Unit 1 Biology Revision #1

Cells with larger SA:V ratios are more likely to survive because they have:

• a high metabolic rate

• A low metabolic rate

• a low rate of material exchange

• a high rate of material exchange

Answer explanation

Due to having a high surface area to volume ratio, the cell is able to exchange material with its external environment at a faster rate. This allows it to gain the materials it needs for the creation of energy to survive and get rid of the cell waste in an efficient manner.

Which of these is true for active transport?

• It requires a cell to expend energy

• It moves molecules down their concentration gradient

• It is exclusively the movement of lipophilic substances

• It requires no expenditure of ATP

Answer explanation

Active transport is the movement of substances against their concentration gradient, which requires energy. An example of active transport is the sodium-potassium pumps in nerve cells.

Molecules which use protein channels to cross the membrane tend to be

• Small & Non-polar

• Large & Polar

• Urea

• Lipophilic & hydrophobic

Answer explanation

Polar, hydrophilic molecules generally have difficulty crossing the plasma membrane through simple diffusion, as they are repelled by the fatty-acid tails of the phospholipids.

Which of the following is true of a spherical cell

• Cell surface area increases faster than cell volume

• Cell volume decreases with increasing cell surface area

• Cell volume increases faster than cell surface area

• Cell surface area decreases with increasing cell volume

Answer explanation

The cell volume of a spherical cell increases faster than its surface area.

Which of these options describes the properties of a phospholipid head?

• Polar & hydrophilic

• Polar & hydrophobic

• Non-polar & hydrophilic

• Non-polar & hydrophobic

Answer explanation

Something that is polar is also hydrophilic ("water-loving") and lipophobic (lipid-fearing").

A cell which has no regular shape would most likely be a

• animal cell

• plant cell

Which of the following is true of plant cells being place in a hypotonic solution

• The cell contents move away from the cell

• Water enters the cell through osmosis until lysis occurs

• Turgor pressure increases until no water enters the cell

• Water leaves the cell through osmosis resulting in the cell membrane to shrink

Answer explanation

Hypotonic solutions mean that the external concentration of water is higher than the internal (cell) concentration of water. Hence, water goes down the concentration gradient into the cell generating a turgor pressure, with the cell contents pushing against the cell wall until water can no longer enter the cell.

Glucose transport involves the use of carrier proteins, which transport glucose into the cell, down its concentration gradient. This is an example of:

Molecule Y is a

• Protein Channel

• Phospholipid

• Glycolipid

• Receptop

Which of these options best describes the properties of a phospholipid tail?

• Non-polar & hydrophilic

• Non-polar and hydrophobic

• Polar & hydrophilic

• Polar & hydrophobic

Answer explanation

Something that is non-polar is also hydrophobic ('water-fearing") and lipophilic ("lipid-loving")