Biological Membranes

Question 1

What is the nature of lipids

Answer 1

They are hydrophobic in nature

Question 2

Describe fatty acids

Answer 2

• they are hydrocarbon carboxyllic acids
• they are amphiphilic or amphipathic

Question 3

What is saturated, what is unsaturated

Answer 3

Saturated: only single bonds present

Unsaturated: double bonds present (creates bend in chain)

Question 4

What conformation is assumed when talking about double bonds (cis or trans)

Answer 4

It is assumed that double bonds are in the cis form unless stated otherwise

Question 5

What end do you start counting from for identifying double bonds

Answer 5

You start counting from the carboxy end of the fatty acid chain

Question 6

How would you describe fatty acids (amphiphyllic or amphipathic) what do these terms mean

Answer 6

Amphipathic

They mean that the molecule has both hydrophobic and hydrophilic parts

Question 7

What do double bonds do to fatty acids molecules

Answer 7

It creates a kink in the chain

Question 8

Can unsaturated fatty acids stack together effectively

Answer 8

No they can not because there is a kink in their chains preventing proper stacking interactions

Question 9

What 2 things are fatty acids melting points affected by

Answer 9

1. Length
2. Unsaturation

Question 10

At what temperatures does each melt at? (Higher or lower)
1. Longer fatty acids
2. Shorter fatty acids

Answer 10

1. Longer fatty acids: melt at higher temperatures
2. Shorter fatty acids melt at lower temperatures

Question 11

What does melting point of fatty acids reflect

Answer 11

The amount of energy needed to separate molecules

Question 12

What temperatures do each melt at
1. Saturated fatty acids
2. Unsaturated fatty acids

Answer 12

1. Saturated fatty acids: melt at higher temperatures
2. Unsaturated fatty acids: melt at lower temperatures

Question 13

What do fatty acids form when placed in water what shape are they

Answer 13

They form a micelle

They are cone shaped

Question 14

What is an ester bond formed between

Answer 14

Between a hydroxyl and a carboxyl group

Question 15

How are fatty acids stored, are they water soluble

Are they amphipathic

Answer 15

They are stored as triglycerides or TAGs

No the are NOT water soluble

No they are NOT amphipathic, they are only hydrophobic

Question 16

How is an acyl group made

What does it contain

Answer 16

By removing one or more hydroxyl groups form an oxo acid

It has a double bonded oxygen and an acyl group

Question 17

What kind of triglyceride is the most common

Answer 17

Mixed TAGS are the most common

Question 18

What is the difference between glycolipids and sphingolipids

Answer 18

Glycolipids have a smaller head group

Sphingolipids have a very large heat group

Question 19

What do glycolipids and sphingolipids form

What is the generic make up

Answer 19

They form bi layers

They have a polar head group and 2 acyl chains

Question 20

What specific thing are sphingolipids involved in

Answer 20

Cell to cell communication

Question 21

What are the three main classes of membrane lipids

Answer 21

• sphingolipids
• glycolipids
• cholesterol

Question 22

Describe cholesterol

Where is it found

Answer 22

Have a very small head group so small it is not considered to be polar

It is found in between phospholipids

Question 23

How many 6 members rings does cholesterol have

How many 5 membered rings does cholesterol have

What is it a precursor for

Answer 23

3 (6 membered rings)

1 (5 membered rings)

It is a precursor to steroid hormones

Question 24

Is cholesterol (hydrophobic or hydrophilic)

What does it maintain (fluid or rigid)

Answer 24

It is mostly hydrophobic

It maintains BOTH fluidity and rigidity

Question 25

Is cholesterol amphipathic? Can Cholesterol form membranes on its own?

Answer 25

Yes it is WEAKLY amphipathic No it can not

Question 26

Is the formation of lipid membranes covalent?

Answer 26

No, they form based on non-covalent interactions

Question 27

Are lipid bilayers stable

Answer 27

Yes but they are still fluid

Question 28

What does the melting temperature or the transition temperature of a lipid bilayer represent

Answer 28

It shows the transition of an ordered gel phase to a liquid crystaline phase

Question 29

How does cholesterol regulate membrane fluidity at high and at low temperatures

Answer 29

High temperatures: keeps the membrane more rigid by limiting the movement of fatty acid tails Low temperatures: keeps the membrane more fluid by preventing them from clustering together

Question 30

Is the transition temperature usually sharp for biological membranes

Answer 30

No but they do have a range of melting temperatures

Question 31

How do lipids move in the lipid membrane bilayer

Answer 31

They only move laterally and quickly

Question 32

True or False: lipids go under transverse diffusion

Answer 32

False lipids do NOT go under transverse diffusion If they do they kneed flippases and flop passes to do it (proteins)

Question 33

Why do lipids not go under transverse diffusion

Answer 33

They do not go under transverse diffusion because they have to cross a large energy barrier to do so because their polar head group would have to pass through a hydrophobic area

Question 34

What are the three types of membrane proteins

Answer 34

- integral membrane proteins - peripheral membrane proteins - lipid linked membrane proteins

Question 35

What carry out most membrane processes

Answer 35

Proteins

Question 36

How can integral membrane proteins be separated from a membrane

Answer 36

Can only be separated from the membrane by agents which disrupt the membrane

Question 37

What kind of proteins are usually found on the outer mito mem layer, are they common

Answer 37

Beta barrels No

Question 38

Is the fluid mosaic model covalent of non-covalent

Answer 38

It is a non-covalent structure

Question 39

What molecules can cross the lipid bilayer by diffusion

Answer 39

Small Non polar molecules, ethanol, and water

Question 40

What are the three things that the rate of simple diffusion depends on

Answer 40

1. Concentration gradients 2. Lipid solubility (polar vs. Non-polar) 3. Size of molecule

Question 41

What kind of proteins are usually used to reduce the activation energy barrier across lipid bilayers (membranes)

Answer 41

Multipass proteins

Question 42

What two membrane proteins are only for passive transport

Answer 42

1. Potin channels (beta) 2. Ion channels (alpha)

Question 43

How to transporter and carrier proteins work

Answer 43

They transport substances across the membrane via conformational changes they are selective for the substrate that they are transporting

Question 44

What membrane proteins can participate in both active and passive transport

Answer 44

Carrier mediated proteins

Question 45

What are the three classifications of carrier proteins Does this apply to ion channels and porins

Answer 45

1. Uniport 2. Symport 3. Antiport No

Question 46

Is there such thing as a secondary active uniport

Answer 46

Nope

Question 47

How is secondary transport created or used

Answer 47

It uses primary active transport to go against another concentration gradient

Question 48

What are the three main purposes for the sodium potassium pump

Answer 48

1. Keep resting membrane potential 2. Effect transport 3. Regulate cell volume

Question 49

Describe the steps involved in the Na and K ATPase (8) steps start at K dissociating from protein

Answer 49

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