Notes 4-2 Respiration

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?