ACE REVISION KIT
  • Notes
    • Edexcel Science >
      • Biology >
        • B1: The Nature and Variety of Living Organisms
        • B2) Structure and Functions in Living Organisms
        • B3) Reproduction and Inheritance
        • B4) Ecology and the Environment
        • B5) Use of Biological Resources
      • Chemistry >
        • C1) Principles of Chemistry
        • C2) Inorganic Chemistry
        • B3) Physical Chemistry
        • C4) Organic Chemistry
      • Physics >
        • C1) Forces and motion
        • C2) Electricity
        • C3) Waves
        • C4) Energy resources and energy transfers
        • C5) Solids, liquids and gases
        • C6) Magnetism and electromagnetism
        • C7) Radioactivity and particles
        • C8) Astrophysics
    • CIE Mathematics
    • CIE Science >
      • Biology >
        • B0: Keywords
        • B1: Characteristics of Living Organisms
        • B2: Cells
        • B3: Biological Molecules
        • B4: Enzymes
        • B5: Plant Nutrition
        • B6: Animal Nutrition
        • B7: Transport
        • * B8 Diseases and Immunity
        • B9: Gas Exchange and Respiration
        • * B10: Excretion in Humans
        • B11: Coordination and Response
        • * B12: Drugs
        • B13: Reproduction
        • B14: Inheritance
        • B15: Organisms and Their Environment
        • * B16: Biotechnology
        • B17: Human Influences on Ecosystem
        • Biological Drawing
      • Chemistry >
        • C0: Keywords
        • C1: The Particulate Nature of Matter
        • C2: Experimental Techniques
        • C3: Atoms, Elements and Compounds
        • C4: Stoichiometry
        • C5: Electricity and Chemistry
        • * C6: Chemical energetics
        • C7: Energy Changes in Chemical Reactions
        • C8: Chemical reactions
        • C9: Acid, Bases and Salts
        • C10: The Periodic Table
        • C10: Metals
        • C11: Air and Water
        • C13: Sulfur
        • C14: Carbonates
        • C15: Organic Chemistry
      • Physics >
        • P0: Keywords
        • P1: General Physics
        • P3: Thermal Physics
        • P2: Work, Energy, Power
        • P4: Properties of Waves, Light & Sound
        • P5: Electricty and Magnetism
        • P6: Electric Circuits
        • P7: Electromagnetic Effects
        • P8: Atomic Physics
    • iPSLE Science >
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      • Systems
      • Interactions
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    • Casio fx-96SG PLUS >
      • Solve Simultaneous Equations
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cell structure

All living things are made of cells.
1) Compare the structure of a Plant Cell with an Animal Cell
Picture
All typical cells have:
  • Cell membrane: partially permeable to allow certain substances to enter and leave the cell.
  • Cytoplasm: where chemical reactions take place.
  • Nucleus: contains DNA and controls what happens inside the cell.
  • Mitochondria: where aerobic respiration happens.
  • Ribosome: makes protein and can be found floating within the cytoplasm.

Only found in Plant Cells:
  • Vacuole: contains a liquid called cell sap which keeps the cell firm.
  • Cell wall: made of tough substance called cellulose which supports the cell.
  • Chloroplasts: contain chlorophyll, which absorbs light energy for photosynthesis.

*

  • ​Cytoplasm contains ribosomes on rough endoplasmic reticulum and vesicles.
  • Almost all cells, except prokaryotes, have mitochondria and rough endoplasmic reticulum.
  • Mitochondria are responsible for producing energy from food substances through the process of aerobic respiration.
  • ​Cells with high rates of metabolism require large numbers of mitochondria to provide sufficient energy.

levels of organisation

2) Specialised cells
  • Cells that have developed certain characteristics to perform a particular function.
Cell
Function
Adaptations
Red blood cell
Transport of oxygen
No nucleus.
Has haemoglobin.
Muscle cell
Contracts to get structures closer together
Long.
Many protein fibres in cytoplasm to shorten cell when energy available.
Ciliated cell
Move and push mucus

​Tiny hair called cilia.

Root har cell
Absorb minerals and water

Elongated shape for more surface area.

Xylem vessel
Transport water and support plant
No cytoplasm so water passes freely.
No cross wall so cells connect to form tubes.
​Lignin makes it strong and waterproof.
Palisade cell
Photosynthsizes

​Many chloroplasts.

Picture
Picture
Picture
Picture
Picture
Picture

size of specimens

3) Calculate magnification and size of biological specimens using millimeters as units
\[magnification=\frac{size of image}{actual size of object}\]

movement in and out of cells

4) Describe the importance of Diffusion of gases and solutes
  • Diffusion is the movement of molecules from a region of high concentration to a region of low concentration down the concentration gradient, as a result of their random movement.
  • The energy for diffusion comes from the kinetic energy of random movement of molecules and ions.
  • Diffusion is important for gases and solutes. Without which, molecules (eg. glucose and oxygen) that are needed for life, would not be able to get to the places they are needed.
  • Substances moves into and out of the cells by diffusion through the cell membrane.

Factors affecting rate of diffusion:
  • Concentration gradient: as the concentration gradient increases, rate of diffusion increases.
  • Temperature: as temperature increases, the rate of diffusion increases. This is because the molecules gain kinetic energy and thus move faster.
  • Surface area: as the surface area increases, the rate of diffusion increases. This is because there is more space available for the substance to diffuse through.
  • Distance: a greater diffusion distance slows the rate of diffusion as molecules must travel further.
5) Describe how Osmosis affect tissues in solutions of different concentrations.
  • Osmosis is the movement of water molecules from a region of high water potential to a region of low water potential, through a partially permeable membrane.
  • Water moves in and out of cells by osmosis through the cell membrane.

​In Animals Cells:
  • Animal cells do not have a cell wall.
  • They change size and shape when put into solution of different concentration to the cell contents.
​
  • In a more dilute solution: water enter the cell by osmosis,  cell will swell and burst.
  • In a more concentrated solution, water leaves the cell by osmosis, cell will shrink, become crenated.
​In Plants Cells:
  • ​​​Plant cells have a strong cellulose cell wall that supports the cell and stop it from bursting when it gains water by osmosis.
​
  • In a more dilute solution, water enter the cell by osmosis, cytoplasm pushes against the cell wall and cell becomes turgid. 
  • In a more concentrated solution, water leaves the cell by osmosis, cytoplasm pulls away from the cell wall (plasmolysis) and the cell becomes flaccid and the plant wilts.
Picture
Picture
6) Explain the importance of Water Potential and Osmosis to Plants and Animals
  • In plants, when water moves into the cells, the vacuole gets bigger, pushing the cell membrane against the cell wall, making the cell rigid and firm. This provide support and strength for the plant, allowing the plant to stand upright with its leaves held out to catch sunlight. If plants do not receive enough water the cells cannot remain rigid and firm (turgid) and the plant wilts.
  • In animals, concentration of body fluid eg. blood plasma, must be kept within strict limits. If cells gain or lose too much water, they will not function efficiently.

* active transport

7) Discuss the importance of Active Transport as a process for movement across membranes
  • Active transport is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using the energy from respiration.
  • It is needed when organism wants to optimize the amount of nutrients it can take up.

Examples:
  • uptake of glucose by epithelial cells in the villi of the small intestine and kidney tubules.
  • uptake of ions from soil water by root hair cells in plants.
8) Explain how Protein Molecules move particles across a membrane during Active Transport
  • Carrier proteins needed to pick up specific molecules and take them through the cell membrane against the concentration gradient.
  • Substance combines with carrier protein molecule.
  • Carrier transports substances across membrane using energy from respiration.
  • Substance released into cell.
Summary

You should know:
  • the structure of an animal cell and a plant cell as seen using a microscope, and able to compare them
  • ​the functions of the different parts of animal cells and plant cells
  • ​how to calculate magnification using millimeters (mm)
  • some examples of specialised cells
  • how diffusion results from the random movement of particles


​
  • the factors that affect the rate of diffusion
  • why diffusion is important to cells and living organisms
  • the importance of water a solvent
  • about osmosis, which is a special kind of diffusion, involving water molecules
  • how osmosis affects animal cells and plant cells
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  • Notes
    • Edexcel Science >
      • Biology >
        • B1: The Nature and Variety of Living Organisms
        • B2) Structure and Functions in Living Organisms
        • B3) Reproduction and Inheritance
        • B4) Ecology and the Environment
        • B5) Use of Biological Resources
      • Chemistry >
        • C1) Principles of Chemistry
        • C2) Inorganic Chemistry
        • B3) Physical Chemistry
        • C4) Organic Chemistry
      • Physics >
        • C1) Forces and motion
        • C2) Electricity
        • C3) Waves
        • C4) Energy resources and energy transfers
        • C5) Solids, liquids and gases
        • C6) Magnetism and electromagnetism
        • C7) Radioactivity and particles
        • C8) Astrophysics
    • CIE Mathematics
    • CIE Science >
      • Biology >
        • B0: Keywords
        • B1: Characteristics of Living Organisms
        • B2: Cells
        • B3: Biological Molecules
        • B4: Enzymes
        • B5: Plant Nutrition
        • B6: Animal Nutrition
        • B7: Transport
        • * B8 Diseases and Immunity
        • B9: Gas Exchange and Respiration
        • * B10: Excretion in Humans
        • B11: Coordination and Response
        • * B12: Drugs
        • B13: Reproduction
        • B14: Inheritance
        • B15: Organisms and Their Environment
        • * B16: Biotechnology
        • B17: Human Influences on Ecosystem
        • Biological Drawing
      • Chemistry >
        • C0: Keywords
        • C1: The Particulate Nature of Matter
        • C2: Experimental Techniques
        • C3: Atoms, Elements and Compounds
        • C4: Stoichiometry
        • C5: Electricity and Chemistry
        • * C6: Chemical energetics
        • C7: Energy Changes in Chemical Reactions
        • C8: Chemical reactions
        • C9: Acid, Bases and Salts
        • C10: The Periodic Table
        • C10: Metals
        • C11: Air and Water
        • C13: Sulfur
        • C14: Carbonates
        • C15: Organic Chemistry
      • Physics >
        • P0: Keywords
        • P1: General Physics
        • P3: Thermal Physics
        • P2: Work, Energy, Power
        • P4: Properties of Waves, Light & Sound
        • P5: Electricty and Magnetism
        • P6: Electric Circuits
        • P7: Electromagnetic Effects
        • P8: Atomic Physics
    • iPSLE Science >
      • Diversity
      • Cycles
      • Systems
      • Interactions
      • Energy
      • Type of Exam Qs
  • Past Papers
  • Type of Exam Qs
  • Calculator Techniques
    • Casio fx-96SG PLUS >
      • Solve Simultaneous Equations
      • Solve Quadratic Equation
      • Calculate Statistics
  • Formulas
    • Mathematics
    • Additional Mathematics
    • Physics
  • Contact