Exam style questions for B2.1-2.3

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

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