Chapter 7 Metabolism

Catabolism

Metabolic pathways that break down larger molecules into smaller ones causing the release energy (break down) Examples: -Glycogen broken down into glucose = end product ATP -Triglycercides broken down into glycerol and fatty acids = ATP -Protein broken down into amino acids = ATP

Metabolism

the combination of chemical reactions through which an organism builds up or breaks down materials

Gluoneogenesis

the making of glucose from noncarbohydrate sources (liver is major site) -muscles and lean body tissue get broken down to provide this energy -protein breakdown and glycerol

What happens in fasting period beyond glycogen depletion (beyond 24 hours)?

-As glycogen stores dwindle, the body begins to break down its protein (muscle and lean tissue) to amino acids to synthesize glucose needed for the brain and nervous system energy. Or proteins can be made into ketone bodies to provide energy for other cells (not favorable because deplete other functions of the body) -The liver converts fats to ketone bodies which serve as an alternative energy source for the brain, thus slowing the breakdown of body protein -Result is body fat and protein loss

Ketones

-Fragments formed by the tissues during incomplete breakdown of fat for energy, and released into the blood when glucose is not available to provide energy for the brain. -Helps provide the energy for the brain by slowing down the protein breakdown.

How is ATP formed from Carbs, proteins, and fats?

-Pyruvate can be used to make glucose -Acetyl CoA cannot be used to make glucose -Amino acids and glycerol can be converted to pyruvate and therefore can provide glucose for the body -Fatty acids are converted to acetyl CoA and therefore cannot make glucose and is stored as fat. -The body must have glucose to fuel the activities of the CNS and RBC production (carbs provide the best energy source) -Oxygen is needed to form this kindo f reaction.

What happens to CHO when you eat in excess?

-Store glucose in liver and muscle as glycogen (give up when needed from liver) -Don't have unlimited storage so glucose gets transformed into fatty acids and glycerol to be stored as fat.

What happens to FAT when you eat in excess?

-Stored in fat cells as glycerol and fatty acids. Almost all of the excess is stored but if needed can be used to provide the body energy.

What happens to PRO when you eat in excess?

-Used to make proteins and meet the bodies needs and if in excess it can excrete it out thru urea or store as extra body fat via ketone bodies -No protein storage in the body so excess is stored as fat by turning into ketone bodies

What is the common energy currency for the body cells?

ATP, its like a rechargeable battery and is the final breakdown product of glucose, FA, glycerol, and amino acids

Why does the brain need an alternate energy source?

Brain needs alternative source of energy because fats cannot cross the BBB and glucose is the only way for energy to be provided to the brain.

Anabolism

Constructive metabolism: the process of building up larger molecules from smaller ones requiring energy (build up) Examples: -glucose + glucose = glycogen -glycerol + fatty acid = triglyceride -amino acids +amino acids = protein

Which body cells use fat for energy?

Other body cells can use fat as an energy source like muscles or organs. But number one choice to use for energy is glucose!

Which body cells rely on glucose for energy?

Red blood cells (RBC), brain, and nervous system require glucose for energy (uses about 50% of the glucose that we consume daily) -can't use fats the same way our body cells can to make energy. Based on carbs or protein breakdown.

What happens in a feasting period?

When a person eats in excess of energy needs, the body stores a small amount of glycogen and much larger quantities of fat. (After a meal, glucose, glycerol, and fatty acids from foods are used as needed and then stored.)

What happens in a fasting period (several hours after eating) ?

When nutrients from a meal are no longer available to provide energy (about 2-3 hours after a meal) the body draws on its glycogen and fat stores for energy -Glycogen is broken down to glucose and used for the energy for the brain, nervous system, and RBC -Fat storage is broken down into fatty acids which provide energy for other cells in between eating and not eating.

energy metabolism

all the reactions by which the body obtains and expends the energy from food