Membrane Structure and Function Flashcards by michael perna

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

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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

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What do these lipid bilayers create?

Barriers between insides and outsides of cells

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Why do lipids form the basic backbone?

It does not require a lot of energy to form the bilayers

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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

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Flat plane molecule which stiffens the plasma membrane - works well to be inserted because of shape

Cholesterol

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Which part of phospholipids face the cytosol? (Aqueous part)

Phosphate groups (polar parts)

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Which part of phospholipid forms the hydrophobic or interior part of the cell?

Fatty acid tails

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Type of membrane protein that is embedded in the membrane, and often functions as channels

Integral Membrane Proteins

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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

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Function of membrane is dependent upon?

Proteins.

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Type of carbohydrate attachment that is a carbohydrate on a lipid

Glycolipid

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Type of carbohydrate attachment that is a carbohydrate on a protein

Glycoprotein

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Where are carbohydrate attachments typically located on the cell membrane?

External surface

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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

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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

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In what type of cells are microvilli important? Where might you find them?

Absorptive. Small Intestine

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What does microvilli have to help preserve its integrity?

Actin Core (microfilament)

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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

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The membrane-membrane adhesions (like glycocalyx) that allow for better fitting by forming groove. These are called

Wavy Contours

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These provide integrity and hold adjacent cells together of the same tissue

Membrane junctions

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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

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Where are tight junctions typically found?

Epithelium

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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

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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