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Biology - key concepts in biology (microscopy (light microscopes work by…
Biology - key concepts in biology
eukaryotic and prokaryotic cells
e: complex, include animal and plant cells
p: smaller and simpler, include bacteria
animal cells
nucleus contains genetic material, controls activity
cytoplasm where chemicl reactions happen, jelly like substance, supports organelles
mitochondria where aerobic respiration takes place
ribosomes involved in translation of genetic material in protein synthesis, used to build protein
cell membrane holds cell together, controls what goes in/out
plant cells
cell membrane, mitochondria, nucleus, cytoplasm and ribosomes
cell wall structure of cell
vacuole keeps cell rigid, stores cell sap
chloroplasts contain chlorophyll, where photosynthesis takes place
bacterial cells
ribosomes and cell membrane
plasmid dna
flagellum helps bacterium move
specialised cells
egg
haploid nucleus - gamete
hardens after fertilisation to stop more sperm entering
cytoplasm lots of nutrients to feed embryo
sperm
long tail to swim to egg
acrosome has enzymes to digest through membrane of egg cell
lots of mitochondria for respiration to swim
haploid nucleus - gamete
ciliated epithilial
lines oviducts to waft egg to uterus from overy
diploid nucleus - body cell
microscopy
light microscopes work by passing light through the specimen
electron microscopes use electrons instead of light and they have higher resolution and magnification
scientific drawing with labels, magnification used and scale
eyepiece lens, objective lens, coarse/fine adjustment knobs, clip, stage, lamp
total magnification = eye piece magnification x objective lens magnification
magnification = image size / real size
enzymes - biological catalysts
a catalyst is a substance which increases the speed of a reaction without being changed or used up
enzyme specificity - enzynme active sites only work with specific substrates like lock and key mechanism
temperature
changing temp changes rate of enzyme catalysed reaction
higher temp increases rate at first
when temp too high, enzyme active site denatures and can no longer bind to substrate, therefore cant catalyse reaction
all enzymes have an optimum temperature
pH
if pH is too high/low enzyme denatures and cant catalyse reaction
all enzymes have an optimum pH
substrate concentration
the higher the substrate conc. the faster the rate
however after a while all active sites are full and rate stays the same
investigating effect of pH
iodine blue/black in presence of strach, orange/brown when not present
amylase (enzyme) solution breaks down starch
put starch solution, buffer (pH) solution, amylase solution in boiling tube immediately mix
use pipette to drop this in dimple tray which already have iodine solution every 10s
continue experiment with different pH buffer solution
controls e.g. conc. & vol. of amylase solution
rate = 1000 / time
heat water beaker to 35° using b.burner, gauze, tripod and put boiling tube in beaker
biomolecules
starch breaks down (amylase) into glucose
starch breaks down (protease) into amino acids
lipids breaks down (lipase) into glycerol and fatty acids
molecules in food are too big to pass through walls of digestive system so digestive enzymes break down into smaller, soluble molecules
digested molecules can enter cells and be used for forming structures, respiration, energy, transporting substances and insulation
testing for biomolecules
sugars - benedicts reagent
add benedicts reagent to sample and place in 75° water bath
if test is positive it will form coloured precipitate
increasing conc. blue to green to yellow to orange to red
proteins - biuret test
add potassium hydroxide solution to make solution alkaline
then add copper(II) sulfate solution
no protein - stays blue, protein - purple
lipids - emulsion test
shake substance with ethanol for ~1 min then pour into water
will form milky precipitate if lipids are present
starch - iodine
add iodine solution to test sample
no starch - stays brown/orange, starch - blue/black
diffusion and active transport
diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration
diffusion occurs in both liquids and gases as their particles are free to move randomly
only very small molecules can diffuse throuh cell membranes like glucose, amino acids etc. starch and proteins cant
active transport is the movement of particles across a membrane against a concentration gradient (i.e. from an area of lower to an area of higher concentration) using energy transferred during respiration
sometimes when there is higher conc of nutrients in blood and lower conc in guts, nutrients can still be diffused to the blood using active transport
osmosis
osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
practical
cut potato cylinders same shape size and from same potato and weigh
place 3 potatoes each in beakers
prepare 6 beakers increasing in solute conc. first being pure water
leave in beakers for ~40mins
remove potatoes and pat gently to remove excess water
weigh again and calc. % change in mass
as the solute conc. increases the potatoes lose mass
calorimetry
test
set a dry food alight using a bunsen burner and hold under boiling tube (dont have b.burner near tube)
pour a set volume of water into a boiling tube and measure its temp
when the flame goes out, relight until it no longer relights again
measure the temp of the water again
energy in food (J) = mass of water (g) x temp change of water (°C) x 4.2
energy per gram of food (J/g) = energy in food (J) / mass of food (g)
