Cellular Membranes

• What is the structure of the membrane and what does it allow?

  Individual molecules can move freely throughout the membrane (it is a fluid structure).
• What is the structure of proteins in the bilayer?

  Proteins embedded in the bilayer resemble a mosaic.
• What substances must pass through the membrane.

  Substances such as nutrients, oxygen, wastes, etc need to pass through the cell membrane.
• The lipid bilayer is..? and allows..?

  ...is permeable to small and lipid-soluble substances, such as oxygen, some water.
• What is the lipid bilayer impermeable to?

  Lipid bilayer is impermeable to water-soluble substances, ions and larger molecules.
• Define Passive Transport?

  Passive Transport doesn't use cellular energy, and relies on the kinetic energy.
• Define diffusion?

  movement from an area of high to low concentration till equilibrium is reached.
• What is facilitated diffusion?

  Facilitated Diffusion - passive transport that uses protein channels or carrier proteins.
• How do small and lipid soluble molecules cross the membrane?

  Small and lipid soluble molecules cross the membrane in the way of diffusion.
• What is Osmosis?

  diffusion of water across a semi-permeable membrane.
• When does osmosis occur?

  Osmosis occurs when the membrane is impermeable to a specific solute.
• What happens when cells are in water?

  When cells are placed in fresh water, water enters the cell.
• What happens to plant cells as water enters?

  as water enters, the vacuole enlarges and puts turgor pressure on the cell wall.
• What happens to animal cells as water enters?

  as water enters, the cytoplasm swells, leading to the cell membrane rupturing.
• What are the three types of active transport?

  The three types of active transport are protein pumps, endocytosis, and exocytosis.
• What is endocytosis?

  when material is engulfed in bulk, by the membrane.
• What is phagocytosis and pinocytosis?

  Phagocytosis is cell eating and pinocytosis is cell drinking, both forms of endocytosis.
• What is exocytosis?

  to release the large molecules out of the cell by merging and release its contents.
• What do glycoproteins do?

  Cell recognition and adhesion.
• What do proteins do?

  Embedded in the membrane, they allow for the transport of substances.
• Define hypotonic?

  A solution with a lower solute concentration compared to water.
• Define hypertonic?

  A solution with a higher concentration of solutes compared to water.
• Define isotonic?

  Two solutions with equal concentrations of both water and solute.
• Why are cells so small?

  Efficiency in exchanging material across the wall as there will be a larger surface area to volume ratio.
• Is a smaller cell or larger cell more ideal for diffusion?

  Smaller cell as there will be faster diffusion and greater relative particle movement.
• What is active transport?

  Transport using cellular energy.
• How have larger animals adapted to become efficient in exchange?

  Specialised organs that increase SA and having a circulatory system to move material between the surface and core of the organism.
• How does nitrogenous waste come to be?

  Excess proteins are deaminated into ammonia a highly toxic by-product.
• How does water, waste come to be?

  By-product of cellular respiration and condensation reactions?
• What are the three forms of cellular waste that require removals?

  Nitrogenous waste, water, and excess ions.
• What is metabolic heat?

  Is generated as a by-product from metabolic reactions, removed by complex internal systems and directly to the environment.
• What 3 features do all cells share?

  Cell membrane, cytoplasm, and DNA.
• What do protein channels do?

  Facilitate transport.
• What does cholesterol do?

  Found in the bilayer, regulates fluidity.