Transport

Question 1

Facilitated Transport

Answer 1

• Proteins in the cell membrane allow molecules to be transported across the membrane
• These proteins are channel proteins, which form protein channels and carrier proteins, which allow carrier-mediated transport.

Question 2

Protein Channels

Answer 2

• To diffuse across a cell membrane, water-soluble molecules must pass through protein channels in the membrane, allowing facilitated diffusion.
• Allows for hydrophilic particles to travel through to cross the cell membrane without touching hydrophobic portion of the membrane.
• Protein channels are small (e.g. water and ions) but larger molecules cannot fit.

Question 3

Carrier-mediated transport

Answer 3

• Carrier proteins are only open on one side of the membrane at a time
• When the specific substance binds to the binding site within the protein, the protein changes shape and opens to the other side.
• The substance can then be released on the side opposite to where it entered.
• Carrier proteins are specific. They will only bind to a particular molecule
• Carrier activity is regulated by substances such as hormones.

Question 4

2 main types of Carrier-mediated transport

Answer 4

Facilitated diffusion: occurs when substances are transported through a protein along the concentration gradient. During carrier-mediated facilitated diffusion the molecule to be transported e.g. glucose), attaches to the binding site on the specific carrier protein.

Active transport: requires energy (ATP) because substances are transported against the concentration gradient.

Question 5

Vesicular Transport

Answer 5

• The movement of substances across the cell membrane in membranous sacs called vesicles.
• This is an active process. Energy is needed to form the vesicle.

Question 6

Endocytosis

Answer 6

• Is taking liquid or solids into the cell by vesicular transport.
• Cell membrane folds around a droplet of liquid or solid particle until the droplet is completely enclosed.

T- he vesicle then pinches off and is suspended in the cytoplasm.

• Taking liquids into the cell this way is called PINOCYTOSIS.
• Taking solids into the cell this way is called PHAGOCYTOSIS.

Question 7

Exocytosis

Answer 7

• When the contents of a vesicle inside the cell are passed to the outside.
• A vesicle that is formed inside the cell migrates to the cell membrane and fuses with it.
• The contents of the vesicle are then pushed out into the extracellular fluid.

Question 8

Microtubules

Answer 8

• Very fine tubes that help to maintain the shape of the cell and hold the organelles in place.
• They also act like railway tracks, guiding organelles or molecules, to particular places within the cell.
• They are not permanent structures but are able to be broken down or built up as needed.