AQA B2 flashcards

  • Created by: rome.mary
  • Created on: 14-04-17 13:04
Explain the function of the nucleus in cells
Controls cell activity and contains genetic material - DNA
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Explain the structure and function of the cytoplasm
A gel-like mixture where most chmical reactions take place.
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Explain the function of the cell membrane.
Controls the passage of substances into and out of the cell.
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Expain the structure and function of the mitochondria
It is where espiration takes place. It produces energy through chemical reactions - breaking down fats and carbohydrates.
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Explain the function of ribosomes
Where protein synthesis takes place. All the proteins needed in the cell are made here.
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How do plant and algal cells differ from animal cells?
They also have a cell wall, and most have chloroplasts and a permanent vacuole.
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What is the purpose of the plant cell wall?
It is made of cellulose that strengthens the cell and gives it support.
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What is the purpose of chloroplasts?
They contain chlorophyll (provides green colour). Chlorophyll absorbs light energy to make food by photosynthesis.
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What is the purpose of the permanent vacuole?
Membrane-bound sacs filled with cell sap. Used for storage, digestion, and waste removal. Rigid to help maintain plant shape.
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What are bacterial cells like?
Single-celled microorganisms with cytoplasm, cell membrane and cell wall. Genetic material floats in cytoplasm - no nucleus.
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Describe the structure of a yeast cell.
Each cell has a nucleus, cytoplasm and a membrane surrounded by a cell wall.
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Explain how leaf cells are specialised for photosynthesis
Lots of chloroplasts for photosynthesis at the top of cells so more exposed to light. Tall so larger vertical surface area for more carbon dioxide absorption. Thin so more are placed at top of leaf.
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Explain how guard cells are specialised to open and close stomata
Lots of water: guard cells become turgid (plump), making stomata open for gas exchange for photosynthesis. Lack of water: guard cells become flaccid, making stomata close to stop water vapour escaping. Sensitive to light: closes at night to save wate
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Explain how red blood cells are specialised to carry oxygen
Concave shape: bigger surface area to absorb oxygen and helps pass through capillaires smoother. Packed w/ haemoglobin: pigment to absorb oxygen. No nucleus: more room for haemoglobin.
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Explain how sperm cells are specialised for reproduction
Long tail and streamlined head to help swimming. Lots of mitochondria in middle section for energy to move. Head contains digestive enzyme to help break outer layer of egg.
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Explain how egg cells are specialised for reproduction
Large cytoplasm containing nutrients and food reserves to help feed embryo and keep it alive. Mitochondria to help cells divide after fertilisation.
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What is diffusion?
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration across a concentration gradient until an equilibrium is reached.
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Give 3 things that can affect the rate of diffusion.
1) Greater difference of concentration, faster. 2) increased temp. particles speed up so more diffusion. 3) increased surface area of cell membraine, more diffusion
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What is a tissue?
A tissue is a group of cells with similar structure and function.
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What is an organ?
A group of different tissues that work together to perform a specific function eg. muscular tissues: stomach wall churns up food, gladular tissues: digestive juices to digest food, epithelial tissues: covers inside and outside of stomach
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What are organ systems?
A group of organs working togehter to perfom a certain function eg. digestive system consists of glands, stomach, liveer, small/large intestines etc.
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What is the equation for photosynthesis?
carbon dioxide + water = glucose + oxygen (through help of sunlight and chlorophyll) (oxygen is a by-product)
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Name each part of a leaf and their function (1)
CUTICLE: thick waxy top layer to stop water evaporating. PALISADE LAYER: packed top layer of cells, lots of chloroplast to carry out more photosynthesis. VEINS: xylems tubes carry water to leaf cells form roots via stem. Phloem tubes carry food
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Name each part of a leaf and their function (2)
PORES: aka stomata, lets gases in and out through diffusion. On bottom, not blocked and shaded to prevent evaporation. Controlled by guard cells. AIR SPACES: lower layers (spongy mesophyll) w/ air spaces to let carbon dioxide move to the surface.
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What factors limit the rate of photosynthesis in plants?
The rate of photosynthesis may be limited by the shortage of light, low temperatures and the shortage of carbon dioxide
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How does light affect photosynthesis?
For most plants, the brighter the light, the faster the rate of photosynthesis. However a point is reached when no matter how bright the light, the rate of photosynthesis stays the same (similar process for carbon dioxide)
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How does temperature affect photosynthesis?
As the temperature rises, the rate of photosynthesis increases as the reaction speeds up. However, photosynthesis is controlled by enzymes. Most enzymes are denatured at high temperatures (40-50 C) so if this occurs the rate of photosynthesis will fa
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What do plants do with the glucose they make?
For respiration, converting starch to storage, making proteins w/ nitrate ions, producing lipids (fats & oils) to storage, converted into cellulose for strong cell walls.
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What factors affect the distribution of organisms in their natural environment?
Temperature, nutrients, the amount of light, water, the availabilty of oxygen and carbon dioxide.
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How can you measure the distribution of living things in their natural environments?
By using random sampling with quadrats or sampling along a transect.
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What is a catalyst?
A substance which increases the speed of a reaction without being changed or used up.
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What is an enzyme and how do they work?
Enzymes are large protein molecules that act as biological catalysts. The amino acid chains are folded to form the active site. The substrate (reactant) fits into the active site of the enzyme and the reaction takes place rapidly.
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What is the effect of temperature on enzyme action?
Like other reactions, the rate of enzyme controlled reactions increases as the temperature increases. However this is true only up to about 40 degrees C. The enzyme becomes denatured, no longer able to function as the active site will have changed.
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Why does a change in pH affect your enzymes?
A change in pH can alter the shape of a molecule and so the enzyme may no longer act as a catalyst. Optimum pH for most enzymes is pH 7 whilst pepsin (stomach enzyme) is pH 2
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What is the name of the enzyme that breaks down starch in your gut?
The reaction is catalysed by amylase which is produced in the salivary glands, pancreas, and small intestine. Starch is converted to maltose and other sugars.
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Which enzymes break down protein in your gut?
Protease produced in your stomach, small intestine, and pancreas. Proteins are converted into amino acids.
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Which enzymes break down fats in your gut?
The reaction is catalysed by lipase made in your pancreas and small intestine. Lipids are converted into glycerol and fatty acids.
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What is bile and why is it so important in digestion?
The liver makes bile and is stored in the gall bladder until needed. Bile neutralises the acid from the stomach and turns the semi-digested food alkaline to make ideal conditions for enzymes in the small intestine.
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How does bile produce a big surface area for lipase to work on?
Bile also emulsifies the fats, breaking up the large drops of fat into smaller droplets, helping enzymes (lipase) to work.
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Why does your stomach contain hydrochloric acid?
To kill bacteria and provide right pH for protease enzymes to work.
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How are enzymes used in the food industry?
Proteases are used in baby foods to make it easier for babies to digest. Carbohydrases are used to convert starch into sugar syrup.
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Why is the enzyme isomerase used to convert glucose syrup into fructose syrup?
Fructose is much sweeter than glucose so much smaller quantities are required to make food taste sweet. So it is used in 'slimming' foods.
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How are enzymes used in biological detergents?
Consists of proteases and lipases to break down animal and plant matter as well as removing stains like food or sweat. Effective at lower temps. saves money, good for environment.
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Name advantages of using enzymes in industry
1) Specific, only catalyses wanted reaction. 2) Lower temps, saves money and energy. 3) Long lifespan. 4) Biodegradable, less environmental pollution.
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Name disadvantages of using enzyme in industry
1) People can develop allergies. 2) Can be denatured w/ a small increase of temp or pH. Tightly controlled. 3) Expensive to produce. 4) Contamination w/ other substances can affect reaction.
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What is respiration?
The process of releasing energy from glucose which goes on in every cell.
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What is aerobic respiration and what is the equation?
It is respiration using oxygen and is the most effecient way to release energy from glucose. Most take place in mitochondria.
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Why do mitochondria have folded inner membranes?
This provides a large surface area where the enzymes which release cellular respiration are found
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How is the energy released in respiration used?
1) To build larger molecules from smaller ones. 2) Allows muscles to contract. 3) Keep body temps. steady in mammals and birds. 4) Build sugars, nitrates etc. into amino acids => proteins.
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How does your body respond to the increased demands for oxygen during exercise.
An increase in heart rate, in breathing rate and in depth of breathing to provide more oxygen and glucose for muscle contraction. Glycogen stores in the muscle are converted to glucose for cellular respiration. The blood flow in the muscle increases.
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What is glycogen?
Your muscles store glucose as the carbohydrate glycogen. Glycogen can be converted rapidly back to glucose to use during exercise.
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What is anaerobic respiration and what is the equation?
It is used when body can't supply enough oxygen to muscles. It is the incomplete breakdown of glucose that produces lactic acid => cramps, muscle fatigue. Inefficient.
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What is oxygen debt?
After exercise, oxygen is still needed to break down the lactic acid which has built up. The amount of oxygen needed to break down the lactic acid to carbon dioxide and water is known as the oxygen debt.
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What are chromosomes?
Chromosomes are long strands of DNA and are arranged in pairs. They are found in the nuclus of animal and plant cells.
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What is mitosis?
Cell division in normal body cells produces two identical cells. All the body cells have the same chromosomes, so the same genetic information. Makes cells for growth and repair.
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What is meiosis?
Cell division that takes place only in the reproductive organs in animals and plants. This results in sex cells called gametes, with only half the original number of chromosomes.
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What is cell differentiation?
In early development, animal and plant cells are unspecialised. Each one of them (stem cell) can become any type of cell needed. By the time a human baby is born, most cells are specialised and do a specialised job.
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What is special about stem cells?
They can be made to differentiate into many different types of cell.
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How can we use stem cells to cure people?
Stem cells have the potential to treat previously incurable conditions. We may be able to grow nerve cells or whole new organs for people who need them.
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What are other sources of stem cells?
The umbilical chord blood of newborn babies and bone marrow.
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Why is Gregor Mendel important when learning about inheritance?
Mendel experimented with pea plants and suggested that offspring inherit factors (genes) from theier parent/s.
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What is DNA?
A double helix structure that carries instructions to make proteins that form most of cell structures.
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What is a gene?
A gene is a small section of DNA that codes for a particular combination of amino acids, which make a specific protein.
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What is an allele?
They are different versions of the same gene and can be either dominant or recessive.
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What is the difference between homozygous and heterozygous?
Homozygous alleles are identical alleles in a pair whilst heterozygous alleles are different in a pair.
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What is a genotype?
The genetic makeup of an individual eg. ** chromosomes
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What is a phenotype?
The physical result of an individual from the genotype eg. ** chromosomes make a female with female sexual organs.
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What is Polydactyly?
It is a genetic disorder that affects no. of fingers or toes. It is a dominant allele so it can be inherited if only one parent is a sufferer.
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What is Cystic Fibrosis?
Genetic disorder of cell membranes. It is a recessive allele so in order to get it, both parents must either be a sufferer or a carrier.
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What are fossils?
Fossils are the remains of organisms from many years ago that are found in rocks.
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What are the reasons for extinction of a species of living organisms?
New predators, new diseases, competition between two species, changes in environment eg. destruction of habitat.
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What is speciation?
It is the development of a new species. It occurs when populations of the same species become so different that they can no longer breed together and produce fertile offsprings.
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What can cause speciation?
Isolation and natural selection. Species divided w/ a physical barrier may be exposed to different environments & so over time the better adapted will survive their respective environments, producing different characteristics & thus different species
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Card 2


Explain the structure and function of the cytoplasm


A gel-like mixture where most chmical reactions take place.

Card 3


Explain the function of the cell membrane.


Preview of the front of card 3

Card 4


Expain the structure and function of the mitochondria


Preview of the front of card 4

Card 5


Explain the function of ribosomes


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