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Flashcards in [2] Class 2:membrane Deck (66)
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1

Sheet like structures that form closed boundaries between different compartments:

Biological membranes

2

Biological membranes mainly consist of _____ and _____. ALso, _____ are linked to lipids and proteins.

Lipids,
Proteins,
Carbohydrates.

3

MEbranes have both a _____ and a ______ unit.

hydrophilic and hydrophobic

4

These are embedded in lipid bilayers and mediate distinct functions

Specific proteins.

5

Biological membranes form ________ assemblies.

Non-covalent

6

Biological membranes are symmetric or asymmetric?

Asymmetric

7

3 common features of biological membranes:

Asymmetric

Fluid structure: lipids and proteins can diffuse rapidly in the plane but not across the membrane.

Electrically polarized: (-) inside

8

Membranes are _________ b/c they contain a hydrophilic unit [polar head] and hydrophobic tail [straight or wavy lines]

Amphipathic

9

Why does oil form a monolayer when placed in water?

Polar heads are in contact w/ the water and the nonpolar hydrophobic lipid tails project into air

10

What is a consequence of the amphipathic nature of the membrane lipids?

Membrane formation

11

What are the 2 possible membrane formations of amphipathic membrane lipids?

Micelle

Lipid bilayer

12

THis is a limited structure

Micelle

13

This is favored structure for phospholipids and glycolipids:

10^6 nm =1mm

Lipid bilayer [bimolecular sheet]

14

Formation of lipid bilayers is a _______ process

Self-assembly

15

3 MAjor driving forces for the assembly of lipid bilayer [bimolecular sheet]:

Hydrophobic interactions- major force

Van der waals

Electrostatic and hydrogen-bonding

16

Attractive forces btw hydrocarbon tails

Van der waals

17

Attractions btw polar head groups and water molecules:

Electrostatic and hydrogen-bonding

18

What predominantly holds the lipid bilayer together?

Hydrophobic interactions

19

Hydrophobic interactions have 3 consequences of lipid bilayer formation:

Inherent tendency to be extensive

Tend to close on themselves leaving no edges exposed w/ hydrocarbon chains-forms compartments

Self-sealing- energetically favorable

20

Lipid bilayer low permeability for

Ions and most polar molecules

21

How difficult is it for water to traverse the membrane?

Easy- it is small, high [ ] and lack of a complete charge

22

Are all biological membranes asymmetric?

Yes

23

Is there even distribution of lipid molecules in lipid bilayers?

No, asymmetrically distributed.

Inner and outer leaf =different

24

Membrane ________ have unique orientations.

Proteins

25

Where is cholesterol present?

Large amounts of cholesterol are present in both leaflets- thought to be about equally distributed in both mono layers

26

Hydroxyl group of cholesterol is positioned wherein the membrane?

Near the polar heads of the phospholipid.

27

Rapid diffusion:

Lateral diffusion
-generally not stationary...fluid mosaic

28

Very slow diffusion:

Tranverse or flip-flop diffusion...Req's more energy

29

Do proteins move in the fluid mosaic model?
What diffusion can they perform?

Yes, laterally they do not flip-flop or tranverse diffuse through membrane.

30

How long does it take a phospholipid molecules to flip-flop?

Once in a several hours.