Transporting Molecules

Question 1

Molecules and ions can move across membranes by 5 ways, name them

Answer 1

• Osmosis
• Diffusion & facilitated diffusion
• Active transport
• Exocytosis
• Endocytosis

Question 2

What is diffusion?

Answer 2

Diffusion is the net movement of particles down a
concentration gradient: from a region of high concentration
to a region of low concentration until equilibrium is
reached

Question 3

What is passive transport?

Answer 3

Movement of molecules from a region of high
concentration to a region of low concentration / down
a concentration gradient without the use of energy
(ATP)

Question 4

Name the three types of passive transport.

Answer 4

 Simple diffusion
 Facilitated diffusion
 Osmosis

Question 5

What is simple diffusion?

Answer 5

 Diffusion through the lipid bilayer without the use of
proteins

Question 6

What is facilitated diffusion?

Answer 6

 Diffusion with the help of protein molecules in
the cell membrane

Question 7

Name the 2 types of proteins involved in facilitated diffusion.

Answer 7

Carrier proteins
Ion channels

Question 8

What is the role of the protein carriers and how do they work?

Answer 8

 Spans the whole membrane (intrinsic protein)
 May be very specific
 Binds to molecules and ions undergoes a change in shape and transports them to the other side of the cell
 Role in active transport

Question 9

What is the role of the Channel Proteins and how do they work?

Answer 9

 Spans the whole membrane (intrinsic protein)
 Open and close to control the passage of selected ions
 Line with polar groups allowing diffusion of ions
 Gated so that they can open and close
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Question 10

Explain how facilitated diffusion takes place.

Answer 10

 Hydrophilic (polar) molecules and ions cannot diffuse
through the bilayer as they are insoluble in lipids.
 Polar molecules cross the membrane by facilitated
diffusion, which involves proteins.
 Channel proteins are integral proteins that span the
membrane and allow for the diffusion of polar molecules.
 Channel proteins are specific and allow only one type of
molecule to pass through.
 Some channels are gated channels – they can open and
close depending on signals such as a voltage or a hormone.
 Carrier proteins are channel proteins that can change
shape when they bind to a molecule to transport the
molecule across the membrane.

Question 11

What is Active Transport?

Answer 11

The movement of molecules from a region of low
concentration to a region of high concentration / against
the concentration gradient with the use of energy (ATP)
with the help of carrier proteins

Question 12

How is ATP produced?

Answer 12

produced by respiration in
mitochondria.

Question 13

What are some examples of Active Transport taking place?

Answer 13

 uptake of glucose and amino acids in the small intestine

 absorption of mineral ions by plant roots

 excretion of hydrogen ions and urea by kidneys

 exchange of sodium and potassium ions in neurons and muscles cells

Question 14

A characteristic of cells that undertake active transport on a large scale

Answer 14

Cells that undertake active transport on a large scale have many mitochondria

Question 15

What is Bulk transport?

Answer 15

When very large molecules or very large
quantities of molecules/ particles need to be transported across
membranes.

Question 16

By what processes can Bulk transport occur?

Answer 16

The two types of bulk transport are endocytosis and exocytosis, and they involve changes to the membrane shape.

Question 17

What is Endocytosis?

Answer 17

Endocytosis is the bulk transport of material in to the cell, and can be split into three processes: phagocytosis, pinocytosis and receptor-mediated endocytosis

Question 18

What is Exocytosis?

Answer 18

Exocytosis is the bulk transport of material out of the cell – essentially the reverse of endocytosis.

Question 19

Who do endocytosis and exocytosis depend on?

Answer 19

Both endocytosis and exocytosis depend on the fluidity of the
membrane.

Question 20

Explain the process of Endocytosis.

Question 21

Explain the process of Exocytosis.