Chapter 6

An Introduction to Energy

Energy makes life possible

Life is highly organized Creating & maintaining this order requires energy

Organisms perform work Movement Manufacturing (new cells, new organelles, new proteins) Making heat to maintain body temperature Activity of nervous system: sensation; thinking

All work requires energy

Forms of energy “Energy” can exist in many forms, not all of

which are obvious

Energy can be transformed from one form to another

ATP: adenosine triphosphate

A versatile form of chemical energy used by all cells

Direct energy source for everything an organism does

Food (sugar, fat) is converted into ATP

Chapter 7

Deriving Energy from Food

From Food to ATP

Cellular Respiration

C6H12O6 + 6 O2 + 36 ADP (glucose)

6 CO2 + 6 H20 + 36 ATP

Cellular Respiration

ATP is produced from food in 3 phases:

Glycolysis

Krebs cycle

Electron transport chain

Insert one glucose:

Electrons carried by

NADH

2 ATP

2 ATP

32 ATP

Glycolysis

First step in breaking down sugar Takes place in cytosol (cytoplasm)

all living things perform glycolysis

In some bacteria, it’s the only phase of energy harvesting

Cellular RespirationATP is produced from food in 3 phases:

Step 1: Glycolysis Happens in cytosol / cytoplas Breaks glucose into 2 smaller molecul Releases a little energy

Step 2: Happens inside mitochondria Releases a lot of energy Waste products are water and CO2

Cellular Respiration

Step 3: Electron transport ATP is made from the energy released in

previous steps Requires oxygen Happens in the mitochondria

Fermentation An alternative to cellular respiration

A different way to get ATP from sugar Does NOT need oxygen

Glycolysis is the same, but steps 2&3 are different

Different products: alcohol is one Makes fewer ATP per glucose (2 vs 36)

Chapter 8

Photosynthesis

Photosynthesis

The work of plants Original source of ALL foods Transforms solar energy into chemical energy

In Chloroplasts Opposite of cellular respiration

Energy + CO2 + H2O Food + O2

Photosynthesis

The oxygen we breathe is a by-product

The CO2 we exhale is cleared from the atmosphere

The “food” is high energy carbohydrates

Photosynthesis

The energy comes from sunlight

Visible light

Red and Blue frequencies are absorbed