Cells and Energy

Chapter 4

CHEMICAL ENERGY AND ATP 4.1

Key Concept

• All cells need chemical energy

Chemical Energy

• The chemical energy used for most cell processes is carried by ATP – molecules in food store chemical energy in

their bonds

Starch molecule

Glucose molecule

Energy Release

• ATP transfers energy from the breakdown of food molecules to cell functions – energy is released

when a phosphate group is removed

– ADP is changed into ATP when a phosphate group is added

ATP Production

• Organisms break down carbon-based molecules (mostly carbohydrates) to produce ATP – not stored in large

amounts

– up to 36 ATP from one glucose molecule

Energy Storage

• Fats store the most energy – 80 percent of the energy in your body

– about 146 ATP from a triglyceride

• Proteins are least likely to be broken down to make ATP – amino acids not usually needed for energy

– about the same amount of energy as a carbohydrate

Energy Sources

• A few types of organisms do not need sunlight and photosynthesis as a source of energy – some organisms live in places

that never get sunlight • In chemosynthesis, chemical

energy is used to build carbon-based molecules – similar to photosynthesis – uses chemical energy instead

of light energy

OVERVIEW OF PHOTOSYNTHESIS 4.2

Key Concept

• The overall process of photosynthesis produces sugars that store chemical energy

Photosynthetic Organisms

• Are producers – make their own

source of chemical energy

– capture energy from sunlight

– make sugars

Chlorophyll

• A molecule that absorbs light energy

• Found in chloroplasts

Chloroplasts

• Where photosynthesis occurs • 2 parts

– grana / thylakoids (stacks) – stroma (space)

Light-Dependent Reactions

• Capture sun energy – takes place in the

thylakoids

– water and sunlight go in

– oxygen comes out

Light-Independent Reactions

• Make sugars – takes place in the

stroma

– carbon dioxide goes in

– sugars come out

Equation

• The equation for the overall process is:

6CO2 + 6H2O C6H12O6 + 6O2

OVERVIEW OF CELLULAR RESPIRATION

4.4

Key Concept

• The overall process of cellular respiration converts sugar into ATP using oxygen

Cellular Respiration

• Makes ATP (energy) by breaking down sugars – an aerobic process (requires oxygen)

– takes place in the mitochondria

ATP

Glycolysis

• First stage of C.R.

• Location: cytoplasm

• What goes in: glucose

• What comes out: 2 ATP + 2 3-carbon molecules

ATP

Kreb’s Cycle

• Second stage of C.R.

• Location: mitochondrial matrix

• What goes in: 3-carbon molecules

• What comes out: ATP, CO2, electron carriers

Electron Transport Chain

• Third stage of C.R.

• Location: inner membrane of mitochondria

• What goes in: electrons, oxygen

• What comes out: ATP, water

ATP

Equation

• The equation for the overall process is:

C6H12O6 + 6O2 6CO2 + 6H2O

ATP

ATP ATP

ATP ATP

P.S. & C.R

• The reactants in photosynthesis are the same as the products of cellular respiration

FERMENTATION 4.6

Key Concept

• Fermentation allows the production of a small amount of ATP without oxygen

Fermentation

Two Pathways

1. Lactic acid fermentation occurs in muscle cells

2. Alcoholic fermentation produces alcohol

Lactic Acid Fermentation

• Anaerobic

• Produces lactic acid

Alcoholic Fermentation

• Anaerobic

• Produces alcohol

Uses

• Food production – yogurt

– cheese

– bread