Topic 6 - Plant Structures & their Functions

Question 1

What are photosynthetic organisms the main producers of

Answer 1

• Food
• Biomass

Question 2

What is photosynthesis

Answer 2

• An endothermic reaction
• Uses light
• Reactants of carbon dioxide and water
• Produces glucose and oxygen

Question 3

What are the limiting factors on the rate of photosynthesis

Answer 3

• Temperature
• Light intensity
• Level of carbon dioxide

Question 4

How does temperature affect the rate of photosynthesis

Answer 4

• Graph is a curve that starts above 0 at the y-axis
• As temp increases to 30-40, particles have greater energy to collide and react
• As temp increases past 40, enzymes denature

Question 5

How does light intensity affect the rate of photosynthesis

Answer 5

• Graph rises to a plateau
• As light intensity increases, rate of photosynthesis increases
• Plateau results from not enough other factors

Question 6

How does the level of carbon dioxide affect the rate of photosynthesis

Answer 6

• Graph rises to a plateau
• As the level of carbon dioxide increases, the reactants for photosynthesis increases
• Plateau results from not enough other factors

Question 7

What is the inverse square law

Answer 7

• Light intensity is directly proportional to 1÷distance²
• Demonstrates how light intensity is inversely proportional to the distance from the light source squared

Question 8

What is the relationship between light intensity and the rate of photosynthesis

Answer 8

Directly proportional

Question 9

How is the root hair cell adapted to absorb water and mineral ions

Answer 9

• Increase surface area by having long root hair, cytoplasmic projections
• The cell membrane of the root hair cell has numerous carrier protein molecules
• Water enters root hair cells via osmosis and moves through it, until it reaches the xylem tissue
• Mineral ions enter the root hair cells via active transport

Question 10

What are the characteristics of xylem

Answer 10

• Moves water and solutes from roots to leaves in one direction
• Cell walls consist of lignin, rather than cellulose, for strength and support
• Consists of rows of dead cells in a continuous tube, without cell walls or organelles
• Face inwards in vascular bundles

Question 11

What are the characteristics of phloem

Answer 11

• Moves sucrose made from photosynthesis and amino acids from the leaves to the rest of the plant in both directions
• Uses energy from respiration to translocate material
• Consists of rows of living cells in a continuous tube, without cell walls or organelles
• Face outwards in vascular bundles

Question 12

What is transpiration

Answer 12

The loss of water by evaporation and diffusion through stomata in leaves

Question 13

How does the transpiration stream work

Answer 13

1. Water from inside the leaf evaporates and diffuses out of the leaf, through the stomata
2. This creates a slight shortage of water in the leaf, and so more water is drawn up from the rest of the plant through the xylem to replace it
3. This causes more water to be drawn up from the roots, and so there’s a constant transpiration stream of water through the plant

Question 14

What is the role of stomata

Answer 14

Gas exchange:
* Carbon dioxide enters
* Oxygen and water vapour leaves

Question 15

What is the structure of stomata

Answer 15

• They are tiny pores on the plant surface
• Surrounded by 2 guard cells
• Contains chloroplasts
• Thin outer wall
• Thick inner wall
• When the plant lacks water, the guard cells become flaccid - closing the stamata
• When the plant has an excess of water, the guard cells become turgid - opening the stomata