Download photosynthesis and respiration

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
Photochemical rxn
From roots
Carbon fixation rxn
Taken in by the
Stomata - leaf
2H combine w/
CO2 to form PGAL
A large 3 C cmpd
Photolysis =
Splits water into
2 H and 1 O
This oxygen will be
Released into the
atmosphere
ATP is formed
during photolysis
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 CO2
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 **
Photochemical rxn
From roots
Carbon fixation rxn
Taken in by the
Stomata - leaf
2H combine w/
CO2 to form PGAL
A large 3 C cmpd
Photolysis =
Splits water into
2 H and 1 O
This oxygen will be
Released into the
atmosphere
ATP is formed
during photolysis
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.
C6H2O6 + ATP
released
2 pyruvic acid + 4 ATP
glycolysis
Oxidative
phosphorylation
Krebs cycle
enzymes
Pyruvic acid + oxygen
water + CO2 + 34 ATP
Total ATP = 38
Anaerobic respiration:
1.
2.
3.
4.
Bacteria and yeast carry on anaerobic respiration.
No molecular oxygen involved.
Less energy release
Takes place in the cytoplasm
2 types:
1. Alcoholic fermentation yeast, E coli
glucose
pyruvic acid
ethyl alcohol + CO2 + 2 ATP
2. Lactic acid fermentation muscle activity, lactobacillus
glucose
pyruvic acid
lactic acid + CO2 + 2 ATP
Glucose from food
Enters cell through
Diffusion.
C6H2O6 + ATP
released
2 pyruvic acid + 4 ATP
glycolysis
**In the absence of oxygen, pyruvic acid
Is changed into ethyl alcohol or lactic acid
Oxidative
phosphorylation
Krebs cycle
enzymes
Pyruvic acid + oxygen
water + CO2 + 34 ATP
Total ATP = 38
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.