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This set should (hopefully) contain everything you need to know for AQA GCSE Biology Paper 1. Made using the specification and Freesciencelessons on YouTube. This is designed to be used in Term → Definition mode. You can do it the other way around for extra revision, but it will not be framed as a question. Topic 1 - Cell biology: Cards 1-73 Topic 2 - Organisation: Cards 74-164 Topic 3 - Infection and response: Cards 165-243 Topic 4 - Bioenergetics: Cards 244-275 (Topics 5-7 will be in the Paper 2 flashcards when I make them) Note: The structure and functioning of cells, mitosis and meiosis, sexual and asexual reproduction, photosynthesis and respiration, metabolism and how materials are cycled can be assessed on either paper. Cards starting with ᵀ are triple/separate/biology only. Cards starting with ᴴ are Higher tier only. (Cards starting with ᵀᴴ are both.) If you want to remove these cards, star all the other cards and then study with starred cards only. Note: There is one line in the specification in Cell biology which states: “Students should be able to explain how the small intestine and lungs in mammals, gills in fish, and the roots and leaves in plants are adapted for exchanging materials.” The small intestine and gills are not mentioned anywhere else in the specification, so they are included in Cell biology in these flashcards. The lungs and leaves are mentioned again in Organisation, so they are included there. The roots are mentioned both earlier in Cell biology and in Organisation, so they are included where they are first mentioned in Cell biology (in cell specialisation).
What types of cells are eukaryotic?
Animal and plant cells
What sub-cellular structures do eukaryotic cells have?
A cell membrane, cytoplasm and genetic material enclosed in a nucleus
What type of cell is prokaryotic?
Bacterial cells
Which are smaller: eukaryotic cells or prokaryotic cells?
Prokaryotic cells
What do prokaryotic cells contain? (excl. genetic material)
Cytoplasm and a cell membrane surrounded by a cell wall
Where is genetic material located in prokaryotic cells?
The genetic material is not enclosed in a nucleus. It is a single DNA loop and there may be one or more small rings of DNA called plasmids.
What is the function of the nucleus (of a cell)?
To enclose the genetic material
What is the function of the cytoplasm?
Where chemical reactions take place
What is the function of the cell membrane?
Controls the molecules that can enter and leave the cell
What is the function of the mitochondria?
Where aerobic respiration takes place
What is the function of ribosomes?
Protein synthesis
What is the function of chloroplasts?
Chloroplasts are the sites of photosynthesis
What is the cell wall made of?
Cellulose
What is the function of the cell wall?
Strengthens the cell
What is the function of the permanent vacuole?
Gives the plant cell its shape
What is the permanent vacuole filled with?
Cell sap
What sub-cellular structures do most animal cells have?
Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
What sub-cellular structures do most plant cells have?
Nucleus, cell membrane, cytoplasm, mitochondria, ribosomes, chloroplasts, permanent vacuole, cell wall
How are sperm cells specialised to carry out their function?
The function of a sperm cell is to join with an ovum (egg cell). This process is called fertilisation. During fertilisation, the genetic information of the ovum and the sperm combine.
Sperm cells contain their genetic information in the nucleus. However, sperm cells only contain half the genetic information of a normal adult cell.
Sperm cells have a long tail which allows them to swim to the ovum. They are also streamlined to make this easier.
Sperm cells are packed full of mitochondria. This provides the energy needed for swimming.
Sperm cells contain enzymes which allow them to digest their way through the outer layer of the ovum.
How are nerve cells specialised to carry out their function?
The function of a nerve cell is to send electrical impulses around the body.
Nerve cells have a long axon, which arrives the electrical impulses from one part of the body to another.
The axon is covered with myelin, which insulates the axon and speeds up the transmission of nerve impulses.
The end of the axon has synapses, which are junctions that allow the impulse to pass from one nerve cell to another.
The body of the nerve cell has dendrites, which increase the surface area so that other nerve cells can connect more easily.
How are muscle cells specialised to carry out their function?
Muscle cells contain protein fibres which can change their length, allowing them to contract (get shorter). When a muscle cell contracts, these protein fibres shorten, decreasing the length of the cell.
Muscle cells are also packed full of mitochondria, to provide energy for muscle contraction.
How are root hair cells specialised to carry out their function?
Root hair cells form root hairs, which increase the surface area of the root, so it can absorb water and dissolved minerals more effectively.
Root hair cells do not contain chloroplasts, because they are underground (chloroplasts are the sites of photosynthesis, but no light can reach the root hair cells).
How are xylem cells specialised to carry out their function?
Xylem cells are found in the plant stem. They form long tubes. These tubes carry water and dissolved minerals from the roots to the leaves.
Xylem cells have very thick walls containing lignin. This provides support to the plant. Because the cell walls are sealed with lignin, this causes the xylem cells to die.
The end walls between the cells have broken down. This means that the cells form a long tube so that water and dissolved minerals can flow easily.
Xylem cells have no nucleus, cytoplasm, vacuole or chloroplasts. That makes it easier for water and minerals to flow.
How are phloem cells specialised to carry out their function?
Phloem tubes carry dissolved sugars up and down the plant.
Phloem vessel cells have no nucleus and only limited cytoplasm. The end walls of the vessel cells have pores called sieve plates. These features allow dissolved sugars to move through the cell interior.
Each phloem vessel cell has a companion cell connected by pores. Mitochondria in the companion cell provide energy to the phloem vessel cell.
When do most types of animal cells differentiate?
At an early stage
When do most types of plant cells differentiate?
Many retain the ability to differentiate throughout life
In mature animals, what is cell differentiation mainly restricted to?
Repair and replacement
What happens as a cell differentiates?
It acquires different sub-cellular structures to enable it to carry out a certain function. It has become a specialised cell.
Describe how to use a light microscope to observe and draw a plant or animal cell.
Place the slide onto the stage. Use the clips to hold the slide in place.
Select the lowest power objective lens. Position the objective lens so it almost touches the microscope slide - to do that, slowly turn the coarse focusing dial. Look at the microscope from the side while doing this to avoid damaging the slide. When the objective lens almost touches the slide, stop turning the dial.
Look down through the eyepiece. Slowly turn the coarse focusing dial, increasing the distance between the objective lens and the slide. Do this until the cells come into focus.
Use the fine focusing dial to bring the cells into a clear focus.
At this point, you can select a higher power objective lens. Adjust the fine focusing dial to bring the cells back into focus.
Use a pencil to make a clear, labelled drawing of some of the cells.
To calculate the total magnification, multiply the magnification of the eyepiece lens by the magnification of the objective lens.
Place a clear plastic ruler over the stage. Measure the diameter of the field of view in millimetres. Show this on the drawing using a scale bar, and write the magnification.
How has electron microscopy increased understanding of sub-cellular structures?
An electron microscope has much higher magnification and resolving power than a light microscope. This means that it can be used to study cells in much finer detail. This has enabled biologists to see and understand many more sub-cellular structures.
What is the equation that links magnification, size of image and size of real object?
Magnification = size of image ÷ size of real object
ᵀ How do bacteria multiply?
Simple cell division (binary fission)
ᵀ How often do bacteria multiply? What environment must they be in for this to be the case?
As often as 20 minutes, if they have enough nutrients and a suitable temperature
ᵀ In what ways can bacteria be grown?
In a nutrient broth solution or as colonies on an agar gel plate
ᵀ What are uncontaminated cultures of microorganisms required for?
Investigating the action of disinfectants and antibiotics
ᵀ When preparing an uncontaminated bacterial culture, why must Petri dishes and culture media be sterilised before use?
It kills any unwanted microorganisms and prevents contamination
ᵀ When preparing an uncontaminated bacterial culture, why must inoculating loops used to transfer microorganisms to the media be sterilised by passing them through a flame?
It kills any unwanted microorganisms and prevents contamination
ᵀ When preparing an uncontaminated bacterial culture, why must the lid of the Petri dish be secured with adhesive tape?
It stops the lid from falling off and unwanted microorganisms entering
ᵀ When preparing an uncontaminated bacterial culture, why must the Petri dish be stored upside down?
It stops moisture from dripping down onto the bacteria and disrupting the colonies
ᵀ When preparing an uncontaminated bacterial culture in a school laboratory, why should the culture generally be incubated at 25°C?
It reduces the chances that harmful bacteria will grow
ᵀ Describe how to investigate the effect of antibiotics on bacterial growth using agar plates.
Clean the bench with disinfectant solution. This kills microorganisms that could contaminate the culture.
Sterilise an inoculating loop by passing it through a blue Bunsen burner flame.
Open a sterile agar gel plate near a Bunsen burner flame. The flame kills bacteria in the air.
Use the loop to spread the chosen bacteria evenly over the plate.
Place sterile filter paper discs containing antibiotic onto the plate.
Secure the lid of the Petri dish with adhesive tape and incubate it upside-down at 25°C.
Calculate the areas of the zones of inhibition using πr².
What does the nucleus of a cell contain?
Chromosomes made of DNA molecules
What do chromosomes carry?
A large number of genes
How are chromosomes normally found in body cells?
In pairs
What are the three stages of the cell cycle (including mitosis)?
Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome.
In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides. Finally, the cytoplasm and cell membrane divide to form two identical cells.
Where is cell division by mitosis important?
The growth and development of multicellular organisms
What is a stem cell?
An undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation
What is the function of stem cells in embryos?
Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells.
What is the function of stem cells in adult animals?
Stem cells from adult bone marrow can form many types of cells including blood cells.
What is the function of stem cells in the meristems in plants?
Meristem tissue in plants can differentiate into any type of plant cell, throughout the life of the plant.
What conditions may treatment with stem cells be able to help?
Diabetes and paralysis
What is therapeutic cloning?
An embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient's body so they may be used for medical treatment.
What disadvantages are there to the use of stem cells?
The use of stem cells has potential risks such as transfer of viral infection, and some people have ethical or religious objections.
What is a use of stem cells from meristems in plants?
Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.
Rare species can be cloned to protect from extinction.
Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.
How may substances move into and out of cells?
Across the cell membranes via diffusion
What is diffusion?
The spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration
Name three substances transported around the body by diffusion, and why.
Oxygen and carbon dioxide are transported in and out of cells in gas exchange.
The waste product urea is transported from cells into the blood plasma for excretion in the kidney.
How does the difference in concentrations (concentration gradient) affect the rate of diffusion?
The greater the concentration gradient, the faster the rate of diffusion
How does the temperature affect the rate of diffusion?
The higher the temperature, the faster the rate of diffusion. This is because the particles have more kinetic energy so they move around faster
How does the surface area of the membrane affect the rate of diffusion?
The larger the surface area of the membrane, the greater the rate of diffusion.
Why are exchange surfaces and a transport system not needed in single-celled organisms?
A single-celled organism has a relatively large surface area to volume ratio. This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism.
Why are exchange surfaces and a transport system needed in multicellular organisms?
Cells on the surface can get enough oxygen simply by diffusion, however not enough oxygen can diffuse into the cells in the centre of the organism. They are too far away from the surface.
How is the small intestine adapted for exchanging materials?
The small intestine is very long. This provides a very large surface area for absorption of the products of digestion.
The interior of the small intestine is covered with millions of villi. Villi massively increase the surface area for the absorption of molecules. Microvilli on the surface increase the surface area even further.
Villi have a very good blood supply so the bloodstream rapidly removes the products of digestion. This increases the concentration gradient.
The thin membrane ensures a short diffusion path.
All of these features mean that there is a rapid rate of diffusion.
Any molecules which cannot be absorbed by diffusion are absorbed by active transport.
How are gills (in fish) adapted for exchanging materials?
The gills are covered in a very large number of fine filaments. This is where gases pass in and out of the blood.
The filaments give the gills a massive surface area.
The filaments also have a thin membrane to provide a short diffusion pathway.
The filaments have an efficient blood supply to take the oxygenated blood away. This ensures that the concentration gradient is always high.
All of these adaptations make diffusion as efficient as possible.
Why are surfaces and organ systems specialised for exchanging materials in multicellular organisms?
To allow sufficient molecules to be transported into and out of cells for the organism's needs.
How can the effectiveness of an exchange surface be increased?
Having a large surface area
Having a membrane that is thin, to provide a short diffusion path
(in animals) Having an efficient blood supply
(in animals, for gaseous exchange) Being ventilated
How may water move across cell membranes?
Via osmosis
What is osmosis?
The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
Describe how to investigate the effect of a range of concentrations of sugar solution on the mass of potato, and how to determine the approximate concentration inside the potato cells.
Peel the potato.
Use a cork borer to produce three cylinders of potato.
Use a scalpel to trim the cylinders to the same length (around 3 cm).
Measure the length of each cylinder using a ruler and the mass of each cylinder using a balance.
Place each cylinder into a test tube.
Add 10cm³ of a 0.5 molar sugar solution to the first tube, 10cm³ of 0.25 molar sugar solution to the second test tube and 10cm³ of distilled water to the third test tube.
Leave the potato cylinders overnight to allow osmosis to take place.
Remove the potato cylinders and gently roll them on paper towel to remove any surface moisture.
Measure the length and the mass of the cylinders again.
Calculate the percentage change in mass for each potato cylinder.
Plot a graph of percentage change in mass against concentration of sugar solution. Where the line crosses the x-axis is the approximate concentration inside the potato cells.
What is active transport?
Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient). This requires energy from respiration.
How does active transport benefit plants?
Active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil. Plants require ions for healthy growth.
How does active transport benefit animals?
Active transport allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. Sugar molecules are used for cell respiration.
What are the differences between diffusion and active transport?
In diffusion, particles move down the concentration gradient, whereas in active transport, particles are moved against the concentration gradient.
Diffusion does not require energy from respiration, whereas active transport does.
What are cells?
The basic building blocks of all living organisms
What is a tissue?
A group of cells with similar structure and function
What are organs?
Aggregations of tissues performing specific functions
How are organs organised?
Into organ systems, which work together to form organisms
Describe the tissues and organs of the human digestive system, including adaptations to function and how the digestive system digests food.
First, food is chewed in the mouth. Enzymes in the saliva begin to digest the starch into smaller sugar molecules.
The food then passes down the oesophagus into the stomach. In the stomach, enzymes begin the digestion of proteins. The stomach also contains hydrochloric acid which helps the enzymes to digest proteins.
The food spends several hours in the stomach. The churning action of the stomach muscles turns the food into a fluid increasing the surface area for enzymes to digest.
The fluid now passes into the small intestine. At this point chemicals are released from the small intestine and the pancreas.
The pancreas leases enzymes which continue the digestion of starch and protein. They also start the digestion of lipids.
The liver releases bile which helps to speed up the digestion of lipids. Bile also neutralises the acid released from the stomach.
The walls of the small intestine release enzymes to continue the digestion of protein and lipids. In the small intestine, the small food molecules produced by digestion are absorbed into the bloodstream either by diffusion or by active transport.
Next, the fluid makes its way through the large intestine, where water is absorbed into the bloodstream.
Finally the faeces is released from the body.
What is the digestive system an example of?
An organ system in which several organs work together to digest and absorb food
What do enzymes do?
Enzymes catalyse specific reactions in living organisms due to the shape of their active site
Explain what happens to an enzyme as the temperature increases.
As the temperature increases, the activity of the enzyme increases (the reaction gets faster). This is because as the temperature increases, the enzyme and substrate are moving faster so there are more collisions per second between the substrate and the active site.
At a certain temperature, the enzyme is working at the fastest possible rate. This is called the optimum temperature. At this point, there is the maximum frequency of successful collisions between the substrate and the active site.
As the temperature increases past the optimum, the activity of the enzyme rapidly decreases to zero.
At high temperatures, the enzyme molecule vibrates and the shape of the active site changes. Now the substrate no longer fits perfectly into the active site. The active site is denatured. The enzyme can no longer catalyse the reaction.
Explain what happens to an enzyme as the pH increases or decreases.
The enzyme has an optimum pH, where the activity is maximum.
If the pH is made more acidic or more alkaline, the activity drops to zero. The active site denatures if the conditions are too acidic or too alkaline.
Use the 'lock and key theory' to explain why enzymes only catalyse certain reactions.
Enzymes have a groove on their surface called the active site. The active site is where the substrate attaches to.
In certain reactions, the substrate fits perfectly into the active site. The enzyme now breaks down the substrate into the products.
In other reactions, the substrate does not fit into the active site. The enzyme cannot break down that substrate.
Enzymes are specific. The substrate must fit perfectly into the active site.
What does amylase do?
Carbohydrases break down carbohydrates to simple sugars. Amylase is a carbohydrase which breaks down starch.
Where is amylase produced?
Salivary glands, pancreas
What do proteases do?
Proteases break down proteins to amino acids
Where are proteases produced?
Stomach, pancreas, small intestine
What do lipases do?
Lipases break down lipids (fats) to glycerol and fatty acids
Where are lipases produced?
Pancreas, small intestine
What do digestive enzymes do?
Convert food into small soluble molecules that can be absorbed into the bloodstream
What are the products of digestion used for?
Building new carbohydrates, lipids and proteins. Some glucose is used for respiration.
Where is bile made?
Liver
Where is bile stored?
Gallbladder
What does bile do?
Bile is alkaline to neutralise hydrochloric acid from the stomach. It also emulsifies fat to form small droplets which increases the surface area. The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.
Describe how to test if a food sample contains starch.
Grind the food sample with distilled water using a mortar and pestle, to make a paste.
Transfer the paste to a beaker and add more distilled water. Stir so the chemicals in the food dissolve in the water.
Filter the solution to remove suspended food particles.
Place 2cm³ of food solution into a test tube.
Add a few drops of iodine solution, which is an orange colour. If starch is present, the iodine solution will turn blue-black. If there is no starch present, the iodine solution will stay orange.
Describe how to test if a food sample contains sugars.
Grind the food sample with distilled water using a mortar and pestle, to make a paste.
Transfer the paste to a beaker and add more distilled water. Stir so the chemicals in the food dissolve in the water.
Filter the solution to remove suspended food particles.
Place 2cm³ of food solution into a test tube.
Add 10 drops of Benedict's solution, which is a blue colour.
Place the test tube into a beaker and half-fill the beaker with hot water from a kettle.
Leave this for around 5 minutes. If sugars are present, the Benedict's solution will change colour: green means there is a small amount of sugar, yellow means there is more sugar present, and brick-red means there is a lot of sugar present.
Describe how to test if a food sample contains protein.
Grind the food sample with distilled water using a mortar and pestle, to make a paste.
Transfer the paste to a beaker and add more distilled water. Stir so the chemicals in the food dissolve in the water.
Filter the solution to remove suspended food particles.
Place 2cm³ of food solution into a test tube.
Add 2cm³ of Biuret solution, which is a blue colour. If protein is present, the Biuret solution will change from blue to a purple or lilac colour.
Describe how to test if a food sample contains lipids.
Grind the food sample with distilled water using a mortar and pestle, to make a paste.
Transfer the paste to a beaker and add more distilled water. Stir so the chemicals in the food dissolve in the water.
Place 2cm³ of food solution into a test tube.
Add a few drops of distilled water, and a few drops of ethanol.
Gently shake the solution. If lipids are present, a white, cloudy emulsion forms.
Describe how to investigate the effect of pH on the rate of reaction of amylase enzyme.
Place one drop of iodine solution into each well of a spotting tile.
Add 2cm³ of starch solution to one test tube, 2cm³ of amylase solution to another, and 2cm³ of pH 5 buffer solution to another.
Place all three test tubes in a water bath at 30°C. Leave them for 10 minutes to allow the solutions to reach the correct temperature.
Combine the three solutions into one test tube and mix with a stirring rod. Return to the water bath and start a stopwatch.
After 30 seconds, use the stirring rod to transfer one drop of solution to a well in the spotting tile which contains iodine. The iodine should turn blue-black, showing that starch is present.
Take a sample every 30 seconds and continue until the iodine remains orange. Record this time in your results.
Repeat the whole experiment several times using different pH buffers (e.g. pH 6, 7 and 8).
Describe the structure of the human heart.
The heart has four chambers: the left and right atria at the top, and the left and right ventricles at the bottom. The atria are separated from the ventricles by valves.
The vena cava brings in deoxygenated blood from the body. The blood passes from the heart to the lungs in the pulmonary artery. (In the lungs, blood collects oxygen.) Oxygenated blood passes from the lungs to the heart in the pulmonary vein. Oxygenated blood is pumped from the heart to the body in the aorta.
The left side of the heart has a thicker muscular wall than the right side.
(Note: Diagrams of the heart appear flipped, so the left aorta would be at the top-right.)
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