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)