Biochemical reactions - LC Biology (photosynthesis and respiration)
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92 Terms
Photosynthesis
the process of plants making food using light
Photosynthesis can only happen when the plant has
chlorophyll and light
Role of photosynthesis
Food for plants - plants are animals food
Oxygen produced
Carbon dioxide removed
Fossil fuels may be formed
Products of photosynthesis
Glucose and oxygen
Glucose
converted into starch and stored or used in respiration
Oxygen mostly escapes…
through the stomata but can be used by the plant in respiration
Chlorophyll is found in the
chloroplasts
Most chloroplasts are found in
the palisade layer
Photosynthesis converts
light energy into chemical energy
Steps in photosynthesis
Light is absorbed
water is split
Products are produced - 4 protons, 4 electrons and oxygen
Light energises electrons
Glucose is formed
Light is trapped in the plant by
chlorophyll in chloroplasts
Split of water equation
2 H2O —> 4H+ and 4e- and O2
**Some of the energy from trapped light is used to do this
What happens to the products of the split of water
Electrons are passed to chlorophyll
Protons are stored in a proton pool
Oxygen may pass out of the leaf or my be used for respiration
Electrons are energised by what
trapped light
Trapped light energises electrons into
high energy electrons
High energy electrons and protons from the proton pool combine with carbon dioxide to form
glucose
Sources of light for plants
Natural sunlight
Artificial light (green houses)
Sources of water for plants
From soil (osmosis) - passes up the stem in xylem vessels
Two stages of photosynthesis
light stage and the dark stage
Light stage happens in the
frana of the chloroplasts
Light stage is not…
controlled by enzymes
the light stage involves
the fast movement of electrons
The light stage (what happens - bullet points)
light must be present
Products = NADPH and ATP
Water is split releasing oxygen
Chlorophyll pigment molecules used
SLIDE 18 19 NOTES!
SLIDE 18 19 NOTES!
Pathway 1
Photophosphorylation
What happens in pathway one
Electrons pass from the first electron acceptor to a series of other electron acceptors and back again to the chlorophyll - the electrons that return are the same ones that left
As the electrons pass the electron acceptors they…
lose energy
The lost electron energy is used to
join a posphate to ADP to form high energy ATP
ADP + energy + P
ATP
Phosphorylation
the addition of phosphate to ADP
CYCLIC … DIAGRAM
CYCLIC … DIAGRAM
What is another name for Pathway 2
Non cyclic photophorylation
2 high energy electrons at a time are
passed from the chlorophyll to the electron acceptor and then along a series of electron acceptors
In non cyclic, the same electrons
DO NOT return to the chlorophyll
Do the electrons gain or lose energy as they move from electron to electron acceptor in pathway 2 - what does this energy form?
Lose - lost energy forms ATP
The protons that were stored in the proton pool… (pathway 2)
are attracted to NADP+ and combine to form NADPH
Pathway 2 formula
NADP+ + 2e- + H+ = NADPH
The chlorophyll molecule in pathway 2 is short of electrons and gains them from
the splitting of water
The splitting of water is called
photolysis
NON CYCLIC DIAGRAM
NON CYCLIC DIAGRAM
SLIDE 29
SLIDE 29
Name two processes that happen in the light stage
phosphorylation - making atp
Photolysis - splitting water
SLIDE 30
SLIDE 30
Final products of the light stage
ATP - energy for the dark stage
NADPH - provides protons and energised electrons for the dark stage
Oxygen - excreted or used by plants for respiration
The dark stage needs
the products of the light stage
Carbon dioxide is reduced to (dark stage)
glucose
Dark stage takes place in
the stroma of the chloroplast
The dark stage is controlled by…
enzymes and therefore is affected by temperature
What are required for the dark stage
NADPH and ATP
How is glucose formed
carbon dioxide from the air enters the chloroplast where it combines with protons and electrons to form glucose
Energy for dark stage formed by
breaking down ATP into ADP + P
Hydrogen ions and electrons are obtained by breaking down
NADPH into NADPH+ + 2 electrons + H+
The addition of electrons to anything
reduction
What happens in the dark stage summary
Co2 is reduced
Oxygen atom is removed
Hydrogen ions added
Electrons added
Gluecose is formed
SLIDE 37
SLIDE 37
Respiration
the controlled release of energy from food
Aerobic respiration
break down of sugar with oxygen to release energy
Anaerobic respiration
the breakdown of sugar to release energy in the absence of oxygen
The breakdown of sugar is a
2 stage process
Both stages of respiration are controlled by
enzymes
Respiration is not efficient - why
a lot of energy is lost as heat
Step 1 of respiration
happens in the cyptoplasm of the cell
gluecose is broken down into two three carbon compounds
No oxygen is required
Very little energy is released
Step 2 of respiration
occurs in the mitochondria of the cell
oxygen is required
a large amount of energy is released
Anaerobic respiration can occur temporarily to
break down gluecose in the absence of oxygen - not for long as the products of anaerobic respiration are toxic
Lactic acid
produced during anaerobic respiration
2 C3 H6 O3
Saccharomyces Cerevistiae (Yeast) continues the breakdown of
the 3 carbon compounds to carbon dioxide and an alcohol (fermentation)
Examples of industrial fermentation
Brewing, making cheese, baking
Microorganisms role in fermentation
used to ferment the substrate to produce the desired product
Beer is made from
barley
Barley stores its food as…… and also contains….
starch and also contains the enzyme amylase which can break down starch and release sugar
Malting of the grain
dampening the grain and keeping it warm so that the barley can germinate
What is produced during germination
Amylase
Aerobic respiration takes place in…
the mitochondria
Anaerobic respiration takes place in…
cyptoplasm
Aerobic respiration releases…
more energy than anaerobic respiration
Anaerobic respiration releases…
less energy than aerobic respiration
Aerobic respiration produces…
carbon dioxide, water and energy
Anaerobic respiration produces…
lactic acid and energy or ethanol, carbon dioxide and energy
After aerobic respiration
gluecose is fully broken down
After anaerobic respiration
gluecose is not fully broken down
Respiration is a…
two stage process
Glycolysis occurs in…
the cyptoplasm/cytosol of the cell
What happens during glycolysis
gluecose (6 carbon sugar) is broken down into two 3 carbon compounds called Pyruvic acid
What is produced during glycolsis
2 ATP molecules
In the absence of oxygen, pyruvic acid is converted into…
lactic acid or ethanol and carbon dioxide
Where does the krebs cycle occur
In the mitochondria if oxygen is present
MAKE KREBS CYCLE NOTES
MAKE KREBS CYCLE NOTES
The electron transport systems are located on the…
inner membrane of the mitochondria
Christae on the inner membrane…
increase the surface area so that more electron transport systems can be present
Each electron transport system consists of…
a high number of molecules - mainly proteins
MAKE NOTES ON ELECTRON CARRIER SYSTEM
MAKE NOTES ON ELECTRON CARRIER SYSTEM
Oxidative Phosphorylation
the production of ATP by the electron transport system