2) Structure and functions in living organisms (a,b,c,d) Flashcards

Question

Food tests - preparing a sample

Answer 1

1. Break up the food 2. Transfer to a test tube and add distilled water 3. Mix the food with the water by stirring with a glass rod 4. Filter the mixture using a funnel and filter paper, collecting the solution 5. Proceed with the food tests

Answer 2

1. Add Benedict's solution to the sample solution in a test tube 2. Heat in a boiling water bath for 5 minutes 3. Take the test tube out of the water bath and observe the colour 4. A positive test will show a colour change from blue to orange / brick red

Answer 3

1. Add drops of iodine solution to the food sample 2. A positive test will show a colour change from orange-brown to blue-black

Answer 4

1. Add drops of Biuret solution to the food sample 2. A positive test will show a colour change from blue to violet / purple

Answer 5

1. Mix the food sample with 4cm3 of ethanol and shake 2. Allow time for the sample to dissolve in the ethanol 3. Strain the ethanol solution into another test tube 4. Add the ethanol solution to an equal volume of cold distilled water (4cm3) 5. A positive test will show a cloudy emulsion forming

Answer 6

Proteins that act as biological catalysts to speed up the rate of a chemical reaction without being changed or used up in the reaction -necessary to all living organisms as they maintain reaction speeds of all metabolic reactions at a rate that can sustain life

Answer 7

-Enzymes are specific to one particular substrate(s) as the active site of the enzyme, where the substrate attaches, is a complementary shape to the substrate -When the substrate moves into the enzyme’s active site - enzyme-substrate complex -After the reaction has occurred, the products leave the enzyme’s active site as they no longer fit it and it is free to take up another substrate

Answer 8

1. Enzymes and substrates randomly move about in solution 2. When an enzyme and its complementary substrate randomly collide an enzyme-substrate complex forms, and the reaction occurs 3. A product (or products) forms from the substrate(s) which are then released from the active site. The enzyme is unchanged and will go on to catalyse further reactions

Answer 9

Breaking the bonds that hold the enzyme together and it will lose its shape -Substrates cannot fit into denatured enzymes as the shape of their active site has been lost -irreversible - once enzymes are denatured they cannot regain their proper shape and activity will stop

Answer 10

-increased temp towards optimum - increases activity - more kinetic energy the molecules have the faster they move and the number of collisions with the substrate molecules increases, leading to a faster rate of reaction -low temp - do not denature enzymes, work more slowly due to a lack of kinetic energy

Answer 11

1. Add 5cm3 starch solution to a test tube and heat to a set temperature using beaker of water with a Bunsen burner 2. Add a drop of Iodine to each of the wells of a spotting tile 3. Use a syringe to add 2cm3 amylase to the starch solution and mix well 4. Every minute, transfer a droplet of solution to a new well of iodine solution (which should turn blue-black) 5. Repeat this transfer process until the iodine solution stops turning blue-black (this means the amylase has broken down all the starch) 6. Record the time taken for the reaction to be completed 7. Repeat the investigation for a range of temperatures (from 20°C to 60°C)

Answer 12

-If the pH is too high or too low, the bonds that hold the amino acid chain together to make up the protein can be disrupted/destroyed -This will change the shape of the active site, so the substrate can no longer fit into it -enzyme will denature, activity stops

Answer 13

1. Add a drop of iodine to each of the wells of a spotting tile 2. Use a syringe to place 2 cm3 of amylase into a test tube 3. Add 1cm3 of buffer solution (at pH 2) to the test tube using a syringe 4. Use another test tube to add 2 cm3 of starch solution to the amylase and buffer solution, start the stopwatch whilst mixing using a pipette 5. Every 10 seconds, transfer a droplet of the solution to a new well of iodine solution (which should turn blue-black) 6. Repeat this transfer process every 10 seconds until the iodine solution stops turning blue-black (this means the amylase has broken down all the starch) 7. Record the time taken for the reaction to be completed 8. Repeat the investigation with buffers at different pH values (ranging from pH 3.0 to pH 7.0)

Answer 14

The movement of molecules from a region of its higher concentration to a region of its lower concentration

Answer 15

-the cell is surrounded by a cell membrane, which can restrict the free movement of the molecules -The cell membrane is a partially permeable membrane - this means it allows some molecules to cross easily, but others with difficulty or not at all -Obtain many of their requirements -Get rid of many of their waste products -Carry out gas exchange for respiration

Answer 16

The net movement of water molecules from a region of higher water potential to a region of lower water potential, through a partially permeable membrane, down a concentration gradient

Answer 17

-Animal cells lose and gain water as a result of osmosis -do not have a supporting cell wall, the results of osmosis can be severe -if placed in a strong sugar solution: lose water, shrivel up -placed into distilled water: gain water by osmosis as it has no cell wall to create turgor pressure -It will continue to gain water until the cell membrane is stretched too far and it bursts

Answer 18

-Plant cells lose or gain water as a result of osmosis -As plant cells have a supporting cell wall, they are protected from cell lysis (the breakdown of a cell caused by damage to its membrane) -placed in strong sugar solution: lose water, vacuole smaller, cell membrane shrivels away from cell wall, becomes flaccid -placed in distilled water: gain water by osmosis, vacuole gets bigger, pushes cell membrane against the cell wall, turgid, high turgor pressure

Answer 19

-water entering the cell makes cell rigid and firm -provide support, strength for plant

Answer 20

The movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration -Energy is needed because particles are being moved against a concentration gradient -across the cell membrane involves protein carrier molecules embedded in the cell membrane

Answer 21

-surface area to volume ratio -diffusion distance -temperature -concentration gradient

Answer 22

-The bigger a cell or structure is, the smaller its surface area to volume ratio is, slowing down the rate at which substances can move across its surface -increased SA:Vol - e.g. root hair cells in plants, cells lining ileum in animals

Answer 23

-The smaller the distance molecules have to travel the faster transport will occur -This is why blood capillaries and alveoli have walls which are only one cell thick, ensure the rate of diffusion across them is as fast as possible

Answer 24

-The higher the temperature, the faster molecules move as they have more energy -This results in more collisions against the cell membrane and therefore a faster rate of movement across them

Answer 25

-The greater the difference in concentration on either side of the membrane, the faster movement across it will occur -This is because on the side with the higher concentration, more random collisions against the membrane will occur

Answer 26

1. cut 2 equally-sized cubes of beetroot 2. Rinse the beetroot pieces 3. Put 5 cm3 of water into 2 test tubes labelled A and B 4. Keep test tube A at room temperature and transfer test tube B to a hot water bath at 90℃ Leave the test tubes for 2 minutes, then add a piece of beetroot into each test tube 5. After 10 minutes, observe the colour of the liquid in both test tubes -at higher temperature, more pigment has leaked out - cell membrane is more damaged/ particles have more kinetic energy

Answer 27

1. Prepare a range of sucrose (sugar) solutions ranging from 0 Mol/dm3 (distilled water) to 1 mol/dm3 2. Set up 6 labelled test tubes with 10cm3 of each of the sucrose solutions 3. Using the knife, cork borer and ruler, cut 6 equally-sized cylinders of potato 4. Blot each one with a paper towel and weigh on the balance 5. Put 1 piece into each concentration of sucrose solution 6. After 4 hours, remove them, blot with paper towels and reweigh them -potato in distilled water will have increased its mass the most

2) Structure and functions in living organisms (a,b,c,d) Flashcards

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