3.1 Overview of photosynthesis

Question 1

Photosynthesis

Occurs in?

Answer 1

In chloroplasts of the leaf

Question 2

Adapted to

a) bring together? (3)
b) remove? (2)

Answer 2

a) CO2, water, light

b) O2, glucose

Question 3

ADAPTATIONS OF A LEAF:
Maximise light? (4)
Short diffusion pathway?
Gaseous exchange? (2)

Network of xylem and phloem? (2)

Answer 3

ADAPTATIONS:

Large surface area - max light
Arrangement of leaves that minimises overlapping - avoids shadowing, max light
Long, narrow upper mesophyll cells packed with chloroplasts - max light
Transparent cuticle and epidermis - light can reach mesophyll cells beneath

Thin - short diffusion pathway

Many air spaces in the lower mesophyll - gaseous exchange
Numerous stomata (respond to LI changes) - gaseous exchange

Network of xylem and phloem
X - Brings water to leaf cells
P - carries glucose away from leaf cells

Question 4

Chloroplasts:

Grana (?)
Site of?
Contains? (2)

Structure adapted to function:
Large surface area?
DNA and ribosomes?
Enzymes?
Proteins?

Answer 4

Grana (stacks of thylakoids)
Site of light-dependent reaction.
Contains 
Chlorophyll.
Inter-granal lamellae - tubular extensions that join up with adjacent thylakoids

attachment of molecules
to manufacture proteins
to manufacture ATP.
hold chlorophyll in place

Question 5

Name 3 steps?

Equation?

Answer 5

1. Capturing of light by chloroplasts
2. Light-dependent reaction
3. Light-independent reaction

6CO2 + 6H2O —> C6H12O6 + 6O2

Question 6

EXAM QUESTION

Explain why CO2 uptake is a measure of net productivity (1)

Answer 6

Shows (gross) photosynthesis/productivity minus
respiration / more carbon dioxide used in
photosynthesis than produced in respiration;

Correct answers are
often shown as: net
productivity = (gross)
photosynthesis –
(minus) respiration.

Question 7

EXAM QUESTION

How would a shade plant be better adapted than a sun plant to growing in low light intensities? (2)

Answer 7

• lower rate of respiration
• less CO2 released at 0 light intensity/in dark
• Greater net productivity

Question 8

EXAM QUESTION

Scientists measured the mean temperature in a field each month between March and October. The table shows their results.

The gross productivity of the plants in the field was highest in July (highest temp). Use the data in the table to explain why. (2)

Answer 8

1. High temperature allows enzymes to work faster/allows more
   collisions/ allows more e-s complexes to be formed
   OR
   A lot of light so light not limiting;
2. Photosynthesis reactions are faster/more photosynthesis;

Question 9

EXAM QUESTION

What measurements should the student have taken to determine the rate of photosynthesis? (1)

Answer 9

Oxygen production/concentration and

time;

Question 10

A student investigated the effect of light on photosynthesis (co2 being removed).The student did not use a buffer solution to maintain the pH of the solution. Explain what would happen to the pH of the solution during this investigation. (2)

Answer 10

1. (pH) increases;
2. As (more) carbon dioxide removed
   (for photosynthesis);

Question 11

Chloroplasts:

Stroma (?)
Site of?
Contains?

Structure adapted to function:
DNA and ribosomes?
Enzymes?
Stroma fluid surrounds grana?

Answer 11

Stroma (fluid-filled matrix)
Site of light-independent reaction
Contains starch grains.

to manufacture proteins
to manufacture ATP.
products of the light-dependent reaction can readily diffuse into stroma.