The 1st Unicram (2)

Question 1

What is polarity?

Answer 1

The separation of electrical charge within a molecule (Forms electric dipole, negative and positive charge)

Dipoles formed due to difference in electronegativity between bonded atoms

Question 2

What properties does polarity lead to?

Answer 2

Increased boiling point

Increased solubility within other polar solvents

Increase surface tension

Question 3

What are lipids?

Answer 3

Broad class of macromolecules, hydrocarbons

Hydrophobic

Question 4

Functions of Lipids?

Answer 4

Separation of two polar environments via hydrophobic bilayer

Energy storage

Signalling through hormones

Vitamins

Question 5

What are triglycerides made of?

Answer 5

3 Long chain fatty acid

Glycerol sugar

Question 6

What are the different states of fatty acids?

Answer 6

Saturated (C-C)
Unsaturated (C=C)
Polyunsaturated (2x C=C)

(ALWAYS CONTAINS COOH)

Question 7

What does altering the length of a fatty acid chain change?

Answer 7

Alters membrane fluidity

Question 8

What are phospholipids made of?

Answer 8

Two fatty acid chains + Phosphate group

Question 9

Why are phospholipids Amphipathic?

Answer 9

Have both a hydrophobic and hydrophilic section

Allows formation of a phospholipid Bi-layer

Question 10

What is a spontaneous grouping of phospholipids called?

Answer 10

Micelles, polar heads face outwards and hydrogen bond to the surrounding water

non polar tails face inwards and make a hydrophobic central core

Question 11

Phospholipid uses?

Answer 11

Make a semi-permeable barrier, separates cells from external environment and organelles from cytoplasm

Allows production of specific and regulated cell environments

Question 12

Steroids properties?

Answer 12

Highly hydrophobic, insoluble in water

Question 13

Uses of sterioids within organisms

Answer 13

Precursor to different steroid hormones

Precursor to vitamin D

Aids in stability and fluidity of animal cell membranes

Question 14

function of cholesterol?

Answer 14

Alters the membrane fluidity, changes these properties of the plasma membrane:

Thickness
Water penetration
Curvature
Endo/exocytosis

Question 15

Fluid Mosaic meaning

Answer 15

Fluid: Free movement of molecules

Mosaic: Plasma membrane is made of several different components

Question 16

Physical conditions that affect the fluidity of the membrane?

Answer 16

Temperature:
Increased K.E allows for increased rearrangement of phospholipids

Phospholipid composition:
Shorter fatty acid chains have less points of movement, less intermolecular forces so less energy needed to freely move. If unsaturated fatty-acid, less packing of phospholipids so more mobility

Cholesterol:
Increases melting point of phospholipid bilayer
Prevents clustering of phospholipids in cold temps

Question 17

FRAP method?

Answer 17

Label plasma membrane with fluorescent chromophore

View small region of cell surface through florescent microscope

Destroy fluorescent molecules with intense light pulse

Monitor region, undamaged chromophores will replace damaged ones.

Question 18

What is the membrane composed of?

Answer 18

*Phospholipid:
- Main molecule
- Forms the cell membrane

*Carbohydrates:
- Attached to proteins which are on outside of membrane layers
- Aids in cell-to-cell recognition

*Cholesterol:
- Embedded between phospholipids of the bilayer
- Retains plasma membrane fluidity

*Proteins:
- Embedded within/surface/across membrane
- Relay signals between internal/external environments
- Transport proteins
- Aid in digestion

Question 19

Use of plasma membrane?

Answer 19

Regulates cellular volume, maintains pH

Concentrates metabolic building blocks, removing toxic substances

Generates and maintains ionic gradients

Question 20

What molecules can move across the membrane?

Answer 20

Gases
Small polar molecules
Small hydrophobic molecules
Charged ions
Large polar molecules

Question 21

Channel proteins?

Answer 21

Channel proteins allow for facilitated diffusion of molecules which cant diffuse across the membrane or ones with slow diffusion rates

Can be opened and closed

Question 22

Carrier proteins?

Answer 22

Bind to specific molecules, undergoes a conformational change and releases on the other side of the membrane

Polar molecules get transported via carrier proteins

Question 23

Facilitated diffusion

Answer 23

Takes place through proteins embedded in plasma membrane

Proteins form water-filled channel where ion can pass down concentration gradient

channels can be opened or closed

Question 24

Ligand gated channels?

Answer 24

Opened/closed by a small signalling molecule or ligand which doesn’t pass through membrane

Acetylcholine opens Na+ channels triggering depolarisation

Gamma Amino Butyric Acid binding at certain synapses in central nervous system admits Cl- ions into the cell and causes hyperpolarisation

Question 25

Internal Ligands

Answer 25

Bind on site to channel protein exposed to cytosol

Secondary messengers regulate channels that initiate impulses in neurons responding to odours and light

ATP needed to open the channel that allows Cl- and bicarbonate ions out of the cell

Question 26

Mechanically gated channels

Answer 26

Sound waves bend cilia on the hair cells of the Organ of Corti and open up K+ channels leading to creation of nerve impulses

mechanical deformation of the cells of stretch receptors open the ion channels leading to nerve impulse creation

Question 27

Active vs Passive transport proteins

Answer 27

• Passive Transport (Facilitated diffusion) occurs without the need for a change in free energy (GLUT)
  Can occur spontaneously with binding of transport molecule
• Active Transport needs a change in free energy to allow movement
  (NA+/K+ ion pumps need hydrolysis of ATP to cause conformational shape change)
  Can use electrochemical gradient to aid transport of molecule

Question 28

Exo/Endocytosis?

Answer 28

Active forms of transportation, a vesicle is used to engulf or export macromolecules through plasma membrane

In -> Exocytosis
Out -> Endocytosis

Question 29

Na+/K+ ion pump key functions?

Answer 29

Formation of resting charge potential across the membrane

Na+ ions can be used as a secondary active transporter molecule to aid in importation of glucose, amino acids, nutrients

Maintains cellular osmolarity