photosynthesis - leaving cert biology

what type of energy is light energy converted into during the first stage of photosynthesis

chemical energy

in which organelle does light energy convert to chemical energy in the first stage of photosynthesis

chloroplast

name the molecule which is the source of electrons involved in converting light energy into chemical energy in the first stage of photosynthesis

chlorophyll

why is cyclical used to describe the movement of electrons in pathway 1

same electrons that leave chlorophyll are returned to it

describe the events of pathway 1

- electrons released from chlorophyll are captured by electron acceptors
- electrons are released slowly along a series of electron acceptors
- electron acceptors produce ATP at each series from ADP and P
- ATP is passed into stroma used in the dark stage
- once electrons passed through acceptors they are passed back to the chlorophyll

describe the events of pathway 2

- light shines on chlorophyll and energy is collected
- 2 electrons are released and captured by electron accpetors
- electrons are passed through a series of electron acceptors and loose energy
-the loss of energy makes ATP from ADP + P
-ATP is passed into the stroma and used for the dark stage
- 2 electrons passed on are reenergised by the sun then captured by NADP+ to become NADP-
- photolysis ...
-NADPH carries 2 electrons and 1 proton to the stroma for the dark stage

Photolysis

In the thylakoid membranes of a chloroplast during light-dependant reactions, two molecules of water are split to form oxygen, hydrogen ions, and electrons.

describe the events of the dark stage

- occurs in the stroma of chloroplast
- will not occur unless it receives products from the light stage ATP and NADPH
- CO2 enters through stroma and enters plant cells via diffusion
- CO2 is reduced wth protons and electrons from NADPH

- energy released from ATP

why is the 2nd stage called the dark stage

not dependant of light

what is the importance of photosynthesis for animals

plants are a source of food for animals they cant make their own food

Which stage of photosynthesis is influenced by heat and why

the dark stage as it is enzyme controlled

which cell organelle contains chlorophyll

Chloroplast

what is the function of chlorophyll in plants

to trap and absorb light energy

why is it an advantage that chlorophyll contains a number of chemicals

to absorb and trap more energy

how is the dark stage necessary for the continuation of the light stage

the products of the dark stage is used in the light stage

describe one way to increase plant production in a greenhouse

heat to an optimum temperature, increase CO2 concentration

Name the type of nutrition exhibited by organisms that carry out photosynthesis

autotrophic

Write the equation for photosynthesis

6CO2 + 6H2O + light energy = C6H12O6 + 6O2.

what is the role of stomata in photosynthesis

gas exchange

what particles are released from chlorophyll during the light independent stage

electrons

products of the light dependant stage

ATP, NADPH, protons, electrons, oxygen

where in the cell does the dark stage take place

Chloroplast

name the plant you used to investigate rate of photosynthesis

elodea

why did you use elodea

it is an aquatic plant that produces bubbles making the gas easily seen

How was the rate of photosynthesis measured?

by counting the amount of bubbles produced per minute

y axis

light intensity

x axis

light intensity

explain the shape of your graph

as light intensity increases rate of photosynthesis increases

how would increasing the concentration of CO2 help plants grow

increased supply of carbon atoms for the dark stage

how would increasing the temperature help plants grow

increased enzyme activity

Is the dark stage anabolic or catabolic?

anabolic

why is the dark stage anabolic

because small molecules such as CO2 and H2O form larager molecules such a glucose

what is the fate of ADP and NADP+ in the dark stage

both return to the light stage

name the 2 types of particles moved from NADPH to CO2 in the dark stage

protons and electrons

in which pathway is oxygen produced

Pathway 2

what is the fate of oxygen

released back into atmosphere

what is the fate of carbon in the dark stage

makes carbohydrate (glucose)

Why is a suitable temperature needed for the dark stage to occur

because it is controlled by enzymes

where precisely in the plant cell does photosynthesis occur

chloroplast

what is the energy source for the dark stage

ATP

name 2 environmental factors which the rate of photosynthesis depends on

CO2 concentration and temperature

suggest one advantage of using genetically modified crops

resistant to disease and drought

Name the first stage of photosynthesis

light dependent stage

Name the second stage of photosynthesis

dark stage or light independent stage

why cant the 2nd stage occur without the first stage

because it requires the products from the first stage

outline one major event of the second stage

sugar is formed from CO2

what happens to yellow light when it strikes a leaf

not absorbed it is reflected

suggest a possible benefit to plants of having more than one chlorophyll pigment

able to absorb more light

what is the main source of carbon dioxide used by plants in the dark stage

respiration

state the role of NADH in the dark stage

transports electrons

state the role of ATP in the dark stage

energy source

name a factor you kept constant during the experiment

temperature

explain how you kept temperature constant during the experiment

water baths

why is it necessary to keep temperature constant

to insure that any change is not due to temperature

from which simple compound does the plant obtain the H used to make compounds of carbohydrates

water

Name the simple compound that supplies the necessary energy for the second stage reactions

ATP

How did you vary light intensity

placed the light source at different distances from the plant

Name the openings in the leaf which allow the entry of carbon dioxide for photosynthesis

stomata

state one factor that influences the diameter of stomata

light

from which substance is oxygen produced

water

role of ATP

provides and stores energy

role of NADP

accepts electrons and carries hydrogen for the dark stage

role of carbon dioxide in photosynthesis

supplies carbon to make carbohydrate in dark stage

role of water in photosynthesis

water is split by photolysis - oxygen is released back into the atmosphere, hydrogen joins with NADP- to form NADPH - electrons are passed back into chlorophyll

2 products of the light stage essential for the dark stage

NADPH ATP

precise role of NADPH in the dark stage

supplies hydrogens

precise role of ATP in the dark stage

supplies energy

what happens the graph once is is fully saturated with light

levels off

2 sources of the carbon dioxide found in the atmosphere

respiration, combustion

what does ATP stand for

adenosine triphosphate

What does ADP stand for?

adenosine diphosphate

what does NADP stand for

Nicotinamide adenine dinucleotide phosphate

what does NAD stand for

nicotinamide adenine dinucleotide

suggest 2 possible sources of carbon dioxide in pond weed

animal respiration and plant respiration

each time light intensity was varied what precaution must be taken

allow time before counting the bubbles

why must you allow time

allow plant to adjust