notes 4-2

Notes 4-2Respiration

Food = Energy? Not exactly! It’s a complicated process… Eat food food broken down into small

molecules by digestive system molecules move through bloodstream to body cells energy from molecules released

Respiration Cells break down food (sugars)

and release their energy The cells of ALL living things

respire (yes, plants do too!) As food is converted into

energy, your cells store the energy until your body needs it

Think of this like a bank account; a bank stores your money until you need it, then you take it out.

Respiration has 2 stages:

Stage 1: Takes place in the

cytoplasm of cells Glucose (sugars from

the food you eat) is broken down into smaller molecules

A small amount of energy is release

No oxygen is involved in step 1

Stage 2: Takes place in the

mitochondria Smaller molecules

combine with oxygen A chemical reaction

occur that releases a lot of energy, along with water and carbon dioxide (this is why the mitochondria is the “powerhouse”)

Two Stages of Respiration

During respiration, cells break down simple food molecules such as sugar and release the energy they contain.

Respiration Equation

The equation states that sugar (glucose) combined with oxygen yields water, carbon dioxide, and energy

Where does it come from?

Where does the sugar come from?

The food we eat!

Where does the oxygen come from?

Plants release it as a waste product during photosynthesis and we breathe it in!

What do we do with it?

What happens to the carbon dioxide we make?

We release it as a waste product when we exhale, and plants then take it in to photosynthesize.

What happens to the water we make?

Some of it is used for normal cellular functions and some of it is release when we exhale.

Photosynthesis and Respiration

You can think of photosynthesis and respiration as opposite processes.

Fermentation Some cells can obtain energy without the

oxygen through fermentation Yields much less energy than respiration! Examples: some single celled organisms that

live deep in the ocean where there is no oxygen

Alcoholic fermentation

Yields alcohol, carbon dioxide and a small amount of energy

Example: carbon dioxide made by yeast during baking makes air bubbles in bread causing it to rise

Example: bubbles in beer and sparkling wine caused by carbon dioxide

Lactic Acid fermentation

Yields a product known as lactic acid When you exercise, your cells

eventually run out of oxygen, yet they still need to provide your body with energy…. They do this by fermentation.

The lactic acid your cells make leave your muscles feeling weak or sore.

How many of you have experienced this?