Metabolism Physiology Flashcards
What is the definition of metabolism?
The total collection of chemical reactions that occur in the body or in a living organism
Includes both catabolism and anabolism
What is catabolism
Breaking molecules down
What is anabolism
Reaction that makes bigger molecules out of smaller molecules (synthesis reaction)
During and after a meal you _______nutrients from the gut
Absorb
This is absorptive state
GI tract with nutrients +are entering blood + lymph
Typical meal takes 4 hours to absorb
Between meals you ______ absorb nutrients from the gut
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)
Carbohydrates in the absorptive state
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)
What is the main energy source for cells during absorptive state?
Glucose
What are uses of glucose in absorptive state?
Used as energy
Can be stored as glycogen
**above the liver takes up glucose and stored it as glycogen
Why is it important to maintain high enough glucose blood levels?
The nervous system (the brain) won’t use other molecules for energy.
Needs to be maintained for survival
Carbohydrates in the postabsorptive state
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
What is gluconeogenesis?
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
Fats- in the postabsorptive state
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
Fats in the absorptive state
Nutrients are abundant and excess food is stored as fat
Carbs are stored as glycogen, but not all because we would be huge
Once glycogen stores are full what happens?
All excess food calories are stored as fat
Excess calories, whether from carbohydrate, fat, or protein are stored as fat
Proteins/amino acids - in the absorptive state
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
Proteins/amino acid in post absorptive state
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
What part of proteins is in urea
The nitrogen group removed in absorptive state for kreb cycle and nitrogen group in gluconeogenesis
Summary of absorptive state
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
Summary of postabsorptive state
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
__________is the main cause of changes occurring when we go from feasting to fasting
Insulin
Response to insulin in absorptive state
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
Why controls insulin secretion?
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
What are the less important controls on insulin secretion
Amino acids, GI hormones, parasympathetic and sympathetic impulses
Sympathetic impulses decreases insulin the rest increase
What major effects does glucagon have on the liver (postabsorptive state)
Causes increased glycogen breakdown (glycogenolysis)
Increased gluconeogenesis
Increased synthesis of ketones, and with a prolonged fast, ketones become elevated in the blood
