transport across membranes and digestion

Question 1

fluid mosaic membrane

Answer 1

phospholipid parts of the membrane are free to move relatice to each other, hence its fluid.
the distribution of protiens within the membrane give it the mosaic look - some can move
structure of the protiens determines their position in the membrane
transmembrane of transport protines that allow passage to ions and plaor molecules through the hysrophobic core

Question 2

what is the phosphlopid bilayer

Answer 2

hydrphobic tails point inwards
hydrophillic heads point outwarsd
act as a barrier to water solubl substances as the non polar fatty acid tils prevent polar molecules or ions from passing across the membrane

Question 3

what are glycoprotiens

Answer 3

protiens with carbohydrate chains attachedwhic project out into whatever fluid i surrouding the cell. Normalluy act as receptors to hormones.

Question 4

what are glycolipids

Answer 4

lipids with carbohydrate chains attached which project out into whatever fluid is surrounding the cell ( found on outer phospholipid layer )

Question 5

what is cholesterol

Answer 5

present in cell membrane where it restricts movement of other molecules making it up the membrane - regulates membrane fluidity.
Animal cells suported by other in a layer would need less cholesterol to maintian their shape, however cells like red blood cells are free in the blood so cholesterol helps maintain its biconcave disc shape

Question 6

what is visking tubing

Answer 6

material used by biologists to model the cell membrane structure.
only substances that are small can pass through the tubing. e.g. glucose, maltose, water

Question 7

what is simple diffusion

Answer 7

passive proccess ( no ATP needed )
movement of small and non polar molecules down a concentration gradient

Question 8

what are micelles

Answer 8

small spheres of phopholipid carrying fatty acids and glycerol, so are soluble in cell membranes and can pass straight through them by diffusion

Question 9

what is facilitated diffusion

Answer 9

passive procces
movement of large, charged molecules down a concetration gradient.
Requires a carrier or a channel protien, complementary to a specific molecule or ion.
substances will move down the concentration gradient until equilibrium will be reached.

Question 10

what is a channel protien

Answer 10

transports ions which are water soluble e.g. sodium

Question 11

what is a carrier protien

Answer 11

transports large molecules such as amino acida and glucose

Question 12

factors that can affect the rate of diffusion

Answer 12

• concentration gradient : the steeper the gradient, the faster the rate of diffusion
• temp : higher the temp, the more kinetic energy, the faster the rate of diffusion
• surface area : the greater the surface area, the faster the rate of diffusion
• thickness : the thinner the membrane, the faster the rate of diffusion due to a short diffusion distance.

Question 13

what is ficks law

Answer 13

represenst how the factors affect the rate of diffusion :
rate of diffusion = ( S.A X difference in conc. ) / lenght of diffusion pathway

Question 14

what is active transport

Answer 14

active process using ATP
movement againts the concentration gradient via a carrier protien.
Mitochondria will supply ATP for active transport
ATP hydrolysis causes the protien to change shape, which carries the substances across the membrane

Question 15

how do you make sure there is no oxygen in a soultion

Answer 15

1) use boiled and then allowed to cool water
2) add a thin layer of oil on top of the solution

Question 16

what is osmosis

Answer 16

passive process, no ATP
water moves by osmosis down the water potential gradient ( from high to low ) across a partially permeable membrane
pure water has max water potential ( 0 kpa)
osmosis requires channel protiens called aqua porins

Question 17

how to prepare a 10 fold dultion series

Answer 17

add 1cm3 from the stock solution to 9cm3 of distilled water
to make the subsequent dilutions, add 1cm3 from the previous dilution to 9 cm3 of distilled water

Question 18

required prac : investigating memebrane permeablity

Answer 18

two different IVS : temperature and alcohol ( ethanol )
both will cause the loss of the red pigement in a beetroot.
ethanol will dissolve the phospholipid bilayer
high temp would denature the membrane protiens and increase fluidity of membrane, so its more permeable. The higher the permeability, the more pigment will leak out and the higher the absorbance on the colorimeter.
using the colorimeter acquire data to produce a standard curve of the absorbance of known concentrations of beetroot extract

Question 19

required prac : what happens if the temp is the IV

Answer 19

1) cut discs from the beetroot of the same size using a cork borer a ruler and scalpel
2) blot dry with a paper towel
3) place the same no. of discs into tubes containing the same volume of ditilled water and fit with a bung
4) place each tube into water baths at diff temps ( 10, 20,30,40, 50 , etc ) for a specifc time
5) moniter temp by taking repeat readings
6) after the specified time pour the liquid into another label tube and discard beetroot discs
7) meaure absorbance of liquifs using a colorimeter
8) using the standard curve created earlier, obtain values from the X axis of the concentrations of beetroot at either the diff temps of diff alchohol concentrations.

Question 20

required prac : what happens if the IV is ethanol

Answer 20

1) cut beetroot using corkborer etc and blot dry
2) place the same no. of discs into tubes containign the same volume of different concentrations of ethanol and fit with a bung
3) place each tube in thermostatically controlled water bath at the same temp for a set amount of time
4) moniter the temp to ensure it stays the same
5) after the specified time pour the liquid into another label tube and discard beetroot discs
6) meaure absorbance of liquifs using a colorimeter
7) using the standard curve created earlier, obtain values from the X axis of the concentrations of beetroot at either the diff temps of diff alchohol concentrations.

Question 21

required prac : determining water potential of plant tissues

Answer 21

1) produce dilution series of diff concentrations of sucrose
2) cut and wiegh potatoe discs, record as initil mass
3) place in a tube containing a different sucrose solution for a set time
4) remove discs blot them dry and reweigh as final mass
5) calculate percentage change in mass of potatoe tisse
6) plot a graph with conc on the x axis and percentage change in mass on the y axis
7) find concentration where the curve crosses the x axis
8) find water potential of sucrose conc

Question 22

how to make a stated volume of solution by diluting from a starting stock solution

Answer 22

1) work out the percentage dilution e.g. 10%
2) final volume require / 100 x percentage dilution = volume of original solution required cm3
3) final volume required - volume of original solution required = volume of distilled water required cm 3

Question 23

how to calculate percentage change

Answer 23

(final mass - initial mass)/initial mass x100

Question 24

how are carbohydrates digested

Answer 24

by amylase which hydrolyses the gylcosidic bonds in starch to produce maltose.
maltase hydrolyses the gylcosidic bonds in maltose producing two glucose molecules.

Question 25

where is amylase found and made

Answer 25

found in mouth and small intestine made in salivary glands and pancreas

Question 26

where is maltase found

Answer 26

embedded in the cell surface membrane of the epithelial cells of the ileum

Question 27

what is the ileum

Answer 27

final section of the small intenstine. The lining is folded and microvilli is present to increase the surface area allowing for faster absroption

Question 28

how is protien digested

Answer 28

pepsin is secreted with hydrochloric acid giving in acidic pH of 2. This mixture enters the small intestine from the stomach. it is mixed with bile salts to neutralise the hydrochloric acid. pancreatic juice containing endo and exopeptidase enzymes. endo - hydolyses internal peptide bonds within a polypeptide to form smaller polypeptide chains, they give more ends for exopeptidases to act on. exopeptidases hydrolyse peptide bonds at the ends of a polypeptide to remove terminal amino acids. membrane bound deipeptidases found within the cel surface membrane of the epithelial cells hyrolyse peptide bonds in a dipeptide to release two amino acids.

Question 29

what are the co transport mechanisms for the absorption of amino acids and monosacharides

Answer 29

sodium ions are actively transported out of the epithelium cell of the iliem into the blood stream ( sodium potassium pump ) creates a conc gradient with a higher conc of sodium in the lumen than in the ilieum cell. allows sodium to diffuse in from the lumen of the iliem down its conc gradient via a co transport protien for either glucose or amino acids co transporter carries glucose/ amino acids into the cell against its conc gradient, resulting in a hig conc of glucose/ amino acids into the cell. the glucose/ amino acids can diffuse out of the epithelial cell via facilitated diffusion

Question 30

how are lipids digested

Answer 30

bile salts secreted into the small itestine they bind to large lipids to form lipid droplets known as emulsification lipid droplet formation via emulsification increases the SA for lipase action for faster hydrolysis of triglycerides - turns into monoglycerides and fatty acids lipase is produced by the pancreas then secrted into the small intestine, where it hydrolyses ester bonds in triglycerides to produce fatty acids and gylcerol

Question 31

what is the role of micelles in the absorption of lipids

Answer 31

micelles include bile salts and fatty acids. They make fatty acids more soluble in water. micelles carry fatty acids into tje cells lining the ilieum. the fatty acids are absrobed by diffusion. triglycerides are reformed in the cells into chlyomicorns at the golgi apparatus, combining triglycerides with protiens they are packaged into vesicles for release by exocytosis as the vesicles move to the cell membrane. * occurs in lymphatic system