Unit 4 - Cell membranes and transport Flashcards
Active transport
The active movement of substances from a low concentration to a higher concentration (up their concentration gradient) with the use of energy in the form of ATP.
Antigen
Marker molecule on the cell surface membrane (usually a protein or glycoprotein) that can be detected by antibodies and triggers an immune response.
Carrier protein
Protein involved in active transport that uses energy in the form of ATP to change conformation.
Cell signalling
Cells release chemicals which bind to complementary receptors on their target and trigger specific responses.
Cell surface receptor
A component on the cell membrane which binds to extracellular signals.
Channel proteins
Transmembrane proteins for transporting large or charged substances. Some are involved in facilitated diffusion and do not use ATP; others are involved in active transport and do require energy in the form of ATP.
Cholesterol
A steroid hormone which adds stability and fluidity to the lipid bilayer. it prevents breaking of the cell in harsh temperatures.
Diffusion
The passive spreading out of substances from a high concentration to a lower concentration (down their concentration gradient) without the use of energy.
Endocytosis
A method of bulk transport into a cell which relies on invagination of the cell membrane and requires energy in the form of ATP.
Exocytosis
A method of bulk transport out of a cell which occurs when vesicles fuse with the cell membrane and release their contents. It requires energy in the form of ATP.
Facilitated diffusion
The passive movement of substances from a high concentration to a lower concentration (down their concentration gradient) through transport proteins without the use of energy.
Fluid mosaic model
A model that describes membrane structure as a sea of mobile phospholipids studded with various proteins.
Glycolipid
A lipid which is bound to a monosaccharide.
Glycoprotein
A protein which is bound to a carbohydrate chain.
Ligand
An ion or molecule that transmits signals within or between cells. It has a role in cellular signalling and recognition.
Osmosis
The passive diffusion of water molecules from a region of high water potential to a region of lower water potential (down a water potential gradient) through a selectively permeable membrane without the use of energy.
Phospholipid
The type of lipid which forms the cell surface membrane bilayer. It is formed by the condensation of one molecule of glycerol, two molecules of fatty acid and a phosphate group. The two fatty acid chains are the non-polar hydrophobic tails whilst the phosphate group is the polar hydrophilic head.
Phospholipid bilayer
hydrophobic tails face each other and hydrophillic phophate group heads ward outward to the watery environment of the cell.
Surface area to volume ratio
The volume of an object compared with the amount of area where it contacts its environment. Calculated by dividing the surface area of an object by its volume.
Water potential
A measure of the tendency of water molecules to move from one area to another measured in kilopascals (kPa) and given the symbol.
Describe channel proteins
- the central tube is lined with polar r groups
- channel proteins can be opened or closed depending on certain stimuli
- can be a single protein or multiple arranged together
describe carrier proteins
- molecules bind to the protein
- the protein can flip between two shapes
- binding site is open to both sides of the membrane
- diffusion affected by number of carrier proteins in the cell membrane
Whats the order of cell signalling
- stimulus/signal
- receptor
- transmission of signal
- target/ effector
- response
Ligands
- secreted from a cell into extracellular space
- transported through that space to target
- bind to surface receptors
- message in ligand is transmitted to cell through a chain of chemical messengers
high water potential
lower solute conc. (more pure water)
low water potential
higher solute conc. (impure water)
describe the process of osmosis
- water molecules on the side with a higher water potential are freeer to move around than the other side.
- this causes them to hit the membrane more often which allows them to diffuse through to the other side.
active transport process
- particle enters the pump from the side with lower concentration
- particle binds with the specific site
- energy from atp is used to change the shape of the pump
- the particle is released on the side w/ higher conc. and returns to its orginal shape
where is active transport used
In root hair cells for inorganic ions and reabsorption in kidneys
hypertonic
has a higher amount of solute
hypotonic
has a lower amount of solute
isotonic
has the same amount of solute
what happens if you put a red blood cell into a hypertonic solution
it becomes crenated as the water content of the cell rushes out.
what happens if you put a plant cell in hypertonic solution
it becomes plasmolysied
