Essential Cell Biology: Chapter 11

What are the advantages of compartmentation?

allows for the creation of ordered systems and efficiency of processes

What are the disadvantages of compartmentation?

obtaining nutrients, energy, and information is harder as well as disposing of waste and information.

What are the primary functions of membranes?

compartmentation, scaffolding, keeping ion imbalance, energy transformation, gas and water exchange, nutrient uptake, catalysis, cellular communication, binding, and transportation.

true or false: the only membrane is that which surrounds the cell.

false. All the organelles are membrane bound, especially the nucleus. These are called inter cellular membranes.

What is a membrane made of?

a hydrophobic phospholipid bilayer

What in the membrane is used for transmission and communication?

proteins embedded in the membrane.

Why is the a hydrophobic lipid bilayer the ideal structure for a membrane?

helps keep hydrophilic molecules in separate compartments

What is the general structure of a phospholipid?

functional group, phosphate group, and a glycerol group make up the head which is attached to two hydrocarbon tails

is the head group of a phospholipid hydrophobic or hydrophilic?

hydrophilic. The head group is polar, which is ideal for a stable interaction with an aqueous environment.

is the tail group of a phospholipid hydrophobic or hydrophilic?

hydrophobic. The tails are made of long hydrocarbons which are non polar and do not have a stable interaction with aqueous environments.

What is the advantage of the structure of a phospholipid?

Because lipids contain polar and non polar groups, they easily form membranes in aqueous environments.

What are triacylglycerol commonly known as?

fats and oils

What is the charge and structure of triacylglycerols?

triacylglycerols are nonpolar making them hydrophobic. a glycerol group has two hydrocarbon tails on one end and one hydrocarbon tail on the other.

what is the charge on cholesterol?

they are polar and tend to be partially charged.

What are the two classes of lipids?

storage and membrane lipids

What is the main storage lipid?

triacylglycerols

What are the two classes of membrane lipids?

phospholipids and glycolipids

What are the two classes of phospholipids?

glycerolphospholipids and sphingolipids

What is the main class of glycolipids?

sphingolipids

What additional group do glycolipids contain?

a monosaccharide group or oligosaccharide group

What is the general structure of glycerolphospholipids?

two fatty acid tails attached to a glycerol group which is attached to a phosphate which is attached to an alcohol

What is the general structure of a sphingolipids

one fatty acid tail attached to a sphingosine attached to a phosphate attached to a choline if it is a phospholipid

OR

one fatty acid tail attached to a sphingosine attached to a monosaccharide or oligosaccharide.

What are the major head groups for glycerolphospolipids? When those head groups are present, what is the lipid name?

choline, serine, ethanolamine, inositol

phosphatidylcholine, phosphotidylserine, phosphotidylthanolamine, phosphotidylinositol

What makes a glycerolphospholipid different from other phospholipids?

there are two alcohols which are linked to one fatty acid chain. The fatty acid chain contains a carbonyl group

What is the defining feature of a sphingolipid?

there is no carboxylic acid group, instead there are 2 hydroxyl groups and an amine group

What are the four major sphingolipids and their defining features?

1. sphingosine is just sphingosine

2. ceramide is a sphingosine group plus a fatty acid. it contains an amide bond

3. sphingomyelin is a ceramide with a phosphocholine head group

4. glycosphingolipids, are ceramide with a mono or ogliosaccharide.

phospholipids are both hydrophilic and hydrophobic because of their polar head an non polar tail. What is another name for something which is bother hydrophilic and hydrophobic.

amphipathic

What does the amphipathic nature of lipids allow for?

the formation of a hydrophobic layer that is still stable in an aqueous environment.

What type of bond links the hydrophobic and hydrophilic parts of a phospholipid? What does this provide?

a covalent bond which provides stability.

What shape does a lipid bilayer form in water?

a sphere. This is due to the need for none of the center of the membrane (hydrophobic) to be exposed to an aqueous environment. This allows for the ability to create a compartment.

true or false: membranes are made of many different types of lipids.

True. Many types of lipids are used to make up a membrane.

What does the composition of the membrane depend upon?

the membrane leaflets, the organelles or the organisms

true or false: membranes tend to be symmetrical

false. most membranes are display asymmetry

What, overall, does the composition of the membrane effect.

the composition of the membrane effects the physiology of the membrane

What are the frequent movement patterns of lipids within a membrane?

lateral diffusion, flexion and rotation

What kind of bonds holds the fatty acid tails of a membrane together?

weak van der waal bonds

what is the infrequent movement pattern that lipids in a membrane perform?

a flip flop

which way is a flip?

towards the cytoplasmic face

which way is a flop?

away from the cytoplasmic face, lumen of organelles, or outer plasma membrane

which proteins can be used to carry out a flip flop motion?

flippase and scramblase

what does the scramblase do?

catalyzes the transfer of RANDOM phospholipids from one layer to another in order to create symmetrical growth of both bilayers. They can move lipids in any direction.

what does the flippase do?

catalyzes the transfer of SPECIFIC phospholipids to cytosolic membrane. This create asymmetric growth of the bilayer which is often observed in organelle membranes. The flippase can only move things in one direction.

Why is fluidity important to a membrane?

fluidity is required for membrane function, though a membrane which is too fluid can compromise the integrity of the compartmentation of the membrane.

how is membrane fluidity measured?

a method called FRAP. Through chemically attaching a flourescent molecule to the protein or lipid of interest. a section of the membrane can be bleached to see how long it takes for the bleached molecules to spread.

what type of double bond in a fatty acid is very rare in nature?

trans fatty acids

what is the process for making trans fatty acids?

hydrogenation (partial)

what are the two main factors which effect membrane fluidity?

composition and temperature

how does the addition on unsaturated fatty acids effect the fluidity of the membrane

due to the kink of the unsaturated fatty acid tail a space is created which allows for more fluidity in the membrane bu reducing bonding

how does cholesterol effect the membrane fluidity?

cholesterol can fit into the kinked space of the lipid bilayer, increasing the bonding and causing the membrane to become less fluid, but there is no data which explains how cells regulate this.

what is the effect of lateral bonding on membrane fluidity?

tighter packed bonding creates a less fluid membrane.

how does temperature effect membrane fluidity?

colder temperatures cause membranes to lose fluidity.

how do cells regulate fluidity of membranes with temperature change?

by regulating the percentage of saturated to unsaturated fatty acids.

how are fatty acids changed from saturated to unsaturated?

oxidation/ reduction mechanism

can fatty acids be converted between saturated and unsaturated?

saturated fatty acids can become unsaturated fatty acids, but unsaturated fatty acids cannot become saturated fatty acids.

what are membrane proteins?

proteins which are embedded in the membrane that aid in the function of the membrane

what are the classes of membrane protein?

transporters/ channels, anchors, receptors, and enzymes

what is the function of a transport or channel membrane protein?

to move things in and out of the cell

what is the function of an anchor membrane protein?

to bind things to the membrane.

what is the function of a receptor membrane protein?

to receive signals

what is the function of an enzyme membrane protein?

to catalyze reactions

What must the electrostatic character of a membrane protein be?

because the membrane is hydrophobic, the outers of the protein must also be hydrophobic, but the inners can be hydrophilic because they do not come in contact with the fatty acid tails

what are the associations of membrane proteins in lipid bilayers?

transmembrane, monolayer associated, lipid linked, and protein attached.

what is a trans membrane protein?

a membrane protein which associated with the lipid bilayer with some of the protein in the membrane and some hanging into the extracellular space.

what is the typical domain of a trans membrane protein?

an alpha helix with one or many domains but beta sheets can also be formed to make a barrel as a channel

what is a mono layer associated membrane protein?

a protein which sits on one side of the lipid bilayer.

what is a lipid linked membrane protein?

a protein where the lipid is not actually in the membrane, but rather is attached to a lipid which is attached to the membrane. The lipid wants to be on the membrane and pulls the protein to the membrane in order for the protein to work.

What is a protein attached membrane protein/

a protein which is not in the membrane but is attached to another protein which is in the membrane.

how do membrane proteins make themselves hydrophobic in order to create a stable situation in a membrane?

a polypeptide chain in (usually) the shape of an alpha helix is composed of around 20 hydrophobic amino acids.

how do membrane proteins allow hydrophilic things to pass through them while still being stable with the hydrophobic membrane?

multiple protein domains each with a hydrophobic side facing out and a hydrophilic side facing in

what is the best form to study proteins in?

their pure form

how are proteins extracted from a membrane?

detergent is used to break up the membrane. from there the proteins can be purified an put in an artificial membrane to study their function.

how can protein structure be determined?

through x-ray crystallography. proteins are highly purified and then crystallized

why is using x-ray crystallography difficult with membrane proteins?

the fluid mosaic nature of membrane proteins make them difficult to crystallize.

what is a glyco protein?

a protein which has a sugar on it's surface.

can glycoproteins be found in all organisms?

no. they are only found in animal cells.

what is a glycoclyx?

many cells which are associated with carbohydrates

what are glycoclyx made of?

glycolipids and glycoproteins

what does the glycoclyx do?

provides a function and specificity. ex. blood type. mostly helping with protection, water retention and specific binding

what is a main example of glycolipids and glycoproteins working?

in white blood cell signalling. They signal for neutraphills to move towards a certain site during infection.