week 2: cell interactions and communication

Question 1

define passive transport

Answer 1

movement of molecules accross cell membrane down a concentraiton gradient without need for energy
- simple (no protien)
- faciliated (requires transport protien for transport of molecules from a hgiher to lower concentration (down the gradient))

Question 2

active transport

Answer 2

the movement of molecules gainst a concentration gradient (goes from lower to higher), requiring ATP and carrier protein

Question 3

considerations for cell transport

Answer 3

• rate needed for cell to be transported at
• size of molecule

Question 4

descirbe the structural components of the cell membrane in Passive and Active Transport

Answer 4

Phospholipid bilayer:
- has selective permeability, is fluid/dynamic, contains channel/carrier ptotiens, receptor protiens that can elecit a response to open ion channels

Channel Proteins:
- from channels/pores in the bilayer
- used in facilitated diffusion
- are selective
- have a concentraiton gradient
- rate of transport through channels is dependent on CG, number of channels, properties of channel
- many channels have gating mechanisms
- can maintatin osmotic balance and water transport
- helps the transport of nutrients and ions
- used in cell signalling. eg. calcium channels for mmuscle contraction

Carrier Proteins:
- also used in faciliated diffusion
- active transport for movement against concentration gradient
- ion transport (eg. calcium ion pump)
- nutrient uptake

Question 5

channel proteins: descrive pores and gated channels

Answer 5

it is what moelecule are tranported through

pores
- less selective and more open, transport depends on size, charge etc

gated channels
- more selective, gate function depends on movement of ion,
- negative structures within channel attract postivley charged ions to open gate

Question 6

carrier protiens: describe an Ion pump

Answer 6

• are membrane proteins that use energy to move ion across via active transport
• ions have charge: pumps result in an electrochemical gradient between extrinsic and intrinsic cell, creating a large voltage across cell membrane underpinning nerve impules and muscle contrations (membrane potential)

Question 7

name an ion pump

Answer 7

sodium potassium pump
- makes sodium high in extracellular space
- makes potassium high in intracellular space
- actively pumps three sodium ions (Na+) out of the cell and two potassium ions (K+) into the cell against their respective concentration gradients

purpose:
- gives the intracellular space a - ve voltage with respect to extracellular space
- leading to membrane potential
- maintains the elctrochemical balance
- indirectly affects osmotic balance
- secondary active transport: by maintaing higher sodium balance outside of the cell, it provides the potential energy for other substances, such as glucose, amino acids, and ions, across the cell membrane.

Question 8

name different substances that use:
- passive..
- facilitated..
- and active diffusion

Answer 8

passive:
- oxygen, carbon dioxide
facilitated:
- glucose, carbohydrates, amino acids, nucleosides, and ions
active:
- amino acids, organic acids and inorganic ions such as sulphate, phosphate and potassium

Question 9

describe transmembrane potential

Answer 9

also known as membrane potential/voltage
- it is the resting difference in electrical charge between the inter and exterior of a cell

Question 10

how does transmembrane potential tie into polarity and AP

Answer 10

transmembrane potential establishes polarity in the cell: the inside of the cell is more negatively charged
- this is a negative resting polarity

AP:rapid change in the transmembrane potential.
- depolarisation: the transmembrane potential becomes more positive from a stimmulus
- repolarisation: membrane potential returns to original charge
- hyperpolarisation: refractory period, becomes more negative

the polarity leads to initiation of action potentials, for electrical signaling in neurons and muscle cells.