5.1 Photosynthesis - The Basics

Question 1

word equation

Answer 1

carbon dioxide + water –> glucose + oxygen

Question 2

symbol equation

Answer 2

6CO₂ + 6H₂O –> C₆H₁₂O₆ + 6O₂

Question 3

explain how leaves are adapted for photosynthesis (max 8 points)

Answer 3

1) Large surface area maximises the absorption of sunlight
2) Mosaic arrangement of leaves minimises overlapping and shadowing
3) Thin maintains a short diffusion pathway for gases
4) Transparent cuticle and upper epidermis allows light to reach the palisade and spongy mesophyll cells below
5) Palisade mesophyll cells are elongated in shape and packed with chloroplasts to maximise the absorption of sunlight
6) Many stomata maximises the rate of gas exchange, they are opened and closed by guard cells to prevent loss via transpiration
7) Many air spaces in spongy mesophyll allows for the diffusion of carbon dioxide and also increases the surface area available for gas exchange
8) Vascular bundles:
xylem transport water and mineral ions, phloem transport dissolved sugars. Water is provided for photosynthesis as well as a way to transport the produces sugars away, and the turgidity of cells is maintained

Question 4

describe 3 main features of a chloroplast

Answer 4

• main photosynthetic site in eukaryotic plants
• disc shaped, typically 2-10 micrometres in length and 1 micrometre in diameter
• has a double membrane and a tertiary thylakoid membrane

Question 5

define thylakoid

Answer 5

a flattened sac in a chlorplast that contains chlorphyll and other photosynthetic pigments

Question 6

define grana and give its singular expression

Answer 6

the term used to describe stacks of thylakoids, singular granum

Question 7

name the extensions that join up two thylakoids located in separate grana

Answer 7

intergrana lamellae

Question 8

define stroma and outline what it contains (2 points)

Answer 8

the term used to refer to the fluid-filled matrix found in chloroplasts. it contains that enzymes for the second stage of photosynthesis, (LIR) and may also contain starch grains which enable the storage of glucose following production in photosynthesis.

Question 9

what do chloroplasts contain?
give an example and state their function

Answer 9

photosynthetic pigments
eg. chlorophyll
they absorb the light energy needed for the first stage of photosynthesis, LDR

Question 10

where are photosynthetic pigments found?

Answer 10

in the thylakoid membranes attatched to proteins

Question 11

define photosystem

Answer 11

photosynthetic pigment attatched to a protein

Question 12

aside from photosystems, what else may be attached to the thylakoid membranes? give an example

Answer 12

enzymes required for photosynthesis eg. ATPsynthase

Question 13

divide photosynthesis into its three main stages and outline each

Answer 13

1) CAPTURING LIGHT ENERGY
- by chloroplast pigments such as chlorophyll
2) LIGHT DEPENDENT REACTION
- transfers light energy into chemical energy
- occurs within the thylakoid membranes of chloroplasts
3) LIGHT INDEPENDENT REACTION
- requires the products of the LDR so stops in prolonged abscence of light
-occurs in the stroma of chloroplasts

Question 14

draw and label a diagram of a chloroplast

Answer 14

(check against notes)

Question 15

draw and label a diagram of the cross sectional area of a leaf

Answer 15

(check against notes)

Question 16

state the main photosynthetic structure in eukaryotic plants

Answer 16

chloroplasts

Question 17

what type of a reaction is photosynthesis energetically and why?

Answer 17

endothermic, as it requires the input of energy