Membrane Structure and Function Flashcards
A fluid mosaic structure, made up of lipids that allow substances to move in and out through it
Mosaic - different types of substances giving it a mosaic appearance
Plasma Membrane Structure
The backbone of the plasma membrane is made up of a lipid bilayer, made up of polar lipids.
Which end does the hydrophilic region face?
The hydrophobic region faces which end?
The aqueous or watery end
Non polar region, non watery
What do these lipid bilayers create?
Barriers between insides and outsides of cells
Why do lipids form the basic backbone?
It does not require a lot of energy to form the bilayers
Type of molecule that is the backbone. Phosphate groups facing cytosol and extracellular fluids, makes it polar. Remove fatty acid chain with phosphate group
Phospholipid
Flat plane molecule which stiffens the plasma membrane - works well to be inserted because of shape
Cholesterol
Which part of phospholipids face the cytosol? (Aqueous part)
Phosphate groups (polar parts)
Which part of phospholipid forms the hydrophobic or interior part of the cell?
Fatty acid tails
Type of membrane protein that is embedded in the membrane, and often functions as channels
Integral Membrane Proteins
Type of membrane protein that forms the internal or external aspects of the membrane. Functions as receptors or enzymes. Don’t go across entire membrane.
Peripheral Membrane Proteins
Function of membrane is dependent upon?
Proteins.
Type of carbohydrate attachment that is a carbohydrate on a lipid
Glycolipid
Type of carbohydrate attachment that is a carbohydrate on a protein
Glycoprotein
Where are carbohydrate attachments typically located on the cell membrane?
External surface
Located within membrane, an area that is found in 20% of outer membrane sphingolipids and cholesterol, useful in cell signaling
-concentration of cholesterol is much higher in these areas.
Lipid Rafts
Specialized membrane strucure that has an actin core (microfilament) holding it in place. This structure is a fold of plasma membrane that increases the cell surface area.
Microvilli
In what type of cells are microvilli important? Where might you find them?
Absorptive. Small Intestine
What does microvilli have to help preserve its integrity?
Actin Core (microfilament)
Adhesive structure in membrane-membrane adhesions that is the glycoproteins and glycolipids
because they are polar sugars, they can interact with sugars of a neighboring plasma membrane.
Glycocalyx
The membrane-membrane adhesions (like glycocalyx) that allow for better fitting by forming groove. These are called
Wavy Contours
These provide integrity and hold adjacent cells together of the same tissue
Membrane junctions
Membrane junction that is fused protein molecules in adjacent membranes, towards the apical portion of the cell, cell that faces lumen of organ or the exterior
Very protective. Also prevent material from coming between cells and entering blood stream
Tight Junctions
Where are tight junctions typically found?
Epithelium
Tough structures made of linker protein and keratin filaments (intermediate filaments). Provide integreity to tissues by holding adjactent cells together.
Common in cells that undergo a lot of torsion
Desmosomes
Where might desmosomes be found?
Epidermis and uterus
Important structural part of membrane for communication. Proteins for hollow passageways between cells which allow materials, usually IONS to flow between cells for quick communication and action potential
Gap Junction
What type of tissues are gap junctions seen?
Cardiac muscle, smooth muscle
3 overarching functions of plasma membranes
Transport Processes
Cell to cell adhesion to form tissues
Communcation
Transport process that requires no energy to be added to a system, the process will occur on its own
Passive Transport
Type of passive transport that is due to the tendency of molecules to randomize, because of which substances will move from an area of high concentration to low. This typically happens across membranes.
Simple Diffusion
Passive transport that is the diffusion of water molecules. Water moves from a high concentration of water to a low concentration of water
Osmosis
Is usually described as water moving from an area of low particle concentration to an area of high particle concentration across a membrane. It is described this way because water is a solvent, not solute.
Osmosis
A solution that has a high particle concentration and therefore attracts water has high or low osmolarity?
High
A solution with a low particle concentration which does not attract water has a high or low osmolarity
Low
Refers to particles per unit liter (volume)
Osmolarity
Refers to particles per unit kilogram (weight)
Osmolality
Passive transport that involves the presence of protein transport proteins
Carrier mediated protein or channel mediated proteins both move from high concentration to low.
Facilitated Diffusion
Passive transport process where water and solutes push through a membrane from high pressure to low pressure
Filtration
Pressure that resists further water entry into a chamber due to osmosis
Osmotic
High osmolality of a solution means high or low osmotic pressure? Will more water be drawn into a chamber or less?
Low osmolality means high or low osmotic pressue? Will more water be drawn into a chamber or less?
High osmotic pressure. More
Low osmotic pressure. Less
Pressure that is exerted by fluid or the walls of a chamber that enclose it
ex: blood pressure
Hydrostatic
Changes in hydrostatic and osmotic pressure can affect…
Tonicity
The ability of a solution to change shape or tone of cells by altering the cells internal water volume
Cellular Tonicity
When the concentration of materials outside the cells is the same as the concentration of materials inside the cell, it is referred to as..
No NET water movement
Isotonic
The solution surrounding the cell is less concentrated than the cytoplasm. Because of osmosis, water moves from outside cell to inside the cell. Causes cell to swell.
Hypotonic
Solution outside the cell is more concentrated than the cytoplasm itself. Causes cell to shrink.
Hypertonic
Energy needs to be added tor a process to occur, it is referred to as
Active Processes
Type of active transport where additional energy is req’d in the form of ATP that moves molecules opposite to diffusion gradient.
Primary Active Transport
This type of active transport can move two molecules at once in either same direction or opposite directions
Primary active transport
When two molecules move across the membrane in the same direction
Symport
When two molecules move across the membrane in opposite directions. Each is being moved against its concentration gradient.
Antiport
Process that involves two phases, concentration gradient is set up by primary active transport. Diffusion of transported substance can occur, dragging another molecule along.
Movement of 2nd molecule wouldn’t occur unless first molecules were pushed across the membrane to escort the 2nd molecule
Secondary active transport
Active transport involving the movement of vesicles to and from a membrane which is taking contents to a membrane to be exocytosed or taking contents in to be endocytosed
Vesicular Active Transport
The 1st step of exoctytosis
The membrane-bound vesicle migrates to the plasma membrane
The 2nd step of exocytosis
The proteins at the vesicle suface (v-SNARES) bind with plasma membrane proteins (t-SNARES)
The 3rd step of exocytosis
The vesicle and plasma membrane fuse and a pore opens up
The 4th step of exocytosis
Vesicle contents are released and diffused into to the cell exterior (no energy required)
Which part of vesicle active transport consumes energy, the vesicle transport or diffusion?
Vesicle Transport
Diffusion is passsive
Type of endocytosis when the plasma membrane engulfs a particle outside the cell and brings it inside the cell via vesicle transport
Phagocytosis
The vesicle in phagocytosis is called the
Phagocyte
Where is phagocytosis commonly seen?
Cells of the immune system
Endocytosis that absorbs liquid usually with nutrient. Vesicle brings fluid and nutrient into cell.
Pinocytosis
Occurs for insulin of LDL’s, a receptor is located on the plasma membrane that binds with a particular molecule and an endocytotic vesicle is brought into cell with the molecule attached to the vesicle
Receptor-Mediated Endocytosis
Cytoplasmic face of the membrane is normally coated in a protein which assists in deforming the membrane, called
Like lipid rafts
clathrin
Tight Junctions are a type of cell to cell adhesion and interaction that form a tissue and prevent, this occurs because it is usually located on the atypical surface of the cell
Invasion
Cell to cell adhesion that is designed to help hold the cells together, are very tough, keeps them from separating with torsion
Desmosomes
Weak adhesive structure that contributes to keeping cells together. (adhesion) by anchoring
Also involved in migration and signaling. Important in embryological development and movement of immune cells like white cells that crawl along tissues as they look for infections
Glycocalyx
Migration and Signaling
To communicate with the environment, there must be two things present
Cell receptor
Ligand
The membrane protein in cell to environment (noncellular) interaction is call the
Receptor
The environment substance, like a hormone, neurotransmitter, or drug is
Ligand
When a ligand binds to a receptor, what occurs?
Change in the metabolic activity of the cell.
Type of receptor that is enzymes; binding of ligand to these receptor proteins causes the recepotor to catalyze a reaction
Ex: insulin receptor that pulls glucose into the cell
Catalytic Protein
Transmembrane (integral) proteins which open and close in response to a specific signal.
These control entrance/exit of specific substances
Channel-Linked Receptors
Channel linked receptors are often ion channels, in these, what is the ligand?
Neurotransmitter
Where are channel linked receptors with ion chanels commonly seen
Nervous system, neuromuscular junction
These receptors utilize the assistance of G-proteins to affect signal (GTP) which causes a cascade of events to a final cellular event that involves a second messenger
G-Protein Linked Receptors
These messengers pass a message from membrane protein to an intracellular protein which will execute the command from the original ligand causing a new metabolic event
Ex: cAMP, Calcium, IP3
Second Messenger
