Chapter 11

Section 1

Taking in Raw Materials

• To grow you need:– Food

– Oxygen• Used to release energy from food that you eat• Carbon dioxide and water are produced as wastes

that are removed when we exhale

– What does a plant need to grow?

Plants Need Food Too

Movement of Materials in Plants

• Plants make their own food using water, carbon dioxide, and inorganic chemicals in the soil

• They produce wastes when they make food

Movement of Materials in Plants

• Most water is taken in through the roots

• Leaves are where gas exchange occurs– Most water taken in leaves through the plant

leaves– Carbon dioxide, oxygen, and water vapor

enter and exit through the openings in the leaves

Leaf Structure and Function

• Outer cell layer is the epidermis– Cuticle prevents the

leaf from drying out– Sunlight reaches cells

inside the leaf through the epidermis

– Contains stomata• Guard cells open and

close

Leaf Structure and Function

• Stomata– More than 90% of water plants take in is lost through

the stomata– Usually open during the day to take in raw materials

to make food– Close during the day if too much water is being lost

• Guard Cells– As water moves into the guard cells they swell and

bend causing the stomata to open– As water is lost they deflate and close the stomata

Leaf Structure and Function

• Spongy cell layer– Has open spaces– Carbon dioxide and water vapor fill in the

empty spaces

• Palisade cell layer– Chloroplasts have chlorophyll here– Most of the food is made here

Leaf Structure and Function

Leaf Structure and Function

Chloroplasts and Plant Pigments

• Chloroplasts are green because they contain the green pigment chlorophyll

• Leaves are green because the color green is reflected

• The other colors of the visible spectrum are absorbed by the chlorophyll

• In the fall some chlorophyll breaks down and other colors are visible

Chloroplasts and Plant Pigments

Food-Making Process

• Photosynthesis:– Process in which chlorophyll traps light

energy and sugar is produced– Only occurs in cells with chloroplasts

Light-Dependent Reactions

• Light-Dependent Reactions need light to occur– Chlorophyll traps light – Light causes water to split into oxygen and

hydrogen– Oxygen leaves the plant – Hydrogen is used in the reactions that don’t

require light

Light-Dependent Reactions

Light-Independent Reactions

• Light-Independent Reactions do not require light– Carbon dioxide is used – Light that was trapped earlier combines with

carbon dioxide to make sugar• 1 important sugar made is glucose

Light-Dependent and Independent Reactions

Light-Independent Reactions

• Glucose is the main source of food for plants – Excess is stored as other sugars and starches

in the plant– When you eat carrots, beets, potatoes, or

onions you are eating stored sugar and starches

Importance of Photosynthesis

• 1: Produces food

• 2: Release Oxygen and take in carbon dioxide

Breakdown of Food

• Cellular respiration: – Series of chemical reactions that breaks down

food molecules and releases energy

Cellular Respiration

• 1st: Sugar molecules are broken down

• 2nd: Smaller molecules enter mitochondria

• 3rd: Oxygen breaks down the molecules into water and carbon dioxide– Releases energy

Importance of Cellular Respiration

• Food contains energy but not in a form most cells can use

• Cellular respiration allows food to change into an energy form all cells can use

• Plants use the energy to transport sugar and to open and close the stomata

Comparing Photosynthesis and Cellular Respiration

Comparing Photosynthesis and Cellular Respiration

• Photosynthesis:– Combines carbon dioxide and water by using

light energy– End products are glucose and oxygen – Energy is stored in food– Occurs only in cells that have chlorophyll

Comparing Photosynthesis and Cellular Respiration

• Cellular Respiration:– Combines oxygen and food– Releases the energy in chemical bonds in

food– End products are energy, carbon dioxide, and

water– Has to have a mitochondria