2-2: Cell EnergyDo you know why you feel

hungry?

It’s your body’s way of telling you that your cells need energy.

Cells use energy to carry out the chemical activities that allow them to live, grow and reproduce.

From Sun to Cell• Almost all energy that fuels life comes

from the sun.

Photosynthesis

-plants capture light energy from the sun

-Change light energy into food (simple sugar = glucose)

Plants

-Have molecules called pigments in cells

-Chlorophyll

-main pigment used in photosynthesis

-gives green color

-found in chloroplasts

Photosynthesis

• Plants use the energy captured by chlorophyll• Change carbon dioxide and water into food• Produces oxygen as a waste product• Photosynthesis takes place in chloroplasts• Energy in glucose is:

– Used by the plant’s cells or,– Some may be stored in the form of carbohydrates or lipids (fats)

Getting Energy from Food

• Your cells get energy from broken-down food molecules.

• Breaking down food molecules releases the stored energy.

• You get energy from food in TWO WAYS:– 1. Cellular respiration (uses oxygen)– 2. Fermentation (does not use oxygen)

Cellular Respiration

• Respiration means “breathing”

Breathing

-Supplies cells with oxygen needed for cellular respiration.

-Gets rid of the carbon dioxide which is a waste product of cellular respiration.

Cellular Respiration is used to obtain energy from food.

Cellular Respiration

• Food (glucose) is broken down into carbon dioxide and water.

-Energy is produced

Some energy is stored in the form of ATP

-ATP is a molecule that supplies energy.

Most of the energy is released in the form of heat

In eukaryotic cells, cellular respiration takes place in the mitochondria.

Fermentation• Sometimes your muscle cells can’t get the

oxygen they need to produce ATP by cellular respiration.

This is why you start to feel a burning sensation in your muscles when you participate in a strenuous activity.

When this occurs, your cells use the process of fermentation.

Fermentation leads to the production of a small amount of ATP and products from the partial breakdown of glucose.

FermentationTwo Major Types of Fermentation

1. -Occurs in your muscles

-Produces lactic acid (contributes to muscle fatigue after a strenuous activity

-Also occurs in the muscle cells of other animals

-Can also occur in some types of fungi and bacteria

2. -Occurs in certain types of bacteria and in yeast.

-Yeast cells make carbon dioxide and alcohol during the fermentation of sugar.

-The carbon dioxide causes bubbles to form in bread.