Exam style questions for B2.1-2.3

Outline the significance of surface area to volume ratio in the limitation of cell size. (4)

• when the cell gets bigger, its surface area to volume ratio gets smaller

• cells divide when maximum size is reached

• when the cell increases in size, so does its chemical activity

• surface area of the cell affects the rate of material exchange

Describe transport across cell membranes by osmosis.(4)

• form of diffusion

• osmosis is the movement of water molecules

• it is a passive transport mechanism/does not use ATP

• movement of water molecules from a high concentration of water to a low concentration of water molecules

Outline active transport, including the benefits of the process. (3)

• moved against a concentration gradient/lower to higher concentration

• energy/ATP required/used

• pump/carrier protein carries out active transport

Outline four types of membrane transport, including their use of energy. (4)

• simple diffusion is passive movement of molecules along a concentration gradient

• facilitated diffusion is passive movement of molecules along a concentration gradient through a protein channel without use of energy

• osmosis is the passage of water through a membrane from lower solute concentration to higher

• active transport is movement of molecules against the concentration gradient with the use of ATP/energy

Outline four different functions of membrane proteins. (4)

• cell recognition

• cell adhesion

• active transport

• facilitated diffusion

Explain how hydrophobic and hydrophilic properties contribute to the arrangement of molecules in a membrane. (7)

• pore of channel proteins is hydrophilic

• phospholipid bilayer in water

• some amino acids are hydrophilic and some are hydrophobic

• integral proteins are embedded in membranes due to hydrophobic properties

• hydrophilic amino acids are on the membrane surface

• hydrophobic amino acids are in phospholipid bilayer

Outline the stages in the production of mRNA by transcription.(4)

• DNA unwinds/strands are separated

• new nucleotides attached to template strand

• complementary base pairing

• mRNA detaches from template

• DNA rewinds

Describe the functions of proteins in cell membranes.(4)

• facilitated diffusion by channel proteins

• active transport by protein pumps

• cell recognition by glycoproteins

• cell adhesion