Chapter 5 Test 5-1

Hypertonic, plasmolysis

A hypertonic solution has a higher solute concentration than the cytosol of a cell. In a hypertonic solution a plant cell will lose water and shrink away from the cell wall, a process called plasmolysis.

Carrier Protein

Assist movement of molecules across the cell membrane in a facilitated diffusion, transport molecules from an area of higher concentration to lower concentration - doesn't require energy

What happens to the movement of molecules at equilibrium?

At equilibrium, the movement of molecules continues, but because there is no concentration gradient, there is no net movement in any particular direction.

How does the interaction between a carrier protein & the substance it transports resemble the interaction between an enzyme & its substrate?

Both involve the binding of a specific substance to a particular kind of protein and a change in shape of the protein as the process (transport or chemical reaction) proceeds. After the process is completed, the protein is unchanged.

Distinguish between diffusion and osmosis.

Both involve the movement of molecules from high concentration to low concentration. Diffusion doesn't need water, while osmosis does. Basically, osmosis is a special kind of diffusion.

. How do carrier proteins transport substances across cell membranes?

Carrier proteins bind to a molecule of the substance on one side of the membrane, change shape, transport the molecule across the membrane, and release the molecule on the other side.

Equilibrium

Concentration of molecules will be the same throughout the space the molecules occupy, molecules still move but its balances

Define the term contractile vacuole. What is a contractile vacuole's function?

Contractile vacuoles are organelles that remove water. They collect the excess water and contract to pump out the water. It is not passive transport because it uses energy.

Explain why diffusion eventually results into equilibrium.

Diffusion is the movement of molecules from an area of higher to lower concentration. Once this occurs, the concentration will eventually even out and equilibrium will be established because the concentrations will be the same throughout the space occupied by molecules.

Use each of the following terms in the same sentence: carrier protein, concentration gradient, facilitated diffusion, and passive transport.

Facilitated diffusion is passive transport because it doesn't require energy, but it uses carrier proteins to travel across the concentration gradient.

Plasmolysis

In a hypertonic environment - water leaves the cell and the cells shrink away from the cell walls (no turgor pressure), reason plants wilt when they don't have enough water

Determine how hypotonic, hypertonic, and turgor pressure are interrelated.

In hypotonic solutions water is diffused into the cell which causes turgor pressure to increase. In hypotonic solutions water is diffused into the cell which causes turgor pressure to increase. In hypertonic solutions water is diffused out of the cell and turgor pressure is decreased, causing the cell the shrivel.

Describe how ion channels assist in the diffusion of ions through a cell membrane.

Ion channels transport ions from areas of higher concentration to areas of lower concentration. Since ions are not soluble in lipids, they cannot diffuse across the phospholipid bilayer. Ion channels provide passageways for ions to diffuse across the cell membrane.

Describe what it means to say that two solutions are isotonic.

It means that the concentrations are equal and there is no net movement of water.

Identify whether all molecules dissolve through cell membranes. Explain.

No, because some are too big or not soluble in lipids, so they have to use facilitated diffusion in order to pass into the cell.

Cytolysis

Occurs in a hypotonic environment when red blood cells have water diffused into them causing it to swell and burst - bursting is cytolysis

Contractile Vacuole

Organelles that remove water, collect the excess and then contract - pump water out of cell, not passive transport because it requires the cell to expend energy

Explain the relationship between plasmolysis and turgor pressure in plant cells.

Plasmolysis occurs when water is lost and the cells shrink away from the cell walls. The turgor pressure is gone because there isn't any pressure against the cell wall. This causes the cell to wilt.

Turgor Pressure

Pressure that water molecules exert against the cell wall

Osmosis

Process by which water molecules diffuse across a cell membrane from an area of higher concentration to an area of lower concentration, does not require cells to expend energy - water is moving from higher to lower concentration - passive transport of water

Diffusion

Simplest form of passive transport, movement of molecules from an area of higher concentration to an area of lower concentration, driven by kinetic energy

Passive Transport

Substances that cross the cell membrane without any input of energy by the cell

Concentration Gradient

The difference in the concentration of molecules across a distance, molecules tend to move down their concentration gradient (to an area with more molecules)

Structures & Functions

The drawings below show the appearance of a red blood cell & a plant cell in isotonic, hypotonic, & hypertonic environments. Label each environment in the spaces provided.

Summarize the factors that determine the direction of net movement of water across a cell membrane.

The factors that determine the directions of net movement of the cell are the concentration of solutes inside and outside of the cell.

. Explain how substances cross a cell membrane through facilitated diffusion.

The movement is assisted by carrier proteins. A molecule bind to a specific carrier protein for transport. As soon as it binds, the shape of the carrier protein changes. Once it's shielded, it can be transported through the cell membrane. The molecules is released on the other side of the cell membrane and the protein to it's original shape.

Determine how the phospholipid bilayer of a membrane forms a barrier to molecules.

The phospholipid bilayer is selectively permeable and only allows certain things to enter through it. It forms a barrier around the cell.

What types of stimuli can cause the gates on ion channels to open or close?

The stimuli are stretching of the cell membrane, electrical signals, and chemicals in the cytosol or external environment.

Concentration gradient, diffusion

They both mean the movement of molecules from higher concentration to lower concentration.

Osmosis, turgor pressure

Turgor pressure is the pressure in plants created by either an excess or lack of water. Osmosis diffuses the water & is the main way that plants can increase or decrease their turgor pressure.

Facilitated Diffusion (transport of glucose)

Type of passive transport - used for molecules that cannot readily diffuse through cell membranes even when there is a concentration gradient across the membrane, movement of molecules assisted by carrier proteins, 2 important properties - can help substances move into or out of a cell depending on concentration gradient, carrier proteins involved are specific for one type of molecule

Ion Channel

Type of transport involving membrane proteins, transport ions from higher to lower concentrations

Hypertonic

When the concentration of solute molecules outside the cell is higher than the concentration of the cytosol, solution is hypertonic to the cytosol, water diffuses out of the cell until equilibrium is established

Hypotonic

When the concentration of solute molecules outside the cell is lower than the concentration in the cytosol, solution outside is hypotonic to cytosol, water diffuses into the cell until equilibrium is established

Isotonic

When the concentrations of solutes outside and inside the cell are equal, water diffuses into and out of the cell at equal rates - no net movement of water

Na+ ions enter cells by diffusion across the lipid bilayer without assistance diffusion through Na+ ion channels binding to Na+ carrier proteins binding to Cl- ions

diffusion through Na+ ion channels

The contractile vacuole of a paramecium should be active when the paramecium is in an isotonic environment a hypotonic environment a hypertonic environment any environment

hypotonic environment

Facilitated diffusion is often used to transport ions water molecules that are not soluble in lipids molecules that are too small to diffuse across the membrane

molecules that are not soluble in lipids

. Substances that can pass through cell membranes by diffusion include a. Na+ ions b. Cl- ions c. glucose d. oxygen

oxygen

When a human red blood cell is placed in a hypotonic environment, it will undergo cytolysis undergo plasmolysis experience a decrease in turgor pressure be at equilibrium

undergo cytolysis