t use other molecules for energy.

Needs to be maintained for survival

Question 10

Carbohydrates in the postabsorptive state

Answer 10

The liver releases glucose from glycogen (via glycogenolysis) to maintain glucose levels for several hours

Also muscles contain glycogen which can contribute to blood glucose indirectly-breakdown of muscle glycogen causes the release of lactate that the liver makes into glucose

Question 11

What is gluconeogenesis?

Answer 11

If long fast occurs this occurs.

It is new glucose formation

The liver (kidneys to less extent) can make new glucose from non carbs (amino acids and glycerol from fat)

Also during postabsorptive state cells other than nervous system can switch to utilization of fatty acids for energy

They use glucose sparingly

Question 12

Fats- in the postabsorptive state

Answer 12

Can be used for energy

In adipose (fat) tissue fat molecules are broken down, fatty acids are released and are used for energy in most cells

Question 13

Fats in the absorptive state

Answer 13

Nutrients are abundant and excess food is stored as fat

Carbs are stored as glycogen, but not all because we would be huge

Question 14

Once glycogen stores are full what happens?

Answer 14

All excess food calories are stored as fat

Excess calories, whether from carbohydrate, fat, or protein are stored as fat

Question 15

Proteins/amino acids - in the absorptive state

Answer 15

Amino acid are used to replace proteins broken during postabsorptive state (for gluconeogenesis) and are used for new proteins if protein anabolism is occurring

We can use amino acids for energy- the liver can remove the nitrogen group and the molecule created can enter the Kreb cycle and can be used to make ATP

Question 16

Proteins/amino acid in post absorptive state

Answer 16

Gluconeogenesis- remove the nitrogen containing group and convert the rest of the amino acid to glucose

Protein is a major source of blood glucose after a few hours in the post absorp state

Question 17

What part of proteins is in urea

Answer 17

The nitrogen group removed in absorptive state for kreb cycle and nitrogen group in gluconeogenesis

Question 18

Summary of absorptive state

Answer 18

Net anabolism
A.) synthesis of glycogen from glucose
B.) synthesis of proteins from amino acids
C.) synthesis of fats

Liver takes up glucose
A.) glycogen synthesis occurs

Glucose use for energy (in cells)
A.) glucose is used for energy in most cells

Question 19

Summary of postabsorptive state

Answer 19

Net catabolism
A.) glycogen breakdown (or glycogenolysis)
B.) protein breakdown
C.) fat breakdown (fatty acids and glycerol released

Liver releases glucose
A.) glycogen breakdown (or glycogenolysis) occurs also the liver releases glucose via gluconeogenesis (from amino acids and glycerol released in 1)

Fat use for energy/ glucose sparing
A.) fatty acids are used for energy in most cells (which spares the glucose, made by the liver, for use by nerve cells-most notably the brain)
B.) during a prolonged fast, ketones increase in the blood. The liver makes ketones (or ketone bodies) from fatty acids. Some ketone bodies are acidic

Question 20

__________is the main cause of changes occurring when we go from feasting to fasting

Answer 20

Insulin

Question 21

Response to insulin in absorptive state

Answer 21

Liver
An increase in plasma insulin causes increase in glucose uptake and glycogen synthesis in the liver. Also inhibits ketone synthesis

Fat cells
Increase in fat synthesis
Increase in glucose uptake and use

Muscle cells
Increase in glucose uptake and use
Increase amino acid uptake and protein synthesis
Increase glycogen synthesis

Question 22

Why controls insulin secretion?

Answer 22

Increased blood glucose causes increased insulin secretion 

Increased blood glucose causes increased insulin from pancreatic beta cells
Causes decreased glucose release abs increased glucose uptake by liver (increased glycogen synthesis) increased glucose movement into fat and muscle cells
Causes decreased blood glucose

Question 23

What are the less important controls on insulin secretion

Answer 23

Amino acids, GI hormones, parasympathetic and sympathetic impulses

Sympathetic impulses decreases insulin the rest increase

Question 24

What major effects does glucagon have on the liver (postabsorptive state)

Answer 24

Causes increased glycogen breakdown (glycogenolysis)

Increased gluconeogenesis

Increased synthesis of ketones, and with a prolonged fast, ketones become elevated in the blood

Question 25

What causes glucagon release?

Answer 25

Decreased blood glucose -direct effect on beta cells

Decreased blood glucose causes increased glucagon from pancreatic alpha beta cells

Increased gluconeogenesis
Increased glycogenolysis
Increased blood glucose

Increased blood ketones (with prolonged fast)

Glucagon acts to increase blood glucose (maintains it high enough)

Question 26

Cortisol, epinephrine, growth hormone, and glucagon have__________effects

Answer 26

Anti-insulin

They are called “insulin antagonists “

Question 27

What is diabetes mellitus

Answer 27

Due to lack of insulin (type 1) -an autoimmune disease, beta cells destroyed by immune cells

Or target cells (cells the hormones affects) are less sensitive to insulin (type 2) decrease responsiveness to insulin

Question 28

What does a lack of insulin cause

Answer 28

Decreased movement of glucose into cells and the liver releases glucose (remember decreased insulin causes increased glycogenolysis and increased gluconeogenesis)

This causes above normal glucose levels in blood which is called hyperglycemia

Question 29

What causes glucose in the urine

Answer 29

When glucose levels are so high that you exceed Tm and the ability of the kidneys to reabsorbed all the filtered glucose

Glucose in the urine equals glucosuria