1.4 membrane structure

Question 1

what are the different ways of transport particle move across membranes

Answer 1

• simple diffusion
• facilitated diffusion
• osmosis
• active transport

Question 2

the membrane is ‘semipermeable’

what does semipermeable mean

Answer 2

to allow some, but not all molecules through.

- controls what goes in and out of the cell

Question 3

what is passive transport

Answer 3

a form of transport which does not require energy as the molecules move from a high to low concentration->down the concentration gradient

Question 4

examples of passive transport

Answer 4

• diffusion
• factiliated diffusion
• osmosis

Question 5

what is active transport

Answer 5

transport through the membrane which does require require energy as the molecule move from a low to high concentration–> moves against the concentratioon gradient

Question 6

examples of active transport

Answer 6

• ion pumps

- phagocytosis

Question 7

what is a concentration gradient

Answer 7

where the concentration is different across an area

-i.e high and low concentration

Question 8

what is the difference between passive and active transport

Answer 8

• passive doesn’t require energy and goes from high to low concentration
• active does require energy and goes from low to high concentration

Question 9

Diffusion is a form of what type of transport

Answer 9

passive transport

Question 10

what is diffusion

Answer 10

passive movement of particles

• down the concentration gradient
• higher to lower concentration
• requires no energy

Question 11

how does diffusion occur

Answer 11

occurs as the consequence of random motion of particles

Question 12

why can’t all substances diffuse

Answer 12

• the mebrane is semi-permeable so many substances can’t diffuse due to size or polarity

Question 13

steep gradient

Answer 13

large difference in concentration between the two areas

Question 14

what affects the speed of diffusion

Answer 14

• the steepness of the concentration gradient
  - steeper concentration gradient= faster diffusion
• size of the molecules
• temperature

Question 15

examples of substances that move via diffusion

Answer 15

mostly gases
- oxygen
carbon dioxide
-glucose

Question 16

facilitated diffusion

Answer 16

passive transport of molecules or ions across a cell membrane

• done through transmembrane integral proteins which transport the molecules

Question 17

polar molecules

Answer 17

• cannot freely diffuse due to the hydrophobic nature of the fatty acid tails of the phospholipids
• are transported by proteins in the form of transmembrane

Question 18

examples of factilated diffusion

Answer 18

- glucose
sodium ions
- chloride ions
- amino acids
- nucleosides

Question 19

ion channels

Answer 19

facilitated diffusion that involves channel proteins

- opens a channel to allow smaller molecules instead of binding to molecules

Question 20

examples of molecules that ion channels allow through

Answer 20

• sodium
• potassium
• calcium
• chlorine

Question 21

why do some molecules use factilated diffusion

Answer 21

the lipid bilayer is impermeable to them

e.g. the glucose molecule is to large to pass through unassisted

Question 22

what is osmosis

Answer 22

the movement of water molecules from an area of higher water concentration to an area of lower concentration through a semi-permeable membrane.

osmosis is a form of passive transport

does not require energy

Question 23

through osmosis, will water move to the hypertonic or hypotonic area and through what type of transport

Answer 23

the hypertonic area ( the low water area)

through osmosis

Question 24

what is osmolarity

Answer 24

the measure of a solutes concentration

Question 25

what osmolarity does water have

Answer 25

zero

Question 26

turgid

Answer 26

when a cell is placed in a low salt/ high water solution, the cell gains water as it is hypertonic and swells- becoming turgid.

Question 27

turgid in a plant cell vs animal cell

Answer 27

plant cell: optimal condition- turgid - will be contained by the cell wall animal cell/protist: no cell wall so therefore may burst, killing the cell -lysed

Question 28

isotonic

Answer 28

when the solution and cell have the same concentration if the cell and the solution have the same concentration then it is isotonic and they remain unchanged isotonic saline solutions are used in medical procedures such as transporting kidneys. - they mast be in a solution with the same osmorlatiy as a a human cytoplasm to prevent osmosis

Question 29

in fresh what cells tend to gain/lose water via what transport and why

Answer 29

gain through osmosis the cytoplasm contains dissolved substances and is therefore hypertonic to the fresh water which is hyoptonic

Question 30

potassium ion channels

Answer 30

they are the most common type of ion channel and are found in most cell types. they form potassium selective pores that spend the cell membrane. potassium ion channels are used to move K+ ions across the membrane the channels work with the sodium-potassium pump in the axons of neurons

Question 31

the axons of neurons

Answer 31

transmit electrical impulses by translocating ions to create a voltage difference across the membrane when at rest, the sodium-potassium pump expels sodium ions from the nerve cell, while potassium ions gather within the cell when the neuron fires, these ions swap locations via facilitated diffusion through the sodium and potassium channels

Question 32

what type of transport is used when the neuron fires

Answer 32

facilitated diffusion via the sodium and potassium channels

Question 33

active transport

Answer 33

the movement of particles from an area of low concentration to and area of high concentration,going against the concentration gradient and requiring energy(ATP). examples include: the uptakes of glucose in the intestines of humans, the exchange of Na and K+ ions in the nerve axons uptake of mineral ions into root hair cells of plants.

Question 34

what are the two main types of active transport

Answer 34

protein pumps - only transport specific substances and in a specific direction, - substance binds to the protein - and energy(ATP) Is used to move the substance along use of vesicles - the fluidity of the membrane allows materials to be taken into cells by endocytosis or released exocytosis - vesicles move materials within the cells.

Question 35

sodium-potassium pumps in nerve axons

Answer 35

nerve cells conduct nerve impules via a 'mexican wave' of Na+ and K+ ions in and out of the nerve. axons contain a pump protein that moves Na+ and K+ ions across the membrane. The ions are moved in opposite directions(antiport). one energy(ATP) molecule is enough to transport three Na+ out and two K+ ions in.

Question 36

what are nerve cells

Answer 36

axons

Question 37

there are two states the sodium-potassium pumps have

Answer 37

In one there is more 'binding site attraction' for K+ ions outside the membrane. - in this state K+ moves in and Na+ moves out. In the other state the reverse occurs - K+ moves out and Na+ moves in ATP energy cause the change from one state to another

Question 38

how does ATP cause the change in the sodium-potassium pump's states

Answer 38

it helps to establish a net charge across the plasma membrane with the interior of the cell being negatively charged with respect to the exterior. this prepares nerve and muscle cells for propagation of nerve

Question 39

what are vesicles

Answer 39

usually small vacuoles containing proteins, that bud off from the endoplasmic reticulum or the Golgi bodies and then travel to the cell membrane

Question 40

exocytosis

Answer 40

secrection when a vesicle fuses with the cell membrane, the contents are expelled and the membrane flattens out again e.g. secrection in substances: hormones, contractile vacoules in paramecin

Question 41

endocytosis

Answer 41

part of the cell membrane is pulled inward, the material in engulfed and the vesicle is pinched off phagocytosis: is engulfing solid material pinocytosis: is engulfing fluid material

Question 42

what are the molecules that make up living things

Answer 42

C.L.P.N.M.W Clay lions paint nails mysteriously well carbohydrates: glucose, starch, cellulose Lipids: fats, waxes, oils Proteins: enzymes, hormones, collagen, muscle Nucleaic acids: DNA Minerals: calcium, iron, sodium Water

Question 43

carbon in living things

Answer 43

carbon is contained in organic compounds which are found in living things. each carbon atom can form four covalent bonds: allows a great diversity of compounds to exist the most common type is C-C and C-H.

Question 44

covalent bonds

Answer 44

hydrogen forms one covalent bond oxygen and sulfer form two nitrogen form three Carbon can form four covalent bonds additional groups added to the C-C molecule give the organic compound it's properties. covalent bonds are relatively strong so molecules are stable. weaker bonds can form between molecules.

Question 44

covalent bonds

Answer 44

hydrogen forms one covalent bond oxygen and sulfer form two nitrogen form three Carbon can form four covalent bonds additional groups added to the C-C molecule give the organic compound it's properties. covalent bonds are relatively strong so molecules are stable. weaker bonds can form between molecules. life is based on carbon compounds including carbohydrates

Question 45

the theory of vitalism

Answer 45

it used to be thought that living organisms were composed of organic molecules that could only be produced by a 'vital force'- made by a living thing this was proved false through biochemistry discoveries which explained the living process: e.g. photosynthesis and respiration, in terms of the chemical substances and chemical reactions. - In 1828 Fredich Wohler synthesised urea artificially using silver isocyanate and ammonium chloride. the structure of DNA has further explained living processes including protein synthesis, inheritance and evolution.

Question 46

synthesis of urea

Answer 46

Urea was discovered in human urine during the 18th century the theory of vitalism would have meant that it could have only been made in living organisms with a vital force. In 1828 Fredich Wohler synthesised urea artificially using silver isocyanate and ammonium chloride which disproved the the theory of vitalism.

Question 47

chemical synthesis

Answer 47

a key aspect to organic chemistry. today most organic compounds that make up living organisms can be synthesised. this is often used by pharmaceutical companies to. identify compounds from plants and animals and artificially synthesise them for use e.g. hormones, enzymes, painkillers.

Question 48

metabolism

Answer 48

metabolism is the web of all the enzyme-catalysed reactions in a cell or organism. reactions may be anabolic or catabolic. a metabolic pathway is a series of chemical reaction within a cell.

Question 49

anabolism

Answer 49

the synthesis of complex molecules from simpler molecules including the formation of complex molecules including the formation of macromolecules from monomers via condensation reactions. examples include the synthesis of sugar from CO2, (photosynthesis), the synthesis of large proteins from amino acid building blocks, and the synthesis of new DNA strands from nucleaic acid building blocks anabolic steriods build muscle and protein

Question 50

catabolism

Answer 50

The breakdown of complex molecules into simpler molecules including the hydrolysis of macromolecules into monomers example respiration where glucose is broken down. into carbon dioxide and water to produce energy(ATP)