AP BIO: membrane transport

Which statement(s) about the sidedness of the plasma membrane is/are correct?

- The two lipid layers may differ in specific lipid composition. - Parts of proteins that are exposed on the cytoplasmic side of the endoplasmic reticulum are also exposed on the cytoplasmic side of the plasma membrane. - Every integral membrane protein has a specific orientation in the plasma membrane. - The asymmetrical distribution of membrane proteins, lipids, and carbohydrates across the plasma membrane is determined as the membrane is being constructed.

The internal solute concentration of a plant cell is about 0.8 M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what total concentration of solutes?

1.0 M

Green olives can be preserved in brine, a 30% salt solution. How does this method of preservation prevent microorganisms from growing in the olives?

A 30% salt solution is hypertonic to the bacteria, so they lose too much water and plasmolyze.

Which correctly states a difference between active transport and facilitated diffusion?

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

Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell __________ because __________.

B ... the diffusion gradient in cell B is steeper

Which statement about cotransport of solutes across a membrane is correct?

Cotransport proteins can couple the "downhill" diffusion of the solute to the "uphill" transport of a second substance against its own concentration gradient.

Which statement describes some aspect of facilitated diffusion?

Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane.

Which statement is false in regard to facilitated diffusion?

Facilitated diffusion requires the hydrolysis of ATP.

Which correctly describes a general property of all electrogenic pumps?

It creates a voltage difference across the membrane.

Which statement about diffusion is true?

It is a passive process of a substance across a membrane with no energy investment

Which statement is correct concerning carbohydrates associated with the plasma membrane?

Membrane carbohydrates function primarily in cell-cell recognition.

Which statement about passive transport is correct?

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

Which statement about the role of phospholipids in the structure and function of biological membranes is correct?

Phospholipids form a selectively permeable structure.

Which statement about the fluid mosaic model is true?

The fluid aspect of the membrane is due to the lateral and rotational movement of phospholipids, and embedded proteins account for the mosaic aspect.

Consider the transport of protons and sucrose into a plant cell by the sucrose-proton cotransport protein. Plant cells continuously produce a proton gradient by using the energy of ATP hydrolysis to pump protons out of the cell. Why, in the absence of sucrose, don't protons move back into the cell through the sucrose-proton cotransport protein?

The movement of protons through the cotransport protein cannot occur unless sucrose also moves at the same time.

Active transport requires an input of energy and can also generate voltages across membranes. Based on that, which statement is true?

The sodium/potassium pump hydrolyzes ATP and results in a net charge of +1 outside the cell membrane.

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

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

The red blood cell contain about 2% solutes but almost no sucrose or urea. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink most when immersed in which solution?

a hypertonic sucrose solution

Which would be least likely to diffuse through a plasma membrane without the help of a transport protein?

a large polar molecule

Which molecule is most likely to passively diffuse across the plasma membrane?

carbon dioxide

A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. How do these molecules probably enter the cells lining the baby's digestive tract?

endocytosis

Which functional process is not a consequence of the association of proteins with biological membranes?

energy, carbon, and nitrogen storage

Which process and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane?

exocytosis and smooth and rough ER

A cell has a membrane potential of -100 mV (more negative inside than outside) and has 1,000 times more calcium ions outside the cell than inside. Which best describes a mechanism by which Ca2+ enters this cell?

facilitated diffusion of Ca2+ into the cell down its electrochemical gradient

Where in the fluid mosaic model of the membrane would carbohydrates be found?

on the outside (external) surface of the membrane

Which pair correctly matches a membrane transport process to its primary function?

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

Which structural arrangement of the components in biological membranes is most consistent with membrane's property of selective permeability?

proteins embedded in two layers of phospholipid

Which enables a cell to pick up and concentrate a specific kind of molecule?

receptor-mediated endocytosis

Which cell structure allows selective permeability between a cell and its external environment?

the plasma membrane

Under the fluid mosaic model, where in the plasma membrane would cholesterol most likely be found?

wedged between phospholipid molecules in the interior of the membrane