PHOTOSYNTHESIS AND RESPIRATION

A few things to remember: The sun is the main source of energy for all organisms Plants trap the energy of the sun and store it in the chemical bonds of carbohydrates Photosynthesis takes place in the chloroplasts Animals digest the carbohydrates obtained from plants ATP and ADP are large compounds made by cells from the nutrients eaten by organisms. Respiration takes place in the mitochondria of cells. Enzymes speed up chemical reactions. Are proteins.

Photosynthesis: 2 stages both stages take place in special areas of the chloroplast: grana and stroma Photochemical reaction= any reaction that involves the absorption of light. Light or energy from the sun is used to split water molecules apart to produce hydrogen and oxygen. This splitting of water is call photolysis. Carbon fixation reaction (sometimes called the Calvin Cycle) causes Carbon dioxide to form carbohydrates. Enzymes in the stroma allow this reaction to proceed.

Photochemical reaction: takes place in the grana 1.Chloroplasts absorb the energy of the sun. 2.This energy is used as activation energy to shake up the electrons in water. Water is supplied by roots. 3.This ‘shake up’ splits the water molecule into 2Hs and 1O = photolysis 4. The oxygen will be released into the atmosphere for our use. 5.The release of energy from splitting the water is put into a large molecule - ATP. ATP will be used later. 6.The 2 Hs are attached to a cmpd – NADP to form 2NADPH. This will store hydrogen for the carbon fixation rxn

Photolysis = Splits water into 2 H and 1 O This oxygen will be Released into the atmosphere From roots Taken in by the Stomata - leaf ATP is formed during photolysis Photochemical rxnCarbon fixation rxn 2H combine w/ CO 2 to form PGAL A large 3 C cmpd 2 PGAL = glucose starch, fat, DNA, protein + water

Carbon fixation reaction: takes place in the stroma carbon is allowed to bond to form organic compounds 1. Carbon dioxide from the light reaction is allowed to react with the 2NADPH molecules. Remember-these molecules were formed earlier and stored. 2.The 2H of the NADPH will bond to the carbon and oxygen of CO 2 This leaves 2NADPs. These are recycled back to the light reaction. 3. The compound formed is a 3 carbon organic compound. It is a starter compound to be used later to make DNA, proteins, starches, sugars, fats ** 4. This reaction needs energy. ATP (formed in the light reaction) will supply this energy. It will be reduced to ADP and will return to the grana for the light reaction to continue. The name of this 3 carbon organic compound is PGAL or phosphoglyceraldehyde-a really BIG molecule=Energy 4.When needed, PGAL molecules will combine to form needed compounds for the plant **

Photolysis = Splits water into 2 H and 1 O This oxygen will be Released into the atmosphere From roots Taken in by the Stomata - leaf ATP is formed during photolysis Photochemical rxnCarbon fixation rxn 2H combine w/ CO 2 to form PGAL A large 3 C cmpd 2 PGAL = glucose starch, fat, DNA, protein + water

Respiration: Aerobic and anaerobic reactions. Aerobic respiration: 1.Glycolysis is the breakdown of glucose by enzymes to produce energy and pyruvic acid. Takes place in the cytoplasm. 2. Oxidative phosphorylation is the enzymatic reaction that makes ATP from ADP. In other words, a process that stores energy. 3.Krebs cycle is a series of reactions that take place in the mitochondria. Oxygen is consumed, water and carbon dioxide are produced, and ADP is made into ATP.

Glucose from food Enters cell through Diffusion. C 6 H 2 O 6 + ATP2 pyruvic acid + 4 ATP glycolysis released Total ATP = 38 Pyruvic acid + oxygen water + CO ATP enzymes Krebs cycle Oxidative phosphorylation

Anaerobic respiration: 1.Bacteria and yeast carry on anaerobic respiration. 2.No molecular oxygen involved. 3.Less energy release 4.Takes place in the cytoplasm 2 types: 1.Alcoholic fermentation yeast, E coli glucose pyruvic acid ethyl alcohol + CO ATP 2.Lactic acid fermentation muscle activity, lactobacillus glucose pyruvic acid lactic acid + CO ATP

Glucose from food Enters cell through Diffusion. C 6 H 2 O 6 + ATP2 pyruvic acid + 4 ATP glycolysis released Total ATP = 38 Pyruvic acid + oxygen water + CO ATP enzymes Krebs cycle Oxidative phosphorylation **In the absence of oxygen, pyruvic acid Is changed into ethyl alcohol or lactic acid

In both processes of photosynthesis and respiration, enzymes play a key role in the production of energy containing compounds, break down of molecules, and the absorption of energy as in photosynthesis. Enzymes are very specific. a.Each enzyme will have a target molecule. Its shape will determine its function and interaction with its target molecule Active site Enzyme names end in –ase: lactose (carbohydrate) lactase (enzyme)

= 104 F

c. Enzymes work best at a pH of 7. Some enzymes need to work in either an acidic or basic Environment.