Lecture 3- cell structure and function

Question 1

Cell boundaries

Answer 1

Eukaryotic cells have internal boundaries
Allows formation of semi fluid cytoplasm
Formation of specialised microenvironments
Segregation of harmful activities

Question 2

Membrane structure

Answer 2

Sheet-like
Composed of lipids, proteins and carbohydrates
Thin (5-8nm) lipid bilayer
Hydrophilic head
Hydrophobic tail
Lipid bilayer spontaneously forms in aqueous solution

Question 3

Amphipathic

Answer 3

Hydrophobic and hydrophilic regions

Question 4

Fluid mosaic model

Answer 4

Protein movement restricted
Flippase (scrambles) enzymes can switch between layers
Integral proteins pass through bilayer

Question 5

Fluid mosaic model- semi-permeable barrier

Answer 5

Allows movement of small non-polar molecules
Resists movement of ions and larger polar molecules
Rapid diffusion of water through aquaporin channels
Allows maintenance of interior and compartmentalisation

Question 6

Fluid mosaic model- transporting solutes

Answer 6

Integral proteins provide passage

Question 7

Fluid mosaic model- flexibility

Answer 7

For cell movement/division

Question 8

Fluid mosaic model- communication

Answer 8

Response to external signals via receptors in membranes
Intercellular communication via surface carbohydrates

Question 9

Fluid mosaic model-Small hydrophobic molecules

Answer 9

Pass through membrane
eg.Oxygen
Carbon dioxide
Nitrogen
Benzene

Question 10

Fluid mosaic model-Small uncharged polar molecules

Answer 10

Pass through membrane
eg.Water
Glycerol
Ethanol

Question 11

Fluid mosaic model-Larger uncharged polar molecules

Answer 11

Don’t pass through membrane
eg. Amino acids
Glucose
Nucleotides

Question 12

Fluid mosaic model-Ions

Answer 12

Don’t pass through membrane

Question 13

How do cells adjust membrane fluidity?

Answer 13

Altering lipid composition

Question 14

Cholesterol and cell membranes

Answer 14

Cholesterol stabilises cell membrane and increases melting point
Found within the membrane

Question 15

Cell walls- bacteria

Answer 15

Peptidoglycan cell wall for rigidity

Question 16

Cell walls- fungi

Answer 16

Chitin cell wall for strength

Question 17

Cell walls- plants

Answer 17

Cellulose cell wall

Question 18

Cell cortex

Answer 18

Protein network under plasma membrane

Question 19

Cell cortex in red blood cells

Answer 19

Spectrin meshwork attached to plasma membrane by anchor proteins
Provides support, cell shape and elasticity

Question 20

Extracelular matrix

Answer 20

Some cells have glycocalyx exterior coating
Some have a more complex matrix
Collagen fibres protect cell surface from mechanical and chemical damage
provides cell identity