structure, function and transport of cell membrane Flashcards
(33 cards)
state 4 functions of the cell membrane
- supports the cell.
- it acts as a physical barrier
- it regulates the passage of materials.
- it is sensitive to changes.
explain how the (CM) supports the cell.
the inside of the membrane is connected to the cytoskeleton.
explain how the (CM) acts as a physical barrier
it separates the contents of the cell from surrounding fluid and cells.
explain how the (CM) regulates the passage of materials.
controlling what enters and exits the cell.
explain how the (CM) is sensitive to changes.
it is the first part of the cell effected by external changes.
how is the CM constructed
it is a phospholipid bilayer containing channel proteins, carrier proteins, cholesterol and cell identity markers.
what are the 2 layers of the phospholipid bilayer
one layer contains a hydrophobic tail (water hating) and a hydrophilic head (water loving). A bilayer is two layers of these.
describe homeostasis
body systems working together to keep the cellular environment constant.
what is the function of a protein channel?
it provides a pathway for hydrophilic particles to travel across the CM without needing to come into contact with hydrophobic tails.
what is the function of a carrier protein?
binds specific molecules and transports them across the membrane.
cell membrane is the…
outer boundary that separates it from the other cells, determine what goes in and out of the cell.
state the 3 methods of transport across the CM
- simple diffusion
- facilitated transport
- vesicular transport
what is simple diffusion
the process of substances moving along the concentration gradient (net diffusion) in a solution or across a semi permeable membrane (no use of proteins)
what is a differentially permeable or semipermeable membrane
a membrane that permits the passage of certain substances but restricts the passage of others.
what can diffuse through the cell membrane
alcohol, steroids and other fat-soluble substances such as O2 and CO2 can diffuse through the phospholipid portion of the membrane.
water soluble substances are unable to pass directly through the lipid portion of the membrane due to the hydrophobic tails.
what is osmosis
the diffusion of water molecules through a differentially permeable membrane from an area of high water concentration to an area of low water concentration.
what is the relationship between the concentration gradient and the rate of diffusion
an increased concentration gradient leads to a higher rate of diffusion.
what is the concentration gradient
a difference in the concentration of a solution, often between the inside and outside of a cell; also called the diffusion gradient.
what is the rate of diffusion
the speed at which a substance crosses a semi permeable membrane.
what is carrier mediated transport?
transport of ions or molecules across a CM by specialised proteins. there are 2 types and they can be active or passive.
facilitated diffusion
the process where carrier proteins allow the movement of substances through the cell membrane along the concentration gradient.
PASSIVE
active transport
the use of energy (ATP) to move substances (ions) across the cell membrane against the concentration gradient.
ACTIVE
vesicular transport
the movement of substances across the cell membrane in membranous sacs called vesicles.
ACTIVE
facilitated transport
proteins in the cell membrane allow molecules to be transported across the membrane.
