Biology 12

Respiration revision• Glycolysis Glucose pyruvate + 2 ATP• Fermentation (plants)Pyruvate alcohol + carbon dioxide• Fermentation (animals)Pyruvate lactic acid• Aerobic respirationGlucose + oxygen carbon dioxide + water +

energy (36 – 38 ATP)

Photosynthesis• Uses light energy to convert inorganic

molecules to organic molecules• Occurs in the chloroplasts of plant cells

and some protists and the cytoplasm of cyanobacteria

• Occurs as a series of reactions, involving many different enzymes

• Involves light dependent and light independent reactions (the Light and Dark reactions)

Photosynthesis 2• Net equation:

carbon dioxide + water + solar energy glucose + oxygen + water

• ATP and ADP are used to transfer energy

• NADP is used as a hydrogen carrier

Where it happens

Structure of the chloroplast

Light reaction• Occurs in the grana (thylakoid membrane) of the

chloroplast• Inputs are light and water • Light strikes photosystem II• Electrons pass along until they reach the primary

electron acceptor • Water is split into hydrogen ions and oxygen atoms • Electrons pass down the electron transport chain to

photosystem I, forming ATP• The three products of the light reaction are NADPH,

ATP, and O2 • NADPH & ATP are then used in the Calvin Cycle

The Grana – photosystems I and II and the electron transport chain

ATP and ADP

• Act as chemical batteries

• Carry and release small amounts of energy

energy

adenosine

phosphateadenosine

ATP

ADP

Carrier proteins

Carry hydrogen ions to electron transport chains

NADP NADPH + H+

Light independent (Dark) reaction

• Occurs in stroma of the chloroplast

• Inputs are NADPH and ATP from the light reaction, and CO2

• First step is carbon fixation

• A series of reactions lead to the production of water, NADP+ and ADP, and sugar

• NADP+ and ADP return to the light reaction • The carbon of the sugar product comes from

CO2

Calvin cycle

Summary of reactions

Summary of photosynthesisLight dependent reactionOccurs in the granaWater is split into hydrogen ions and oxygenInputs are light and waterOutputs are ATP, hydrogen ions and oxygenInvolves photosystems I and II and electron transport chain

Light independent reactionOccurs in the stromaCarbon is fixedInputs are ATP, hydrogen ions and carbon dioxideOutputs are glucose, water and ADPInvolves the Calvin cycle

Comparison between respiration and photosynthesisRespiration Photosynthesis

Inputs Oxygen & glucose Carbon dioxide, light, water

Products Carbon dioxide, water & energy (ATP)

Oxygen, glucose & water

Type of cells All cells Plants & some protists & bacteria

Location in cells Cytoplasm (anaerobic) & mitochondria (aerobic)

Chloroplast

Where energy comes from

Carbon compounds (chemical breakdown)

Light

Role of ATP End product Carries energy of light reactions into dark reactions

Names of reactions

Glycolysis, fermentation, Krebs cycle

Light reactions – Photosystems I & II & electron transport chain

Dark reactions – Calvin cycle