SAC 1

Question 1

Scientific Method

Answer 1

• Hypothesis:
  o A cause (independent variable) + effect (dependent variable)
  o Use: “That/if ‘x’ is increased/decreased, then ‘y’ will happen/increase/decrease”
  o E.g. That light exposure will increase the rate of O2 bubbles produced (indicating increased rate of photosynthesis)
• Aim:
  o Use: “To investigate the effect of…” OR “To investigate whether…”
• Control + experimental group: one without IV, one with. Needed for comparison to measure effect of IV
• Sample size: 20-100 individuals in each group
• Controlled variables:
  o Use: at least 2 factors that must be kept the same that are specific and different to those used in the questions
  o E.g. same species, temperature, amount of water, same age, etc.
• State DV
• Expected results:
  o Can include diagrams
  o Use: “Hypothesis would be supported/rejected if…”
• Experiments should be REPEATED to increase amount of data + ­ validity of conclusions
• In questions do: IV, SS, CV, DV, Repeat experiment

Question 2

Plasma Membrane

Answer 2

• Present: all cells
• Function: controls the entry of dissolved substances into and out of the cell
• Structure:
  o Pliable
  o Phospholipid bilayer with protruding proteins + glycoproteins
  § Some of these proteins form channels that allow for passive and active transport (fluid mosaic model)
  § Is a bilayer because the hydrophobic lipid must associate with a lipid, and can’t associate with water
  § The phospholipids are not bound (not a polymer)
  o Semipermeable/partially permeable/differentially or selectively permeable
  o Has cholesterol throughout it, which adds flexibility

Question 3

Diffusion

Answer 3

• Definition: The passive net movement of a substance from and area of high concentration to an area of low concentration
• Substances: small hydrophobic molecules (e.g. O2, CO2, steroids) + small uncharged hydrophilic molecules (alcohol, urea)

Question 4

Hydrophilic

Answer 4

• Polar = water soluble = lipid insoluble = associates with water

Question 5

Hydrophobic

Answer 5

• Non-polar = water insoluble = lipid soluble = associates with lipids
• Can cross plasma membrane easily

Question 6

Facilitated Diffusion

Answer 6

• Definition: The passive net movement of a substance from and area of high concentration to an area of low concentration. Occurs only through specific protein channels embedded in the membrane
• Substances: large, uncharged, hydrophilic molecules (e.g. glucose) + ions (e.g. salts)
• Involves: specific protein channels

Question 7

Osmosis

Answer 7

• Definition: When water moves through a semipermeable membrane from a low solute solution (high concentration of water) to a high solute solution (low concentration of water). No energy is required.
• Other terms relating to osmosis:
• Substances: water
• Involves: phospholipid bilayer

Question 8

Isotonic

Answer 8

-two solutions of the same concentration of solutes t/f no overall/net movement of water (water will still move, but at an even rate)

Question 9

HypOtonic

Answer 9

• lower solute solution t/f has a high concentration of water molecules. The cell would burst if it was an animal cell, or become turgid if it was a plant cell (vacuole is full) as they have cell walls preventing the bursting
• lOwer, Opens

Question 10

HypErtonic

Answer 10

• o Hypertonic: higher solute solution t/f lower concentration of water molecules. An animal cell would shrink or crenate. A plant cell would be plasmolysed or flaccid.
• Excited, Eenie meenie

Question 11

Active Transport

Answer 11

• Definition: The net movement of substances from an area of low concentration to an area of high concentration. Requires energy in the form of ATP and specific protein channels
• Substances: large, uncharged, hydrophilic molecules (e.g. glucose) + ions (e.g. salts)
• Involves: specific protein channels

Question 12

Bulk Transport

Answer 12

• Definition: For the movement of very large materials in bulk
• Endocytosis:
  o Bulk transport of material into a cell
  § Phagocytosis: solid material
  § Pinocytosis: liquid material
  o Part of plasma membrane engulfs particles, forming a vesicle, which is then carried into cell
• Exocytosis:
  o Bulk transport of material out of a cell
  o Vesicle within cytosol fuses with the plasma membrane, and vesicle contents are released out of the cell
• Substances: protein hormones being released from a cell

Question 13

Biomacromolecules

Answer 13

• nucleic acid/polynucleotides: nucleotides (monomer)
• LARGE carbohydrates/polysaccharides: monosaccharides (monomer)
• proteins/polypeptides: amino acids (monomer)
• lipids: gylcerol + fatty acids (sub-unit)