GCSE Additional Biology (B2)(Edexcel)

Based on the dark blue revision guide by CGP

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What 4 things do plant and animal cells have in common?
Nucleus, cytoplasm, cell membrane and mitochondria
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What are the 3 extras that only plant cells have?
Large vacuole, rigid cell wall and chloroplasts
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What is the function of the mitochondria
This is where most of the reactions for respiration take place. Respiration releases energy that the cell needs to work
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What are 5 features of bacterial cells?
No nucleus, chromosomal DNA, plasmids, flagellum and cell wall
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Describe the large vacuole?
Contains cell sap, a weak solution of sugar and salts
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Describe the cell wall?
Made of cellulose, gives support for the cell
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Describe the chromosomal DNA?
One long circular chromosome which controls cell activities and replication, it floats free in the cytoplasm
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Describe the plasmids?
Small loops of extra DNA that aren't part of the chromosome, plasmids contain genes (eg drug resistance) and can be passed between bacteria
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Describe the flagellum?
A long hair like structure that rotates to make the bacterium move
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When were light microscopes invented?
In the 1590's
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When were electron microscopes invented?
In the 1930's
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What's the formula for magniffication?
Image length/actual specimen length
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What are the 4 base pairs of DNA?
Adenine, cytosine, guanine and thymine
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How do the 4 DNA bases pair?
A-T and C-G
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What base changes when DNA becomes MRNA
Uracil replaces thymine
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What are genes?
Sections of DNA that code for a specific protein
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How many different amino acids are there?
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What 3 things can mutations be?
Harmful, beneficial or neutral
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What is a catalyst?
A substance that speeds up a reaction without being used up or changed
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What are the 3 variables to measure in an enzyme controlled reaction?
Temperature, ph and substrate concentration
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Why does a higher temperature increase reaction rate to a degree?
More heat means the enzymes+substrate have more energy. They move about more and are more likely to collide and react
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What happens if an enzyme gets too hot?
Some of the bonds holding the enzyme together break and it becomes denatured permanently
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What enzyme breaks down proteins in the stomach?
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What PH is pepsin at its optimum?
PH 2
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How many genes did the human genome project attempt to map?
Around 25000
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What is the basic idea of genetic engineering?
To move useful genes from one organism's chromosomes into the cells of another
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What method do scientists use to create GM organisms?
Use enzymes to 'cut' out the useful gene and 'cut' a gap to insert it in the other organism
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How can genetic engineering help reduce vitamin A deficiency?
By creating golden rice which can produce beta-carotene which produces vitamin A. Particularly beneficial in south Asia and Africa
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How can genetic engineering help produce human insulin?
The human insulin gene is inserted into bacteria. Lots of human insulin can be produced quickly and cheaply to treat diabetes
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How can genetic engineering help increase crop yield?
GM crops can be modified to make them resistant to herbicides. Fields can be sprayed with herbicides and all non GM plants are killed, more crops produced=more food
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Describe the events of MITOSIS?
Before division DNA is in long strings, DNA copied and forms x shaped chromosomes (each arm=duplicate), chromosomes line up in centre then cell fibres pull them apart, membranes form around DNA and become nuclei, cytoplasm divides
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What's asexual reproduction?
no genetic variation
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How many chromosomes do gametes have?
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Are gametes haploid or diploid?
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Describe the events of MEIOSIS?
DNA copied into x shaped chromosomes, division one gives each cell different x shaped chromosome pairs, division two splits chromosomes (like mitosis), four cells are formed
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Describe the method of making cloned mammals?
Remove nucleus from unfertilized egg cell (enucleation), diploid nucleus from adult cell inserted into 'empty' cell, egg cell stimulated via electric shock, cell divides by mitosis, implanted into surrogate mother when a ball of cells
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3 uses of cloning?
Help with the shortage of organs for transplants, greater understanding of the embryo and ageing, preserve endangered species
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3 issues surrounding cloning?
Reduced gene pool (fewer alleles in a population) leading to increased death from disease, cloned mammals may not live as long (dolly lived 6 years instead of 12), many risks and problems (often fails, genetic defects, weak immune system)
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What's the process of stem cells becoming specialized?
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3 uses of embryonic stem cell research?
Already been used to cure sickle cell anaemia (and other diseases), stem cells extracted from human embryos can be differentiated under controlled conditions, it might be possible to use stem cells to replace damaged ones
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Why are some people against embryonic stem cell research?
They say each human embryo used is a potential human life (therefore it's murder) and scientists should fin another source of stem cells
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Why do some people disagree with the people who are against embryonic stem cell research?
The aim of curing patients is more important than the embryo and the embryos used are unwanted and would otherwise be destroyed
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What is respiration?
The process of breaking down glucose to release energy, which goes on in every living cell
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What's the energy from respiration used for?
Build larger molecules (eg proteins), contract muscles, maintain a steady body temperature
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What's the equation for aerobic respiration?
Glucose+Oxygen into Carbon Dioxide+Water (+Energy)
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What does the circulatory system do?
Carries glucose, oxygen and co2 around the blood in the body
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Where does the glucose needed for respiration come from?
Breaking down food in the digestive system
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What are capillaries?
The smallest blood vessels in the body, all cells in the body have capillaries nearby to supply them with glucose and oxygen and to take away the waste carbon dioxide
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What process is involved when substances move between capillaries and cells?
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What's diffusion?
Movement of particles from a high concentration to a lower one
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What affects rate of diffusion?
The difference in concentration
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Why do muscles need energy from respiration?
To contract
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What's the formula for cardiac output?
Heart rate x stroke volume
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When does anaerobic respiration occur?
When not enough oxygen is available
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What's the formula for anaerobic respiration?
Glucose into Lactic Acid (+Energy)
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What happens after anaerobic respiration stops?
You have an oxygen debt
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What's the effect of lactic acid?
Builds up in the muscles and causes pain+cramps
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What's the term for the amount of oxygen required in the 'oxygen debt'?
Excess post exercise oxygen consumption (EPOC)
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What does the heart do to toxic lactic acid after exercise?
Converts it into co2 and water
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What's the investigation for the effect of exercise on breathing and heart rate?
Measure breathing rate after different times after exercise
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What's the equation for photosynthesis?
Carbon dioxide+water (via sunlight and chlorophyll) into glucose+oxygen
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How are leaves adapted for efficient photosynthesis?
Broad shape for a large surface area exposed to light
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What are the stomata?
Little holes which open and close to let gases (eg co2 and oxygen) escape and water vapour
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What's the loss of water vapour from leaves called?
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What are the limiting factors for photosynthesis?
Light intensity, co2 concentration and temperature
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What's the investigation for work out ideal conditions for photosynthesis?
Measure the oxygen produced by a gas syringe after changing the limiting factors
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What temperature fo photosynthesis enzymes de-nature?
45 degrees celsius
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What is osmosis?
The movement of water molecules through a membrane
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Describe the practical to show osmosis?
Cut a potato into pieces the same length, put into different concentrations of sugar solutions, compare length measurements, longer ones have more water in them
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How do plants get water from soil?
Root hairs take in water by osmosis
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How do plants get minerals from soil?
Root hairs take in minerals using active transport
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What is active transport?
Moving against the concentration gradient using energy from respiration
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What does the xylem do?
Transports water and minerals from the root to the rest of the plant
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What does the phloem do?
Transports sugars from the leaves (where they're made) to growing and storage tissues
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What is transpiration?
The loss of water from the plant
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What causes transpiration?
Evaporation and diffusion of water through the stomata
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What is the transpiration stream?
A stream of water that flows through the plant to negate the water shortage caused by transpiration
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What's a habitat?
The place where an organism lives
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What's the distribution of an organism?
Where it's found
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How can we study the distribution of an organism?
Measure how common it is in 2 samples then compare
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What are the 5 ways of measuring how common an organism is?
Pooters, pitfalls, sweep nets, pond nets and quadrats
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Which 3 devices would you use to study ground insects?
Pooters, pitfalls and sweep nets
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What's a pooter?
Jar with rubber bung and 2 tubes, **** one tube and insect is pulled through other, compare 2 samples
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What's a pitfall trap?
Container in ground with raised lid, insects fall in, compare 2 samples
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What's a sweep net?
Strong net, collect by sweeping, compare 2 samples
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What's a pond net
Net used to collect pond creatures, compare 2 samples
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What's a quadrat?
Square enclosing a known area, compare 2 sample areas
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How do you calculate population size?
Mean number of organisms per m^2 x total m^2
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What's a belt transect?
A line of quadrats to track change across an area
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Name 3 environmental factors and how to measure them?
Temperature (measured by thermometer), light intensity (measured by light sensor) and soil ph (measured using indicator liquid or electronic meter)
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What's a fossil?
Any trace of an animal or plant that lived long ago
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What are the 3 ways fossils can be formed?
Gradual replacement, casts/impressions and preservation?
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What's gradual replacement?
The original substance is replaced by minerals as it decays, forms rocky substance in original shape
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What's casts/impressions?
Organism is pressed in a soft material (eg clay) then decays and the cast/impression is left when soft material hardens
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What's preservation?
No decay happens because conditions aren't suitable for microbes (too cold, too acidic, no oxygen, no moisture)
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What 3 things do fossils found in rock layers tell us?
What the organism looked like, how long ago they existed (deeper rock=older organism) and how they've evolved (by comparing different fossils)
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Why is the fossil record incomplete?
Very few organisms actually become fossils (most just decay), some body parts (eg soft tissue) decay away completely and not all fossils are discovered?
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What does the term 'missing links' refer to?
The incompletion of the fossil record
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An example of something that provides evidence for evolution?
The pentadactyl limb
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What's a pentadactyl limb?
A limb with 5 digits
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3 examples of animal groups where the pentadactyl limb can be seen?
Mammals, reptiles and amphibians
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Are all pentadactyl limbs the same?
They have a similar bone structure however perform different functions (eg humans are hands but bats are to fly)
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How does the pentadactyl limb provide evidence for evolution?
The similarity in bone structure means that everything with the limb evolved from a common ancestor (that had a pentadactyl limb), if we all evolved from different ancestors the bone structure would be different
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What's growth?
An increase in size or mass
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What are the 3 ways to measure growth of an organism?
Size (eg height, length, circumference), wet mass (mass including water) and dry mass (mass without water, only measured once dead)
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What 3 processes cause growth?
Cell differentiation, cell division (eg mitosis) and cell elongation (plant cell expands, plants only)
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What's the difference between plant and animal growth?
Animals grow at different rates during their life, cell differentiation is lost at an early stage in animals, plants grow continuously and keep differentiating (eg new leaves or roots)
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What's the 50th percentile in a babies mass percentile graph?
50% of babies have reached this mass by this age
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What's the 'normal' range of babies growth in reference to percentiles?
2nd percentile to 98th percentile
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What 3 things to cells make up?
Tissues, organs and systems
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What's a tissue?
A group of similar cells that work together to carry out a particular function
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What's an organ?
A group of different tissues that work together to carry out a particular function
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What's an (organ) system?
A group of organs that work together to carry out a particular function
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What are the four chambers of the heart?
Left and right atrium, left and right ventricle
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What are the 4 blood vessels of the heart?
Pulmonary artery, pulmonary vein, aorta and vena carva
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What does the right atria do?
Receives deocygenated blood from the body (through the vena carva)
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What happens to the deoxygenated blood after it is received by the right atria?
It moves through to the right ventricle which pumps it to the lungs (through the pulmonary artery)
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What does the left atriia do?
Receives oxygenated blood from the lungs (through the pulmonary vein)
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What happens to the oxygenated blood after it is received by the left atria?
It moves through tot he left ventricle which pumps it around the whole body (through the aorta)
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Are the ventricle walls the same?
The left ventricle has a much thicker wall because it needs more muscle to pump blood around the whole body (instead of just the lungs)
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What do valves do?
Prevent the back flow of blodod
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What do red blood cells carry?
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What's the job of red blood cells?
Carry oxygen from the lungs to all body cells
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What shape are red blood cells?
Bi-concave disk
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What substance do red blood cells contain?
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What does haemoglobin contain?
A lot of iron
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What does haemoglobin do?
Combines with oxygen in the lungs to become oxyhaemoglobin, in body tissues the reverse happens to release oxygen into cells
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What does a lack of iron lead to?
Anaemia (where the blood can't carry enough oxygen)
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What do white blood cells do?
Defend against disease
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How do white blood cells defend against disease?
Change shape as well as produce antibodies and antitoxins
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What does a low white blood cell count mean?
More susceptible to infection
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What does a high white blood cell count mean?
You have an infection
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What do platelets do?
Help blood clot
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What are platelets made up of?
Small fragments of cells
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What can lack of platelets cause?
Excessive bleeding and bruising
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What is plasma?
The liquid that carries everything in the blood
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What does plasma transport?
red and white blood cells and platelets, nutrients like glucose and amino acids, carbon dioxide (removed in the lungs), urea (waste formed in the liver and removed in the kidneys), hormones (from glands to organs) and antibodies/antitoxins
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What are the 3 different types of blood vessel?
Arteries, capillaries and veins
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What do arteries do?
Carry blood away from the heart under pressure
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What do capillaries do?
Capillaries are involved with the exchange of material with the tissues
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What do veins do?
Carry blood to the heart
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Describe the artery walls?
Strong and elastic to cope with the high pressure, thick compared to the lumen (hole down the middle), contain thick layers of muscle
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Describe the capillaries?
Really small, arteries branch into capillaries, carry blood very close to every cell to exchange substances, permeable walls for diffusion, supply food+oxygen and carry away waste (co2), walls only 1 cell thick to increase rate of diffusion
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Describe the veins?
Capillaries eventually join up to form veins, blood is at lower pressure so walls are thinner, bigger lumen (hole in the middle) than arteries to help blood flow, have valves to prevent back flow
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What are the 3 big molecules?
Starch, proteins and fats
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Why are the molecules described as big?
They're too big to pass through the walls of the digestive system
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What are the 4 smaller molecules?
Sugars, amino acids, glycerol and fatty acids
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What are the 3 digestive enzymes?
Carbohydrase, protease and lipase
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What does carbohydrase do?
Digests carbohydrates into sugars
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What does amylase do?
Catalyses the breakdown of starch
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What role does the mouth play in digestion?
Salivary glands moisten food, salivary glands produce amylase, food is chewed to form a ball of food (bolus) before swallowing
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What's the oesophagus?
A tube that takes food from the mouth to the stomach, lined with muscles that contract (peristalsis)
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What does the liver do in digestion?
Produces bile which neutralizes stomach acid and emulsifies fats
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What does the gall bladder do in digestion?
Stores bile before it's released into the small intestine
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What does the stomach do in digestion?
Pummels food with muscular walls, produces pepsin, produces hydrochloric acid to kill bacteria and give the right ph for protease (PH 2)
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What does the small intestine do in digestion?
Produces protease, amylase and lipase to complete digestion, food is absorbed into the body
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What does the pancreas do in digestion?
Produces protease, amylase and lipase enzymes and releases into small intestine
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What does the large intestine do?
Absorbs excess water from food
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What is visking tubing used for?
To model the gut
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Why is visking tubing a good model for the gut?
Only lets through small molecules, cheap, easy to use, less messy than animal gut
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Why isn't visking tubing a good model for the gut?
Gut is longer and has much higher surface area so absorption speed is different
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How do you test for starch?
Add the same volume of starch suspension and 0.25% amylase solution to visking tube, rinse outside of tube under tap, put tube in boiling tube with distilled water, test 1 drop from around the tube with iodine, record colour
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How do you test for sugar?
Add the same volume of starch suspension and 0.25% amylase solution to visking tube, rinse outside of tube under tap, put in boiling tube w/ distilled water, test 5 drops with Benedict's, record colour, change from blue to green/yellow/orange/red
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Does enzyme concentration affect rate of reaction?
Yes but only up to a certain point
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What iodine colour shows no starch?
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What does peristalsis involve?
Longitudinal and circular muscles
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Where are the longitudinal muscles?
Down the length of the gut
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Where are the circular muscles?
Running in circles around the gut
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What's peristalsis?
Squeezing food along the digestive system
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What's an alternate name for the gut?
Alimentary canal
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What do the circular muscles do in peristalsis?
Push food along the gut
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What do the longitudinal muscles do in peristalsis?
Run slightly ahead of the circular muscles to keep food in a ball
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What does bile do?
Neutralizes stomach acid and emulsifies fats
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Why is neutralization of the stomach acids necessary?
Because the PH is too low for the enzymes in the small intestine to work properly
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What does emulsifying fats mean?
Converting them into tiny droplets so they've a larger surface area for quicker digestion
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Why does the small intestine have villi?
To provide a very large surface area
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What are the 3 features of the villi which make absorption into the blood efficient?
Large surface area, single layer of surface cells (short distance), very good blood supply (capillaries)
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What is a functional food?
A food that has some kind of health benefit beyond basic nutrition
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What are probiotics?
Live bacteria that replicate bacteria that are in the gut naturally
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What are the supposed benefits of probiotics and prebiotics?
Stronger immune system and healthy digestive system
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What are prebiotics?
Carbohydrates that we can't digest, food supply for good bacteria
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What is plant stanol ester?
A chemical that lowers blood cholesterol and reduces the risk of heart disease
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How is plant stanol ester produced?
By using bacteria that convert sterol (plant fat) into stanol
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What 4 things should be found out when looking at functional foods evidence?
Scientific study in reputable journal? written by a qualified person (separate from retailers) was the sample large enough? Do other studies support these results?
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What are the 3 extras that only plant cells have?


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Card 3


What is the function of the mitochondria


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Card 4


What are 5 features of bacterial cells?


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Card 5


Describe the large vacuole?


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