cell structure and function Flashcards
describe the general cell structure
Plasma membrane is outer bylipid membrane layer containing all contense of cell keeping interior and exterior separate. Within plasma membrane there is cytoplasm which is fluid like substance more gelatinous that water containing all dissolved nutrients and substances supporting and maintain cell. Organelles are in this substance. The nucleus is brain of cell containing all DNA so genetic info of cell and important for reproducing cells
describe the function of the cell membrane
Membrane is point of contact with external environment and has to control what enters and exits cell.
describe the contentse of the cell membrane
Its formed by a bilipid layer called phospholipid bilayer, it has other molecules embedded and attached to it such as cholesterol, proteins and carbs giving the cell a particular nature to cell, these help recognise molecules withing cell and hep facilitate their movement and interaction with cell
describe the bilayer of the membrane
Heads hydrophilic water loving
Hydrophobic tails that are fatty acid in nature facing interior of bilayer
There’s pore forming proteins for movement of particular substances, some are gated and can open or close by messages
Receptors in bilayer recognise particular substances and transmit the message they receive from exterior to interior, and interact with neurotransmitters etc
Each cell type has its own chemical identity depending upon molecules attached
what are the 4 functions of the cell membrane
Barrier between inside and outside of cell
Controls entry of materials - Transport
Receives chemical and mechanical signals
Transmits signals between intra- and extra cellular spaces
So important for communication
explain body fluid pools
Majority is Intracellular (ICF) (inside cells)
2/3 of total in body
Extracellular (ECF) :
- Between cells bathing them helping to support and maintain the cells = Interstitial
- In blood vessels = Plasma, fluid within blood
- In lymphatic vessels = Lymphatic – similar to blood as circulates and moved round body
what is a solvent
doing the dissolving
such as water in cells
what is solute
- material dissolved.
Often a salt for ex
what is concentration in terms of solutions
Amount of solute in a given amount of solvent
what is the concentration gradient
Difference in concentration between two areas of solution,
such as high salt conc in one area compared to another
what are the 5 different types of membrane transport mechanisms
Simple Diffusion – molecules move passively though membrane with molecule size and conc gradient being barrier
Facilitated Diffusion – doesn’t require energy but depends upon channel forming pores
Osmosis – deals with water molecule movement
Active Transport – does require energy (ATP) doesn’t depend on conc gradients
Transport in vesicles-
explain simple passive transport diffusion
Concentration gradient of solute
Can diffuse across a membrane, so are small
Passive transport: Diffusion
either dissolve in the lipid membrane
e.g. O2, CO2, lipid soluble vitamins
if charged must go through channels
Specialised ion channels that can open and shut = (gated channels) that are voltage or ligand gates deepening upon charge or molecule binding
describe facilitated diffusion
Requires a carrier in membrane
Only goes down concentration gradient
Saturates = maximum speed. (saturation can be achieved as molecules are competing for sites within the carrier so may be a maximum speed on process, this doesn’t occur in simple diffusion)
Maximum speed dependent on carrier number
describe osmosis
Diffusion of water
Must have a semi - permeable
membrane, (this is what the plasma membrane is)
ex of osmosis experiment: At start there’s particular conc of water inside compared to outside, over time water moves from high to low conc such as by moving tonto tube and causes an equilibrium
describe osmosis is red blood cells
when red blood cells exposed to diff concs of solutes they change size due to osmosis .
in isotonic solution theres no change as water content in cell and out cell is same
Hypotonic solution – low solute content, so more water molecules in the jar than cell so water moves into cell not out. This causes cell to swell and burst
Hypertonic – more water in cell so water moves out. This causes cell to shrink and lose water
