Biochemistry 3380G Lecture Notes - Lecture 7: Beta Sheet, Cytosol, Hydrogen Bond

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2 Feb 2015

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Example: potassium channel: has four different subunits coming together to make a channel. Ion doesn"t go through the alpha helix, multiple alpha helices come together and form a hole in the middle. Application: toxins target ion channels: the venoms of poisonous animals contain small peptides, some of which bind to ion channels, disrupting their function, result: prey is paralyzed, example: cone snails. Transmembrane proteins: proteins usually span membranes as alpha-helices, single alpha-helix of about 20 hydrophobic amino acids, multiple alpha-helices, often with hydrophilic centre, proteins can also span membranes as beta, hydrophobic exterior, hydrophilic interior. Mobility of integral membrane proteins sheets: proteins can diffuse in plane of bilayer, except when restricted. Peripheral membrane proteins: protein-attached proteins, they can usually be removed from membranes under relatively mild conditions that leave the lipid bilayer intact. Membrane proteins are often modified by carbohydrates; such proteins are called glycoproteins.

Related Questions

PART A) Which statement is false? A) Amphipathic molecules may form micelles rather than bilayers, depending on their structures. B) All biological membranes contain lipids.

C) Biological membranes typically contain proteins. D) All biological membranes have the same composition.

PART B) Which statement is true? A) Once a membrane is synthesized, the lipid composition of each monolayer does not change. B)Hydropathy analysis provides a measure of H-bonding within the transmembrane portion of a membrane-spanning protein. C)Proteins may be embedded in, but never span, a biological membrane. D)For all glycoproteins of a plasma membrane, the glycosylated domains are always found on the extracellular face of the bilayer.

PART C) Which statement is true? A)Lipid bilayers are essentially impermeable to polar solutes. B)The fluid mosaic model considers biological membranes to be a sea of lipids floating in the aqueous fluid of the cytoplasm. C)Membrane phospholipids always comprise the majority (by weight %) of a cell membrane. D) All membranes in a given cell have the same lipid composition.

Please help with 1,2,3 Thanks

A set of erythrocytes is placed in a beaker of 0.9% NaCl.Nothing appears to happen to the cells. Why?

0.9% NaCl is hypertonic to the cells.

Sodium blocks the movement of water.

0.9% NaCl is hypotonic to the cells.

0.9% NaCl is iostonic to the cells.

water has not moved at all.

Question 2

Select one answer.

Which substance would be mostlikely to pass through a lipid bilayer/plasma membrane withoutembedded proteins?

water

a steroid hormone

a large fatty acid

a large peptide hormone

a sodium ion

Question 3

Select all that apply.

Which of the following can cross the cellâs plasmamembrane without the assistance of protein transporters?Select all that apply.

large polar molecules

positively charged ions

small hydrophobic molecules

gasses

Question 4

Select one answer.

Biological Membranesare:

symmetrical.

impermeable.

static.

dynamic.

Question 5

Select one answer.

How does the selectivepermeability of the membrane help the cell.

This allows the cell to maintain the proper shape.

This allows the cell to regulate what enters and exits

This allows the cell to maintain a constant temperature.

All of these

Question 6

Select one answer.

What is the role of carbohydratesin the plasma membrane?

cellular identification

adhesion

transport materials across the membrane

help maintain fluidity

Question 7

Select one answer.

Which component of the plasmamembrane has the widest variety of functions?

sterols

carbohydrates

phospholipids

proteins

Question 8

Select one answer.

All of the following have aneffect on the fluidity of a membrane except:

interactions among fatty acids in the core of the bilayer

the cholesterol content

the ratio of saturated to unsaturated fatty acids

the presence of integral proteins in the membrane

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Biochemistry 3380G Lecture Notes - Lecture 7: Beta Sheet, Cytosol, Hydrogen Bond

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