Photosynthesis

Question 1

define photosynthesis

Answer 1

the process by which plant cells containing chlorophyll, produce food substances, from CO2 and water, in the presence of light energy. Oxygen is produced as a product

Question 2

importance of photosynthesis

Answer 2

1. food for all
2. oxygen to breathe

Question 3

describe chloroplasts

Answer 3

double mebraned organelle
thylakoids are close packed flattened sacs
grana is a pile of thylakoids
stroma is the colourless ground substance in which grana is present
chlorophyll is in the thylakoids
chloroplasts are present in the mesophyll cells of upper and lower epidermis

Question 4

which lights does chlorophyll absorb

Answer 4

blue and red

Question 5

the closing and opening of stomata depends on

Answer 5

movement of water in and out of guard cells (they have thick inner wall and thin outer wall)

Question 6

ATP is used to… (in relation to potassium ion concentration theory)

Answer 6

pump potassium ions of neighbouring epidermal cells into the guard cells

Question 7

describe sugar concentraton theory

Answer 7

during daytime, photosynthesis occurs and sugar/glucose is produced. the osmotic pressure is increased and water is drawn in, making the guard cells turgid and opens stomata. the stomata closes when water falls short and exosmosis occurs

Question 8

what are the steps of light dependent phase

Answer 8

it occurs in thylakoids.
1. activation of chlorophyll: chlorophyll is activated by absorbing photons
2. splitting of water: absorbed energy splits water molecules (called photolysis, occuring in grana)

Question 9

end result of products of photolysis

Answer 9

1. hydrogen ions are picked up by NADP to form NADPH
2. oxygen released
3. electrons are used to convert ADP to ATP by adding one phosphate group

Question 10

full form of NADP and NADPH

Answer 10

Nicotinamide adenine dinucleotide phosphate
Nicotinamide adenine dinucleotide hydrogen phosphate

Question 11

define phosphorylated

Answer 11

addition of phosphates

Question 12

define photophosphorylation

Answer 12

energy used in phosphorylation comes from light

Question 13

steps in light independent phase

Answer 13

1. conversion of glucose into starch and other chemicals : polymerisation takes place.

Question 14

define polymerisation

Answer 14

the process of conversion of simple and smaller molecules into a complex, bigger molecule (eg: glucose to starch)

Question 15

adaptations in leaves for photosynthesis

Answer 15

1. large surface area
2. leaf arrangement
3. cuticle and upper epidermis
4. numerous stomata
5. thin leaves
6. chloroplasts
7. extensive vein system

Question 16

how is glucose used

Answer 16

1. immediately used
2. stored as starch
3. converted to sucrose
4. used to synthesise fats

Question 17

define photorespiration

Answer 17

some oxygen released may be used for respiration by leaves

Question 18

external factors affecting photosynthesis

Answer 18

1. light intensity
2. carbon dioxide
3. water content
4. temperature

Question 19

relation between temperature and rate of photosynthesis

Answer 19

for increase of 10 degrees of optimum temperature, rate is doubled

Question 20

internal factors affecting photosynthesis

Answer 20

1. chlorophyll
2. protoplasm
3. structure of leaf

Question 21

importance of photosynthesis

Answer 21

1. provides food
2. provide oxygen

Question 22

steps of carbon cycle

Answer 22

1. photosynthesis
2. food chains
3. respiration
4. decay
5. combustion
6. heating limestone