Eduqas A level Biology Component 1

Component 1 Except for starred cards with are Component 2

What are the planetary boundaries?

1. Climate change
2. Biosphere integrity
3. Land system change
4. Biogeochemical flows
5. Stratospheric ozone
6. Ocean acidification
7. Fresh water use
8. Aerosols
9. Introduction of novel entities

Which planetary boundaries have been crossed?

1. climate change
2. biosphere integrity
3. land system change
4. biogeochemical flows

Which planetary boundaries are avoidable?

1. Ocean acidification
2. Fresh water use

Which planetary boundaries have not been quantified?

1. Aerosols
2. Introduction of novel entities

Which planetary boundary has been crossed?

stratospheric ozone

Define population

all the organisms of a particular species in a particular location at one time

Define community

all the organisms of all species living in one location at one time

Define ecosystem

A characteristic community of interdependent species and their habitat

Define niche

the role of a particular species in its ecosystem, including its microhabitat, feeding and breeding behaviour etc

Define ecology

the study of how living organisms interact with each other and their environment

Define environment

the physical and biological conditions under which an organism lives

Define biotic

the biological components of an ecosystem

What does the size of a population depend on?

• Birth rate
• Death rate
• Immigration into the population
• Emigration away from the population

What are the limiting factors on population size?

• Predation
• Parasitism
• Disease
• Overcrowding
• Competition from other species for food
• Accumulation of toxic waste
• Climate

What are density dependent factors that regulate population size?

• Disease
• Parasitism
• Accumulation of toxic waste
• Food supply

What is abundance?

a measure of how many individuals exist in a habitat

How do you measure animal abundance?

• Capture-mark-recapture experiments
• Kick sampling in a stream and counting aquatic invertebrates

How do you measure the distribution of animals?

• Direct observations of their nests
• Faecal deposits
• Markings on vegetation

What is a food chain?

a diagram which shows a simple, un-branched feeding relationship with usually only one organism at each trophic level

What is gross-primary productivity?

the rate of production of chemical energy in organic chemicals by photosynthesis and is measured in KJm-2year-1

What is net primary productivity?

GPP minus the chemical energy generated in respiration and used up by the metabolism of producers
NPP=GPP-R

What is photosynthetic efficiency?

a measure of how much light energy a plant captures from the sun

Define succession

the change in structure and species composition over time

What are the types of succession?

primary and secondary

What is the climax community?

the final stable group of organism after which there is no change

Why do plants and animals need nitrogen?

to make:
• Amino acids
• Proteins
• Nucleic acids
• Atp
• Chlorophyll

What are the processes of the nitrogen cycle?

1. Nitrogen fixation
2. Ammonification
3. Nitrification
4. De-nitrification

What is nitrogen fixation?

the process that causes the strong 2-carbon nitrogen molecules found in the atmosphere to break apart so they can combine with other atoms.
Nitrogen gets fixed when it combines with oxygen or hydrogen

What ar the ways in which nitrogen gets fixed?

1. Atmospheric fixation

What are the types of nitrogen fixing bacteria?

1. Azotobacter
2. Rhizobium

What is ammonification?

decomposition by bacteria and fungi breaks down amino acids from dead animals and plants, faeces and urine and waste into ammonia
also called peutrification

What is nitrification?

nitrite ion is converted to nitrate ions by nitrobacter

What is denitrification?

In waterlogged soil with anaerobic conditions where anaerobic bacteria such as pseudomonas can reduce nitrate ion back into nitrogen gas

How do humans alter the nitrogen cycle?

• Industrial production of inorganic fertilisers using the haber process
• Intensive animal production which produces slurry
• If too much of it is used, it can leach into lakes and rivers causing eutrophication

What is the function of the plasma membrane?

its a barrier between the environment and the cytoplasm. it controls the entry and exit of substances in and out of the cell. approx 7nm

What is the function of the cell wall?

it prevents lysis in hypotonic solution

What is the cell wall made from?

peptidoglycan/murein

What is the function of circular DNA?

it contains the gene necessary for normal functioning bacteria

What is the function of the capsule?

it is an outer layer of mucopolysaccharide slime which can glue bacteria together, stick them to surfaces and protect the bacteria from attack by other cells

What is the function of ribosomes?

protein synthesis

What is the function of pilli?

attaching to surfaces and for transferring plasmids by conjugation

what is the function of the plasmid?

circular dna which contains extra bacterial genes including genes for antibiotic resistance. can be exchanged between bacteria during conjugation allowing the spread of antibiotic resistance

What are prokaryotes?

• No membrane-bound organelles
• Free and naked circular dna
• Smaller ribosomes than eukaryotes (70s)
• Cell wall is made of peptidoglycan/murein

What is the cell wall like in gram positive bacteria?

• Has a thick layer of peptidoglycan which holds onto the crystal violet dye which isn't washed out y ethanol
• They appear purple
e.g. staphylococcus, streptococcus, bacillus

What is the cell wall of gram negative bacteria like?

• Thin layer of peptidoglycan and a thick outer layer of lipopolysaccharide
• Crystal violet is removed when washed with ethanol
• They appear pink
e.g. e. coli

Describe how to conduct a gram stain

1. Smear bacteria onto slide, air dry and heat fix
2. Apply crystal violet, stand 1 min and rinse with water
3. Add iodine, stand 30 sec and wash with water
4. Wash with ethanol
5. Add counterstain safranin, stand 1 min and rinse

What does bacteria need to grow?

• Suitable temperature
• Suitable pH
• Oxygen
• Carbon source

What does the asceptic technique prevent?

• Contamination of the environment by the microbes being handled
• Contamination of microbial cultures by unwanted microbes from the environment

What are examples of asceptic techniques?

• Autoclave glassware at 121oc for 15 mins
• Flaming loos and wires until red hot and glass spreaders with ethanol
• Open petri dishes at a small angle

What are streak plates?

they are used to seperate mixed cultures into pure ones by seperating out individual colonies which can then be used to innoculate fresh plates

Why is it important to estimates population growth?

1. Environmental health monitoring

Describe how to conduct a serial dilution

1. 9cm3 sterile water in 6 tubes
2. Use a sterile pipette to add 1cm3 bacterial solution to the first tube
3. Use a sterile pipette to transfer 1cm3 from this tube to the next until all tubes are done
4. Transfer 0.5cm3 from each dilution on to a plate each using asceptic techniques and incubate at 25oc for 24-48 hrs
5. Count colonies on each plate that has 50-100 colonies on it and calculate number of microbes in the original sample

What are the disadvantages of viable counts?

• May underestimate the population as you can't be sure that each colony has grown from a single bacterium
• Takes a long time to get a count
• If culture is mixed, some may take longer to grow

What are the advantages of total cell counts?

• Quick

What are the disadvantages of total cell counts?

• Hard to count clumps
• Doesn't always discriminate between live and dead cells
• Bacteria can be difficult to count under a microscope

What is glycolysis?

• Chemical reactions in the cytoplasm that breaks down glucose into 2x3c pyruvate
• Uses 2 ATP to get 4 ATP in return when breaking down one glucose to give a net of 2 ATP
• When glucose is broken down, NAD gets reduced to NADH

Define anaerobic

reactions where no oxygen is required

what is fermentation?

an anaerobic process that follows glycolysis to continue ATP production until oxygen is available

What are the types of fermentation?

1. Lactic acid fermentation
2. Alcohol fermentation

What is lactic acid fermentation?

a series of anaerobic reactions in which pyruvate uses NADH to form lactic acid and NAD+
• NAD+ is recycled in glycolysis and fermentation
• Allows 2 ATP molecules to form from glycolysis
• Lactic acid builds up in muscles and causes muscle fatigue
• Lactic acid leaves the muscles and goes to the liver to be converted back to pyruvate

What is alcoholic fermentation?

anaerobic process in which cells convert pyrivate into C02 and ethanol
• Pyruvate is broken down to a 2c molecule by releasing co2
• Electrons are transferred from NADH to 2x2c molecules producing ethanol
• Yields 2 net ATP form glycolysis
• Used by fungi and bacteria to release alcohol and CO2

What is the structure of mitochondria?

• Inner and outer phospholipid membrane
• Outer-membrane is smooth and inner membrane is folded to form cristae which increases the surface area
• Between the inner and outer membrane is the inter-membranal space
• Matrix is a mixture of proteins and lipids enclosed by the inner membrane

What are the functions of the inner mitochondrial membrane protein?

1. Electron carriers
2. ATP synthase
3. Transport proteins

What are the stages of aerobic respiration?

1. Glycolysis
2. Link reaction
3. Krebs cycle
4. Electron transport chain and chemiosmosis

Describe the link reaction

Pyruvate enters the mitochondrial matrix. it is decarboxylated and dehydrogenated and bonds with co-enzyme A to form acetyl co A. This creates NADH and H+

Describe the krebs cycle

1. Acetyl co A combines with a 4c compound to form a 6c compound
2. CO2 is released from the 6c to form a 5c
3. CO2 is released from the 5c compound to leave a 4c compound
4. The 4c compound is converted to a new 4c compound
5. The new 4c is converted to the 4c that started the cycle

Describe the electron transport chain

1. NADred and FADred are re-oxidised when they donate H atoms which are split into H+ ions and e-
2. The e- are passed along a chain of electron carriers and then donated to oxygen which is the final acceptor
3. H+ stays in solution in the matrix
4. When the e- are transferred to O2, H+ is removed from the mitochondrial solution to reduce it to water

Describe chemiosmosis

As electrons flow along the electron transport chain, energy is used to pump H+ across the intermembrane space. This builds up a proton/pH/electrochemical gradient

What is oxidatidative phosphorylation?

The formation of ATP by adding a phosphate groupd to ADP in the presence of oxygen

How many:
NADH

FADH

ATP
are produced in glycolysis?

2 NADH (Net production, as 2 NADH are produced per glucose molecule)

2 ATP (Net production, 4 ATP are produced, but 2 ATP are used in the initial steps)

0 FADH (FADH is not directly produced in glycolysis)

How many:

NADH

FADH

ATP

are produced in the link reaction?

For each molecule of glucose:

• 2 NADH are produced (one for each molecule of pyruvate that enters the link reaction)

• 0 FADH are produced in the link reaction.

• 0 ATP is directly produced in the link reaction. No ATP is generated directly, the energy is conserved in the form of NADH.

How many:

NADH

FADH

ATP

are produced in krebs cycle?

The Krebs cycle occurs twice per glucose molecule (since each glucose molecule produces two pyruvate molecules, which are converted into two acetyl-CoA molecules that enter the Krebs cycle).

Per one turn of the Krebs cycle:

• 3 NADH are produced

• 1 FADH2 is produced

• 1 ATP (produced by substrate-level phosphorylation)

Therefore, for each original glucose molecule (two turns of the Krebs cycle):

• 6 NADH are produced

• 2 FADH2 are produced

• 2 ATP are produced

How many ATP does NADred produce?

3 ATP each

How mnay ATP does FADred produce?

2 ATP each

What is a respiratory substrate?

An organic molecule that can be oxidised to produce usable energy in the form of ATP

What do chloroplasts contain?

• Stroma
• Grana

What is the function of the stroma?

• Site of light independent reactions
• CO2 fixed to produce sugar
• ATP and NADPH2 required

What is the function of thylakoids?

• Site of light dependent reactions
• chlorophyll absorbs light energy
• ATP and NADPH2 produced

What is the function of granum?

stacks of thylakoids produce a large surface area for absorption of light energy

What is the function of the starch grain?

• Excess carbohydrates stored as a starch grain
• Starch doesn't affect water potential

What is the function of the double membrane in chloroplasts?

controls movement in and out of the chloroplast

What is chromatography?

a seperation technique used to sperate pigments

What is an Rf value?

It shows how far a component has traveled compared with the solvent front.
it is the ratio of the distance of the component moved: solvent front

What is the absorption spectrum?

a graph shwoing the degree of absorbtion of light by a pigment.
chlorophylls absorb strongly in the blue-violey?red regions
Carotenoids absorbs in the blue-green regions

What is the action spectrum?

a graph showing the degree to which different wavelengths affect the rate of photosynthesis

Describe Engelmann's experiment

as the spiral chloroplast of the spirogyra photosynthesised, oxygen gas is produced as a waste product.
the aerobic bacteria move towards the parts of the chloroplast exposed to the red and blue parts of the spectrum

Define photosynthesis

The process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water

What are photosystems?

photosynthetic pigemnts are grouped in clusters called antenna complexes. photons of light are transferred through the antenna complex until they reach the primary pigment which is chlorophyll A in the reaction centre

What happens in photosystem 1?

The reaction centre is called p700 as it contains chlorophyll, a molecule with a maximum absorption at a wavelength of 700nm

What happens in photosystem 2?

The reaction centre is called p680 as it contains chlorophyll which has a maximum absorption at a wavelength of 680nm

Describe cyclic photo-phosphorylation

1. Light energy is absorbed by the accessory pigments and passed to chlorophyll A at the reaction centre
2. Electrons are emitted and passed to a high energy level where they are received by electron acceptors
3. Electrons pass along a chain of electron carriers, generating sufficient energy to synthesise ATP by chemiosmosis
4. Electrons return to the reaction centre at photosystem 1

Descrbe non-cyclic photophosphorylation

1. Photons are absorbed by PS1 and PS2, passed to reaction centre
2. This displaces 2 electrons from PS2 and picked up electron acceptors and pass along a chain of electron carriers to PS1, energy lost by electrons is used to convert ADP=Pi to ATP
3. PS2 gets 2 electrons from the photolysis of water

What is photolysis?

water molecules dissociate into hydrogen ions, electrons and oxygen gas

Describe the production of ATP by chemiosmosis

1. As electrons pass along the electron transport chain from PS1 to PS2, they provide energy to actively transport H+ from the stroma across the thylakoid into the thylakoid space
2. An electrochemical/proton gradient is established
3. H+ ions flow down their concentration gradient through a protein channel associated with ATP synthase
4. The flow of H+ ions is great enough to generate enough energy to phosphorylate ADP+Pi to ATP

Describe the clavin cycle

1. CO2 combines with molecule of Ribulose Biphospahte (RuBP) to form a 6c (unstable) molecule which is catalysed by a rubisco
2. 6c molecule breaks down to 2x3c GP molecules
3. 2xGP are converted to 2xTP by ATP and NADPH2
4. Through a series of reactions of 2xTP to RuP (5c) with the extra carbon being used to make glucose
5. RuP is phosphorylised by ATP to make RuBP
6. For every 6CO2, 2xTP are used to make 1 glucose

What is nitrogen used for in photosynthesis?

protein synthesis and nucleic acids, its usually transported as nitrate in the xylem and as amino acids in the phloem

What are the effects of a lack of nitrogen?

• Stunted growth of all organs
• Hindered cell division
• Chlorosis

What is magnesium used for?

• Required for chlorophyll manufacture
• Activation of ATPase

What is the function of the nucleus?

contains dna which codes for protein synthesis

What is the function of the nuclear envelope?

seperates the dna from the cytoplasm