Module 1 - cells as the basis of life

Question 1

Fluid Mosaic Model of the cell membrane

Answer 1

The cell membrane controls the exchange of material between the internal and external environments of the cell. It is permeable, allowing only certain molecules in and out of the cell. The model describes the cell membrane as a double layer of lipids (lipid bilayer) and ability to flow and change shape. Both proteins and phospholipids help control exchange of material.

Question 2

Lipid component - Phospholipids

Answer 2

Each phospholipid in these layers is represented as a head and tail. The head (hydrophilic) ables to absorb water or dissolve. The fatty acid tails known as hydrophobic avoid water. As they form a bilayer, cholesterol is interpreted.

Question 3

Membrane proteins

Answer 3

These proteins are scattered and suspended in the bilayer. they form channels that allow materials to cross through the membrane. These proteins enable interaction and communication and exchange of substances.

Question 4

Movement of materials in and out of cells

Answer 4

Substances required by cells for their function need to move into their internal environment of cells and waste substances. Substances needed by cells are gases, nutrients and water. The cell membrane is in direct contact with cytoplasm making it selectively permeable and can control what passes through it.

Question 5

Permeability of substances

Answer 5

Size, electrical charge and lipid solubility. Small molecules can move across membranes quickly. Electrically charged molecules are not very soluble and have low permeability, where neutral have high.

Question 6

Diffusion

Answer 6

Movement of materials into/out of cells takes place either passively or actively. Diffusion is the movement of any molecules from a region of high concentration to low concentration, until equilibrium is reached

Question 7

Diffusion across cell membrane

Answer 7

Small uncharged particles move easily through the cell membrane by diffusion. These particles pass through the phospholipid molecules from a region of high concentration to a region of low.

Question 8

Osmosis

Answer 8

A solution is formed when a solute dissolves in solvent. A concentrated solution has high concentration of solute and low concentration of water. Osmosis is by which water moves from a region of high concentration of water to a region of low concentration of water. (requiring no energy)

Question 9

Active transport

Answer 9

Movement of molecules from low concentration to high concentration and requires energy. This movement goes against the concentration gradient and involves movement across a cell membrane. it requires a carrier protein that spans the membrane to actively move chemicals.

Question 10

Endocytosis and Exocytosis

Answer 10

Endocytosis is when a large particle has been moved into a cell and the cell membrane changes it shape by engulfing. Where exocytosis is specialised animal and plant cells that have a variety of substances and these substances are transported externally.

Question 11

Surface area to volume

Answer 11

It is important as a cell needs to have enough surface to supply its volume with requirements and move wastes. Has a large impact on the movement of substances. A smaller surface area to volume ratio allows faster movement.

Question 12

Difference between smaller and larger surface to area volume cells

Answer 12

A larger sell has a smaller ratio and has more efficiency and obtains its nutrients and removes its wastes which increases the size.

Question 13

Prokaryotic cells

Answer 13

Exsist as single cells, have no membrane bound nucleus or organelles. Bacterial and Archea contain these cells

Question 14

Eukaryotic cells

Answer 14

Eukaryotic cells have a membrane bound nucleus and membrane bound organelles.

Question 15

Enzymes

Answer 15

Protein molecules that control all metabolic reactions in the cell. They act as catalysts and speed up reactions by lowering activation energy.

Question 16

Factors that effect enzymes

Answer 16

Affected by substrate concentration. As it increases the activity of enzymes increases until all are saturated. As well as an optimum pH which makes it function effectively.

Question 17

Lock and key model vs Induced fit

Answer 17

Lock and key model is that the activity site is rigid and the small substrate molecules are shaped and fits exactly into the active site. where as induces fit model is based on that proteins aren’t rigid and the active site of an enzyme alters it shape slightly.

Question 18

Light vs electron microscopes

Answer 18

Light microscopes pass light rays through thin specimens that are magnified by glass lenses where as electron uses electron beams and electromagnets instead.