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23 Cards in this Set

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What is passive transport?

Transport that doesn't require or use energy from respiration but relies on the natural motion of particles

What is diffusion?

A passive and microscopic process that involves the net movement of particles from an area of high conc. to an area of low conc. until it reaches equilibrium

Particles have KE and move randomly and collide, causing them to lose energy so ROD is at a slower rate over a longer distance

What are the 4 factors affect diffusion?

Temperature (more KE in particles so higher ROD)

Conc. difference (greater the net movement of particles so higher ROD)

SA (larger exchange surface means higher ROD)

Thickness of membrane (has to travel less distance so higher ROD)

Why is the cell membrane partially permeable?

Because polar molecules (water) are repelled by hydrophobic core of the membrane so it is harder for it to diffuse through

What is facilitated diffusion?

Diffusion through a plasma membrane through channel proteins that are selectively permeable.

(This relies on the natural KE and motion of the particles, as it moves down a conc. gradient)

What can affect ROFD?

Number of channel proteins present in the membrane

What is active transport?

The movement of particles across plasma membrane against a conc. gradient that requires energy from ATP

How does active transport occur?

1. Molecules bind to receptors outside of the cell

2. ATP binds to the outside of the cell and is hydrolysed to ADP and phosphate

3. The binding of the phosphate to the proteins causes it to change shape and open up the inside of the cell

4. Molecules are released and ADP and phosphate recombine to form ATP and protein returns to its original shape

What is bulk transport?

A form of active transport where molecules like hormones / enzymes are transported

What is endocytosis and what are the 2 forms?

The bulk transport of material into a cell where the cell surface membrane invaginates and the membrane can fuse forming vesicles

Phagocytosis and pinocytosis

What is exocytosis?

The bulk transport of material out a cell where vesicles (usually produced by the Golgi) fuse with the cell surface membrane and the contents are excreted

What is ATP needed for in bulk transport?

Movement of vesicles in the cytoskeleton, changing the shape of the membrane and fusion of vesicles and membrane

What is osmosis?

The movement of water through a partially permeable membrane from an area of high water potential to an area of low water potential (this is passive)

What is the highest water potential?

0kPa, any solutes dissolved in it will lower this value

What moves across the partially permeable membrane in osmosis?

Just free water molecules until equilibrium is achieved with the same number of water molecules on both sides

What happens if too much water enters an animal cell?

There is a build up of hydrostatic pressure which can be damaging

What happens if an animal cell has an imbalance in water?

The cell membrane can't stretch that much so it can burst (cytolysis)

Or volume of water can decrease and the cell shrivels (crenation)

How does blood prevent cytolysis and crenation?

The blood plasma has an equal water potential to the cells, to allow free movement of water

What happens if there's an imbalance of water in plant cells?

Too much water causes the membrane to push against the cell wall (turgor) making the cell turgid

Or the cell membrane moves away from the cell wall (plasmolysis)

What is hypotonic?

When 1 of 2 solutions has more water and less solute

What is hypertonic?

When 1 of 2 solutions has more solute and less water

What is isotonic?

When both solutions have the same water potential and osmotic pressure

How can a glycoprotein act as a receptor?

It allows a chemical to bind to it as it has a specific shape that is complementary to the molecule