unit 3 and practical skills

practical 1

semi-quantitative method with benedict's reagent to estimate the concentration of starch

semi-quantitative

results are estimated, for example colors

benedict's reagent

blue to red

iodine test

starch, blue black

How to improve reliability

repeat, outliers, mean

make semi-quantitative into quantitative

bigger range, smaller intervals

stock solution

concentrated solution used to prepare working solution

practical 2

titration with vitamin C against DCPIP

why is a syringe used for titration and not burette

easier to control, more precise measurements

DCPIP

vitamin c; blue to colorless

how to use citations

name. (year) title. publisher, issue, page.

practical 3

membrane permeability against alcohol and temperature

why are beetroots red

pigment betalain in vacuoles

control temperature

thermostatic water bath

equipment in practical 3

cork borer, thermostatic water bath, automatic pipette, colorimeter with green filter

effect of ethanol on membrane permeability

ethanol dissolves phospholipid bilayer, more holes, pigment can escape

improving validity

controlled variables, keep all factors constant in repetitions

practical 4

effect of temperature, pH, enzyme and substrate concentration on rate of reaction

trypsin

breaks down milk proteins, decreases absorbance

why measure initial rate of reaction

reaction is the fastest, all enzymes are working

effect of temperature on enzyme activity

higher temperature means faster rate of reaction, kinetic energy - more collisions

effect of pH on enzyme activity

optimal pH, denaturation

effect of enzyme concentration on enzyme activity

higher concentration means faster rate of reaction

effect of substrate concentration on enzyme activity

higher concentration means faster rate of reaction, until all active sites are occupied

practical 5

using a light microscope

eyepiece unit

(number of eyepiece divisions * 100 micrometers) / number of stage micrometer divisions

magnification equation

I \= AM

blue stain for cheek cells

methylene blue

practical 6

prepare a root tip squash to observe mitosis

how to see mitosis under a microscope

count the number of cells with visible chromosomes

stain for chromosomes

acetic orcein

why is the root tip heated with HCl

to stop any more mitosis/metabolic processes

mitotic index

number of cells in mitosis/total number of cells

practical 7

observing roots, stems and leaves under a microscope

stain for plant cells

toluidine blue O

practical 8

tensile strength of plant fibres

accuracy

number of correct responses

practical 9

antimicrobial properties of plants

aseptic technique

sterile conditions, alcohol disinfectant, soap

how to measure antimicrobial properties

measure and compare zone of inhibition of garlic, mint and two controls

why are aseptic techniques important

bacteria may mutate to form pathogens, the culture might have been contaminated, we don't know the full hazard