photosynthesis

Question 1

what is an organic compound?

Answer 1

a compound that contains carbon e.g CO2/ lipids/ manure

Question 2

what is an inorganic compound?

Answer 2

a compound that does noy contain carbon e.g phosphate

Question 3

redux meaning

Answer 3

oxidation and reduction

Question 4

what are co-enzymes?

Answer 4

non protein molecules that help enzymes to work by transferring other molecules around

Question 5

phosphorylation meaning

Answer 5

adding a phosphate (ADP + Pi = ATP)

Question 6

photo- phosphorylation meaning

Answer 6

using light energy to add a phosphate

Question 7

what is photolysis?

Answer 7

using light energy to split a water molecule

Question 8

what is an electron transport chain?

Answer 8

when electrons flow through proteins (electron carriers) in a membrane

Question 9

proton meaning

Answer 9

a hydrogen ion (H+)

Question 10

what is the light dependent reaction?

Answer 10

uses light energy to make ATP and NADP
takes place on the membrane of the thylakoid (large SA)
sometimes called photo phosphorylation

Question 11

what is the light independent reaction?

Answer 11

uses the products of LDR (ATP AND NADP) to make useful organic compounds
takes place in the stroma
also called the calvin cycle

Question 12

wheee does photosynthesis take place?

Answer 12

the leaf is the main photosynthetic structure in eukaryotic plants, chloroplasts are the cellular organelles within the leaf where photosynthesis takes place

Question 13

the chloroplast…

Answer 13

absorbs light energy which is used for photosynthesis to make useful organic compounds

Question 14

the thylakoid…

Answer 14

has a high surface area to increase the rate of photosynthesis
contains photosynthetic pigments (chlorophyll a chlorophyll b and carotene)
some have tubular extensions called inter-granas lamellae which join to thylakoids in adjacent grana

Question 15

structure of a chloroplast

Answer 15

grana are stacks of thylakoids (LDR)
the stroke is a floyd filled matrix (LIR)
(starch grains and chloroplast dna)

Question 16

what are the raw materials of photosynthesis

Answer 16

water carbon dioxide and light

Question 17

what are the products of photosynthesis?

Answer 17

oxygen and glucose

Question 18

how are leaves adapted for photosynthesis?

Answer 18

1. large SA absorbs sunlight
2. arrangement of leaves that avoids overlapping/ shadowing of leaves
3. thin (light absorbed within first few micrometers and short gas diffusion distance)
4. transparent cuticle and epidermis that let light through to the photosynthetic mesophyll cells beneath
5. long narrow upper mesophyll cells packed with chloroplast that collect sunlight
6. numerous stomata for gas exchange mesophyll cells only a short diffusion pathway for one another
7. stomata that open/close in response to light
8. many air specs in lower mesophyll rapid diffusion of gases (o2 and co2)
9. network of xylem and phloem

Question 19

stages of the LDR

Answer 19

photo phosphorylation: occurs in the membrane of thylakoids
1. photosynthetic pigments (chlorophyll) absorb light energy
2. this excites an electron which leaves the chlorophyll molecule (in PS2) so chlorophyll becomes ionised (photoionisation)
3. the electrons that leave the chlorophyll are taken up by a molecule called the electron carrier. chlorophyll oxidised. electron carrier reduced.
4. electron moves along the electron transport chain by electron carriers in a series of oxidation- reduction reactions
5. the electron releases energy as each carrier is at a slightly lower energy level
6. this energy is used to join ADP + Pi to make ATP
7. NADP is reduced to form reduced NADP (NADPH)
8. photolysis of water makes protons (H+) electrons (e-) and oxygen

Question 20

what is the chemiosmotic theory (ATP)

Answer 20

1. each thylakoid is in an enclosed chamber into which protons (H+) are pumped from the strong using protein carriers in the thylakoid membrane called proton pumps
2. the energy comes from when electrons are released in photolysis which also produces protons increasing their concentration inside the thylakoid space
3. this creates and maintains a concentration gradient of protons across the thylakoid membrane (high in thylakoid space, low in stroma)
4. protons cross the thylakoid membrane through ATP synthase channel proteins. the rest is impermeable. these channels form small granules so are known as stalked granules
5. as protons pass through ATP synthase channels they cause changes to the structure of enzymes which then catalysis the combination of ADP with inorganic phosphate to form ATP

Question 21

what is photolysis

Answer 21

the loss of electrons when light strikes a chlorophyll molecule leaves it short of electrons. if chlorophyll is to continue absorbing light energy these must be replaced. These are provider from water molecules that are split using light energy. this also yields protons.

Question 22

what happens to the protons yielded in photolysis of water

Answer 22

they pass out of the thylakoid space through ATP synthase channels and are taken up by an electron carrier (NADP). the NADP becomes reduced. this is the main product of the LDR stage and enters the LIR stage taking with it the electrons from the chlorophyll molecules . NADPH is a potential source of chemical energy to the plant

Question 23

photolysis equation

Answer 23

2H2O —— 4H+ + 4e- + O2
water ——— protons + electrons + oxygen

Question 24

adaptations of chloroplasts for photosynthesis

Answer 24

thylakoid membrane large SA
network of proteins in the grana hold the chlorophyll in a way that allows maximum absorption of light
granal membranes have ATP synthase channels that catalyse the production of light. semi permeable to establish a proton gradient
contain DNA and ribosomes so can manufacture proteins involved in LDR

Question 25

what is the calvin cycle?

Answer 25

used the products of the LDR (ATP AND NADPH) to convert CO2 into useful organic compounds eg lipids amino acids and glucose

Question 26

stages of the calvin cycle

Answer 26

1. CO2 from atmosphere diffuses into the leaf through stomata and dissolves in water around the walls of the mesophyll cells. then diffuses into the chloroplast / stroma
2. co2 combines with 5 carbon compound RuBP catalysed by the enzyme rubisco
3. this makes two molecules of the 3 carbon glycerate 3- phosphate (GP)
4. reduced NADP is used to reduce GP to triose phosphate using energy supplied by ATP.
5. the NADP is reformer and goes back to LDR
6. most TP is regenerated to form RuBP using energy from ATP
7. some of the TP is converted into useful organic compounds eg lipids glucose amino acids

Question 27

how is the chloroplast adapted to the LIR

Answer 27

-the fluid of the stroma contains all the enzymes needed and is membrane bound which means a chemical environment to high conc of enzymes and substrates can be maintained in it
- the stroma fluid surround the grana do products of LDR can easily diffuse into stroma
-contains both DNA and ribosomes so can quickly and easily manufacture some of the proteins involved in the LIR

Question 28

what is a limiting factor

Answer 28

at any given moment, the rate of a physiological process is limited by the factor that is at its least favourable value

Question 29

how does light intensity work as a limiting factor

Answer 29

the higher the light intensity the more energy there is for the LDR so the faster the rate of photosynthesis.
light needs to be the right wave length. they look green because they reflect green light and absorb red light. different pigments also absorb different wave lengths