Animal Cells - Tissues, Cell Connections & Transport

Question 1

When cells stick together in cell-cell attachments, what three structures can they form?

Answer 1

Sheets, clusters and tissues.

Question 2

What are the four types of cell junctions?

Answer 2

Adherens junctions, desmosomes, tight junctions and gap junctions.

Adherens junctions and desmosomes are sometimes grouped together as ‘anchoring’ junctions.

Question 3

Which type of cell junction acts like a band of welds between the cells and is anchored to the actin filaments of the cytoskeleton, allowing cells to join together in strong sheets?

Answer 3

Adherens junctions.

Question 4

Where are adherens junctions typically located?

Answer 4

In epithelial cells, e.g. cardiac cells.

Question 5

Can substances pass through the intracellular space between two cells joined by an adherens junction?

Answer 5

Yes, they can.

Question 6

What is cadherin?

Answer 6

A protein that crosses the intracellular space, strengthening and reinforcing the cell junction and maintaining the cell’s phenotype.

Question 7

Which type of cell-cell junction is immensely strong and acts like rivets or spot welds, forming an abrasion-resistant sheet of cells?

Answer 7

Desmosomes.

Question 8

In what type of tissue are desmosomes typically found?

Answer 8

In most types of strong epithelial tissue, e.g. the gut, skin etc.

Question 9

Which cell junction is crucial in tissue development?

Answer 9

Desmosomes.

Question 10

Do desmosomes allow substances to pass through the intracellular space?

Answer 10

Yes.

Question 11

Name the cell junction:
‘tightly packed rows of protein ridges form impermeable junctions between cells and ensure that adjacent cell membranes are held tightly together’

Answer 11

Tight junctions.

Question 12

Tight junctions hold two cell membranes closely together. Where in the body might this be useful?

Answer 12

In sealing off body cavities, e.g. intestinal epithelial cells and endothelial cells lining the brain’s capillaries (the blood-brain barrier).

Question 13

This cell junction can be likened to tunnels linking the cytoplasm of adjacent cells, allowing the passage of small molecules from cell to cell. WhIch cell junction is this?

Answer 13

Gap junction.

Question 14

Gap junction are formed of six molecules of which protein, which can be opened or closed as needed?

Answer 14

Connexin.

Question 15

Gap junctions help to maintain electrophysiological interactions, allowing co-ordinated cell responses. Where might they be found?

Answer 15

In nerve cells and heart cells.

Question 16

Which is the only type of cell junction which prevents materials passing through the intracellular space?

Answer 16

Gap junctions.

Question 17

What is the difference between transcellular and paracellular?

Answer 17

Transcellular means through the cell, paracellular means through the intracellular space.

Question 18

How many types of cell membrane transport are there? Name them.

Answer 18

Five: osmosis, simple (passive) diffusion, facilitated diffusion, active transportand vesicular transport.

Question 19

‘The passage of water across a membrane from a region of low solute concentration to a region of high solute concentration’ - what mode of cell membrane transport does this describe?

Answer 19

Osmosis.

Question 20

Define:
1. Hypotonic.
2. Hypertonic.
3. Isotonic.

Answer 20

1. Hypotonic soolutions have a lower concentration of solute than their surroundings, meaning water will flow out of them.
2. Hypertonic solutions have a higher concentration of solutes than their surroundings, meaning water will flow into them.
3. Isotonic solutions have the same solute concentration on both sides of a membrane.

Question 21

True or false? In isotonic solutions, water does not move across the membrane because the solute concentration is the same either side of the membrane.

Answer 21

False. In an isotonic solution, even though the solute concentration either side of the membrane is the same, water still moves across the membrane by diffusion, but at the same rate and in both directions.

Question 22

What are the specific water channels, found in most membranes, called?

Answer 22

Aquaporins.

Question 23

Name some osmotically active solutes.

Answer 23

Ions, proteins and glucose.

Question 24

What can be described as ‘the passage of solutes by random molecular motion from a region of high solute concentration to a region of low solute concentration’.

Answer 24

Simple (passive) diffusion.

Question 25

Does simple diffusion require any energy input?

Answer 25

No, other than the heat energy of the molecules which maintains their motion.

Question 26

In simple diffusion, what does the net rate of solute movement depend on?

Answer 26

The molar concentration gradient.

Question 27

When talking about passive diffusion, how would one describe two solutions with the same concentration of solute?

Answer 27

Equimolar.

Question 28

What is expressed by a solute's reflectance coefficient?

Answer 28

The ability of a solute to diffuse across a cell membrane.

Question 29

If a solute has a reflectance coefficient of 1, is there no diffusion, or is the solute freely diffusible?

Answer 29

No diffusion. e.g. glucose, amino acids.

Question 30

A solute with a reflectance coefficient of 0 is...

Answer 30

...freely diffusible. e.g. water, O2, CO2, fatty acids, steroid hormones.

Question 31

A selectively diffusible solute with have a reflectance coefficient of...

Answer 31

0-1. e.g. inorganic ions.

Question 32

What can be describes as 'the passage of solutes across a membrane, down a concentration gradient, helped by a transporter protein'.

Answer 32

Facilitated diffusion.

Question 33

In faciitated diffusion, the net rate of solute movement can depend on two factors. Name them.

Answer 33

1. Concentration gradient. 2. The activation state of the transporter protein.

Question 34

Is energy input required for facilitated diffusion?

Answer 34

No, although transporter proteins may need a 'signal' to open them.

Question 35

True or false? Transporter proteins can act like 'gates', opening and closing to allow solutes through.

Answer 35

True.

Question 36

Name the mode of cell transport: 'the passage of solutes across the membrane, up a concentration gradient, helped by a transporter protein'.

Answer 36

Active transport.

Question 37

Does active transport require energy input?

Answer 37

Yes, ATP is required to drive the transporter 'pump'.

Question 38

In active trasnport, the net rate of solute movement depends on the supply of ............ to the transporter protein.

Answer 38

Energy (ATP).

Question 39

What is an ATPase?

Answer 39

A transporter protein involved in active transport.

Question 40

Give an example of a common active transport 'pump' and where it might be found in the body.

Answer 40

The Na+/K+ pump. Found in the red blood cell membrane, stomach membrane and renal tubule. Sodium is pumped out of the cell and potassium is pumped into the cell. The concentration of sodium is higher outside the cell, so the sodium is being pumped out against the concentration gradient.

Question 41

What is the difference between uniport, symport and antiport?

Answer 41

Uniport: transports one substance. Symport: transports more than one substance. Antiport: exchanges one substance for another.

Question 42

What is a vesicle, involved in vesicular transport?

Answer 42

A vesicle is a structure consisting of liquids / molecules enclosed by a lipid bilayer, which can transport molecules into and out of cells.

Question 43

Define endocytosis.

Answer 43

Endocytosis describes the transport of molecules into a cell in membrane-wrapped vesicles.

Question 44

Define exocytosis.

Answer 44

Exocytosis is the transport of vesicles to the cell surface. Molecules are then expelled from teh cell by fusion of the vesicle with the cytoplasmic membrane.