Membranes and Transport

Lipid portions of molecules:

Are hydrophobic and are comprised primarily of Carbons and Hydrogens

Long, saturated fatty acid tails ______________ lipid mobility and ______________ membrane fluidity.

reduce; decrease

True or False: purified phospholipids will gather together and form membranes only if the appropriate enzyme is present

False

All cells have:

Genetic information

The interior region of a phospholipid bilayer can be characterized as being:

Hydrophobic

Synthesis of a protein destined to function in the nucleus occurs:

In the cytosol

A protein pump that requires ATP hydrolysis to provide energy to move a molecule across a membrane is involved in

Primary active transport

The sodium/potassium pump is an example of:

Antiporter

Which of the following does NOT occur in prokaryotes?

Protein trafficking through the endomembrane system

A lipid bilayer would be least fluid if the membrane's lipid groups were exclusively of this type:

Saturated fatty acids

Which of the following molecules would most likely require a transport protein to cross the plasma membrane of a red blood cell?

C6H12O6

What factors are required for facilitated diffusion to occur?

A. a concentration gradient B. a plasma membrane C. a transport protein

Imagine you have radioactively labeled a protein in the lumen of the endoplasmic reticulum. Where would you predict the labeled protein might end up?

A. in the lumen of the Golgi apparatus B. in the lumen of a vesicle C. outside the cell

Which of the following is part of the endomembrane system of a eukaryotic cell?

A. nuclear envelope B. Golgi apparatus C. vesicles

Which type of cell has a biological membrane that separates the extracellular environment from the interior of the cell?

A. prokaryotes B. eukaryotes C. archaea D. bacteria

Some diseases can result from defective transport across the membrane. For example, cystic fibrosis results from a chloride ion transporter that does not function. Which of the following would be affected when this transporter does not function?

A. the chloride concentration gradient B. the electrical gradient of the cell

Which one of the following would be least likely to cross a lipid bilayer?

ATP (this is a ribonucleotide triphosphate)

A cell's plasma membrane contributes to homeostasis by:

Acting as a selective barrier

What is aquaporin?

An H2O channel

A phospholipid molecule in a membrane can:

Both spin (rotate around its vertical axis) and move side-to-side (lateral movement).

Large molecules, such as mRNAs and tRNAs, are able to exit the nucleus

By moving through pores in the nuclear envelope

An amphipathic molecule is one that:

Contains both polar and non polar regions

Which of the following accurately describes the path travelled by a new protein as it is synthesized and released from the cell?

Cytosol → ER → Golgi → transport vesicle → plasma membrane → external environment

Movement of cellular material from the endoplasmic reticulum to the outside of the cell is an example of:

Exocytosis

The process of a vesicle fusing with the plasma membrane and depositing its contents into the extracellular space is most specifically referred to as:

Exocytosis

Blood glucose concentration after a meal containing carbohydrate rises above 5 mM in humans. Glucose concentration inside muscle cells is not much higher than 0 mM. If muscle cells have facilitative glucose carriers in their plasma membranes, which way would glucose diffuse after a meal?

Into muscle cells

Which of the following molecules would not easily diffuse across a plasma membrane without participation of a protein?

Large polar molecules

During osmosis, water moves from a region of _________ to a region of _________.

Low solute concentration; high solute concentration

RNA molecules are transported from the nucleus to the cytoplasm in eukaryotes through:

Nuclear Pore Complexes

What type of molecule would you not expect to find as a component of a cell's membrane?

Nucleic Acid

The movement of water into or out of a cell is an example of:

Osmosis

An mRNA is transcribed in the nucleus of a eukaryotic cell. Where is this mRNA translated?

The cytosol

Protein synthesis can occur in all of these subcellular locations EXCEPT

The nucleus

Which one of the following is not considered part of the cytoplasm?

The nucleus

Predict how phospholipids would arrange themselves if they were placed into a nonpolar solution.

The phospholipid tails would orient toward the solution.

What is secondary active transport?

The use of the electrochemical gradient of one molecule to move a second molecule, when primary active transport maintains the electrochemical gradient

Amphipathic lipids can form lipid bilayers in water because:

Their polar and/or charged head groups associate well with water and the lipid tails associate away from water

To pump Na+ and K+ against their concentration gradients, the Na+/K+ ATPase harnesses energy from the exergonic reaction of hydrolysis of adenosine triphosphate (ADP) to adenosine diphosphate (ADP) and an inorganic phosphate (Pi). What prevents ATP from being completely depleted from a cell?

There are metabolic pathways that can couple exergonic reactions to the formation of a new phosphoanhydride bond on ADP to regenerate ATP (ADP + Pi --> ATP).

Intravenous fluids generally contain NaCl or other solutes so that the concentration of dissolved molecules in the fluid is similar to the concentration of dissolved molecules in the bloodstream. Why is this?

This prevents the osmotic fluid shifts into cells that would occur if the intravenous fluid were hypotonic

Why does active transport require ATP energy?

To allow the movement of molecules from low to high concentration