Aqa a level Biology - Topic 5

What is photosynthesis?

Occurs ONLY in plants. The plant makes glucose from light, carbon dioxide and water

What is the equation for photosynthesis?

6CO2 + 6H2O -> C6H12O6 + 6O2

How is energy stored in plants?

In the glucose until plants release it by respiration

What is a metabolic pathway?

A series of reactions that are catalyzed by different enzymes and result in one or more products - photosynthesis

What is aerobic respiration?

Respiration with oxygen

What is anaerobic respiration?

Respiration without oxygen

What is respiration?

The release of energy from glucose

What is the chemical equation for aerobic respiration?

C6H12 + 6O2 > 6CO2 + 6H2O + energy

What does anaerobic respiration produce in plants and yeast?

Ethanol, carbon dioxide and releases energy

What does anaerobic respiration produce in humans?

Lactate and releases energy

What is ATP?

Adenosine Triphosphate - immediate source of energy in a cell

In respiration, the energy released from glucose is used to make.....

ATP

Describe the structure of ATP

Adenine base, combined with ribose sugar and three phosphate groups

how is ATP synthesized?

Via a condensation reaction between ADP (adenosine diohosphate) + P ( inorganic phosphate) using energy from an energy releasing reaction eg the breakdown of glucose in respiration

Where is energy stored in ATP?

In the phosphate bond

What enzyme catalyses the synthesis of atp?

ATP synthase

What is phosphorylation?

Addition of a phosphate group

How does ATP release energy in a cell?

Diffuses to part of cell that needs energy, here it is broken down back into ADP+P by hydrolysis- chemical energy is then released from the phosphate bond that was broken

What enzyme catalyses the breakdown of ATP

ATP hydrolase

6 ATP properties that make it so useful

1. Stores or releases only small manageable amount

2. Small soluble so easily transported

3. Easily broken down

4. Quickly remade

5. Can make other molecules more reactive by transferring phosphate group

6. Can't pass out of cell

What is the compensation point for light intensity?

When there is a particular level of light intensity at which the rate of photosynthesis exactly matches the rate of respiration

How do you work out the compensation point in plants?

Measure the rate at which oxygen is used at different light intensities - photosynthesis produces oxygen and respiration uses it so the compensation point is the light intensity at which oxygen is being used as quickly as it's produced

Where does photosynthesis take place?

Chloroplast

Chloroplasts are small flattened organelles surrounded by a double membrane. ..........1........... are stacked into structures called ................. which are linked tighter by bits of .........1...... membrane called .................

Thylakoids

Grana

Lamellae

What are photosynthetic pigments?

Coloured substances that absorb light energy needed for photosynthesis

Photosynthetic pigments are found in the ................. ..................... and they're attached to ................... . This is called a .........................

Thylakoid membrane

Proteins

Photosystem

What are the two photoSystems?

Photosystem 1 - absorbs light best at wavelength of 700nm

Photosystem 2 - absorbs light best at 680nm

Describe stroma

Gel like substance contained within the inner membrane of a chloroplast and surrounding the thylakoids , contains enzymes, sugars and organic acids

Carbohydrates produced by photosynthesis and not used straight away are stored as............

Starch grains in the stroma

What are redox reactions?

Oxidation-reduction reactions. Electrons are transferred from one molecule to another

If something is reduced It has .................. electrons and may have gained hydrogen or lost ................

Gained

Oxygen

If something is oxidised it has .............. electrons and may have lost hydrogen or .............. oxygen

Lost

Gained

Oxidation on one molecule always involves ................. of another molecule

Reduction

What is a coenzyme?

AIDS the function of an enzyme- work by transferring a chemical group from one molecule to another

What is NADP and what does it do?

A coenzyme used in photosynthesis - transfers hydrogen from one molecule to another ( it can reduce or oxidise a molecule)

What are the 2 stages that make up photosynthesis?

The light dependent reaction

The light independent reaction ( the Calvin cycle)

the light dependent reaction needs ............... it takes place in the ................ .............. of the chloroplasts. Light energy is absorbed by ..................... in the photoSystems. The light energy excites the ................... in the chlorophyll giving them more energy which eventually causes them to be ............... from the chlorophyll molecule. This process is called ............................

Light

Thylakoid membrane

Chlorophyll

Electrons

Released

Photo ionisation

After photoionisation in the light dependent reaction, the chlorophyll molecule is now a ........................ charged ion. Some of the energy released from electrons is used to add a ........................... to adp to form atp and some is used to .............. NADP to form ............ NADP. ATP transfers .............. and NADP transfers ................. to the light independent reaction.

Positively

Phosphate group

Reduce

Reduced

Energy

Hydrogen

Briefly describe the light independent reaction ( Calvin cycle)

Doesn't use light energy directly but uses the products of the light dependent reaction, takes place in the stroma of the chloroplast . The atp and reduced NADP supply the energy and hydrogen to make glucose from co2

What are electron carriers?

Proteins that transfer electrons

What is chemiosmosis?

The process of electrons flowing down the electron transport chain and creating a proton gradient across the membrane to drive atp synthesis.

A proton is the same thing as

A hydrogen ion

What are the two types of photophosphorylation?

Non cyclic

Cyclic

The Calvin cycle makes a molecule called ............ ..................... from .................. and ................ ............................. ( 5 carbon compound)

Triose phosphate

Co2

Ribulose bisphosphate

Draw a diagram of the Calvin cycle

What happens in the 1st stage of the Calvin cycle?

Co2 is combined with ribulose bisohosphate - catalysed by enzyme rubisco

This gives an unstable 6 carbon compound which breaks down into two molecules of a 3 carbon compound called glycerate 3-phosphate

What happens in the 2nd stage of the Calvin cycle?

Formation of triose phosphate- glycerate 3 phosphate is reduced to a compound called triose phosphate , some is converted into useful organic compounds such as glucose and some continues in the Calvin cycle

What is the final stage of the Calvin cycle

Regeneration of ribulose bisphosphate five of the six triose phosphates are used to regenerate ribulose bisphosphate not male glucose

What is a hexose sugar?

Simple 6 carbon sugar like glucose

How is a hexose sugar made?

By joining two molecules of triose phosphate together

How many times does the Calvin cycle need to turn to produce 1 hexose sugar?

6 times

How many ATP and reduced NADP is needed from the light dependent reaction for 6 turns of the Calvin cycle?

18 ATP

12 reduces NADP

Why is it important that ribulose bisphosphate is regenerated in the Calvin cycle?

If it wasn't then glycerate 3 phosphate wouldn't be formed, Calvin cycle would stop and photosynthesis would stop

The Calvin cycle is also called ...........

Carbon fixation because carbon from co2 is fixed into an organic molecule

What are the inputs and outputs of Calvin cycle?

Inputs- co2, atp, reduced NADP

Outputs- organic substances, ribulose bisphosphate

What 3 things are made from triosphosphate and glycerate 3phosphate molecules?

Carbohydrates, lipids and amino acids

What are the 4 ideal conditions for photosynthesis?

1. High light intensity of a certain wavelength

2. Temperature around 25 degrees

3. C02 at 0.04%

4. Right amount of water

What are the coenzymes used in respiration?

NAD and FAD - transfer hydrogen from one molecule to another

Coenzyme A - transfers acetate between molecules

What are the 4 stages of aerobic respiration?

Glycolysis

Link reaction

Kerbs cycle

Oxidative phosphorylation

What are the 2 stages of glycolysis?

Phosphorylation

Oxidation

What are the products of glycolysis is aerobic respiration?

2 reduced NAD

2 ATP

2 pyruvate

What happens to pyruvate produced by glycolysis in anaerobic respiration?

Converted into ethanol or lactate using reduced NAD

What does the link reaction do?

Converts pyruvate produced by glycolysis into acetyl coenzyme A

What does the Krebs cycle produce?

Reduced coenzymes and atp

What happens in oxidative phosphorylation?

Where energy carried from electrons is used to make more ATP

What can be affected by mitochondrial diseases

ATP production, can affect how proteins involved in oxidative phosphorylation or the Krebs cycle function reducing atp production

What may mitochondrial diseases cause in the body?

May cause anaerobic respiration to increase leading to lots of lactate being produced causing muscle weakness

What are producers and consumers?

Producers- plants algae that photosynthesise

Consumers- animals get energy from eating other organisms

What are primary and secondary consumers?

Primary- animals that eat plants

Secondary- animals that eat primary consumers

What are decomposers?

Organism that breaks down and obtains energy from dead organic matter

What is a trophic level?

Each step in a food chain or food web

What is the net primary production?

The energy left and stored for the next trophies level = gross primary production- respiration losses

The primary consumer will only use about .......% of the net primary production for growth

10%

Secondary and tertiary consumers use about .......% of their energy for growth

20

What are some factors causing low rate of energy exchange ?

Not all of organism might be consumed

What is consumed may not be digestible and lost in faeces

What is energy lost as in respiration?

Excretion and heat

Most food webs contain at most ......... trophic levels

5

Levels of energy stored are .............. as you move to high trophic levels

Lower

What is the equation for efficiency of energy transfer?

Energy available after transfer / 100 X energy available before transfer

What can ecological pyramids show?

Quantative measurements of food webs and chains - can show the number of a species, the biomass or the amount of energy stored at each trophic level

What is biomass?

Total mass of living organisms in a particular place

What is the problem with pyramids of biomass and numbers?

Only show data for a particular time , do not illustrate seasonal variation

Why are pyramids of energy more reliable?

Because even 2 organisms with the same biomass may contain different amounts of energy

What is energy in pyramids of energy measured in?

Kilojoules per square meter per year

What is net productivity?

The amount of energy which a crop can pass on to the next trophic level

What is the equation of net production of consumerS?

I ( chemical energy store in injected food) - (F +R)

F = chemical energy lost to environment

R = respiratory loses

Which 4 requirements must pesticides/ dangerous chemicals fulfil?

1. Must be specific

2. Biodegradable

3. Must be metabolised and egested

4. Cost effective

What are biological controls of pests?

Predators or parasites that will control pests

What are the advantages and disadvantages of biological controls?

Advantages - specific, reproduce naturally, pest will never build resistance to them

Disadvantage- work slowly, control organism might become pest

What do integrated pest control systems aim to do?

Reduce number of pests while being gentler on environment

What are the 4 main ways in which intensive rearing of livestock increases efficiency of energy transfer?

- less energy is used in muscle contraction

- less energy used on maintaining body temp

- easily be given best food for growth

- protected from predators

Briefly explain the nutrient cycle from producer to decomposers

Producer will take simple inorganic molecules and form large complex organic molecules

Consumers then ingest these and use them for growth an respiration

Carbon and nitrogen remain within food chain until excreted or consumer dies

Detrivores and decomposers feed on waste products and dead tissue

What is a saprobiotic?

Micro organisms that digest the dead tissue and waste, releasing the elements back into the cycle

What is mycorrhizae?

mutualistic associations of fungi and roots

How does fungi in symbiotic relationships with plants benefit the plant and what does it get in return?

Fungi is made up of strands call hyphae , these connect to the plant roots and increase the surface area so plant absorbs more ions, increases uptake of water by the plant .

In turn the fungi obtains organic compounds like glucose, from the plant

What is a symbiotic relationship?

Where 2 species live closely together and one or both depends on other for survival

What are the 4 processes in the nitrogen cycle?

Nitrogen fixation

Ammonification

Nitrification

Denitrification

What is nitrogen fixation?

When nitrogen gas in the atmosphere is turned into nitrogen containing compounds

What bacteria carries out biological nitrogen fixation and what does it do?

Rhizobium - turns nitrogen into ammonia which goes on to form ammonium ions in solution that can be used by plants

Explain where rhizobium are found and their relationship with plants

Found inside root nodules of leguminous plants

They provide the plant with nitrogen compounds and the plants provide them with carbohydrates