Cell Membranes

Question 1

What is the purpose of cholesterol?

Answer 1

• restricts lateral movement of other molecules in the cell membrane
• decreases fluidity in higher temperatures; this prevents water (and dissolved ions) from leaking out of the cell

Question 2

What are the 2 types of proteins imbedded in the membrane?

Answer 2

peripheral and integral

Question 3

What is the function of peripheral proteins in the cell membrane?

Answer 3

• mechanical support
• connect with carbs to make glycoproteins
• cell recognition (receptors)

Question 4

What is the function of integral proteins in the cell membrane?

Answer 4

• carrier/ channel proteins

Question 5

What are carrier proteins?

Answer 5

• used in co-transport
• bind to larger molecules (eg glucose and amino acids), change shape to transport them to the other side of the membrane

Question 6

What are channel proteins?

Answer 6

• tubes filled with water : enable water-soluble ions to diffuse through

Question 7

What kinds of molecules can and can’t pass through the partially permeable plasma membrane?

Answer 7

• can: lipid-soluble substances + very small molecules
• can’t: water-soluble (polar) substances (eg sodium ions) + large molecules (eg glucose)