Ch.7 Quiz (BIO)

Which of the following particles could diffuse easily through a cell membrane?

Oxygen (O2) -Small nonpolar molecules such as oxygen can diffuse across cell membranes.

Pinocytosis

or "cell drinking," the cell engulfs extracellular fluid, including molecules such as sugars and proteins. These materials enter the cell inside a vesicle. Epithelial cells in capillaries use pinocytosis to engulf the liquid portion of blood at the capillary surface. The resulting vesicles travel across the capillary cells and release their contents to surrounding tissues, while blood cells remain in the blood.

What name is given to the process by which water crosses a selectively permeable membrane?

osmosis -Osmosis is the passive transport of water.

Plant Cell (Tonicity)

-When plant Cells are exposed to HYPERTONIC environment, water rushes out of the cell, and the cell shrinks away from the rigid wall. These cells are dehydrated and lose most or all physiological functions while in the shriveled state. -Plants cells are surrounded by a rigid cell walls. When plants cell are exposed to hypotonic environments, water rushes into the cell, and the cell SWELLS but is kept from breaking by the right wall layer.

Solute

A solute is a substance that creates a solution when dissolved in a solvent. For example, when sugar (solute) is dissolved in water (solvent).Solute can change its physical state but solvent and solution are of same phase.e.g sugar is solid before getting dissolved in water, and after dissolution it changes its phase to a liquid.

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane.

Which of the following correctly describes some aspect of exocytosis or endocytosis?

Exocytosis and endocytosis change the surface area of the plasma membrane. -The fusion or budding of transport vesicles at the plasma membrane either adds or removes proteins and phospholipids, thus changing the surface area.

Isotonic

Having the same solute concentration as another solution

Hypotonic

In comparing two solutions, referring to the one with a lower solute concentration.

How can a lipid be distinguished from a sugar?

Lipids are mostly nonpolar. -Lipids are nonpolar molecules, whereas sugars are polar.

Turgid

The desired state of most plant tissue, where the cell expand and held in place by other plant cells.

Passive Transport

The diffusion of a substance across a biological membrane.

Osmosis

The diffusion of water across a slectively permeable membrane.

True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.

The hydrophilic, or water-loving, portion of a phospholipid is the polar head, whereas the hydrophobic portion is the nonpolar tail.

Exocytosis

The movement of materials out of a cell via membranous vesicles -The cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane. -This process occurs predominantly in secretory cells, such as mucus-producing cells or pancreatic cells, that secrete enzymes into the digestive tract.

Facilitated Diffusion

The spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients.

Diffusion

The spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area.

In facilitated diffusion, what is the role of the transport protein?

Transport proteins provide a hydrophilic route for the solute to cross the membrane. -This is the most general description of facilitated diffusion by membrane transport proteins.

True or false? Osmosis is a type of diffusion.

True -Osmosis is the diffusion of water across a selectively permeable membrane.

Molecule

Two or more atoms held together by covalent bonds.

Animal Cell (Tonicity)

When exposed to a hypertonic environment, water rushes out of the cell, and the cell SHRINKS. When exposed to a hypotonic environment, water rushes into the cell, and the cell SWELLS. And eventually burst open or lyse.

Which of the following factors would tend to increase membrane fluidity?

a greater proportion of unsaturated phospholipids

If the concentration of phosphate in the cytosol is 2.0 mM and the concentration of phosphate in the surrounding fluid is 0.1 mM, how could the cell increase the concentration of phosphate in the cytosol?

active transport -For the cell to accumulate phosphate, it must move calcium against the concentration gradient. This process requires energy.

Aquaporins

are integral membrane proteins from a larger family of major intrinsic proteins (MIP) that form pores in the membrane of biological cells.[1]

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly..

embedded in a lipid bilayer.

Endocytosis

is the movement of materials into a cell via membranous vesicles. -The cellular uptake of macromolecules and particulate substances by localized regions of the plasma membrane that surround the substance and pinch off to form an intracellular vesicles. -This process can take different forms, each involving its own specific cell machinery:

The permeability of a biological membrane to a specific polar solute may depend on which of the following?

the types of transport proteins in the membrane -The lipid bilayer will be impermeable or very poorly permeable to polar or charged solutes. The presence of the correct transport protein will determine the permeability.

Transport Protein

A transport protein (variously referred to as a transmembrane pump, transporter protein, escort protein, fatty acid transport protein, cation transport protein, or anion transport protein) is a protein which serves the function of moving other materials within an organism. Transport proteins are vital to the growth and life of all living things. There are several different kinds of transport proteins.

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?

Amphipathic nature -Detergents form micelles around the grease, which are then washed away because the polar head groups facing outward on the micelle are water-soluble.

Carrier Proteins

Carrier proteins are proteins involved in the movement of ions, small molecules, or macromolecules, such as another protein, across a biological membrane.[1] Carrier proteins are integral membrane proteins; that is they exist within and span the membrane across which they transport substances. The proteins may assist in the movement of substances by facilitated diffusion (i.e. passive transport) or active transport. These mechanisms of movement are known as carrier mediated transport.[2] Each carrier protein is designed to recognize only one substance or one group of very similar substances. Research has correlated defects in specific carrier proteins with specific diseases.[3] A membrane transport protein (or simply transporter) is a membrane protein[4] which acts as such a carrier.

What cannot pass through the SP membrane easily?

On the other hand, some hydrophilic molecules (like water and glucose) can pass only slowly, and ions (such as sodium ions and hydrogen ions) cannot pass directly through the phospholipids of the plasma membrane. They must pass through specific membrane transport proteins. 1. water (slowly) 2. glucose (slowly) 3. ions (pass through specific membrane transport proteins)

Phospholipids have a hydrophilic head and hydrophobic tails.

The hydrophilic head includes a glycerol molecule attached to a single phosphate group, which is then attached to another small molecule. The phosphate group and its attachments are either polar or charged. Water molecules are polar and therefore are attracted to these charged regions of the phospholipid head. The hydrophobic tails are two fatty acids attached to the glycerol molecule of the head. Water molecules are not attracted to the tails because C-H bonds are relatively nonpolar and therefore do not result in charged regions in the tails.

Which of the following factors does not affect membrane permeability?

The polarity of membrane phospholipids -Phospholipids contain both a polar head and a nonpolar hydrocarbon tail, both of which are necessary for their ability to form membrane bilayers.

Which of the following statements about a typical plasma membrane is correct?

The two sides of the plasma membrane have different lipid and protein composition. -Because the membrane serves different functions on the cytoplasmic and exterior surfaces, the structure and composition of the surfaces must be different.

Polar Molecules

Hydrophilic, Have difficulty crossing the hydrophobic part, and transport protein is required to cross efficiently.

Ions

Hydrophillic, have difficulty crossing the hydrophobic part, and transport protein is required to cross efficiently.

What can pass through the SP membrane easily?

Hydrophobic molecules-- those that are soluble in lipids -- can easily pass through. In addition, small molecules like O2 can sneak between the phospholipid

Nonpolar Molecules

Hydrophobic, can cross the lipid bilayer easily and no transport protein required.

If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?

Hypotonic -The salt concentration in the solution is lower than it is in the cell, so water enters the cell, causing it to burst.

Hypertonic

In comparing two solutions, referring to the one with a greater solute concentration.

The structure of the plasma membrane makes it selectively permeable, enabling it to regulate the transport of substances into and out of the cell.

-Small, nonpolar molecules are hydrophobic, so they can easily cross the phospholipid bilayer of the plasma membrane. -Polar molecules and ions are hydrophilic, so they cannot very easily cross the hydrophobic portion of the plasma membrane (formed by the phospholipid tails). Water is an unusual molecule because, despite the fact that it is polar, it is small enough to pass directly through the hydrophobic interior of the lipid bilayer, albeit slowly. -Polar molecules and ions generally cross the plasma membrane with the help of transport proteins. For example, water crosses the bilayer rapidly via transport proteins called aquaporins.

Which of the following processes includes all others? 1. Passive Transport 2. Diffusion of a solute across a membrane. 3. Facilitated Diffusion 4. Transport of an ion down its electrochemical gradient 5. Osmosis

1. Passive Transport

Different Forms of Endocytosis

1. Phagocytosis (cell eating) 2. Pinocytosis (cell drinking) 3. Receptor-mediated (very specific)

Which of the following statements about osmosis is correct? 1. If a solution outside the cell is hypertonic compared to the cytoplasm, water will move into the cell by osmosis. 2. The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis. 3. Osmosis is the diffusion of water from a region of lower water concentration to a region of higher water concentration. 4. Osmotic movement of water into a cell would likely occur if the cell accumulates water from its environment. 5. If a cell is placed in an isotonic solution, more water will enter the cell than leaves the cell.

2. The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis. -Aquaporins facilitate water movement across membranes and thus speed up the process of osmosis

Protein

A three-dimensional polymer constructed from a set of 20 different monomers called amino acids.

Active and passive transport of solutes across a membrane typically differ in which of the following ways?

Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy.

Receptor-mediated endocytosis

Unlike phagocytosis and pinocytosis, receptor-mediated endocytosis is very specific. It is triggered when membrane receptors bind to specific external molecules, such as protein-cholesterol complexes or proteins bound to iron. Membrane vesicles pinch off, and the external protein and its cargo are brought into the cell.

Selectively Permeability

a property of biological membranes that allows some substance to cross more easily than others.

The movement of glucose into a cell against a concentration gradient is most likely to be accomplished by which of the following?

cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis x-Facilitated diffusion of the glucose using carrier protein x- Movement of glucose into the cell through glucose channel x-passive diffusion of glucose through the lipid bilayer x- receptor-mediated endocytosis

Which of the following is least likely to be important in holding the components of a biological membrane together?

covalent interactions between the phospholipid and protein components of the membrane -This is not an important interaction because there are rarely covalent bonds between the phospholipids and integral membrane proteins.

Based on Figure 7.21 in your textbook, which of these experimental treatments would increase the rate of sucrose transport into the cell?

decreasing extracellular pH

Cholesterol

helps to stabilize the structure of the plasma membrane.

Phagocytosis

or "cell eating, the cell engulfs debris, bacteria, or other sizable objects. Phagocytosis occurs in specialized cells called phagocytes, which include macrophages, neutrophils, and other white blood cells. Invagination produces a vacuole, which usually fuses with one or more lysosomes containing hydrolytic enzymes. Materials in the vacuole are broken down by these enzymes and degraded.

Which of the following best describes the structure of a biological membrane?

two layers of phospholipids with proteins either crossing the layers or on the surface of the layers -The membrane proteins can be found either embedded in or attached to the surface of the phospholipid bilayer.