Topic 5 Last

Question 1

2 reactions of photosynthesis

Answer 1

• Light dependent
• Light independent

Question 2

Structure of cholorplast

Answer 2

• Double membrane
• Stroma
• Thylakoid membrane
• Granum
• Linked by lamellae

Question 3

How does the structure of the thylakoid membrane relate to the light depedent reaction?

Answer 3

• Large surface area for the attachment of:
  Chlorophyll
  Electron carriers
  Enzymes
• Permeable membrane for gas diffusion
• Fluid in the strom contains all enzymes required to make carbohydrates for the light indepedent reaction.

Question 4

Light dependent reaction?

Answer 4

• Photoionisation
• Chlrophyll absorbs lightt, electrons are excited and are donated to an electron carrier that moves the electrons down the chain.

-Photolysis
- Electrons are replaced by the splitting of water into hydrogen, oxygen and electrons.

Chemiosmosis
- Excited electrons lose energy as they move down the ETC.
- This energy is used to pump Hydrogen ions into the thylakoid space via a proton pump.
- Creates a favourable concentration gradient for the diffusion of H+ ions into the stroma via ATP synthase, which catalyses ADP+Pi to form ATP.

Formation of NADPH
- Electrons from ETC and H+ ions that have diffused through ATP synthase are used to form Reduced NADP.

Question 5

Light independent reaction

Answer 5

• occurs in the stroma
• Rubisco catalyses reaction of RuBP and CO2 to temporarily give an unstable 6-carbon compound which breaks down into 2 GP molecules.
• GP is reduced to TP using NADPH, using energy from ATP hydrolysis.
• TP is converted into useful organic compounds such as glucose and amino acids
• In one cycle 10 TP molecules are converted into RuBP but only 2 TPs are converted into useful compounds.

Question 6

What factors limit the rate of photosynthesis

Answer 6

• Temperature (Involve enzymes which require optimum temperatures)
• CO2 concentration as the light independent reaction requires a source of carbon so fixation is slowed.
• Light intensity as energy from sunlight is needed to excite electrons in chlorophyll

Question 7

What is glycolysis?

Answer 7

• Conversion of glucose into pyruvate

1) Occurs in the cytoplasm
2) Glucose is converted in glucose phosphate via ATP hydrolysis
3) 2xTP molecules are formed
4) 2 TP molecules are converted into 2 pyruvate molecules via redox reactions where ATP is oxidised and NAD is reduced

• 2 ATP net gain
• 2 NADH
• 4 ATP molecules

Question 8

What happens in anaerobic respiration?

Answer 8

Animals
- Pyruvate is converted to lactate during redox with NADH
- Lactate regenerates NAD which is fed back into glycolysis, meaning ATP is still produced.

Plants
Pyruvate is converted to ethanal, producing CO2 in the process, then ethanal is converted to ethanol during a redox reaction that converts NADH to NAD.

Question 9

What happens during the link reaction?

Answer 9

• Link reaction happens in the mitochondrial matrix
• Pyruvate loses carbon as CO2 and is converted to a 2C Acetate via a redox reaction of NAD.
• Acetate reacts with coA to form Acetyl coA.
• Link reaction would happen twice per glycolysis.

Question 10

What happens in the Krebs Cycle?

Answer 10

• Mitochondrial matrix
• Acetyl coA reacts with 4C compound to produce 6C citrate
• Series of redox reactions produces 2 CO2 molecules, 3 NADH molecules, 1 FADH2 molecules and 1 ATP molecule.
• coA is regenerated

Question 11

Oxidative phosphorylation

Answer 11

1) H atoms released from NADH and FADH2
2) Hydrogen atoms split into hydrogen ions and electrons.
3) Electrons move down the ETC
4) Energy lost by electrons at each carrier are used to pump hydrogen ions into the intermembrane space via a proton pump creating a favourable concentration gradient for diffusion of hydrogen ions into the matrix via ATP synthase causing it to spin.
- Catalysed ADP+Pi -> ATP.
- O2 combines with hydrogen ions and electrons to form water.

Question 12

Why is oxygen considered the last electron acceptor.

Answer 12

• Oxygen accepts H+ ions and electrons to form water
• ETC would stop and no pumping of hydrogen ions, no gradient for the diffusion of hydrogen ions so no ATP molecules produced.

Question 13

What is biomass?

Answer 13

• The mass of carbon or dry mass of tissue per given area.

Question 14

What is calorimetry

Answer 14

1) Dry the sample, burn the sample
2) Use this to heat a known volume of water
3) Measure temperature change and use this to calculate the chemical energy that was stored in the dry biomass.

Question 15

What is the Gross Primary Production

Answer 15

• The chemical energy store in plant biomass, in a given area or volume.

Question 16

What is the Net Primary Production

Answer 16

• The chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.

Question 17

Formula for NPP

Answer 17

NPP=GPP-R

Question 18

What is the energy from the NPP used for?

Answer 18

• Available for plant growth and reproduction. It is also available for other trophic levels in the ecosystem.

Question 19

How do we calculate the net production of consumers

Answer 19

N=I - (F+R)

N - Net production of consumers
I = Chemical energy store
F = Energy lost in faeces and urine
R = Respiratory losses in the environemtn

Question 20

Why is so much energy lost at each trophic level

Answer 20

• In plants, some light energy is reflected or transmitted through loveaves or not of the right wavelength so the efficiency of photosynthesis is very low.
• Energy is lost to the surrounding as heat from respiration.
• Energy lost in faeces or urine.
• Some parts of the organism are not eaten, so some energy is not transferred to the next trophic level.

Question 21

Why are food chains often limited to 4-5 trophic levels?

Answer 21

• Energy is lost at each trophic level so the efficiency of energy transfer is very low.
• Total biomass is less at higher trophic levels
• Insufficient energy available to support a large enough breeding population.

Question 22

How does farming maximise energy>

Answer 22

• Simplify food webs by using pesticides so that energy isn’t lost.
• Reduce respiratory losses within a human food chain such as controlling the conditions livestock are kept in such as restricting their movement or keeping them warm (unethical) .
• More biomass so greater chemical energy store so more biomass and a higher chemical energy store so more NPP and efficiency of transfer.

Question 23

Primary and Secondary productivity

Answer 23

• The rate of primary and secondary production respectively
• kJ per hectare per year

Question 24

What is the role of microorganisms in nutrient cycles ?

Answer 24

• Break down organic molecules into simple inorganic molecules and ions, that plants can make use of.
• Saprobionts feed by extracellular digestion by secreting digestive enzymes and absorb the soluble nutrients released.
• Converts organic into inorganic compounds
• DNA, RNA and amino acids into phosphates and nitrates

Question 25

What are detritovores?

Answer 25

- Break larger leaves into smaller leaves, increasing the surface area for saprobionts to act upon.

Question 26

Stores of nitrogen in plants animals?

Answer 26

- DNA, protein, RNA.

Question 27

What happens when plants animals die in the nitrogen cycle?

Answer 27

- Decomposition of DNA, RNA, protein - Produced ammonium ions (ammonification)

Question 28

What happens to ammonium ions in the nitrogen cycle?

Answer 28

- Undergo nitrification which involves ammonium ions being converted to nitrite ions and nitrate in aerboic conditions by nitrifying bacteria as these bacteria need oxygen to function.

Question 29

What happens to nitrate ions in the nitrogen cycle?

Answer 29

- Taken in by active transport during Assimilation

Question 30

What is denitrification?

Answer 30

- Conversion of the nitrate ions into nitrogen gas. - Done by denitrifying bacteria and is done in anaerobic conditions.

Question 31

What is nitrogen fixation

Answer 31

- Conversion of nitrogen gas into bacteria.

Question 32

Outline the entire nitrogen cycle?

Answer 32

- Animals and plants store nitrogen through DNA, RNA, proteins - When animals die, sacrobionts decompose this into ammonium ions. - Ammonification converts ammonium into nitrite ions and then nitrate ions via nitrification. - Nitrate ions move via active transport during assimilation into root hair cells or are converted into a gas during denitrification. - Nitrogen fixation is the take up of nitrogen gas from the atmosphere.

Question 33

During the phosphorus cycle how are inorganic ions introduced into rivers?

Answer 33

- Process of weathering

Question 34

How is phosphate recycled?

Answer 34

- Phosphate ions move by seas and rivers and are stored in sedimentary rocks. - Tectonic plate movements pushes phosphate ions into higher regions again. - The phosphate is then recycled again through rivers and seas. - Phopshate ions can enter roots by active transport/assmiliation - Plants can feed on the phosphate ions and incorperate it into its DNA.

Question 35

What are micorrhizae?

Answer 35

- Fungi that associate with the roots of plants - They grow in and around the root system, increasing the surface area for absorption of water and mineral ions.

Question 36

What are mutualistic relationship?

Answer 36

- Where both species benefit from the interaction. - Micorrhizae recieve sugars from the plant for growing in and around the root.

Question 37

Why are fertilisers needed?

Answer 37

- Crops taking in mineral ions from the soil to build their own tissues. - When they are harvested, this means no mineral ions are returned to the soil as the crops don't die and decompose there. - So we need fertilisers to replace lost minerals.

Question 38

Natural and Artificial fertilisers

Answer 38

- Organic matter is an example of a natural fertiliser - Artificial fertilisers are pure inorganic ions blended together to give the appropritate balance of mineral ions for a particular crop.

Question 39

Why are mineral ions needed?

Answer 39

Nitrate ions (protein synthesis, ATP synthesis, nucleic acids) Phosphate ions (ATP synthesis) Potassium ions (stomatal regulation) Sulphur ions (sulfur containing R-groups)

Question 40

What are NPK fertilisers?

Answer 40

- The blending of nitrogen, potassium and phosphate ions.

Question 41

What is leaching

Answer 41

-Loss of soluble susbtances from the top layer of the soil when water drains through. - Occurs when fertilisers are applied before rainfall events because there has not been enough time for ions to be taken up by plants and free mineral ions in the soil are washed away.

Question 42

What is eutrophication?

Answer 42

- Leaching of excess mineral ions from fertilisers into waterways. - Algal boom is the rapid growth of algae in ponds and rivers which happens after the increase of mineral ions. - Algae grow rapidly and block sunlight from reaching the plants below. - The plants do not photosynthesise so they die. - Bacteria feed on dead remains and decompose it so oxygen levels decrease. - Fish and other organisms die because not enough oxygen is available. - Leads to oxygen depletion so the ecosystem dies out.