(29-32) Plasma Membrane and Membrane Transport

The cell is a — bound structure

membrane

How does a cell compartmentalize cellular processes?

it uses membranes to separate processes into “rooms”

7 major compartments of the cell

endoplasmic reticula, nucleus, mitochondria, golgi apparatus, lysosomes, peroxisomes and cytoplasm

Cytoplasm

compartment of the cell that surrounds all the other compartments of the cell

2 categories of membrane in the cell and their function

plasma membrane- functions in any interaction between the cell and its environment ; internal membranes- surround compartments or organelles of the cell to contain their processes

Plasma membrane makes up –% of total cell membrane while internal membrane is –%

5;95

The cell is a — barrier and — in nature

semi-permeable; dynamic

The interior of the phospholipid bilayer is — and the exterior is — and it is about — thick

hydrophobic; hydrophilic; 4-5 nm

Draw a basic phosphatidyl choline

4 primary phospholipids in the phospholipid bilayer

phosphatidyl- choline; ethanolamine; serine; or inositol

Phospholipid

formed by two fatty acids and a phosphate group connected to a R-group attaching to a sugar alcohol. makes up the bulk of the lipid component of a membrane. The R-group example used was choline.

Sphingolipids

a complex class of phospholipids that are part of the plasma membrane

How my phospholipids move?

spinning or lateral movement

What are the consequences of a “too fluid membrane”? What if it isn't fluid enough?

the barrier is no longer selective if too fluid but if isn’t fluid enough then its packed tight and needed material may not move through

How does temperature affect membrane fluidity?

higher temp results in higher fluidity

How does phospholipid tail length affect membrane fluidity?

shorter tails=more fluid

How does unsaturated fatty acid content affect membrane fluidity? why?

more unsaturated fatter acid= more fluid (kinks cause it to be harder to pack together)

How does saturated fatty acid content affect membrane fluidity? why?

more saturated fatty acid= less fluid (they can pack together tighter)

Can phospholipids switch monolayers?

no

What environmental signals cause an organism to change the concentration of saturated vs unsaturated fatty acid in their membranes?

temperature or pressure

What phospholipid comprises most of the outer layer of the phospholipid bilayer? This gives the outer layer a more — charge

phosphatidyl choline; positive

What phospholipid types always face the inside of the cell? (even on vesicles)

ethanolamine; serine; inositol

What phospholipid type always faces away from the cell

choline

Certain cells have a more exaggerated difference in the — between the outer and inner layer of the bilayer. — or — cells are examples of cells that have a larger difference

charge; muscle or nerve

Draw a basic structure of a sterol

Sterols are relatively — in nature and have — groups attached to the — part of their structure. This creates a — ringed area and a — chain area on the molecule

planar; hydroxyl; ringed; polar; nonpolar

How does cholesterol content in a membrane affect fluidity? why?

more cholesterol=less fluidity (it impedes phospholipid movement)

Glycolipid (structure and function)

structure- some type of lipid (usually a phospholipid) that has a sugar attached to it (usually in the form of an oligosaccharide). function-acts as a marker for the cell to identify the type of cell that it is

Glycolipids are always found in the — monolayer and the sugar points — from the cell

outer; away

Certain cells, like nerve cells, depend on — to do their function

glycolipids

What class of molecule is myelin?

glycolipid

In cell membrane lipids are more — while proteins are more —

structural;functional

In general there is about a — ratio of proteins to lipids by mass but a — ratio of proteins to lipids by molecule which indicates that the proteins are —

50/50; 1/50; bigger

Transmembrane protein

membrane protein which spans the whole lipid bilayer

Peripheral protein

membrane protein which interacts with only one monolayer of the lipid bilayer and does not flip monolayers

Domains of a transmembrane protein include?

cytoplasmic, transmembrane, and outside domain

With transmembrane proteins — and — structures are usually found in the transmembrane domain

alpha helix and beta sheets

Draw an example of a “buttonhole” transmembrane protein and and a peripheral protein with a hydrophobic “anchor” region

What ways does a peripheral protein anchor to its monolayer?

a hydrophobic domain, a lipid attachment (lipoprotein), or binding to another membrane protein via a weak bond

Because proteins are larger, they don’t — as much as lipids and may not even — at all

move

Diffusion and what molecules may diffuse through a cell

moving from an area of high concentration to low concentration across a barrier. Molecules that can diffuse through a cell membrane include water, small molecules, or ions.

Cell must manage both — and — homeostasis

osmotic and ionic

t/f water may be pumped (explain you reasoning)

false, it either pass through the membrane by diffusion or it follows ions

The plasma membrane is not a barrier, it is a —

selective filter

Membrane transport proteins

specific transmembrane or peripheral proteins that will physically bind molecules and move them from one side of the plasma membrane to the other

t/f membrane transport proteins are faster than diffusion (explain why)

true; diffusion is based on a gradient where as the proteins are based on binding and releasing

t/f all membrane transport proteins require energy

false

Active transport vs facilitated/passive transport

active transport refers to membrane transport proteins that require energy to work where as passive or facilitated do not

Advantages of membrane transport proteins over diffusion

may move against a gradient, faster,

t/f membrane transport proteins can move macromolecules (explain answer)

false, that's a different mechanism altogether

Carrier protein

membrane transport protein family that includes uniport, symport and antiport carrier proteins

Uniport carrier protein

membrane transport protein which binds to one unique molecule and moves it in one direction

Symport carrier protein

membrane transport protein which binds to 2 unique molecules and moves them in one direction. Important to gut epithelium.

Antiport carrier protein

membrane transport protein which binds to 2 unique molecules and moves them in 2 different directions

Sodium potassium ATPase

antiport carrier protein which transports sodium in one direction and potassium in the other. 10-30% of cell energy goes to this protein

Channel proteins and their benefits

membrane proteins which act as "gates" for molecules to move across via diffusion; benefits-they are specific for certain ions and allow for a quick redistribution of molecules

2 ways to open channel protein gates

ligand binding or voltage

Most channel proteins are designed to move — via — properties

ions;diffusive

true/ false channel proteins physically bind the molecules that they move across the membrane

false

How do voltage channel proteins open

for a split second the polarity across the membrane changes which causes the gate to open and then it closes as it depolarizes

Voltage channel proteins are important to what specific type of cells?

nerve cells

What type of molecules do not need membrane transport proteins to cross the cell membrane?

nonpolar molecules such as steroids

— is the process of bringing in groups of molecules into the cell while — is releasing a group of molecules from the cell

endocytosis;exocytosis

Endocytosis

process by which a group of molecules is brought into the cell. Forms a vacuole/vesicle with the molecules in the cell. Results in loss of some of the cell membrane. Occurs all the time and anywhere on the cell surface

Exocytosis

process by which material (often waste) is exported from a cell. Happens only when signalled and at specific locations on the cell surface. Results in the gain of some cell membrane

Phosphatidyl choline point which direction in a vesicle within a cell?

towards the inside of the vesicle

Vesicles are attached to — which pull them their desired location

actin microfilaments

Phagocytosis

form of endocytosis, larger vesicles and usually filled with organic macromolecules

Pinocytosis

form of endocytosis, smaller vesicles and usually fluid filled

Normally exocytotic vesicles bind to a region with a large amount of —

calcium ions

How do cells “order” specific molecules?

it uses LDL (low density lipoprotein) receptors which are inserted into the plasma membrane

LDL

low density lipoprotein. Binds to LDL receptors of cells

Clathrin (draw a picture of one as well)

coats the inside of endocytotic vesicles which involve LDLs. huge homotrimer which crosslinks with itself to protect the vesicle and ensure it reaches a specific target location

t/f clathrin is involved in all endocytotic processes (explain answer)

false, clathrin and receptors are used only in receptor mediated endocytosis

Receptor mediated endocytosis

endocytosis which involves the binding of LDLs to LDL receptors on a cell as well the formation of a clathrin coat within the vesicle

What happens to a clathrin coat when its vesicle reaches its location?

it breaks apart back into individual trimers