Topic 3

Question 1

what are lipids

Answer 1

water insoluble molecules composed mostly of carbon and hydrogen molecules (hydrocarbons)

Question 2

what are biological lipids? (examples)

Answer 2

triglycerides (energy storage)
phospholipids (membranes)
sterols (membranes)

Question 3

what are fatty acids?

Answer 3

a long chain of C atoms with a carboxyl group at one end
-hydrocarbons

Question 4

how do fatty acid molecules vary?

Answer 4

the number of hydrocarbons in the chain (normally between 12 and 24)
-presence and number of carbon-carbon double bonds

Question 5

what is the difference between an unsaturated fatty acid and a saturated fatty acid?

Answer 5

unsaturated fatty acids have one or more double bonds that create a kink in the chain (veg oil)
-saturated fatty acids only have single bonds (animals)

Question 6

what are triglycerols?

Answer 6

energy storage molecules
-three fatty acids bound to a glycerol anchor

Question 7

what are phospholipids?

Answer 7

a component of membranes

Question 8

what are phospholipids composed of?

Answer 8

head group
tail

Question 9

characteristics of phospholipid heads?

Answer 9

polar
water soluble (hydrophilic)
form noncovalent hydrogen bonds

Question 10

characteristics of the phospholipid tail?

Answer 10

water insoluble (hydrophobic)
nonpolar
composed of hydrocarbon chains
have vanderwaals interactions

Question 11

characteristics of the phospholipid tail?

Answer 11

water insoluble (hydrophobic)
nonpolar
composed of hydrocarbon chains
have Vanderwaals interactions

Question 12

what are membranes?

Answer 12

selectively permeable barriers
-scaffolds for communication and chemical reactions

Question 13

what is the fluid mosaic model?

Answer 13

lipids and proteins coexist in a membrane
-molecules (lipids and proteins) can move laterally (side to side) in the membrane

Question 14

functions of membrane proteins?

Answer 14

transport = chanels/carriers
enzymes = proteins
signals bind to hormones
attachment to other cells

Question 15

what is membrane fluidity?

Answer 15

the viscosity of a lipid bilayer (how easily things can flow through it)

Question 16

what factors increase membrane fluidity?

Answer 16

shorter fatty acid tails
unsaturated fatty acids
presence of sterols
increase in temperature

Question 17

what factors decrease membrane fluidity?

Answer 17

long fatty acid tails
saturated fatty acids
presence of sterols
decrease in temperature

Question 18

how do sterols regulate membrane fluidity?

Answer 18

they prevent freezing by stopping phospholipids from packing too tightly
-prevent melting by filling gaps between phospholipids

Question 19

what are sterols?

Answer 19

cholosterols (normally animal) that are inserted into bilayers

Question 20

what does membrane fluidity affect?

Answer 20

permeability of the membrane

Question 21

what happens when membranes are leaky?

Answer 21

more solutes can pass through the bilayer more quickly

Question 22

why are viscous membranes better barriers?

Answer 22

fewer solutes can pass by the bilayer less quickly

Question 23

which molecules cannot diffuse across a lipid bilayer?

Answer 23

large charged and polar molecules, ions

Question 24

which molecules can diffuse accross a lipid bilayer?

Answer 24

small, uncharged and barely polar molecules

Question 25

why do cells need selective barriers?

Answer 25

cells are in dynamic environments where conditions are always changing -helps maintain homeostasis by transporting only what the cell needs -allows for different concentration inside the cell compared to the outside -transport of molecules is regulated by the cell

Question 26

what is diffusion?

Answer 26

the tendency of dissolved molecules to evenly distribute themselves in a solution

Question 27

characteristics of diffusion?

Answer 27

molecules move from high concentration to low concentration -equilibrium is eventually reached -energy comes from the concentration gradient -increase in entropy when molecules are evenly dispersed

Question 28

what happens in diffusion once equilibrium is reached?

Answer 28

the concentration gradient has been eliminated -lower energy state

Question 29

what is osmosis?

Answer 29

the diffusion of water -low solute concentration to high solute concentration

Question 30

what is tonicity?

Answer 30

the solute concentration difference across a lipid bilayer

Question 31

what does tonicity affect?

Answer 31

diffusion/osmosis accross a membrane

Question 32

what are the three major types of tonicity?

Answer 32

isotonic hypotonic hypertonic

Question 33

what is isotonic?

Answer 33

same concentration on the outside as the inside -no movement of water, cells don't change in shape or size

Question 34

what is hypotonic?

Answer 34

lower concentration outside the cell than inside -water diffuses inward and the cell swells

Question 35

what is hypertonic?

Answer 35

higher concentration inside the cell than outside -water diffuses out of the cell and the cell shrinks

Question 36

what are the two types of passive transport?

Answer 36

facilitated diffusion simple diffusion

Question 37

what is simple diffusion?

Answer 37

small hydrophobic polar molecules diffuse directly across the membrane

Question 38

characteristics of simple diffusion?

Answer 38

moves down with the gradient -powered by potential energy in the concentration gradient -greater gradient= grater rate of movement

Question 39

what is facilitated diffusion?

Answer 39

large charged and polar molecules get help crossing the membrane by protiens

Question 40

characteristics of facilitated diffuesion?

Answer 40

down with gradient -does not require ATP -transporter is specific to molecule -rate is gradient specific -direction of transport is reversible -channel for small molecules, carrier for large molecules

Question 41

why do cells need to concentrate molecules in the cell?

Answer 41

because cells live in dilute environments

Question 42

how do cells establish a concentration gradient?

Answer 42

cells move solutes away from equilibrium

Question 43

what is required in establishing a concentration gradient?

Answer 43

an energy source like atp (active transport)

Question 44

what is primary active transport?

Answer 44

highly specific protein pumps that cross the membrane to move solutes against its concentration gradient

Question 45

how does primary active transport function?

Answer 45

it uses ATP to power the transporter of the molecule -can generate both chemical concentration gradient and electrochemical concentration gradients

Question 46

what is secondary active transport?

Answer 46

specific protein pumps that cross the membrane to move solutes against its concentration gradient

Question 47

how does secondary active transport function?

Answer 47

powered by energy released as a different solute moves down its concentration gradient -uses symporters and antiporters

Question 48

what are symporters?

Answer 48

both solutes move in the same direction

Question 49

what are intiporters?

Answer 49

solutes move in opposite directions