Which of the following is true of the structures labeled c in the cell membrane?

This is a quiz of multiple choice style questions about the structure of membranes, topic 1.3

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What term refers to a property of fatty acid chains of a phospholipid?

Hydrophobic

Hydrophilic

Amphipathic

Polar

Long hydrocarbon chains are nonpolar and will not mix with water so are hydrophobic.

This student diagram shows the arrangement of molecules in the fluid mosaic model of cell membranes.

Which of the following correctly identifies the labels A to D?

A = integral protein, B = cholesterol, C = phospholipid, D = peripheral protein

A = integral protein, B = glycoprotein, C = fatty acid tails, D = peripheral protein

A = integral protein, B = phospholipid, C = peripheral protein, D = cholesterol

A = peripheral protein, B = cholesterol, C = phospholipid, D = integral protein

It is important to be able to draw and recognise the components of cell membranes.

Which of the following best describes an integral protein?

A protein attached to the surface of the membrane  

A protein within the cytoplasm  

A protein enclosed in a vesicle

A protein embedded in the phospholipid membrane

Integral proteins can be transmembrane - going across the membrane to be exposed on both sides - or embedded on one side of the membrane.  If an integral membrane is removed, the membrane will be disrupted.

Which of the following is the term describing a protein attached to the surface of the membrane?

Cytoplasmic protein

Peripheral protein

Integral protein

Transmembrane protein

Peripheral proteins can be removed from the membrane without the disruption of the membrane.

Cells are able to take in droplets of fluid or small particles from outside of the cell to form vesicles containing this liquid. 
Which of the following best describes this transport mechanism?

Endocytosis by the formation of mesosomes

Endocytosis by infolding of the plasma membrane

Exocytosis leading to endosymbiosis

Exocytosis by infolding of the plasma membrane

Endocytosis occurs by infolding of the plasma membrane to take in or engulf particles or liquid.

Which of the following helps maintain the structure of a cell membrane?

Hydrophobic interactions with phosphate heads

Hydrophobic interactions between fatty acid chains

Hydrogen bonding between water and cholesterol

Hydrophilic interactions between water and fatty acids

Phospholipids are amphipathic - having both hydrophobic fatty acid chains that repel water and polar heads that are hydrophilic and so attract water. Hydrophobic interactions between the fatty acid chains hold the phospholipid bilayer together.

During exocytosis, the following events occur. What is the correct sequence of these events?

I. Formation of a vesicle by the Golgi apparatus
II. Secretion of the vesicle's contents
III. Fusion of the vesicle with the plasma membrane
IV. Movement of the vesicle towards the plasma membrane

I, II , III, IV

IV, II, III, I

I, IV, III, II

II, III, IV, I

Exocytosis is the release of materials from the cells.  Vesicles are made by the Golgi apparatus for exporting from cells.

Which part of a plasma membrane is responsible for preventing the free movement of ions into and out of the cell?

Glycoproteins

Cholesterol

Phospholipid bilayer

Channel proteins

Phospholipids have nonpolar tails in the interior of the membrane which would repel the charged ions.  Ions tend to move through channel proteins or by active transport selective pumps.

Which of the following describes facilitated diffusion?

The passive movement of a particle across a cell membrane via a channel protein.  

The movement of a particle up a concentration gradient helped by active pumping.  

The movement of a particle down a concentration gradient helped by active pumping.  

The passive movement of a particle through the phospholipid bilayer of the cell membrane.  

Facilitated diffusion is passive transport
Active transport moves molecules up a concentration gradient so B is wrong.

Facilitated diffusion involves a channel protein.

A membrane protein could have which of the following functions?

Enzymatic action  

Thermal insulation  

Energy storage  

Oxygen uptake  

Enzymatic action by immobilised enzymes are critical functions of membranes, so D is correct.

Energy storage would be by glycogen in animals or starch in plants.

Oxygen uptake is by hemogolobin which is within red blood cells.

Thermal insulation is done by layers of fat under the skin not at the membrane level

Which statements are characteristics of the diffusion of oxygen through membranes?
I. Molecules are transported in channel proteins.
II. Molecules pass through the phospholipid bilayer.
III. Molecules more down a concentration gradient.

II and III only  

I and III only  

I, II and III  

I and II only  

Oxygen molecules are small, non-polar and uncharged. They can pass through the phospholipid bilayer of membranes by simple diffusion.  They move from a high concentration to a lower concentration, down a concentration gradient.

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