unit 5

Question 1

phospholipid molecule

Answer 1

• contains phosphate group on one end called the ‘head’
• two side by side chains of fatty acids make up lipid tails (one saturated one unsaturated)
• head is polar (- charge) and hydrophilic
• lipid tail is hydrophobic

Question 2

phosphate groups on phospholipid molecule are attracted to:

Answer 2

extracellular fluid (interstitial fluid) and intracellular fluid

Question 3

two proteins often associated with cell membrane are

Answer 3

peripheral and integral

Question 4

integral protein

Answer 4

imbedded in the membrane- channel proteins for example- allows certain ions and molecules to pass in and out of the cell

Question 5

glycoprotein

Answer 5

is a protein that has carbohydrate molecules attached, which extend into the extracellular matrix. The attached carbohydrate tags on glycoproteins aid in cell recognition. The carbohydrates that extend from membrane proteins and even from some membrane lipids collectively form the glycocalyx

Question 6

glycocalyx

Answer 6

is a fuzzy-appearing coating around the cell formed from glycoproteins and other carbohydrates attached to the cell membrane. The glycocalyx can have various roles. For example, it may have molecules that allow the cell to bind to another cell, it may contain receptors for hormones, or it might have enzymes to break down nutrients. The glycocalyces found in a person’s body are products of that person’s genetic makeup

Question 7

peripheral protein

Answer 7

• are typically found on the inner or outer surface of the lipid bilayer but can also be attached to the internal or external surface of an integral protein
• perform specific functions
• for example in intestines, can act as enzyme and break down nutrients to sizes that can flow into bloodstream

Question 8

cell membrane selectively permeable

Answer 8

• hydrophobic
• only non polar molecule can pass through (lipid tail on phospholipids in non polar)
• polar molecules that are hydrophilic are repelled by hydrophobic tails of phospholipid bilayer and must get help to cross membrane

Question 9

passive transport

Answer 9

moves across membrane with own kinetic energy, doesn’t require chemical energy

Question 10

active transport

Answer 10

requires ATP or hydrolysis

Question 11

concentration gradient

Answer 11

difference in concentrations across a space

Question 12

diffusion

Answer 12

movement of materials from area of higher concentration to lower

Question 13

O2 and CO2 diffusion

Answer 13

• higher concentration of O2 outside cell than inside cell, so O2 diffuses through interstitial fluid into cytoplasm of a cell.
• because CO2 produced as a byproduct of metabolism, CO2 is higher concentration inside the cell. Moves from cytoplasm to interstate fluid
• both are small and non polar so they can diffuse easily across membrane= simple diffusion

Question 14

simple diffusion across cell (plasma) membrane

Answer 14

The structure of the lipid bilayer allows small, uncharged substances such as oxygen and carbon dioxide, and hydrophobic molecules such as lipids, to pass through the cell membrane, down their concentration gradient, by simple diffusion.

Question 15

facilitated diffusion

Answer 15

used for cells that can’t get across due to charge, polarity, size

Question 16

carrier-mediated facilitated diffusion

Answer 16

Glucose and other relatively large polar molecules typically bind to transport proteins that change shape to allow the molecules into the cel

Question 17

sodium diffusion

Answer 17

highly concentrated outside the cell. membrane proteins form “sodium channel” to cross. Na moves from outside to inside cell

Question 18

does facilitated diffusion require energy?

Answer 18

no, passive process

Question 19

water passing membrane

Answer 19

simple diffusion, aquaporins allow water to pass

Question 20

osmosis

Answer 20

refers to movement of water across semipermeable membrane

Question 21

isotonic

Answer 21

When cells and their extracellular environments are isotonic, the concentration of water molecules is the same outside and inside the cells, and the cells maintain their normal shape (and function).

Question 22

hypertonic

Answer 22

A solution that has a higher concentration of solutes than another solution. water tends to move into hypertonic solutions

Question 23

hypotonic

Answer 23

lower concentration, water diffuses out of

Question 24

importance of homeostasis

Answer 24

-Cells in a hypotonic solution will take on too much water and swell, with the risk of eventually bursting.
-A critical aspect of homeostasis in living things is to create an internal environment in which all of the body’s cells are in an isotonic solution.
- Various organ systems, particularly the kidneys, work to maintain this homeostasis

Question 25

active transport

Answer 25

energy released from ATP hydrolysis is required to move a substance across a membrane, often with the help of carrier proteins, and usually against the concentration gradient of the substance being moved.

Question 26

Na/K pump

Answer 26

Na out and K in against their concentration gradients. lots found in nerve cells for electrical gradient. 3 Na+ ions out of the cell and 2 K+ ions into the cell per ATP molecule hydrolyzed.

Question 27

electrical gradient

Answer 27

- difference in electrical charge across a space (between inside and outside) -The Na+/K+ pump is crucial for maintaining the electrical gradient and accounts for most of a nerve cell's ATP usage

Question 28

secondary active transport

Answer 28

When active transport (e.g., sodium-potassium pump) creates a concentration gradient that powers passive transport (e.g., sodium diffusion into the cell).

Question 29

endocytosis

Answer 29

The cell engulfs material by wrapping it in a portion of its membrane, which then pinches off to form an intracellular vesicle.

Question 30

pinocytosis- "cell drinking"

Answer 30

A form of endocytosis that brings in fluid and dissolved substances into the cell via membrane vesicles.

Question 31

phagocytosis and pinocytosis

Answer 31

Both take in large portions of extracellular material and are generally not selective.

Question 32

receptor mediated endocytosis;

Answer 32

- A selective form of endocytosis where the cell membrane has receptors specific to certain substances. - Process: Once enough of a specific substance binds to the surface receptors, the membrane forms a vesicle to bring it into the cell.

Question 33

exocytosis

Answer 33

When the vesicle membrane fuses with the cell membrane, the vesicle releases its contents into the interstitial fluid. The vesicle membrane then becomes part of the cell membrane. Cells of the stomach and pancreas produce and secrete digestive enzymes through exocytosis