SBI4U Test 3

Question 1

Distinguish between oxidation and reduction. (8 marks)

Answer 1

Oxidation: loss of electrons, loss of hydrogen, oxygen is added, also referred to as dehydration

Reduction: gain of electrons, gain hydrogen, oxygen is lost, also referred to as hydrogenation

Question 2

Distinguish between substrate-level phosphorylation and oxidative phosphorylation.

Answer 2

Question 3

Draw and label a mitochondrion.

Answer 3

Question 4

Draw and label a chloroplast.

Answer 4

Must include: outer membrane, intermembrane space, inner membrane, thylakoid, lamella, DNA, ribosomes, granum, stroma

Question 5

What evidence do scientists have to support the idea that chloroplasts and mitochondria were at one time independent organisms that became symbiotic?

Answer 5

1. They have their own circular DNA like bacteria
2. They have special ribosomes - 70s like bacteria (80S ribosomes are found in eukaryotic cells)
3. They reproduce like bacteria through binary fission (mitosis)

Question 6

Write the balanced chemical equation for cellular respiration.

Answer 6

C6H12O6 + 6O2 —> 6CO2 + 6H20 + 36ATP

Question 7

For glycolysis, state the location, input & output materials, and whether or not it is an aerobic or anaerobic process.

Answer 7

Location: cytoplasm

Input materials: Glucose, 2ATP, 4ADP, 4Pi

Output materials: 2ATP (net), 2NADH (2H20, 2 pyruvate, 2ADP)

Aerobic/Anaerobic: Anaerobic

Question 8

For Kreb’s Cycle, state the location, input & output materials, whether it is aerobic or anaerobic.

Answer 8

Location: in the matrix of the mitochondrion

Input Materials: 3 pyruvate/pyruvic acid, 4NAD, ADP, CoA

Output Materials: 2ATP, 8NADH, 2FADH2

Aerobic/Anaerobic: aerobic

Question 9

For the Electron Transport Chain, state the location, input & output materials, and whether it is aerobic or anaerobic.

Answer 9

Location: across the inner mitochondrial membrane

Input materials: NADH, FADH2, H+, ADP, Pi, O2

Output materials: 32 ATP, NAD, FAD, H2O

Anaerobic/Aerobic: aerobic

Question 10

What is the balanced equation for photosynthesis?

Answer 10

6CO2 + 6H2O + energy –> C6H12O6 + 6H2O

OR

6CO2 + 12H2O + energy –> C6H12O6 + 6O2 + 6H2O

Question 11

Distinguish between carotenoids and chlorophylls

Answer 11

Chlorophyll

• green pigment used in photosynthesis
• consist of a metal atom (magnesium) in the centre of the porphyrin ring
• absorb photons in the 700nm (red) and 400nm (blue-violet) range

Carotenoids

• yellow & orange pigments
• accessory light absorbing pigments
• absorbs a wide range of photons (380nm - 750nm) but not efficiently

Question 12

Distinguish between chlorophyll a and b.

Answer 12

Chlorophyll a - more crucial to photosynthesis, contains a -CH3 group (methyl), occurs less frequently

Chlorophyll b - less important to photosynthesis, contains a -CHO group (carbonyl aldehyde), occurs more frequently

Question 13

Explain how a CAM plant has overcome the problem of low CO2 levels.

Answer 13

CAM plants open their stoma during the night and take in CO2, then converting it into organic acids (e.g. crassulacean acid) which is then stored in the vacuoles. During the day, when the guard cells are closed, organic acids are converted back into CO2 and used in the Dark Rx.

Question 14

Name 5 factors that effect the rate of photosynthesis

Answer 14

1. Light Intensity (Brightness)
2. Light Quality
3. Temperature
4. CO2 Concentration
5. Water Supply

Question 15

What is the relationship between rate of photosynthesis and light intensity/brightness?

Answer 15

As intensity increases, so does rate of photosynthesis.

Question 16

What is the relationship between rate of photosynthesis and light quality?

Answer 16

Photosynthesis functions most effectively in the blue/violet ranges of the visible spectrum.

Question 17

What is the relationship between rate of photosynthesis and temperature?

Answer 17

As temperature increases, so does rate of photosynthesis (up to 34 degrees).

Question 18

What is the relationship between rate of photosynthesis and CO2 concentration?

Answer 18

As concentration increases, so does photosynthesis rate until about 0.02% where it levels off.

Question 19

What is the relationship between rate of photosynthesis and water supply?

Answer 19

Water supply is only a factor when it is very limited.

Question 20

Why is a C-4 plant better able to connect to CO2 for the dark reaction than a C-3 plant?

Answer 20

This is because in C-4 plants, the compound PEP found in the mesophyll cell fixes carbon from carbon dioxide, forming the 4-carbon compound OAA. OAA is then converted into malate. Malate then leaves the mesophyll cell and takes its extra C to the bundle sheath cell where the Dark Rx occurs. CO2 is dropped off at the Calvin cycle and pyruvate is left, which then converts back into PEP and the cycle starts over again.

**The point of this is that there is no oxygen present in the bundle sheath cell where the Calvin Cycle occurs (only CO2) so Photorespiration (oxygen being fixed to RuBP instead of CO2) cannot happen because of the absence of oxygen. **

Question 21

For the Light Rx, state the location, input materials and output materials.

Answer 21

Location: Thylakoids

Input: Light, NADP+, water

Output: Oxygen, NADPH, H+

Question 22

For the Dark Rx, state the location, input materials and output materials.

Answer 22

Location: Stroma

Input: 6CO2, 18ATP, 12NADPH

Output: 18ADP, 18Pi, 12NADP+, 2PGAL

*amounts are for 2 turns of the Calvin Cycle

Question 23

How do poisons affect respiration?

Answer 23

They inhibit cellular respiration by disrupting chemiosmotic mechanisms.

Question 24

How does cyanide inhibit cellular respiration?

Answer 24

1. It blocks the passage of electrons from cytochrome a3 to O2.
2. It plugs the ETC as a result of protons not being pumped –> no ATP produced

Question 25

How does dinitrophenol interfere with cellular respiration?

Answer 25

It “shortcircuits” the proton pump by allowing the membrande to leak H+ > no proton gradient > no ATP

Question 26

How does oligomycin interfere with cellular respiration?

Answer 26

It interferes with the operation of ATPase