Cells and Movement across Membranes

• Name the shape and structures in the animal cells

  Round, Cytoplasm, Cell membrane, Nucleus, Mitochondria
• Name the shape and structure of plant cells

  Cytoplasm, Cell membrane, Nucleus, Mitochondria, Cell wall, Vacuole, Chloroplasts
• Function of cytoplasm

  Site of most cellular reactions
• Function of Nucleus

  Stores genetic information, controls cellular activities
• Function of cell membrane

  Controls the entry and exit of materials into and out of the cell
• Function of mitochondria

  Site of aerobic respiration in which energy is released
• Function of the cell wall

  Made from cellulose, provides strength, prevents the cell bursting when water enters by osmosis.
• Function of vacuole

  Contains cell sap (a solution of salts, sugars and organic acids), supports the cell, maintaining its turgidity.
• Function of chloroplasts

  Site of photosynthesis
• What is magnification

  Number of times bigger an image appears compared to the size of the specimen
• What is resolution

  Smallest distance between two objects that can be distinguished
• What is Cell differentiation

  Produces specialised cells with specific functions e.g. red blood cells, sperm cells.
• Name the definition and example of a tissue cell

  A group of similar cells which work together to perform a specific function, muscle and xylem tissue
• Name the definition and example of an organ

  A group of tissues that work together to perform a specific function, brain and heart
• Name the definition and example of an organ system

  A collection of organs that work together to perform a specific function, digestive and nervous system
• Name the definition and example of an organism

  An animal or plant that is able to function independently, human and sunflower
• What is diffusion

  Diffusion is the net movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient, it does not require energy
• What factors affect rate of diffusion

  Temperature - the higher the temperature, the more kinetic energy possessed by molecules and the faster the rate of diffusion

  Concentration gradient - the steeper the concentration gradient, the faster the rate of diffusion
• What is osmosis

  Osmosis is the net movement of water molecules from an area of high water concentration to an area of low water concentration across a partially permeable membrane
• What is active transport

  Active transport is the movement of molecules across a cell membrane from an area of low concentration to an area of high concentration, against the concentration gradient, using energy.
• What do enzymes do

  Enzymes increase the rate of a reaction, they are biological catalysts.
• What are enzymes made up of

  They are proteins that are made out of amino acids. The order of amino acids determines how the amino acid chain folds and its structure. Its function is determined by the shape of the enzyme.
• How does an active site work

  Substrate collides with the active site of an enzyme

  Substrate binds, enzyme-substrate complex forms

  Substrate converted to products

  Products are released from the active site. The active site is now free to bind to another substrate
• How does temperature effect enzymes controlled reactions

  ● Temperature increases

  ● Molecules have more KE

  ● Movement of molecules increases

  ● Probability of a successful collision increases

  ● More enzyme-substrate complexes form

  ● Rate of reaction increases

  ● Temperature increases above the optimum

  ● Increased vibrations break bonds in enzyme’s structure

  ● Active site changes shape, enzyme is denatured

  ● No more enzyme-substrate complexes can form

  ● Rate of reaction decreases
• how does pH effect enzymes controlled reactions

  ●Enzymes have an optimum pH

  ●pH shifts from the optimum

  ● Bonds in the enzyme’s structure are altered

  ● Active site changes shape, enzyme is denatured

  ● Rate of reaction decreases
• If a piece of potato is placed into a salt solution with a lower water concentration than the potato cell contents, in which direction will the net movement of water be?

  Out of potato
• If an animal cell, eg a red blood cell, is placed in a solution of very high water concentration such as pure water, what will happen to the cell?


  will take up so much water by osmosis that its cell membrane will no longer be able to contain the contents and it will burst.
• Which substances are needed for active transport to occur?

  Glucose and oxygen
• What happens to an animal cell if its placed in a more dilute solution

  Higher concentration of water surrounding solution

  Water enters cells by osmosis

  Pressure inside cells and cell bursts
• What happens to an plant cell if its placed in a more dilute solution

  High water concentration of water in surrounding solution

  Water enter cells by osmosis

  Cell wall resists increase in pressure and cell turgids
• Describe what happens to an animal cells when placed in a more concentrated solution

  Lower concentration of water surrounding solution

  Water leaves cell by osmosis

  Pressure inside cell decreases and cell shrinks
• Describe what happens to an plant cells when placed in a more concentrated solution

  Lower concentration of water in surrounding solution

  Water leaves cell by osmosis

  Pressure inside cell decreases and cytoplasm shrinks

  Cytoplasm pulls away from cell wall
• Describe what happens to a cell when placed if its placed into a solution of equal water concentration

  No net movement of water molecules into or out of cells
• Describe how DNA controls the production of a specific enzyme

  DNA codes for a specific sequence of amino acids

  Order of amino acids determine how enzyme folds

  Shape of enzyme determines its function
• Variables you would change during an enzyme controlled reaction

  Temperature - put test tubes into different temperature water baths

  effect of pH - use range of different pH buffers