Unit 4, Section 2

HideShow resource information

what do plants and animals need energy for?

PLANTS = photosynthesis, active transport, dna replication, cell division, and protein synthesis

ANIMALS= muscle contraction, maintence of body temp. , acrive transport, dna replication, cell division and protein synthesis

1 of 18

what is the photosynthesis?

the process where energy from light is converted into chemical energy 

6CO2 + 6H2O = C6H12O6 + 6CO2

energy is stored in glucose, until the plants release it in respiration  

2 of 18

outline respiration

the release of energy from glucose, in plants and animals

2 types-
+ Aerobic - using oxygen
+Anaerobic - without oxygen

overall equation is -

C6H12O6 + 6O2 = 6CO2 + 6H2O

3 of 18

How is ATP made?

ATP - adenine triphosphate

Synthesised from ADP and inorganic phosphate (Pi), using energy from the rbeakdown of glucose in respiration.
~Energy is stored in the phosphate bond.
~ATP synthase catalyses this reaction

ATP diffuses to the part of the cell that needs energy

when broken down, energu is relaesed from the phosphate bond, forming ADP and Pi,    this is catalysed by ATPase.

the ADP and Pi are recycled

4 of 18

what makes ATP a good energy source?

ATP stores or releases a small manageable amount at a time - no waste

small and soluble molecule so it can be -easily transported around the cell

ATP cant pass out of the cell  so the cell always has -immediate energy supply

can transfer energy to other molecules by -transferring a phopshate group

5 of 18

what are the co-enzymes used in photosynthesis and

NADP - transfers hydrogen from one molecule to another , this means it can reduce or oxidise a molecule.

NAD and FAD transfer hydrogen molecules from one ot naother, this means they can reduce or oxidise a molecule
Co-enzyme A transfers acetate between molecules

6 of 18

describe the structure of a chloroplast.

~the site of photosynthesis

~ double membrane -called the chloroplast envelope
~ thylakoids are stacked to form grana
~grana are linked by thylakoid membranes- called lamallae
~contain photosynthetic pigments ie. chloryphyll
~chlorophyll is attached to a protein to make a photosystem
~the stroma is a gel-like substance containing, enzymes, sugars and organic acids
~carbohydrates are stored as starch grains

7 of 18

outline the two stages of photosynthesis

1. Light dependant- ~ needs light energy
                                ~ takes place in thylakoid membranes (in chloroplasts)
                                ~ light energy absorbed by pigments in the photosystems and converted to chemical energy

2. Light independant- ~ doesnt need light directly, however uses products of light dependant reaction
                                   ~ takes place in the stroma of the chloroplast
                                   ~ ATP and reduced NADP from the light dependant reaction supply the energy and hydrogen to make glucose from CO2

8 of 18

what is cyclic photophosphorylation?

the light dependant reaction is NON-cyclic photophosphorylation

cyclic photophosphorylation only uses photosystem 1. - its called cyclic because the electrons arent passed onto NADP

9 of 18

what are the stages of the light dependant reactio

1. light is absorbed by photosystem 2

2. light energy splits water into protons, electons and O2

3. this light energy excites the electrons, so they move to a higher energy level

4. high energy electrons move along the electron transport chain

5. as the electrons mnove along the electron transport chain they lose energy, as ATP is made via chemiosmosis (the movement of H+ ions across a membrane to produce ATP)

6. at photosystem 1, the electrons are excited to an even higher level

7. NADP is the electron acceptor and is reduced by a H+ ion as it recieves the electron

8. The ATP and reduced NADP are passed on to the light INdependant reaction

10 of 18

what are the stages of the light independant react

1. CO2 enters the leaf and then diffuses into the stroma

2. CO2 combines with RUBP, catalysed by the enzyme rubsico

3. ATP from the light dependant reaction provides enery to reduce GP (3c)x2 into TP (3c)x2

4. Reduced NADPx2 is oxidised (loses H+) , to reduce the GP (3c)x2 to TP(3c) x2

5. for each turn of this cycle one carbon molecule is donated from TP to form glucose. One molecule of glucose is produced from 6 turns of the cycle.

6. ATP from the light dependant reaction is used to turn the remaining 5c from TP into RUBP.

This cycle needs to turn six times to make one hexose sugar, as each turn donates one carbon from TC and glucose (hexose sugar) is a 6-carbon molecule

11 of 18

what are the limiting factors of photosynthesis?

1. light intensity
2. temperature
3. CO2 concentration

Optimum conditions

high light intensity of certain wavelength
temperature around 25 degrees
CO2 at 0.4%   ( the air is at a concentration of 0.04%)

12 of 18

what are the 4 stages of respiration, and where do

1.        Glycolysis . = cytoplasm of cell

2.        Link reaction . = mitochondrial membrane

3.        Krebs cycle . = Matrix of mitochondria

4.        ETS . = Cristae of mitochondria

13 of 18

what are the two substages of glycolysis?

Phophorylation and Oxidation.

Phosphorylation- Glucose is phosphorylated, adding 2 phosphates from 2 molecules of ATP. (2 ATP used)
                          - This creates two molecules of triose phosphate (3C).

Oxidation - Triose phosphate is oxidised, (loses H+), forming 2 molecules of pyruvate
                -  NAD collects the H+ ions, forming 2 reduced NAD
                -  4 ATP are produced   (2 have been used)


glycolysis is an anareobic process

14 of 18

what happens in the link reaction?

1. pyruvate loses a C in the form of CO2

2. NAD is reduced - collects H+ from pyruvate forming acetate (2C)

3. Acetate is combined with co-enzyme A (CoA), to form acteyl CoA


this happens twice per glucose molecule, so 2 molecule of acetyl CoA go to Krebs cycle, 2 CO2 are waste and 2 molecules of NAD are made 

15 of 18

what happens during Krebs cycle?

Acetyl CoA (2C) combines with a 4C compund to form citrate (6C)
Co-enzyme A goes back to the link reaction to be re used

Citrate loses a carbon atom in the form of CO2
Citrate loses a H+ ion which is used to reduce NAD.   {now a 5C compound}

The 5C compound loses a carbon in the form of CO2.
The 5C compund is oxidised, producing 2 molecules of reduced NAD and a molecule of FAD.
ATP is produced through substrate level phosphorylation.
    {now back to the original 4C}

Twice per glucose molecule, so eg. prodcues 4 molecules of reduced NAD

16 of 18

what happens in ETS?

the generation of ATP through oxidative phosphorylation

The electrons move along the ETS, made up of electron carriers, ie. NAD and FAD, losing energy at each one.
The carriers are oxidised as the electrons pass from carrier to carrier, due to increased electronegativity.

ATP is made via chemiosmosis.
The energy from the electrons is used by the carriers to pump H+ into the intermembrane space. This creates a concentration gradient of ions.
The H+ ions move down the concentration gradient back into the mitochondrial matrix, via ATP synthase.
This movement synthesises ATP from ADP+Pi

17 of 18

what is pyruvate converted to in anaerobic respira

in plants -       pyruvate is converted into ethanol , loses a molecule of CO2, and it oxidises a molecule of reduced NAD,   regenerating a molecule of NAD.

in animals -       pyruvate is converted into lactate , the pyruvate is reduced, regenerating a molecule of NAD

lactate can be converted back , but ethanol cant as it has lost a C molceule.

glycolysis can continue, so a small amount of ATP can be produced

18 of 18


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes resources »