Plasma Membrane and Organelles Flashcards
what must a cell do
- Manufacture cellular materials
- Obtain raw material
- Remove waste
- Generate the required energy
What must they (cells) do
- Many different processes
- Require different conditions
- Need separate compartments; Organelles
describe what Organelles do
- provide special conditions for specific processes
- keep incompatible processes apart
- allow specific substances to be concentrated
- form concentrations gradients
- package substances for transport or export
what organelles do plants and animals cells have in common and not
in common:
- nucleus
- plasma membrane
- Golgi apparatus
- mitochondria
- ER (endoplasmic reticular)
not in common:
- Lysosome
- chloroplasts
- central vacuole
- cell wall
what are cells bounded by
describe it
- bounded by the plasma membrane
- is a semi-permeable barrier
- controls movement of substances in and out of the cell
- this interaction with the environment limits the maximum size of the cell
- a small cell has a greater surface area to volume ratio than a larger cell
describe the phospholipid bilayer
- is made up of lipids that have a hydrophilic head and a hydrophobic tail
- the head likes water, the tails dont
- the temperature will affect how fluid the phospholipid bilayer
how does different temperatures affect the phospholipid bilayer
- the higher the temperature the more connected energy they have so they move around resulting in unsaturated tails that prevent packing
- low temperatures mean there’s less movement so the saturated tails pack together
how does cholesterol help with the phospholipid bilayer
- the cholesterol stabilizes the membrane fluidity as it packs itself in the hydrophobic tails
what is passive transport and the 2 subtypes of it
- is movement across the semi-permeable plasma membrane that requires no energy
- diffusion
- facilitated diffusion
describe diffusion
- membranes are permeable to lipid soluble (hydrophobic) molecules such as steroid hormones and gases
- they move down their concentration gradient and therefore require no energy
- it restricts movement of water soluble and charged molecules such as glucose, ions and water
describe facilitated diffusion
- movement of hydrophilic molecules that requires membrane proteins called channels and carriers
- aid the movement if specific substances down their concentration gradient
- no energy requires, but some channels open and close in response to signals
describe carriers and channel membrane proteins
- carriers undergo a shape change to help guide molecules
- movement across the cell membrane requires channels called aquaporins
what is active transport and the 2 subtypes
- is movement across the membranes that requires energy
- active transport
- co-transport
describe Active transport
- requires transport proteins which are carriers that use ATP
- move specific substances against their concentration gradient
- It allows a cell to have an internal concentration of a substance that is different from its surroundings
- example the sodium-potassium pump
describe Co-transport
- indirect active transport (still needs energy)
- one substance pump across the membrane
- and its concentration gradient used to power the movement of a second substance against its concentration gradient
what are the roles of Membrane Proteins
- they are transporters
- they have more roles that are often specific to a cell type
