Chapter 4

What are the factors that affect the rate of diffusion? State how does each factor affect diffusion?

(1) Temperature- the more elevated the temp, the greater the speed of molecular movement & net flux (2) Mass of the molecule-large molecules such as proteins have a greater mass and lower speed than smaller molecules such as glucose (3) surface area- the greater the surface the area between two regions, the greater the space for diffusion therefore faster net flux (4) the medium through which the molecules are moving- molecules diffuse more rapidly in air than water because collisions are less frequent in gas phases

What are the six types of membrane transport?

1. Simple Diffusion 2. Facilitated Diffusion 3. Osmosis 4. Active Transport 5. Endocytosis 6. Exocytosis

There are two major types of membrane transport. One is called active and the other is called passive. How do they differ?

Active Transport- uses energy to move a substance UPHILL across a membrane AGAINST the concentration gradient. Passive Transport- doesn't require energy and goes with concentration gradient.

What is the formula for Fick's law of diffusion?

F= PA(Co-Ci)

Define hypertonic, hypotonic, and isotonic.

Hypertonic- Solution with lower concentration of solutes Hypotonic- Solution with higher concentration of solutes Isotonic- Concentration of solutes is the equal

Explain what happens to a cell submerged in hypertonic solution. Hypotonic solution. Isotonic solution.

In a hypertonic solution a cell would

What are ion channels? What are they made of? What specifically pass through them? Do they require energy?

Ion channels allow ions to diffuse across the membrane. a single protein may have a conformation resembling that of a donut with a hole in the middle providing the channel for ion movement. they can show selectivity based on the channel diameter.

How are ion channels gated? Be specific.

Most ion channels are gated—that is, they open and close either spontaneously or in response to a specific stimulus, such as the binding of a small molecule to the channel protein (ligand-gated ion channels) or a change in voltage across the membrane that is sensed by charged segments of the channel protein

Does simple diffusion require energy?

No, it is a passive transport

Diffusion can occur in the cell in two ways. What are they?

Passive Diffusion & Facilitated Diffusion

What is primary active transport and what types of substance pass through them? Give an example of a type of protein that uses primary active transport?

Primary active transport utilizes energy in form of ATP to transport molecules across a membrane against their concentration gradient. Therefore, all groups of ATP-powered pumps contain one or more binding sites for ATP, which are always present on the cytosolic face of the membrane.

What is active transport? Does it always require the use of ATP?

active transport differs from facilitated diffusion because it uses energy to move a substance UPHILL across a membrane (against the concentration gradient). facilitated diffusion requires a substance to bind to the transporter on the membrane. because these transporters move the substance UPHILL they are referred to as pumps.

What is the name of proteins that allow mediated transport to occur?

channels, carriers, pumps

What is mediated transport and how does it differ from ion channels?

consists of Active transport & Facilitated diffusion. The transport solute must first bind to a specific site on a transporter, a site exposed to the solute on one surface of the membrane.

What are the two types of mediated transport?

facilitated diffusion and active transport

What is secondary active transport and what types of substance pass through them? Give an example of a type of protein that uses secondary active transport?

form of active transport across a biological membrane in which a transporter protein couples the movement of an ion (typically Na+ or H+) down its electrochemical gradient to the uphill movement of another molecule or ion against a concentration/electrochemical gradient. Thus, energy stored in the electrochemical gradient of an ion is used to drive the transport of another solute against a concentration or electrochemical gradient.

What is osmosis? Does it require energy?

movement of water because the membrane in insoluable to the solute. No

What is the difference between primary active transport and secondary active transport?

primary active transport is the hydrolysis of ATP by a transporter provides the energy for primary active transport. the transporter itself is an enzyme called ATPase that catalyzes the breakdownof ATP. secondary active transport is the movement of an ion down its electrochemical gradient is coupled to the transport of another molecule such as a nutrient like glucose or an amino acid.

Define simple diffusion and state through what part of the membrane does it happen?

refers to a process whereby a substance passes through a membrane without the aid of an intermediary such as a integral membrane protein. The force that drives the substance from one side of the membrane to the other is the force of diffusion

Does mediated transport require energy?

yes? (needs assistance)