Booklet 1 - Plasma Membrane Flashcards
Phospholipid bilayer
Consists of a hydrophilic head and a hydrophobic tail consisting of two fatty acid chains
Transport proteins (passive transport)
Allows some substances, such as ions, to move through the membrane by facilitated diffusion
There are 2 types of transport proteins for this purpose: channel proteins and carrier proteins
Can become saturated
Transport proteins
A gated protein channel that opens to transport a specific molecule in response to contact with another molecule, such as a hormone
Plasma membrane
Binds all living cells, acts as a barrier between the internal and external environment, controls what substances enter and leave the cell
Transport proteins (active transport)
Protein pump is involved in active transport and requires the input of ATP.
These proteins sometimes are referred as carrier proteins.
Catalytic proteins
Enzymes speed up the rate of chemical reactions occurring across the membrane
Receptor proteins
Hormones & other substances bind to them affecting the cell’s activities. Different types of cells have different receptor proteins.
e.g. glycoproteins
Recognition proteins
Act as markers called ‘antigens’, which enable the immune system to recognize ‘self’ cells from ‘non-self’ cells, e.g. glycoproteins.
Adhesion proteins
Join cells together in multi-cellular organisms. Includes; occluding, communicating and anchoring junctions.
Cytoskeleton proteins
Anchor the cytoskeleton to the membrane
Cholesterol
Steroid lipid, amphipathic, embedded within the phospholipid bilayer, regulates membrane consistency, maintains firmness stability and fluidity, reduces permeability to some solutes
Glycolipids
Found on the plasma membrane, play a role in tissue recognition
Glycoproteins
Found on outer plasma membrane, function as cell surface markers, also known as antigens
Simple diffusion
Simple diffusion is the net movement of a substance (molecule or ions) across the phospholipid bilayer from a region of high concentration to a region of low concentration of that substance.
Osmosis
Osmosis is the net movement of water from a low solute concentration (hypotonic) to a high solute concentration (hypertonic) across a selectively permeable membrane
Hypotonic
Hypotonic refers to a solution with a low concentration of solutes compared to the solute concentration inside a cell.
There will be a net movement of water into the cell from surrounding solution.
Hypertonic
Hypertonic refers to a solution with a high concentration of solutes compared to the solute concentration inside a cell.
There will be a net movement of water out of the cell into surrounding solution.
Isotonic
When the surrounding fluid is of equal concentration to the solution inside the cell, it is said to be isotonic.
There will be no net movement of water (water will diffuse equally in both directions).
Osmotic pressure
Pressure caused within turgid cells
Turgid
Swollen
Crenated
Shrunken
Haemolysis
Swelling and bursting within animal cells
Facilitated diffusion
Use channel proteins and carrier proteins to transport charged particles and larger molecules passively across the plasma membrane
Carrier proteins
Carrier proteins combine with the molecule or ion and carry it across the membrane.
Once the molecule has bound to the protein, the protein changes shape and releases its content to the inside of the membrane. (or to the outside)
Channel proteins
Channel proteins are channels, which open and close to allow specific water-soluble molecules and ions through
Active transport
Active transport is the movement of molecules or ions from a region of low concentration to a region of high concentration.
Exocytosis (bulk transport)
Substances are actively transported out of the cell by moving them in small vacuoles called vesicles.
The membrane of vesicles are filled with secretions that are not permeable in the membrane. E.g. digestive enzymes, hormones, wastes and carbohydrates.
The vesicle membrane fuses with the plasma membrane, releasing the content to the outside of the cell.
Requires energy (ATP)
Endocytosis
Substances are actively transported into the cell. Requires energy (ATP).
Factors affecting diffusion
Size of the particle (molecular weight) Temperature Concentration difference Diffusion distance Surface area Permeability
Factors affecting active transport
Number and type of carrier proteins and protein pumps per unit area Surface area ATP availability Temperature pH
Other factors affecting the membrane
pH
Molecules that disrupt the lipid layer
Electrical gradient
Temperature
Ribosomes
- Smallest organelle composed of rRNA and protein
- It is not surrounded by a membrane therefore can be seen in both prokaryotic and eukaryotic cells
- Site of protein synthesis
- Each cell contains thousands
- Composes 25% of cell’s mass
- Stationary type: embedded in rough endoplasmic reticulum
- Mobile type: injects proteins directly into cytoplasm
Golgi apparatus
- Proteins are modified
- Packaging of molecules, e.g. proteins
- A membrane structure found near nucleus
- Composed of numerous layers forming a sac
- Molecules are packaged in vesicles
- Abundant in cells that export cell products
Excretory vesicles
- Proteins are packaged into excretory vesicles.
- Vesicles break free from the golgi apparatus.
- Vesicles move to and merge with the plasma membrane
- Proteins are removed from cell by exocytosis
