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Cell membrane and transport - Coggle Diagram
Cell membrane and transport
function
All cells are engulfed in a membrane
8nm thick
Regulates a lot of transport in and out of the cell
Membrane is semipermeable
structure
Cell membrane is made up of two layers of phospholipids and that's why it is called a phospholipid bilayer!
A phospholipid itself is composed of two parts:
A hydrophilic head (water loving): this part is a glycerol molecule with a phosphorous (not too important for now)
And a hydrophobic tail (water fearing). This part is just two fatty acid chains
If you put a lot of these phospholipids in an aqueous (watery) solution they arrange themselves in a way so that the hydrophilic heads are exposed to the water and the hydrophobic tails hide in the middle of the bilayer. This is exactly how phospholipids make the cell membrane!
Cell membrane is called fluid because its not motionless or static. In fact the phospholipids constantly move long and mix with each other. This is why cells and tissues (like your skin) is soft and not rigid!
Cell membrane is mosaic: there are proteins and carbohydrates in the membrane too
a complete cell membrane
lipids
there are some molecules of cholesterol inserted into the membrane and in between the phospholipid molecules.
proteins
integral
integral: inserted in the lipid bilayer
They are integrated into the membrane
peripheral
Peripheral: loosely attached to the lipid bilayer They are in the periphery of membrane
carbonhydrates
Are attached to either lipids or proteins
transport
Passive transport
Molecules move down the concentration
Simple diffusion
If a molecule is small and hydrophobic (nonpolar) enough they can simply squeeze between the phospholipid bilayer and cross. This is a simple diffusion.
Facilitated diffusion
If a molecule is large or hydrophilic (polar) then they need help. The help is provided by membrane proteins. These proteins are two categories:
Carrier proteins
these channels are not always open, if the right molecules binds/attach to them then they change shape and transport that molecule from high to low concentration.
Channel proteins
they are always open and allow the molecules to pass through according to their concentration gradient
Active transport
It is called active because it needs energy expenditure. Energy is needed because the molecules are being transported AGAINST the CONCENTRATION!!
Cellular energy (ATP) is needed here
bulk transport (when the material is too big)
Endocytosis
A part of the plasma membrane sinks inward
Eventually the inward growing pocket pinches in, forming a vesicle (e.g. a food vacuole)
Phagocytosis
s simply the uptake of large solid matter like food from outside by a cell
Endocytosis
when cells bring in material in large amounts from outside
Exocytosis
When cells push large amounts of material out from inside
Pinocytosis
type of endocytosis in which cell take up fluid from outside. Of course the cell is very interested in the content of
Diffusion
Water can diffuse too. Diffusion of water molecules is called Osmosis
Channel proteins that allow osmosis are called aquaporins
movement of molecules to spread evenly into the space
Molecules diffuse down their concentration gradient
From high towards low concentration
tonicity
ability of a solution to make a cell to gain or lose water
Isotonic Solution
No net movement of water in or out of the cell
Cells are happy here
Hypotonic Solution
Cell gains water as water diffuses (by osmosis) into the cell
Swell and burst
Hypertonic Solution
Cell loses water as water diffuses (by osmosis) out of the cell
Cells shrink