ANAT 262 Lecture : 3, Carriers and channels.pdf

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ceruleanprairie-dog589

21 May 2012

School

McGill University

Department

Anatomy & Cell Biology

Course

ANAT 262

Professor

John Presley

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Document Summary

Carriers, channels and electrical properties of the membrane: Membrane transport is, of course, selective in nature and it has some important functions: Allows a cell to take in and release compounds in accordance with its biological function: e. g. the uptake and release of oxygen by red blood cells in response to cell needs. Allows cells to regulate characteristics of this transport: e. g. the increased transport of glucose into muscle cells during activity again, depending on the need. The membranes define the exterior edges of cells and divide them into compartments. They are composed of amphipathic phospholipid, meaning a portion of the molecule is charged, while the rest is uncharged or hydrophobic. The lipids align to form a bilayer, with the charged (polar, hydrophilic) portions, or heads facing the aqueous environment and the uncharged (non- polar, hydrophobic) portions or tail interacting with each other within the bilayer. The cell membrane is composed of various types of lipids and proteins including:

Related Questions

(Multi-select question)

Membrane transport -

a) Traverses the entire bilayer

b) hydrophilic amino acids interact with the interior of the bilayer

c) transport of polar molecules across membrane through channels

d) hydrophobic amino acids interact with the aqueous cytoplasm

violetcat892

Predict what amino acids line the inner channel of a protein that transports protons (H⁺) across membranes compared to the inner channel of a protein that transports a negatively charged substance across membranes.

A.Both channels are lined with hydrophobic amino acids

B.Both channels are lined with hydrophilic amino acids

C.The H⁺ transporterâs inner channel is lined with hydrophobic amino acids; the other transport proteinâs inner channel is lined with hydrophilic amino acids.

D.The H⁺ transporterâs inner channel is lined with hydrophilic amino acids; the other transport protein is lined with hydrophobic amino acids.

E.One cannot answer this question without knowing what the other transported substance is.

blackmule728

1. What biochemical feature of a phospholipid molecule allows phospholipids to spontaneously form closed compartments when placed in an aqueous solution?

a) they are amphipathic

b) they are charged

c) they are spherical

d) they have a single fatty acid tail

2. Other than phospholipids, what molecule do cells use to alter the fluidity of biological membranes?

3. What distinguishes active transport from passive transport?

a) active transport can utilize channel proteins

b) passive transport does not utilize carrier/transporter proteins

c) active transport requires the input of energy

d) active transport only occurs at the plasma membrane

4. In the case of active transport, the Na+/K+ pump undergoes a sequence of conformational changes that allows the movement of Na+ and K+ across a membrane against their electrochemical gradients, while in the case of ER protein import SRP undergoes a sequence of conformational changes to allow the signal sequence to interact with the translocation pore. What drives these conformational changes?

a) hydrolysis of a high energy phosphate bond

b) binding of a solute or protein

c) both

d) neither

5. Is protein import into the ER co-transcriptional, or co-translational?

burgundyhyena124

ANAT 262 Lecture : 3, Carriers and channels.pdf

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