Chapter 9Cell Respiration

Cell Respiration• Food provides living things with the energy

needed to live and reproduce• Energy in food is measured in calories

– Energy to raise 1 g water 1°C

– Calorie = 1000 calories

• The process of releasing energy from glucose starts with a pathway called glycolysis.

Energy Options

Overview of Cell Respiration

• Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

• Chemical equation: C6H12O6 +6O2 6CO2 + 6H2O + energy … exact opposite of photosynthesis… this makes a cycle

Cell Respiration = glycolysis, Krebs cycle, electron transport chain

GlucoseGlycolysis

Cytoplasm

Pyruvic acid

Electrons carried in NADH

Krebs Cycle

Electrons carried in

NADH and FADH2 Electron

Transport Chain

Mitochondrion

Mitochondrion

Glycolysis• Glycolysis is process in which one molecule

of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound

- Occurs in cytoplasm of cell- The energy from glycolysis is stored in 2

ATP molecules- 4 high-energy electrons are accepted by

NAD+ to make NADH, which goes to the electron transport chain

Glycolysis

Energy in Absence of Oxygen

o Fermentation: releases energy from food without using oxygen… known as anaerobic respiration “not in air”

o Fermentation starts with glycolysis and then converts NADH to NAD+ to allow glycolysis to continue producing ATP

o There are 2 main types:–Alcoholic fermentation

• produces ethyl alcohol, carbon dioxide NAD+

• Carried out by yeast and other microscopic organisms

• Used in bread making

–Lactic acid fermentation• Produces lactic acid, NAD+ • Occurs in your muscles when there is not enough oxygen and unicellular organisms

• Results in cramps because lactic acid builds up

• Used in production of cheese, yogurt, buttermilk, sour cream

The Krebs cycle

• During the Krebs cycle, pyruvic acid from glycolysis is used to make carbon dioxide, NADH, ATP, and FADH2.

Electron Transport• The electron transport chain used

high-energy electrons from the Krebs cycle to convert ADP to ATP.

Net ATP Production

Glucose

2 Pyruvic acid

Krebs Cycle

Energy and Exercise

• A runner has enough stored ATP for about 50 meters, then the muscles need to use lactic acid fermentation to produce ATP in addition to cellular respiration – last about 90 seconds

• Your body stores long-term energy in the form of the carbohydrate glycogen (15-20 minute store), then as fats… these are broken down for exercise longer than 90 seconds

Comparing Photosynthesis and Cellular Respiration

Photosynthesis Cellular Respiration

Function Energy capture Energy release

Location Chloroplasts Mitochondria

Reactants CO2 and H2O C6H12O6 and O2

Products C6H12O6 and O2 CO2 and H2O

Equation 6CO2 + 6H2O + energy C6H12O6 +6O2

6CO2 + 6H2O + energy C6H12O6 +6O2