Cell Membrane - Composition and Transport week 3

The products of the decomposition can diffuse out of the lysosome and into the ________ or be removed from the cell via the process called _________.

cytoplasm; exocytosis

1.Which way does Cl- move throught the CFTR channel?

From inside to outside the cell

__________: Molecules move from regions of higher concentration to regions of low concentration.

Diffusion:

A protein that spans the cell membrane is termed a(n)

integral protein.

__________ Neurotransmitter release from a cell.

Exocytosis:

_________ :vMovement of water molecules toward the solution with more impermeant solute.

Osmosis:

3. Changes in the membrane potential trigger the opening or closing of __________.

voltage-gated channels

3. During one cycle, the sodium-potassium pump binds and moves

3 Na+ and 2 K+

A cell placed in a hypotonic solution will _______.

expand

4. Diffusion is one of the processes whereby materials are exchanged between a cell and its environment.

true

Indicate three functions of proteins in the cell membrane.

1. Receptors to bind to chemicals 2. Adhere adjacent cells to each other 3. Channels for ions to move through

Water, oxygen, carbon dioxide, ethanol, and urea are examples of molecules that readily cross cell membrane by simple diffusion. They pass either directly through the lipid bilayer or through pores created by certain integral membrane proteins. The relative rate of diffusion is roughly proportional to the concentration gradient across the membrane. For example, oxygen concentrations are always higher outside than inside the cell. Therefore, oxygen diffuses down its concentration gradient into the cell. Which concentration gradient would result in a faster diffusion of oxygen?

95% concentration outside: 45% concentration inside

Which of the following correctly describes the structural organization of the cell membrane?

A bilayer of phospholipid molecules in which protein molecules are embedded and can move

The difference between active and passive transport is that active mechanisms use __________.

ATP

____________: Carrier molecules transport molecules from regions of low concentration to high concentration.

Active Transport

2. Which of the following does not affect the rate of diffusion?

Amount of ATP present

The CFTR channels in cells that line the respiratory tract move _____ ions out of the cell. The movement of this ion causes the _____ to follow. The resulting compound of NaCl creates an osmotic pull that _____ water to the outside of the cell. The _____ in water in the respiratory tract helps to _____ mucus that is naturally found lining the tract.

Cl-; Na+; attracts; increase; thin

_________: Exchange of oxygen between the air in the lungs and the blood.

Diffusion

Cells that are experiencing a net movement of water toward the ______ due to osmosis are bathed in hypertonic solutions.

ECF

Other processes are needed that allow quicker movement of individual molecules and ions across the cell membrane. Additionally, some substances are just too big to move using protein channels. Which of the following represents the bulk movement of material out of the cell using energy?

Exocytosis

Many small and uncharged molecules diffuse across the plasma membrane by virtue of their kinetic energy of motion. In most cases, such molecules are hydrophobic and nonpolar and, therefore, can dissolve into and out of the lipid bilayer. Bearing a charge or having a large size virtually abolishes the ability to be transported across lipid membranes by simple diffusion. Luckily, membranes have other means to facilitate such transport. What is the means of transport for large molecules and ions?

Facilitated diffusion

___________: Movement of glucose through a cell membrane.

Facilitated diffusion

_________: With assistance of a carrier protein, molecules move from regions of high concentration to lower concentration.

Facilitated diffusion:

_________: Smaller molecules are forced through porous membranes down a pressure gradient.

Filtration

__________ Water molecules leaving blood capillaries due to blood pressure.

Filtration:

Sodium (Na+) and chloride (Cl-) form the compound NaCl-, salt. Due to the CFTR channel, and the natural movement of ions, there will be a higher concentration of NaCl outside the cell than inside the cell. This difference in solute concentration will cause the movement of water. Based on osmosis, which way will water move in this example?

From inside to outside the cell.

In a hypothetical situation, two solutions are separated by a membrane. Solution A is a 10% sodium solution and solution B is a 40% sodium solution. Which way would the sodium pumps within the membrane move sodium ions during active transport?

From solution A to solution B

A cell is surrounded by an extremely thin, flexible membrane. Why is the membrane selectively permeable?

It allows some substances to pass through and excludes others based on size, polarity, and other factors.

3. What would happen to a red blood cell placed in a hypertonic medium?

It would shrink.

So what about water? Water crosses cell membranes very readily—the amount of water that diffuses back and forth across the membrane of the red blood cell every second is roughly equivalent to 100 times the volume of the whole cell. Water is NOT lipid soluble and is polar. However, it seems that water is small enough and has sufficient kinetic energy that it can diffuse through the lipid bilayer with minimal interference. What is the special name for the diffusion of water across a membrane?

Osmosis

___________: White blood cell engulfing a microbe.

Phagocytosis

Cell membranes are described as a fluid mosaic that maintains stability while still allowing movement. What component maintains most of the flexibility of the membrane?

Phospholipid bilayer

2. Which of the following will pass through a cell membrane most easily?

Small nonpolar molecules

Which of the following is a cation that would be attracted to chloride?

Sodium

2. What is the source of energy used to power the sodium-potassium pump?

The breakdown of ATP

Physiological saline solution is isotonic to human tissue and is commonly used in clinical procedures. If a kidney removed for transplantation is accidentally placed in tap water, what would happen to the kidney?

The kidney would swell.

4. A 5% urea solution is hypotonic to a 10% urea solution.

True

4. The sodium-potassium pump is a transmembrane protein.

True

5. If a cell is placed in an isotonic medium, there will be no net movement of water.

True

5. The binding and release of sodium or potassium ions at the Na-K pump are due to conformational changes in the transport protein.

True

A molecule or ion that crosses the membrane by moving down a concentration gradient and without expenditure of cellular energy is said to be transported passively. Another name for the process described is diffusion.

True

All molecules and ions are in constant motion and it is the energy of motion, kinetic energy, that drives passive transport. Transport of uncharged substances across a membrane is dictated by the differences in concentration of that substance across the membrane, that is, by the prevailing concentration gradient. If there was 100mEq of Na+ inside the cell and 50mEq of Na+ outside the cell, the concentration is said to be higher inside the

True

Glucose, sodium ions, and chloride ions are just a few examples of molecules and ions that must efficiently get across the plasma membrane and to which the cell membrane alone is impermeable. Therefore, their transport must be "facilitated" by proteins that span the membrane and provide an alternative route or bypass. Facilitated diffusion is the name given this process. Facilitated diffusion is similar to simple diffusion, but will also allow movement due to electrical gradients.

True

2. Ouabain is a poison that binds to the Na+/K+ pump in the cell membrane and inhibits its action. The expected result of this poison on secondary active transport is __________.

a loss of the ion concentration gradient that drives this process

Movement of a substance across the cell membrane against its concentration gradient is _______ transport.

active

Peripheral proteins that allow cells to bind to one another are called __________.

cellular adhesion molecules (CAM's)

The membrane is stiffened in some spots, decreasing its fluidity, by the presence of _________ molecules.

cholesterol

Water you drink is absorbed into the blood from the digestive tract. An increase in water intake causes a(n) __________ in the plasma osmolarity.

decrease

In patients with cystic fibrosis, the CFTR channel is malfunctioning, preventing movement of Cl- ions. The effect is a(n) _____ in water movement out of the cell and, therefore, a _____ mucus. The resulting mucus is harder to move, and thus causes blockages in the narrow lung passages.

decrease; thicker

2. A reduction in the number of glucose carrier proteins within the plasma membrane __________ the rate of glucose diffusion.

decreases

The cell membrane is composed of a __________ layer of phospholipids. The __________ portion forms the extracellular and intracellular membrane surfaces, and the __________ portion forms the interior of the membrane.

double; phosphate; fatty acids

1. Cellular products such as hormones and neurotransmitters are released by the process of __________

exocytosis

2. Simple and facilitated diffusion differ because __________.

facilitated diffusion requires the presence of a transport protein within the plasma membrane, while simple diffusion does not

3. The molecules in a solid lump of sugar do not move.

false

Movement of fluids through a selectively permeable membrane caused by hydrostatic pressure is referred to as __________.

filtration

1. The __________ determines if glucose moves into or out of the hepatocyte.

glucose concentration gradient between the intracellular and extracellular fluid

Simple diffusion describes the net movement of particles from an area of __________________________________________________________

high concentration to an area of low concentration.

2. The movement of water by osmosis is always from a __________.

high to low water concentration

2. Some individuals have defective genes for LDL receptors rendering them nonfunctional. Individuals with these mutations typically have __________.

higher than normal blood cholesterol levels due to inability of peripheral cells to uptake LDLs

Water diffusion through a _________ cell membrane is made easier by membrane proteins called aquaporins.

hydrophobic

Fluids and small solutes are forced between cells of the blood vessel lining due to _______________________

hydrostatic (blood) pressure.

1. Physiological saline is a solution containing 0.9% NaCl. A cell in 1.5% NaCl is in a(n) __________ solution.

hypertonic

A ________ solution has a solute concentration higher than the solute concentration inside the cell.

hypertonic

2. An IV solution of 0.45% NaCl is __________ and induces the movement of water __________.

hypotonic; into cells

Distilled water given intravenously will cause cells to expand due to rapid movement of water _____ the cells via osmosis.

into

When completely surrounded, the microbe is brought ______ the cell in a structure called a ________.

into; vesicle

Normal saline solution is ________ to the human blood cells.

isotonic

1. An individual displaying a larger than normal number of LDL receptors is __________ likely to develop artherosclerosis.

less

In a plasma membrane, 98% of the molecules are _______.

lipids

The major components of the cell membrane are

lipids and proteins.

If a chloride ion was to move via active transport, it would move from an area of ______ concentration to an area of ______ concentration.

low; high

The movement of water from an area of ______ solute concentration to an area of ______ solute concentration describes osmosis.

low; high

A _______ fuses with the vesicle and its ________ degrade and digest the microbe.

lysosome; enzyme

1. Primary and secondary active transport proteins differ in that primary active transport proteins __________.

move both molecules down their gradients, while secondary active transport proteins couple the movement of an ion down its gradient with the movement of another molecule against its gradient

2. The Na+/K+ ATPase moves sodium in the __________ direction compared with the direction it travels through sodium leakage channels.

opposite

Movement away from high solvent concentration or toward a high solute concentration describes _________.

osmosis

This pressure results in the movement of water toward the area with a higher solute concentration, a process known as _____________.

osmosis

Water moves via ______ from areas of ______ solute concentration to areas of ______ solute concentration. Thus, it can be said that water follows ions.

osmosis; low; high

Because of the inability of RBCs and albumin to pass through the filtration membrane of the renal corpuscle, they exert a small amount of _______ on the tubular fluid toward the glomerulus.

osmotic pressure

Because of the inability of red blood cells and proteins to pass through the blood capillary wall, they exert a small amount of __________________

osmotic pressure.

A portion of the cell's membrane projects _______ to encircle the microbe.

outward

Movement of a substance across the cell membrane down its concentration gradient is called ______ transport.

passive

Cellular adhesion molecules are

peripheral proteins.

A _________ a cell that can take in solid particles, encounters a microbe in the body.

phagocyte

2. Phagocytosis and pinocytosis differ in that __________.

phagocytosis allows for the transport of larger particles than pinocytosis

The _________ of the membrane are flexible, keeping the membrane fluid.

phospholipids

Active transport requires a _______ channel.

protein

Dispersed throughout the membrane are _______ that may be peripheral or integral.

proteins

3. The most specific type of endocytosis is __________.

receptor-mediated endocytosis

1. The sodium-iodide symporter plays a role in the accumulation of iodide in the thyroid gland. Here, one iodide gets converted to one iodine, which is utilized for the formation of either of the two types of thyroid hormones, T3 and T4. T3 and T4 are named after the number of iodines found in each of these hormones. To produce a single molecule of T3, a total of __________ sodium ions must move down their concentration gradients by secondary active transport. The movement of iodide ions occurs in the __________ direction as sodium ions.

six; same;

1. The sodium-potassium pump functions to pump

sodium ions out of the cell and potassium ions into the cell.

1. When sugar is mixed with water, equilibrium is reached when

the dissolved sugar molecules are evenly distributed throughout the solution.

1. The directional movement of ions by facilitated diffusion through protein channels is determined by __________.

the electrochemical gradient of the ion being transported

1. Osmosis is best defined as the movement of

water molecules from an area of low impermeable solute concentration to an area of higher impermeable solute concentration.