Biology: Energy transfer in and between organisms

Question 1

What is biomass?

Answer 1

The dry mass of an organism

Question 2

What are the units for biomass?

Answer 2

grams or kilograms/m^-2

Question 3

what are saprobionts?

Answer 3

Microbes which feed on dead organisms, decomposing them.

Question 4

Why are saprobionts important?

Answer 4

When a plant or animal dies, saprobionts release nutrients back into the soil as they decompose the dead matter, making the soil fertile.

Question 5

What is an ecosystem?

Answer 5

An area in which organisms live, contains all of the biotic and abiotic factors of an area.

Question 6

Describe the process of calorimetry.

Answer 6

• Weigh the sample and burn it in pure oxygen.

- Measure the temperature change of the water in order to obtain the estimate amount of energy in the sample.

Question 7

Define NPP

Answer 7

Net primary production, the energy produced by a plant, taking expenses into consideration.

Question 8

Define GPP

Answer 8

The amount of energy/biomass created by a plant.

Question 9

What is the equation for NPP in plants?

Answer 9

NPP = GPP - R

R = energy used for growth, repair etc.

Question 10

What is the equation for NPP in animals?

Answer 10

NPP = energy taken in - (energy lost in respiration + energy lost in faeces)

Question 11

Why do most food chains only have around 4 trophic levels?

Answer 11

Because a 5th trophic level would have insufficient energy to support life as energy is lost at each stage of a food chain.

Question 12

What is the role of mycorrhizae?

Answer 12

It exists in a mutualistic relationship with plants. They absorb water/nutrients etc. to keep it close to plant roots in order to keep the plant alive.

Question 13

Why are fertilisers needed on farmed land and not natural habitats?

Answer 13

In farmed land, plants take up nutrients from the soil, but are removed from the ground before they die and are able to return the nutrients to the soil. This means that fertilisers are needed to keep the soil fertile. In natural habitats, plants die and return nutrients to the soil, so the soil is always fertile.

Question 14

What is nitrification?

Answer 14

When ammonia ions and converted into nitrite ions.

Question 15

what is denitrification?

Answer 15

When nitrate ions and converted into nitrogen gas.

Question 16

How does applying high concentrations of fertiliser to the soil reduce plant growth?

Answer 16

Too much fertiliser changes the water potential of the soil, making it more negative. This results in water being lost from the plant due to osmosis.

Question 17

What is the difference between natural and artificial fertilisers?

Answer 17

• Artificial fertilisers are mined from rocks and can be made for specific plants.
• Natural fertilisers are non-specific and organic.

Question 18

What is leaching?

Answer 18

When water is washed deep within the soil due to rainfall.

Question 19

Describe the process of eutrophication.

Answer 19

• Farmers fertilise fields.
• It rains, fertiliser is washed from the soil and into water sources.
• Water becomes very nutrient rich, algae and bacteria populations thrive.
• A thick algal bloom covers the surface of the water, plants below it die due to lack of oxygen.
• Bacteria feed off the dead plants, food is no longer a limiting factor.
• Bacteria use up all of the oxygen, the water become anoxic and all respiring organisms die.
• The water becomes putrid as they decompose.

Question 20

What happens in the ammonification stage of the nitrogen cycle?

Answer 20

Saprobionts feed on dead and decaying organic matter. This releases ammonia ions.

Question 21

What happens in the nitrification stage of the nitrogen cycle?

Answer 21

Nitrifying bacteria convert ammonia ions into nitrite ions

Question 22

What happens in the nitrogen fixation stage of the nirtogen cycle?

Answer 22

Nitrogen gas is converted into nitrogen containing compounds by free-living and mutualistic bacteria.

Question 23

What happens in the denitrification stage of the nitrogen cycle/

Answer 23

Denitrifying bacteria convert nitrates into nitrogen gas.

Question 24

What is a biosphere?

Answer 24

Regions of the surface and atmosphere of earth occupied by living organisms.

Question 25

Describe what happens in the phosphorus cycle.

Answer 25

• Over time, rain and weathering cause rocks to release phosphate ions and other minerals. This inorganic phosphate is then distributed in soils and water.
• Plants take up inorganic phosphate from the soil. The plants may then be consumed by animals. Once in the plant or animal, the phosphate is incorporated into organic molecules such as DNA. When the plant or animal dies, it decays, and the organic phosphate is returned to the soil.
• Within the soil, organic forms of phosphate can be made available to plants by bacteria that break down organic matter to inorganic forms of phosphorus. This process is known as mineralisation.
• Phosphorus in soil can end up in waterways and eventually oceans. Once there, it can be incorporated into sediments over time.

Question 26

Which cells make up the upper mesophyll layer?

Answer 26

Which cells make up the upper mesophyll layer?

Question 27

Where does the light dependent reaction occur?

Answer 27

Thylakoid membrane

Question 28

Describe the process of photoionisation

Answer 28

light hits chlorophyll, causing it to lose electrons

Question 29

What happens to an electron when it enters the ETC?

Answer 29

• travels along the chain, being taken in by electron acceptors.
• it reaches photosystem II and is boosted to a higher energy level.
• it continues to travel along the ETC, losing energy as it does so.
• it reaches photosyetem I and its energy level is boosted a second time.
• when it reaches the end of the ETC, it’s absorbed by NADP, reducing it.

Question 30

What happens to the energy lost from electrons?

Answer 30

It’s used to actively transport protons into the thyklakoid. this forms a concentration gradient, protons then travel back into the stroma through ATP synthase, which phosphorylates ADP.

Question 31

What is made in the photolysis of water?

Answer 31

protons, electrons, oxygen

Question 32

How is chlorophyll reduced after it loses its electrons?

Answer 32

photolysis of water results in electrons, which are used to reduce chlorophyll.

Question 33

What are the 3 stages of the light independent reaction?

Answer 33

carbon fixation, reduction, regeneration

Question 34

which 5C compound binds with CO2 during the light independent reaction?

Answer 34

RuBP

Question 35

which enzyme catalyses the reaction between RuBP and CO2?

Answer 35

rubisco

Question 36

after CO2 binds to RuBP, an unstable 6C compound is made and is broken into 2 3C compounds, what are they called?

Answer 36

GP

Question 37

How many times does the calvin cycle need to happen in order to produce 1 glucose molecule?

Answer 37

6

Question 38

What are the products of the light-dependent reaction?

Answer 38

ATP, NADPH (reduced NADP)

Question 39

where does the light-independent reaction take place?

Answer 39

stroma of the chloroplasts

Question 40

state the process of the calvin cycle

Answer 40

• CO2 diffuses into the leaf through the stomata and into the stroma.
• CO2 joins with RuBP to form an unstable 6C compound in a reaction catalysed by the enzyme rubisco.
• the 6C compound is unstable and so it breaks up into 2 3C compounds calles GP.
• NADPH is used to reduce GP into triose phosphate using energy from ATP.
• NADP is reformed and goes back to the light dependent reaction.
• 1/6 triose phosphate molecules are used to make organic molecules. the rest regenerate RuBP.

Question 41

what is aerobic and anaerobic respiration?

Answer 41

AEROBIC:
requires oxygen. produces CO2, water and much ATP.

ANAEROBIC:
takes place in the absence of oxygen and produces lactate and little ATP

Question 42

what are the 4 stages of aerobic respiration?

describe each

Answer 42

Glycolysis: the splitting of the 6C glucose molecule into 2 3C pyruvate molecules.

Link reaction: the 3C pyruvate molecules enter a series of reactions which lead to the formation of acetylcoenzyme A, a 2C molecule.

Krebs cycle: the introduction of acetylcoenzyme A into a cycle of redox reactions that make ATP and NAD, FAD

Oxidative phosphorylation: the use of electrons associated with reduced NAD and FAD to synthesise ATP

Question 43

describe the process of glycolysis

Answer 43

phosphorylation of glucose into glucose phosphate: glucose has 2 phosphate molecules added to it to make it more unstable. the phosphate comes from the hydrolysis of 2 ATP molecules. this provides the energy at activate glucose + lowers activation energy of reactions that follow.

splitting of phosphorylated glucose: each glucose is split into two 3C molecules called triose phosphate.

oxidation of triose phosphate: hydrogen is removed from each triose phosphate molecule. They’re transferred to a hydrogen carrier molecule called NAD, this forms reduced NAD.

production of ATP: 3C molecules converted into pyruvate. 2 molecules of ATP regenerated from ADP in the process.

Question 44

what happens in the link reaction?

Answer 44

• pyruvate oxidised into acetate. hydrogens are accepted by NAD and forms reduced NAD which is later used to produce ATP.
• the 2C acetate combines with coenzyme A to produce acetylcoenzyme A.

Question 45

what happens in the krebs cycle?

Answer 45

• acetylcoenzyme A joins with a 4C molecule.
• the 6C molecule loses carbon dioxide to give a 4C molecule and a single ATP molecule.
• the 4C molecule can join at acetylcoenzyme A to start the cycle again.

Question 46

describe the process of oxidative phosphorylation.

Answer 46

happens in the mitochondria

• hydrogen atoms produced in glycolysis and the Krebs cycle combine with NAD and FAD.
• rNAD and rFAD donate the electrons to the first molecule on the electron transport chain.
• electrons pass through the electron transport chain, the energy they release causes the active transport of proteins across the inner mitochondrial membrane and into the inter-membranal space.
• protons accumulate in the inter-membranal space before they diffuse back into the matrix through ATP synthase.
• at the end of the chain, electrons combine with protons and oxygen to form water, oxygen is therefore the final acceptor of electrons in the electron transport chain.