Lecture 4

Which of the following statements about passive transport is correct?

• Passive transport does not occur in the human body.

• Passive transport operates independently of diffusion.

• Passive transport operates independently of the concentrations of the moving solute.

  
  

• Passive transport permits the solute to move in either direction, but the net movement of solute molecules occurs down the concentration gradient of the molecule.

A single plant cell is placed in an isotonic solution. Salt is then added to the solution. Which of the following would occur as a result of the salt addition?

• The added salt makes the solution hypotonic compared to the cell. Water will enter the cell by osmosis.

• Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease.

• There would be no osmotic movement of water in response to the added salt.

• Water would enter the cell by osmosis, and the cell would swell.

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Which of the following is a correct difference between active transport and facilitated diffusion?

• Active transport involves transport proteins, and facilitated diffusion does not.

• Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot.

• Facilitated diffusion requires carrier proteins, but active transport requires channel proteins.

• Active transport requires energy from ATP, and facilitated diffusion does not.

Which of the following pairs correctly matches a membrane transport process to its primary function?

• None of the listed responses is correct.

• osmosis: passive diffusion of water and small solutes across a membrane

• pinocytosis: the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane

• phagocytosis: secretion of large particles from the cell by fusion of vesicles with the plasma membrane

Which of the following molecules is most likely to passively diffuse across the plasma membrane?

• 
  Carbon dioxide

• DNA

• glucose

• sodium ion

Answer explanation

Carbon dioxide is a small, nonpolar molecule, which allows it to passively diffuse across the plasma membrane without assistance

The type of bond that forms to join monomers (such as sugars and amino acids) into polymers (such as starch and proteins) is a(n) __________ bond.

• ionic

• Van der Waals

• Covalent

• Peptide

• Hydrogen

Answer explanation

Monomers are joined together by a dehydration reaction in which two molecules are covalently bonded to each other through the loss of a water molecule.

A polysaccharide that is used for storing energy in human muscle and liver cells is __________

• starch

• glycogen

• glucose

• cellulos

A substance moving from outside the cell into the cytoplasm must pass through __________.

Answer explanation

The plasma membrane defines the boundary between the cytoplasm and the outside of the cell.

Your intestine is lined with individual cells. No fluids leak between these cells from the gut into your body. Why?

• The intestinal cells are bound together by the extracellular matrix.

• The intestinal cells are bound together by plasmodesmata.

• The intestinal cells are bound together by gap junctions

• The intestinal cells are bound together by tight junctions.

Basal bodies are most closely associated with which of the following cell components?

• Central vacuole

• nucleus

• cilia

• golgi apparatus

Answer explanation

The microtubule assembly of a cilium or flagellum is anchored in the cell by a basal body.