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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