Cell Energy

Main Topics

• Photosynthesis• Cellular Respiration

Objectives

• Know the roles of photosynthesis and cell respiration in the ecosystem

• Describe reactants and products in both photosynthesis and cellular respiration

• Compare and contrast systems in plants and animals for nutrient absorption, hormone response, and gas exchange

Vocab

• Photosynthesis• Cellular Respiration• Autotroph• Heterotroph• Aerobic• Anaerobic

How do organisms obtain and use energy?

All cells use chemical energy carried by ATP

• Autotroph- can make their own food– Ex: plants, algae

• Heterotroph- cannot make their own food– Must eat others for food– Ex: animals, humans

Photosynthesis

• A process that captures energy from sunlight to make sugars that store chemical energy.

• Sun’s energy >>> Chemical energy (sugar)• Takes place in the chloroplastNote: energy for almost all organisms begins as sunlight.

Photosynthesis

Factors that affect photosynthesis

• Water • Temperature• Light intensity

Chlorophyll

• A molecule in chloroplasts that absorbs some of the energy in visible light

• Two main types of chlorophyll (a and b)– Absorb mostly red and blue wavelengths of light– Reflect green wavelength of light

Chloroplast

Chloroplast overview

• Two main parts of the chloroplast needed for photosynthesis are the grana and the stroma.

• Grana (granum)- stacks of coin-shaped compartments called thylakoids.

• Stroma- fluid that surrounds the grana inside a chloroplast.

• Thylakoids- membranes of thylakoids contain chlorophyll.

Photosynthesis in detail• Light-dependent reactions– Capture energy from sunlight– Take place in membrane of thylakoids– Water and sunlight needed

• Light-independent reactions– Also called the Calvin Cycle– Uses energy from light-dependent reactions to

make sugars– Take place in the stroma– Carbon dioxide needed

Light-dependent reactions

• Water molecules are broken down• Oxygen molecules are released• Energy carried along thylakoid is transferred to ATP

Light-independent reactionsCalvin cycle

• Carbon dioxide is added• Energy from light-dependent reactions is used• Sugar is formed (usually glucose)

• Photosynthesis video

Plant anatomy (nutrient absorption)

Plant anatomy (gas exchange)

Cellular Respiration

• Process that releases chemical energy from sugars and other carbon-based molecules to make ATP when oxygen is present.

• Aerobic process- it requires oxygen• Takes place in the mitochondria

Mitochondria

3 steps of cell respiration

1. Glycolysis2. Krebs Cycle3. Electron Transport

Glycolysis

• Splits glucose into two three-carbon molecules and makes two molecules of ATP

• Anaerobic process- does not require oxygen• Takes place in the cell’s cytoplasm (not in the

mitochondria)

Krebs cycle

• Takes place in the interior space, or matrix, of the mitochondrion

• Uses the three-carbon molecules from glycolysis

• Small number of ATP molecules are made• Carbon dioxide given off as waste• Energy is transferred to the electron transport

chain

Electron transport

• Takes place in the inner membrane of the mitochondrion

• Energy from the Krebs cycle is transferred to the inner membrane

• Oxygen enters the process• Large number of ATP molecules are made• Water and heat are given off as waste

Cellular Respiration

• Up to 38 ATP molecules are made from the breakdown of 1 glucose molecule

• Used when oxygen is present

Fermentation

• Does not make ATP, but it allows glycolysis to continue

• Used when oxygen is not present• Produces lactic acid, which causes your

muscles to burn during hard exercise

• Crash Course: Cell Respiration