Osmosis and diffusion

Question 1

Homeostasis

Answer 1

-REGULATORY MECHANISMS: keep variables (temp, pH, nutrients) within optimal range
-crucial for sustaining life: supports cellular, tissue and organ func.
-maintains stable internal conditions despite external changes
-collaboration: nervous and endocrine systems work together to detect and correct deviations

Question 2

phospholipid bilayer

Answer 2

-cell membranes are lipid bilayers which are impermeable to most essential molecules and ions
-lipid bilayers are not permeable to:
-ions e.g. K+, Na+
-macro molecules e.g. rna dna
-small hydrophilic molecules e.g. glucose

Question 3

Methods of transport across membranes

Answer 3

-diffusion
-osmosis
-facilitated diffusion
-active transport

Question 4

Diffusion

Answer 4

-movement of molecules (high to low conc)
-movement from one side of a membrane to another, unfacilitated
-continues until all molecules are evenly spread

Question 5

Osmosis

Answer 5

-water moves freely through pores
-fluid moves to one side of the membrane to the other not the molecules
-diffusion of water through a selectively permeable membrane
-water moves high to low conc.
-tonicity: hypotonic, hypertonic, isotonic

Question 6

hypotonic

Answer 6

low solute; high water
-water moves from solution into cell (inside): cell swells and bursts open (cytolysis)

Question 7

hypertonic

Answer 7

high solute; low water, water moves from inside cell into solution: cell shrinks (plasmolysis)

Question 8

Isotonic

Answer 8

Both solutions have same conc. of solute, water moves equally in both directions and cell remains same size

Question 9

Types of transporters

Answer 9

uniporter
symporter
antiporter

Question 10

uniporter

Answer 10

moves one type of molecule in one direction

Question 11

symporter

Answer 11

moves 2 different types of molecules in same direction

Question 12

antiporter

Answer 12

moves 2 different types of molecules in opposite directions

Question 13

facilitated diffusion

Answer 13

-facilitates the passage of larger or charged molecules
-high to low conc.
-transport proteins are selective, allowing only specific molecules to cross

Question 14

osmotic

Answer 14

groups of molecules/solute that are osmotically active
-ions, sugars, proteins

Question 15

Functions of membranes

Answer 15

1. protect cell
2. control incoming and outgoing substances
3. maintain ion conc. of various substances
4. selectively permeable - allows some molecules in, others are kept out
5. all of this maintains homeostasis (internal balance)