Lecture 3 - Cell membrane structure & fxn

Question 1

What is the plasma (cell) membrane composed of?

Answer 1

phospholipids & proteins to prevent the loss of enzymes, nucleotides, & other water-soluble molecules

Question 2

T or F: In the fluid-mosaic model, the distribution of proteins are uniform

Answer 2

False

Question 3

What are some other fxns of the proteins in the plasma membrane?

Answer 3

• structural support
• transport molecules
• enzymatic control of cell surface reactions
• receptors
• antigens that identify the cell to the immune system

Question 4

What are 2 structural classes of integral transmembrane proteins?

Answer 4

alpha-helical bundles & beta-barrels

Question 5

What is phagocytosis?

Answer 5

bulk transport of larger portions of the extracellular environment into the cell

Question 6

What 2 molecules form pseudopods?

Answer 6

Neutrophils & macrophages form pseudopods to protect the body from invading microorganisms and remove extracellular debris

Question 7

Phagocytes recognize what?

Answer 7

“eat me” signals (phosphatidylserine) on the plasma membrane surface of apoptotic cells

Question 8

What is pinocytosis?

Answer 8

plasma membrane invaginates to engulf large molecules to engulf large molecules such as proteins from extracellular fluid

Question 9

What is receptor-mediated endocytosis?

Answer 9

• Extracellular molecules bind to very specific receptor proteins in the plasma membrane causing the membrane to invaginate, fuse, & pinch off to form a vesicle
• Example 1: Cholesterol attaches to specific proteins to be taken up into artery cells (atherosclerosis
• Example 2: Viruses

Question 10

What is exocytosis?

Answer 10

• Cellular products are secreted into the extracellular environment
• Vesicles are packaged within the Golgi complex, transported to the membrane, & fuses to the membrane to release contents
• The surface area added to the cell from exocytosis is meant to replace the surface area lost during endocytosis
• Nerve endings use exocytosis to release neurotransmitters

Question 11

What is cilia?

Answer 11

tiny hairlike structure that project from the surface of a cell into the extracellular fluid

Question 12

What is the arrangement of motile cilia?

Answer 12

“9+2” - move like rowers in a boat

Question 13

What is the arrangement of non-motile cilia?

Answer 13

“9+0”

Question 14

What are flagella?

Answer 14

• only found on sperm cells
• single whiplike structure
• 9+2 microtubule arrangement
• Planar, propellor motion