Chapter 9 - Membranes Flashcards
Membranes
Living membranes are structurally organized to
Separate the inside of the cell from the outside
Membranes
What are living membranes?
Plasma membranes of cells
Membranes
Proteins embedded in the living membrane allow
2.
- Passage of specific molecules into and out the cell
2. Communication between cells and with the environment
Membranes
True or False
Biochemical organization of plasma membranes are well established
False
biochemical organization of plasma membranes are not well established
Membranes
Cell membranes contain 4 main components which are
Phospholipid bilayer
Transmembrane proteins
Interior protein network
Cell surface markers
Membrane: Phospholipid bilayer
Composed of three main types of lipids which are
Glycerol Phospholipids
Sphingolipids
Sterols (cholesterol)
Membranes: Phospholipid Bilayer
Cell membrane composed of
Phospholipids
Sphingolipids
Cholesterol
Membranes : Phospholipid bilayebranes
Phospholipids and/or sphingolipids form
A bilayer, aka non polar fatty acid chain pointing inward, polar head group pointing outwards
Membranes: phospholipid bilayer
Have diverse head groups that can be positively and negatively charged ,
Or just primarily negatively charged
Glycerol phospholipids
Membranes : phospholipids
Phospholipids can have different fatty acid chain length and composition, with it being either saturated or cis - unsaturated (T/F)
True
Membranes: Phospholipid bilayer
Generally contain saturate fatty acid chain aka (hydrocarbon)
Sphingolipids
Membranes: Phospholipid bilayer
Cell membranes cannot be differently structured (T/F)
False
Different lipid and or protein composition
Membranes: Phospholipid bilayer
What forms spontaneously due to the tendency of water molecules to form the maximum number of hydrogen bonds
Phospholipid bilayer
Membranes: Phospholipid bilayer
When placed in water, spontaneously forms bilayer
Nonpolar group orient to each mother while polar head groups orient towards charge water molecules
Phospholipid
Membrane: phospholipid bilayer
Is a lipid bilayer stable?
Yes because waters affinity for hydrogen bonding never stops to
Hydrogen bonding of water holds a membrane together
Phospholipid bilayer is fluid
Membranes
Membrane fluidity of a cell varies with or is determined by the (lipid) composition of the membrane itself (T/F)
True
Membranes : Phospholipid bilayermbranes
Describe Fluid Mosaic Model
Globular proteins embedded in the lipid bilayer are/ inserted into the lipid bilayer
Nonpolar Amino Acids are in contact with the nonpolar interior, aka fatty acids
Polar (amino Acids) portions , aka hydrophilic heads protrude out from membrane surface (polar exterior)
These proteins can float around the plasma membrane due to the nature of the nonpolar and polar contacts
Creates barrier for all elements inside and outside the cell
Membranes: Phospholipid bilayer
-
Saturated fatty acids
Mono cis - saturated fatty acids
Membranes: Phospholipid bilayer
What type of fatty acid chain results in a thicker membrane
Unsaturated fatty acid chain
Membranes: Phospholipid bilayer
What type of fatty acid leaves more space for cholesterol?
Why is cholesterol important?
Unsaturated fatty acids
Gives membranes it’s fluidity
Membranes: Phospholipid bilayer
Endoplasmic Reticulum membrane is composed of_________________
and had very little_______________
Unsaturated phospholipids
Cholesterol
Membranes: phospholipid bilayer
Is the plasma membrane thinner than the endoplasmic reticulum?
No.
The endoplasmic reticulum(20 amino acids) is thinner than the plasma membrane (thick; 25amino acids)
Membranes: proteins
Allows certain molecules to enter or exit the cells
Transporters
Membranes: proteins
Perform chemical reactions on the interior surface of the plasma membrane
Enzymes
Membranes: proteins
Detects external chemical signal
Cell surface receptors
Membranes: proteins
Pro retina that identify the cell type as “self vs no self”
Cell surface identity markers
Membranes: proteins
Proteins that allow two cells to stick together
Cell to cell adhesion molecules
Membranes: proteins
Proteins that allow a cell to be anchored to the cytoskeleton
Attachments to cytoskeleton
Membranes: proteins
Proteins can be anchored to phospholipids via
Hydrophobic heads
Membranes: proteins
Proteins that can span the lipid bilayer _____________
The part of the protein that extends through the lipid bilayer and is in contact with the non polar interior are ___________ or ___________
Transmembrane proteins
A helices or B-pleated sheets
Membranes: proteins
Membrane spanning region is called ___________
This region anchors_____________
Transmembrane domain
Integral membrane proteins
Membranes: proteins
Can span the lipid bilayer and FORM pores
Proteins formed from ß-sheets
Transport through membranes
- Transport can be _________ or ____________.
- ____________ transport does not expend energy
- _____________ expends energy
- Passive or Active
- Passive
- Active
Transport through membranes : passive transport
Movement of molecules from higher concentration to lower concentration until equilibrium is reached
Nonpolar molecules can move freely through the nonpolar bilayer
Diffusion
Transport through membranes
- Polar molecules need specific protein membranes to allow for diffusion to occur ( channel proteins & carrier proteins)
- The diffusion of molecules or ions through carrier proteins or ions channels
Requires a concentration gradient, but not any input of energy
Facilitated diffusion
Transport through membranes : passive transport
A difference between the concentration on the inside of the membrane and that on the outside
Allows ion and molecules to pass through membrane easily
Concentration gradient
Transport through membranes : facilitated diffusion
A transmembrane protein with a hydrophilic interior that provides aqueous channel allowing diffusion of species that cannot cross the membrane
Usually allows passage for K+, Na+, Ca+
Channel protein
Transport through membranes : facilitated diffusion
A membrane protein that binds to a specific molecule that cannot cross the membrane and allows passage through membrane
Carrier protein
Transport through membranes : facilitated diffusion
Possesses a hydrated interior that spans the membrane,
ions can diffuse through the channel in either direction, depending on the relative concentration across the membrane
Ion channels
Transport through membranes : passive transport
Adds PHOSPHATE GROUP to GLUCOSE once it enters a cell , to keep glucose concentration levels low
Increases inward diffusion of glucose
Glucose transporter binds(carrier protein) glucose on extracellular side, then releases it in the intracellular side
Red blood cells
Transport through membranes : passive transport
Diffusion of water molecules down their concentration gradient
Concentration of solutes(ions) determines direction of water movement
Osmosis
Transport through membranes: Passive Transport—> Osmosis
- More solutes/higher concentration =
- Less solutes/ less concentration =
- Equal solutes/ same concentration =
- Hypertonic
- Hypotonic
- Isotonic
Transport through membranes: Passive transport
Aquaporins
Proteins that form channels that allows water transport
Transport through membranes : passive transport
Concentration of all solutes in a solution determines the____________
Osmotic concentration
Transport through membranes : passive
When water changes the shape of the cell
The amount of water that enters the cell depends on the difference in solute concentration between the cell and the extracellular fluid.
Osmotic pressure
True or false
Diffusion, facilitated diffusion and osmosis are passive transport process that move materials down their concentration gradient
True
Transport through membranes :
Expenditure of energy, typically from ATP
Moves substances ACROSS a cell membrane UP their concentration gradients
What am I?
Active transport
Transport through membranes : Active Transport
Carrier protein that transports one type of molecule
Uniporters
Transport through membranes: Active Transport
Carrier proteins that transport 2 molecules in the SAME DIRECTION
Symporters
Transport through membranes : Active Transport
Carrier proteins that transport 2 molecules in OPPOSITE DIRECTIONS
Antiporters
Transport through membranes—> Active Transport: uses ATP to move molecules up their concentration gradient
Best Example: Na+/ K+ pump
- cell has a lot of K+, little Na+
- Describe the steps for this pump.
- Carrier in membrane binds intracellular sodium
- ATP phosphorylates protien with bound sodium
- Phosphorylation causes conformational change in protein, reducing its affinity for Na+. Na+ then diffuses out
- This confirmation has higher affinity for K+. Extracellular potassium binds to exposed sites
- Binding of potassium causes dephosphorylation of protein
- Dephosphorylation of protein triggers change back to original conformation, with low affinity for K+, K+ diffuses into the cell, and the cycle repeats
Transport through membranes: Active Transport Glucose (uses N+ gradient)
Molecules moved against their concentration gradient by using the energy stored in a gradient of a different molecule
Uses energy of N+ moving down concentration gradient to couple to glucose transport
Coupled transport
Bulk Transport -> 2 Processes
- Into the cell =
- Out the cell =
- Endocytosis
2. Exocytosis
How do large polar molecules, or substances cells require for growth get into cells?
Bulk Transport
- endocytosis
- exocytosis
Bulk Transport
In this process the plasma membrane envelopes food particles and fluids
Things are transported out of the cell in bulk via vesicles
Vesicles fuse with plasma membrane, spilling its contents into the extracellular space
Used to release hormones, neurotransmitters, enzymes, and other substances
Endocytosis
Bulk Transport: endocytosis
Cell use three major types of endocytosis which are :
Phagocytosis
- “eats cell”
- fragments of organic matter, includes other cells
Pinocytosis
- drinks, or engulfs liquids
Receptor-mediated endocytosis
- Molecules bind to receptors on cell surface, which are then taken up by the cell
