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Edexcel GCSE Biology > Paper 1 Collection > Flashcards

Flashcards in Paper 1 Collection Deck (164)
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SB1b CP - How do you use use a microscope?

  • Put a thin sample of tissue (e.g. onion epidermis) onto a microscope slide
  • Add a few drops of a suitable stain/dye (e.g. iodine), so that the sample can be seen
  • Place a coverslip on top of the tissue and place the slide onto the microscope stage.
  • Use the objective lens with the lowest magnification, and focus on the sample.
  • Increase the magnification and refocus to see different features of the cell.
  • If you record the image you see, note down the magnification it was taken at


Option 2: You microhope you're doing it right



SB1a - What determines how good a microscope is at showing small details?

  • Magnification: How much it can zoom in
  • Resolution: The smallest distance between two distinctly different points


SB1a - What has the development of the electron microscope allowed us to do?

It has allowed us to see sub-cellular structures as they have a much more powerful resolution and magnifcation


SB1a - SI units - For Chris's benefit

[i.e definitely not becuase I dont' know it]

  •  milli = x10-3
  • micro= x10-6
  • nano=x10-9
  • pico=x10-12


SB1b - How are animal cells different to plant cells?

  • Animal cells, do not have cell walls, chloroplasts or vacuoles like plants do.
  • They only have nuclei, ribosomes, mitochondria, cytoplasm and a cell surface membrane.


SB1b - What do the sub-cellular structures in eukaryotic cells do?

  • Cell membrane: controls what enters and leaves the cell
  • Nucleus: contains DNA that controls cell activities
  • Cytoplasm: fills the cell and where reactions occur
  • Mitochondria: Where respiration takes place
  • Ribosomes: Where protein synthesis takes place

Plant only:

  • Cell wall: Protects the cell
  • Chlorplasts: Contain chlorophyll used in photosynthesis
  • Vacoule: Stores cell sap


SB1c - What are the adaptations of the following cells:

  • Egg cell
  • Sperm cell
  • Cilliated epithelial cell
  • Cells lining the small intestine

  • Egg cell: Has a haploid nucleus, with a special cell membrane to allow only one sperm cell in and many nutrients in its cytoplasm
  • Sperm cell: Has an acrosome with enzymes to penetrate the egg cell with lots of mitochondria and a tail to swim
  • Ciliated epithelial cell: Lined with cilia and packed with mitochondria this allows the cell to have a 'wavy' movement to move an egg along
  • Microvilli: The cells lining the small intestine have small folds called microvilli which increase its surface area making absroption easier


SB1c - What is the function of a gamete?

  • Gametes are sex cells used in reproduction.
  • Examples are sperm and egg cells.


SB1d - What are the functions of structures in bacteria?

  • Single loop of DNA: Contains chromosomes and genes
  • Plasmids: Contain additional genes
  • Flagellum: Used to propel the bacteria
  • Flexible cell wall: for support
  • Cytoplasm: Containing prokaryotic ribosomes


SB1d - What are the differences between eukaryotic and prokaryotic cells?

Eukaryotic cells have a nucleus, prokaryotic cells do not



Jefferson has beliefs; burr has none


SB1e - What are enzymes and what are they made up of made up of?

  • Enzymes are biological catalysts that speed up reactions.
  • They break down protiens/substances called substrates.
  • Enzymes are made up of amino acids and they are proteins.
  • They are needed to speed up reactions we cannot live without


SB1g - How do enzymes work?

  • Each type of enzyme is in a shape that is specific to their substrate.
  • They can be re-used as long as they don't become denatured
  • The idea that an enzyme bonds with a specific substrate is the lock-and-key mechanism


SB1e - What is a polymer?

  • A polymer is a chain of single substances called monomers.
  • The formation of a polymer is called synthesis.
  • Enzymes often break down polymers into monomers


SB1e - What are the three main nutrient based enzymes? Where are they found and what do they do?

  • Amylase: Found in saliva. breaks down starch into Sugar
  • Protease: Found in the stomach, breaks down proteins into amino acids
  • Lipase: Found in the stomach and pancreas, breaks down lipids into fatty acids and glycerol


SB1f CP - What tests are used to identify main components in food?

  • Starch: Iodine will go from yellow to blue-black
  • Proteins: Biruet's solution will go from blue to purple
  • Lipids: Add ethanol and shake and a white emulsion-fatty layer - should form is it is present
  • Sugars: Benedict's solution while heating which will turn anywhere from green to yellow to red, indicating how much sugar is present This is a semi-quantitative test. It mostly gives non-measurable values


SB1f- How can we use a calorimeter?

  • Burn a known mass of the food under a boiling tube filled with a known volume of water.
  • Calculate the change in temperature of the water.


SB1g - What is the function of the active site of an enzyme?

The active site is unique to an enzyme so each enzyme can only work on specific substrates and is where the substrate must be for anything to take place


SB1g- How are enzymes denatured?

  • Changes in pH and temperature can affect the shape of an enzymes active site.
  • When temperatures are too high/ pH is too far from optimum, enzymes can no longer accept substrates
  • When the active site can no longer accept any substrates, it is said to have become denatured.


SB1h - How is enzyme activity affected by temperature, pH and substrate concentration?

  • Temperature: As temperature increases, molecules move faster and so more successful collisions occur between enzymes and substrates so the rate of reaction increases. Until the temperature causes the enzyme to change shape causing it to denature
  • pH: An enzyme has an optimum pH where it works best. The furhter away from this, it will get slower till it becomes denatured
  • Substrate concentration: Increasing this will increase the rate of reaction as there are more collisions occurring. This is until a point when all enzymes are full up and rate of reaction will no longer increase


SB1i - What is the difference between diffusion and osmosis?

  • Diffusion is when particles move from a high concentration to a low concentration.
  • In osmosis this is the same principal except across a semi permeable membrane where a solvent moves from and area of high concentration to an area of low concentration


SB1i - How do cells transport substances against a concentration gradient?

  • Using active transport which is carried out by transporter proteins on membranes which require energy to run.
  • They take in the molecule and then change shape to move it through the membrane.
  • This works against the concentration gradient.


SB1i CP - Describe the method you would use to investigate osmosis through potatoes

  • Cut discs of raw potato, blot them dry, and measure their mass.
  • Put each disc in a sugar (or salt) solution of different concentrations
  • After 30 minutes, measure the mass of each disc again.
  • Subtract the initial mass from the final mass of each disc.
  • Divide this number by the initial mass and then multiply by 100 to give a percentage change in mass.
  • The highest change in mass means there was a greatest difference between water concentration as osmosis works with the concentration gradient This can work with any semi-permeable membrane


SB2a - When a regular human body cell divides, what is this process called, and how does it occur?

Mitosis - (Imaginary pickpockets meet around the city)

  • Interphase
    • Copies of the chromosomes are formed in the nucleus
  • Prophase
    • The nucleus starts to break up and spindle fibres appear.
  • Metaphase
    • The chromosomes are lined up on the spindle fibre across the middle of the cell
  • Anaphase
    • The chromosome copies are separated and moved to either side of the cell
  • Telophase
    • A membrane forms around each set of chromosomes to from a nuclei
  • Cytokeniesis
    • Cell surface membrane forms separating the two cells (In plants, a cell wall is also formed)
  • The cycle repeats


SB2a - What are the products of mitosis called?

Daughter Cells


SB2a - What type of organisms do not require mitosis to occur?

Unicellular organisms


SB2a - How many types of chromosones are in a human cell and what is it called when these are alone or paired up?

  • 23 types of chromosomes.
  • When they are paired up to have 46 chromosomes this is a diploid cell and a haploid cell only has 23 chromosomes.
  • Gametes are haploid cells while all other cells in a human are diploid.


SB2a - How are tumors formed?

  • When cells mutate, they can become cancer cells.
  • This means that they will divide even when they don't require to divide.


SB2a - Why does asexual reproduction require mitosis?

  • As asexual reproduction only needs one parent, the offspring will have the same DNA as the parent.
  • As the offspring are clones and their chromosomes are identical, their cells are formed by mitosis.


SB2b - Define growth.

The increase in size as a result of an increase in size of or numbers (due to cell division) of cells.


SB2b - How is the growth of a baby monitored and how does this work?

Using a percentile growth curve:

  • This graph has many lines showing you how a babies conditions compare to the average.
  • The healthiest position would be at 50% as half of the population is above or below you.
  • Being above 98% or below 2% is reason for concern as only 2% of the population is above or below you.