Cells and Cell Structure

Question 1

Cell Theory

Answer 1

• all organisms are composed of cells
• all cells come from pre-existing cells
• the cell is the smallest living organisational unit

Question 2

Why are they requirements for life

Answer 2

• are the source of energy –> growth, maintenance and repair
• the amount of energy depends on cell type, growth stage and activity
• need nutrients (organic compounds/materials) –> must be obtained from the environment
• plants use inorganic materials to manufacture organic materials –> photosynthesis
• all cells use organic materials to produce through cellular respiration

Question 3

Energy in Cells

Answer 3

Carbohydrates –> monosaccharides, disaccharides, polysaccharides –> sugars

Lipids –> fatty acids, glycerol

Proteins –> amino acids

Question 4

Wastes emitted from cells

Answer 4

Wastes are emitted when cells use energy and these can be harmful or useless:

• CO2
• oxygen
• urea
• water
• metabolic heat –> Cellular Respiration

Question 5

What is the Cell Membrane

Answer 5

• the phospholipid bilayer and embedded proteins which sperate the intracellular from the extracellular environment
• thin boundary of the cell - 5-10nm thick

Question 6

Function of the CM

Answer 6

• separates intracellular and extracellular environments
• bouncer of the cell: controls transport in and out (selectively permeable)
• allows for specialised internal environment and is involved in cell-to-cell communication

Question 7

Phospholipids - Structure

Answer 7

• stable yet flexible because of the amphiphilic nature of phospholipids

1 phosphate head –> polar, hydrophilic, charged –> always face watery environments
2 fatty acid tails –> non-polar, hydrophobic, uncharged –> always avoid watery environments

Question 8

Proteins

Answer 8

• long chains of amino acids

Integral Proteins - permanent
Peripheral - temporary
Transmembrane - spanning the membrane
Glycoprotein - carbohydrate attached

Question 9

Protein Functions

Answer 9

Transport Channels - control what enters and exists the cell –> makes membrane selectively permeable

Catalysis - speeding up chemical reaction with the help of enzymes

Communication - receives signals or recognises cells and molecules

Adhesion - sticks to other cells, the extracellular matrix or the cytoskeleton

Question 10

Carbohydrates

Answer 10

• chains of carbohydrates attach to either phospholipids or proteins
  Two types:
• Glycolipid - phospholipid
• Glycoprotein - protein

Question 11

Carbohydrate Functions

Answer 11

Cell-to-Cell communication

Signaling

Recognition of self or non-self (foreign) molecules

Adhesion

Question 12

Cholesterol

Answer 12

• lipid steroid that embeds itself between the fatty acid hydrophobic tails

Main function is to regulate fluidity of the membrane:

• at higher temperatures, the cholesterol keeps phospholipids bound together
• at lower temperatures, cholesterol disrupts the fatty acid tails, stopping phospholipids from becoming a solid boundary

Question 13

Fluid-Mosaic Model

Answer 13

Explains that;

• molecules that make up the membrane are not held static in one place (fluid)
• many different types of molecules are embedded in the plasma membrane (mosaic)