KPE260 Flashcards — Metabolism & Fuel Pathways

2 metabolic states

absorptive & postabsorptive

absorptive state

Food comes in, nutrients are absorbed, used/stored

postabsorptive state

No food comes in, body uses nutrients stored

carbohydrates mainly absorb

glucose/monosaccharides

What happens to glucose after absorption?

Enters the GI tract to blood to cells

Glucose can be used for

energy/storage

What happens to glucose when it is broken down for energy?

Glucose → CO₂ + H₂O + energy

What can skeletal muscle do with glucose?

use it for energy/store glycogen

what is glycogen

stored glucose

why does muscle use a lot of glucose?

a lot of muscle mass mainly from skeletal muscle

what can adipose tissue do with glucose?

Glucose → triglycerides (fat storage)

proteins are broken down into

amino acids

what happens to amino acids after absorption

Amino acids → blood → tissues then make protein

What can the liver use amino acids to make?

proteins, enzymes & plasma proteins

What happens when the amino group is removed from an amino acid?

becomes alpha-keto acid

what happens to triglycerides during fat breakdown

Triglycerides → glycerol + fatty acids

lipolysis

The breakdown of triglycerides during fat breakdown

fatty acids can be used for

energy

3 important processes in maintaining blood glucose

Glycogenolysis, lipolysis, gluconeogenesis

glycogenolysis

breakdown of glycogen

liver glycogen pathway

Liver glycogen → glucose → blood

purpose of liver glycogenolysis

helps maintain blood glucose

what happens to muscle glycogen

Muscle glycogen → glucose → energy for the muscle

lipolysis

breaks down triglycerides

What does lipolysis produce?

glycerol + fatty acids

What happens to glycerol?

It can go to the liver → help make glucose.

gluconeogenesis

makes new glucose

function of gluconeogenesis

It helps maintain blood glucose when food isn't coming in.

What can be used to make new glucose?

amino acids + lactate + glycerol

Where does most gluconeogenesis occur?

liver

glucose sparing

Using more fat for energy so glucose can be saved.

Why does the body spare glucose?

To preserve glucose for tissues that need it, especially the brain.

What happens to fat use during prolonged fasting?

fat use increases

When are ketones produced?

During prolonged fasting when fat use increases.

ketones

An alternative energy source made from fat.

Why are ketones useful?

They provide energy and help spare glucose.

Explain what happens to carbohydrates after eating.

→ Carbs → glucose → blood → cells

Then:

→ Muscle: glucose → energy OR glycogen
→ Adipose: glucose → triglycerides → storage

what happens when you enter the postabsorptive state

No nutrients coming in → body uses stored fuel.

→ Liver glycogen → blood glucose
→ Muscle glycogen → muscle energy
→ Triglycerides → glycerol + fatty acids
→ Amino acids/lactate/glycerol → new glucose

Explain the fat pathway during fasting.

Triglycerides → glycerol + fatty acids

→ Fatty acids → energy
→ Glycerol → can help make glucose

. Explain what happens during prolonged fasting.

↑ fat breakdown → ↑ fat use → ↑ ketones → glucose sparing