Photosynthesis and Cellular Respiration

Energy Use in Living Organisms

Step 1 Convert sunlight

energy into chemical food energy

Ends in Glucose

Step 2 Convert chemical food

energy into chemical energy that the cell can use

Ends in ATP

Adenosine Triphosphate (ATP)

AdenineThree phosphate

groups

Ribose

Energy Cycle

• ATP is a charged battery for cell• Made during cellular

respiration• Used up to complete activities

for cell• Energy in ATP is stored in

high energy bonds between phosphate groups

• ADP is a used battery for cell• one phosphate has been

removed• Phosphate must be added

back on to recharge battery

ADP

ATP

ATP and ADP

What do Plants do?

Plants do step 1 with chloroplasts

Plants do step 2 with mitochondria

Because plants make their own food and then eat it, they are called autotrophs

What do Animals do?

Only do step 2 with mitochondria

Because animals must eat food that others have made, they are called heterotrophs

Step 1: Photosynthesis

Convert sunlight energy into glucose

Chloroplast performs photosynthesis

Plants, algae, some bacteria, and some protists all perform photosynthesis

Overall reaction 6CO2 + 6H2O → C6H12O6 + 6O2

Occurs in two stages Light dependent reactions Light independent reactions

Chloroplast

Found only in Plant cells Thylakoid- coin-shape structure containing

chlorophyll and proteins; also called photosystems Grana- stacks of thylakoids Stroma- fluid inside chloroplast (similar to cytoplasm)

Light Dependent Reactions

Energy from sunlight is absorbed by chlorophyll and other pigments in the thylakoid membrane

Water is split into oxygen (given off as waste), H+, and electrons

Electrons go through a series of proteins in the membrane called the electron transport chain

Electrons provide energy for hydrogen protein pumps to pump H+ into the thylakoid

More sunlight energy is absorbed Electrons are added to NADP+ to create NADPH Hydrogen ion diffuse through another membrane protein The diffusion fuels the production of ATP by the enzyme ATP

synthase

Light Dependent Reactions

Light Independent Reactions

Occurs in the stroma Also called the Calvin cycle Is a series of reactions controlled by enzymes The ATP and NADPH made during the light

dependent reactions are used to fuel the reactions CO2 provides the carbon used to make the sugars

Simple sugars (primarily glucose) are made during the cycle

Light Independent Reactions

Factors that Affect Photosynthesis

Water Water shortages can slow or stop

photosynthesis Plants in dry climates

Waxy coating Thin leaves (needles on cactus)

Temperature Low temps slow or stop photosynthesis

Enzymes do not work well at low temps

Factors that Affect Photosynthesis (cont) Light Intensity/Amount

Increase in light, increase in photosynthesis until at maximum level

Plants still perform photosynthesis in periods without light

Density of Other Plants Crowded plants complete for light and

resources Reduces photosynthesis

Cellular Respiration

Convert glucose into ATP Mitochondria performs cellular respiration All organisms Process is called aerobic because it requires

oxygen Overall reaction

C6H12O6 + 6O2 → 6CO2 + 6H2O

Mitochondria

Found in animals and plants

Outer and Inner membrane

Cristae- folding of inner membrane

Matrix- area inside of inner membrane

Glycolysis

Occurs in cytoplasm of cell

Anaerobic (oxygen not needed)

2 ATP’s are used to start the process

Glucose (a 6 carbon sugar) is broken into two three carbon sugars

4 ATP’s, 2 NADH’s, and 2 pyruvates are made

What comes next?

With oxygen Other

processes of cellular respiration occur in the mitochondria

Without oxygen Fermentation

occurs in the cytoplasm

Krebs Cycle

Occurs in the matrix Pyruvate is broken into a 2 carbon molecule

producing 2 NADH and CO2

Coenzyme A attaches to the 2 carbon molecule and enters the Krebs cycle

It is converted into citric acid Citric acid is broken down through a series of steps

producing 3 more NADH’s. one ATP, one FADH2, and two more CO2’s

Two turns of the cycle are needed to process the 2 pyruvates from glycolysis

Krebs Cycle

Electron Transport Chain

Occurs along the inner membrane of the mitochondria

Electrons from NADH and FADH2 are used

Electrons fuel hydrogen protein pumps which pump H+ out of the matrix

H+ diffuses through a membrane protein and fuels ATP production by ATP synthase

Oxygen picks up the electrons and H+ to form water

Summary of Cellular Respiration

Fermentation

Occurs when oxygen in unavailable

In humans occurs as lactic acid fermentaion (some yeast and plants do alcohol fermentation)

Pyruvates are converted to lactic acid and NAD+ is formed

No more ATP are produced

Comparison

Ps Rs

Function Make food for plantsMake energy for ALL

organisms

Location in cell

Chloroplast Mitochondria

Uses what? Water, CO2, SunlightOxygen,

Food/Glucose

Makes what? Oxygen, Food/glucose

Water, CO2, Energy/ATP