Chap 23 –Nutrition, Part III (Energy

Metabolism)Learning Objectives

The student will be able to:1. Discuss the use of glucose as energy for our cells including

the storage of excess glucose as either glycogen or fat.2. Explain metabolism.3. Discuss the two types of metabolic processes (anabolism

and catabolism).4. Describe the importance of cellular respiration (and its

components such as Kreb’s cycle).5. Define ATP and explain its importance as the cell’s “energy

currency”.6. Explain the 3 major stages involved in the processing of

energy-containing nutrients in the body.

Focus: Carb-Loading in Athletes

This runner has a marathon to run in 3 days.

He is eating a diet heavy in carbs (70% or more) and reducing his activity prior to the big race.

How will this make a difference or will it?

Carb-Loading continued When we eat carbs they are basically converted into

__________ (blood sugar) for our cells to use.

Sometimes, when we eat too much carbohydrate (more than our bodies need at the present time), the reserve is stored as either:

- ___ (*fats account for 80-85% stored energy) - _________ (*accounts for the remaining15 – 20% and is

temporarily placed in the muscles).

So, the athlete’s goal is to eat so much carb that there is excess stored as ________ in the muscle.

When exercising, ______ reserves from the muscles are burned off first. In other words, glycogen is the most readily available fuel. On average, you have to continue aerobic exercise for more than 30 minutes to touch fat reserves.

Quick Check

• What is glycogen?

What is glucose?

Opening Question

• When we say “metabolism”, what are we really talking about?

Discussion Once food is digested, how do our cells

‘use’ the energy we consume from food?

Now, for the rest of the story…

The 2 Basic Metabolic Processes

Metabolic processes are either:

1. Anabolic - ________________

Example: The bonding together of amino acids to make ________

2. Catabolic - _______________

Example: Digestion of food in the GI tract

3 Stages of Metabolism of Energy-Containing Nutrients

Stage 1

In a very simplified way we can say that…

- ________ are broken into amino acids

- _____ into glucose and other sugars

- ____ into glycerol and fatty acids

… which are taken up by the small intestine and reach tissues via the bloodstream.

Stage 2 - Glycolysis

• Occurs in the cell’s _________• Newly delivered nutrients are either built into lipids,

carbs, and proteins through ___________ processes

OR

torn apart (broken down) by ___________ processes into pyruvic acid and acetyl CoA

Stage 3 – Kreb’s Cycle

• Occurs in the __________ of the cell

• Almost completely ____________

• Requires ___• Completes the

breakdown of foods• Produces ____,

________, and large amounts of ______

What is ATP?

• An organic molecule known as

• _______________ that releases and stores chemical energy for use in body cells

• You will die without its production

Check out “Metabolic Poisons” page 849 in the section called, “Homeostatic Imbalance”.

A Closer Look at Stage 3 (Kreb’s Cycle) Named after the man who discovered it – Hans Kreb (Nobel Prize in Medicine, 1953)

Summary

• The average person at rest uses about 100 kcal/hour or roughly 116 watts which is slightly more than a ______ _______.

• This corresponds to an energy capture rate of about _____ making cells far more efficient than any human-made machines (which typically only use _______ of energy available to them.

Chap 23 Wrap-Up & Review

• See handout

• Estimated time = 10 minutes

• If not able to finish in class, becomes homework (use it to study for your next exam as well)