Ch. 5 - Membranes Flashcards
What are all membranes made of?
Lipids.
How many layers make up a membrane?
2 layers.
What type of lipid is located in membranes?
Phospholipids.
What are the 3 parts of a phospholipid?
1) Glycerol
2) Phosphate group (polar, hydrophilic)
3) Two fatty acids chains (non-polar, hydrophobic)
What happens when phospholipids are put into water
They form a lipid bilayer.
How is the lipid bilayer formed when phospholipids are placed in water?
The lipid bilayer is formed by hydrophobic exclusion; the non-polar tails align and the hydrophilic head align.
How is the lipid bilayer held together?
By Hydrogen bonding.
What determines the fluidity of the membrane?
The fatty acid chains; Chains with lots of double bonds typically are more fluid than chains without double bonds.
What do surface proteins do with the membrane?
Float on the membrane (actually in the membrane) like boats on a pond.
What is the Fluid Mosaic Model?
A depiction of how models were inserted into the plasma membrane.
What are the four parts of membranes?
1) Lipid bilayer
2) Transmembrane proteins
3) Supporting fibers
4) Exterior proteins and glycolipids
What are transmembrane proteins?
What are 3 functions?
Proteins that are inserted in the membrane.
1) Receptors
2) Channels
3) Act as Enzymes
What are supporting fibers?
What is the function of supporting fiber?
Fibers attached to transmembrane proteins.
Function: Help the cell maintain shape.
How are the exterior proteins and glycolipids created?
What are they made of?
What are the functions?
Membrane proteins are made in the ER and transported to the Golgi.
A coating made of carbohydrates and lipids.
Function:
1) “Self” recognition
2) Recognizing other cell types
What are the 6 kinds of transmembrane protein?
1) Transporters
2) Enzymes
3) Receptors
4) Surface identity markers
5) Cell adhesion points
6) Attachment to the cytoskeleton.
What is the function of transporter transmembrane proteins?
Used to move molecules in and out of the cell.
1) Channels and carriers; allow certain molecules to diffuse into the cell.
2) Pumps; These transport proteins are often used for active transport when the cell need to expend energy.
What are the function of enzymes in the transmembrane proteins?
Many chemical reactions are carried out by enzymes that are attached to the plasma membrane.
What is the function of receptor transmembrane proteins?
What is an example?
These types of proteins are very sensitive to specific chemicals, once the chemical attaches to the receptor protein, a series of chemical reaction is initiated in the cell.
Example: Hormones; When it attaches to the specific receptors of the desired cell, the reaction starts.
What is attached to surface identity marker proteins?
glycocalyx.
What are cell adhesion points?
Where cells stick to each other.
What is the function of attachment proteins for the cytoskeleton?
Anchoring points for the actin fibers of the cytoskeleton.
What is diffusion?
Is diffusion considered active or passive transport, and why?
The net movement of a substance from an area of high concentration to a lower concentration.
Passive transport; requires no energy from the cell.
What three proteins do facilitated diffusion utilize?
Is facilitated diffusion considered active or passive transport?
1) Transport proteins
2) Ion channels
3) Carrier proteins
Passive transport.
How do transport proteins work in regards to facilitated diffusion?
These proteins are selective, allowing only certain types of molecules to pass through, but is activated via diffusion (Flow from areas of high concentration to low concentration).
What is the difference between facilitated diffusion and diffusion?
Facilitated requires proteins to allow certain larger molecules to pass through the membrane.
What do ion channels allow?
For hydrophilic ions to diffuse into the cell.
What are carrier proteins?
How is the process done?
Similar to channel proteins except that the molecule that is going to be transported binds to the carrier proteins and is “carried” across the plasma membrane.
Done via diffusion.
What is an aqueous solution?
A mixture of something in water.
What is a solvent?
The liquid part (water).
What is a solute?
The solid part (what is dissolved).
What is osmosis?
The net movement of water across a membrane via diffusion?
Can water diffuse across the plasma membrane?
Why?
No
Water is highly polar, which cannot cross the hydrophobic plasma membrane. This means water requires a special channel protein to diffuse in and out of the cell (facilitated diffusion).
What are aquaporins?
Specialized channel proteins for water.
What is osmotic concentration?
The concentration of all of the solute in the water.
What does it mean if a solution is hyperosmotic (hypertonic)?
A solution with a higher osmotic concentration.
What does it mean if a solution is hypo osmotic (hypotonic)?
A solution with a lower osmotic concentration.
What does it mean if a solution is isosmotic (isotonic)?
A solution with equal osmotic concentration.
What happens to cells in a hypertonic solution?
Cells lose water.
What is osmotic pressure?
The pressure that must be applied to stop the osmotic movement of water across a membrane.
What is an example of osmotic pressure?
A cell in a hypotonic solution; the pressure of water moving into the cell.
What is hydrostatic pressure?
The pressure from the water in the cell.
How many methods are used to solve osmotic problems?
What are they?
3
1) Extrusion
2) Isotonic solution
3) Turgor
What is extrusion?
What types of cells use this?
The process of getting rid of excess water in vacuoles.
Used by many single cell organisms.
How can isotonic solutions resolve osmotic problems?
Often, organisms that live in hypertonic environments can adjust by allowing their cells to maintain the same concentrations as the solution.
What is turgor?
What types of cells does this happen too?
The cell wall prevents the membrane from splitting and the high hydrostatic pressure helps keep non-woody tissues upright (celery).
Organisms with cell walls do this. The cells are hypertonic and absorb lots of water.
What is endocytosis?
A process whereby the plasma membrane envelopes something and forms a vacuole.
What are the three kinds of endocytosis?
1) Phagocytosis
2) Pinocytosis
3) Receptor mediated endocytosis
What is phagocytosis?
Taking in particulate matter.
What is pinocytosis?
Taking in liquids via same method.
What is receptor mediated endocytosis?
Once receptors are filled with a specific target molecule, the whole are forms a vacuole and the material is brought into the cell.
What is exocytosis?
The opposite of endocytosis.
Molecules are ejected from the cell by the fusion of a vesicle with the plasma membrane.
What is active transport?
If a cell needs to move something against the concentration gradient and requires the cell to expend energy.
What is a sodium/potassium pump?
Used by a cell to actively transport sodium out and potassium into the cell; requires ATP (energy).
Once ATP is used during active transport, what does it turn into?
ADP (Adenosine diphosphate)
What is the ratio of sodium ions to potassium ions going out/into the cell?
3:2
3 sodium ions leave per 2 potassium ions entering.
What is a proton pump?
How does it work?
A pump that moves protons across membranes.
1) Proton binds to protein
2) Protein changes shape
3) Proton is ejected
What are proton pumps important for?
Important for the manufacture of ATP.
