practicals P1 Flashcards

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1
Q

ways of measuring the rate of enzyme activity

A
  • gas produced - how fast the product is made eg gas released into upside down cylinder
  • biochemical tests - how fast substrate broken down eg testing for starch using amylase, none left = broken down
  • change in mass
  • change in pH
  • colour change
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2
Q

variables in enzyme experiments

A

temperature
concentration of enzyme
pH (use buffers)
substrate concentration

keep all same except independent

control - repeat with denatured enzyme (check it is making change in DV)

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3
Q

effects of temperature on enzyme activity

A

vary temperature using a waterbath or beaker with ice

measure using thermometer

control all other variables

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4
Q

effects of substrate/enzyme concentration of enzyme activity

A

stock solutions diluted to make necessary concentrations
- dilution series

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5
Q

effects of pH on enzyme activity

A

use buffer to maintain pH

check buffer doesn’t affect rate of reaction - use control

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6
Q

how to calculate rate of reaction

A

change in DV
over
time

if DV is time then = 1 over time

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7
Q

how to calculate rate of reaction on graph

A

linear - calculate gradient
curved - draw tangent then calculate gradient

g = change in Y
over change in X

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8
Q

how to prepare root tip cells to view mitosis

A

cut 1cm from the tip of a growing root
- tip as that is meristem, so mitosis is happening

used mounted needle to spread cells on slide - thin so light can shine through

add stain - makes chromosomes easier to see

place cover slip gently - don’t smear or will damage chromosomes

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9
Q

what is the mitotic index?

A

proportion of cells undergoing mitosis
(high rate may mean cancerous growth)

no. of cells with visible chromosomes (undergoing mitosis)
over ——–
total number of cells visible

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10
Q

how to calculate cells in stages of mitosis

A

number of cells in stage
over
number of cells

x length of cell cycle

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11
Q

how to calculate magnification

A

actual = size over magnification
I
M A

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12
Q

How to measure light concentration without colorimeter

A

Use known concentration of X
Prepare dilution series
Compare to colour standards = concentration

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13
Q

eyepiece graticules and stage micrometer

A

graticule - fitted onto eyepiece, scale with numbers, no unit

micrometer - placed on stage, accurate scale with units
used to work out division of graticule

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14
Q

how to prepare slide

A

pipette small drop of water onto slide
use tweezer to place thin specimen (light through)
add a drop of stain
carefully lower cover slip, one side then the other to avoid air bubbles
press down firmly - thin layer so light can pass through

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15
Q

how to prepare plant tissue for osmosis

A

cut safely using cork borer
= same surface area

dry cylinders before weighing to remove cytoplasm from cut cells

dry before weighing to remove surface water

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16
Q

how to calculate % change in mass

A

final mass - initial mass
over
initial mass
x100

(as a ratio = final over initial)

17
Q

how to plot calibration curve

A

% change in mass on y
concentration of solution on x

18
Q

why does increasing concentrations of alcohol increase pigment?

A

phospholipids dissolve in alcohol

increased concentration = more dissolve so more pigment leaves

eventually lose structure

19
Q

why does increasing temperature increase pigment?

A

rate of diffusion increases so pigment leaving increases

phospholipids have more kinetic energy = more fluid

eventually proteins denature = large quantities of pigment

20
Q

control variables

A

time
volumes/ surface area
temperature
pH
type of plant material

21
Q

how to use calorimeter

A

measure absorbance
calibrate with distilled water
use opposite colour to sample
(blue for red beetroot)

22
Q

risk assessment with dissections

A

equipment sharp
- cut onto board not hand
- cut away from you

disinfect
- tools in disinfectant, blade down
- surface
- hands with soap

dispose of parts and equipment in separate bin

23
Q

aseptic techniques

A

prevent contamination

  • wash hands with soap
  • disinfect working area

use bunsen burner flame
- equipment sterilised
- neck of bottle
- glass spreaders in alcohol first

  • not remove pertinent dish lid, lifted
  • tape, allows o2 in, no microbes out

incubate at 25c - prevents harmful pathogens growing

24
Q

zone of inhibition

A

larger zone = better substance is at killing microbe

measure diameter

control using disc soaking in distilled water - should have no effect on growth

25
Q

chromatography

A

separate mixtures into individual components
relies on differences in solubility
- higher solubility = travel further

larger molecules move slower = seperated
can be used to separate monosaccharides

add to line on paper - in pencil so doesn’t run/mix with the ink
suspend above solution

26
Q

biochemical test for reducing sugar
(eg monosaccaride such as glucose and maltose/lactose)

A

add benedicts
heat in water bath
positive = coloured precipitate
blue - brick red (depending on conc.)

use excess to make sure all sugar reacts

27
Q

biochemical test for non-reducing sugar (eg sucrose)

A

obtain negative reducing sugar test
break down non-reducing into monosaccharides first

add dilute HCl (acid)
heat in water bath
neutralise with sodium hydrocarbonate (alkali)

carry out Benedict’s for reducing sugar
positive = coloured precipitate
blue - brick red

28
Q

biochemical test for starch

A

add iodine dissolved in potassium iodide solution
positive = orange to blue/black

29
Q

biochemical test for lipid

A

test for lipids/fats

add ethanol
shake
add water

positive = milky emulsion
intensity = concentration

30
Q

biochemical test for proteins

A

add sodium hydroxide (alkaline)
add copper (II) sulphate solution

postive = purple]negative = stays blue