key concepts Flashcards
prokaryote
organism made of one prokaryotic cell (single celled organism)
eukaryote
organism made of eukaryotic cells (multicellular organism)
cell membrane
holds cell together and controls what goes in and out of the cell
cytoplasm
gel like substance where most chemical reactions occur
contains enzymes which control these reactions
nucleus
contains genetic material
controls the cell’s activities
ribosomes
involved in protein synthesis, in translation
mitochondria
where most of the reactions for aerobic respiration occur, transferring energy for the cell to work
cell wall
made of ceullolose
supports and strengthens the cell
vacuole
contains cell sap ( a weak solution of sugar and salts)
maintains internal pressure to support the cell
chloroplasts
where photosynthesis occurs to make food
contains chlorophyll
chromosomal dna
one long circular chromosome which controls activities and replication
floats free in the cytoplasm
plasmid dna
small loops of extra dna containin genes for things like drug resistance that can be passed between bacteria
flagellum
long hair like structure that rotates to move the cell
away from toxins and towards beneficial things like nutrients
specialised cells
cells which have a structure which makes them adapted to their function
functions of the egg cell
to carry the female dna
to nourish the developing embryo in the early stages
adaptations of the egg cell (4)
contains nutrients in cytoplasm for embryo
relatively large (large target for sperm to swim to)
haploid nucleus
straight after fertilisation, the membrane changes structure to prevent more sperm from entering, ensuring that the offspring has the right amount of dna
function of a sperm cell
to transport the male dna to the female egg
adaptations of the sperm cell (4)
long tail to swim to the egg
lots of mitochondria in the middle section to have energy to swim to the egg
acrosome contains digestive enzymes to pentrate the egg’s membrane
haploid nucleus
enzyme
a biological catalyst that speeds up the rate of metabolic reactions
substrate
the molecule changed in the metabolic reaction
active site
the region where the substrate binds to the enzyme and is catalysed
what is the lock and key hypothesis
enzymes are highly specific for their substrate
if the substrate’s shape doesn’t match the shape of the active site, then the reaction won’t be catalysed
(the substrate fits into the enzyme like a key fits into a lock)
denaturisation
when an enzyme loses the specific shape of its active site, preventing the enzyme from functioning
what 3 factors affect enzyme activity
temperature
pH
substrate concentration
how does temperature affect enzyme activity
at first a higher temperature increases the rate of reaction because kinetic energy increases and there are more collisions
HOWEVER
if the temperature become too hot, some of the bonds holding the enzyme together will start to break down, changing the shape of the active site and denaturing it
how does pH affect enzyme activity
if the pH is too high or too low then the enzyme will denature
the typical optimum pH is 7 but not always, a stomach enzyme may have an optimum pH of pH2
how does substrate concentration affect enzyme activity
the higher the substrate concentration, the faster the reaction up to a point
as the enzyme is more likely to collide and react with a substrate molecule but after a point there are so many substrate molecules that al active sites are full and adding more has no effect
how do you investigate how changing the pH affects the activity of amylase
- place one spot of iodine into every well of a spotting tile
- place bunsen burner on heatproof mat with a tripod and gauze and place a beaker of water on top - heating it to 35°C
- add 3cm^3 of amylase solution to 1cm^3 of buffer solution with pH5 to a boiling tube which should then be place in the beaker and wait for 5 mins
- add 3cm^3 of starch solution to the boiling tube and mix
- start a stop clock
- every 10 seconds take a fresh sample from the tube and place into a well
- repeat the experiment with buffer solutions of different pHs
rate (formula)
1000/time or 1/ time
units of rate
s^-1 (per unit of time)
role of digestive enzymes
break down food molecules into smaller, soluble molecules which can pass through the walls of the digestive system and be absorbed into the bloodstream
how do plants store energy
plants store energy as starch which when needed can be broken down by enzymes to sugars and respired to produce energy
what does carbohydrase do
breaks down simple carbohydrates into simple sugars
what do proteases do
break down protein molecules into amino acids
what do lipases do
break down lipids into glycerol and fatty acids
synthesis
organisms are able to synthesise carbohydrates, proteins and lipids from their smaller components using enzyme catalysed synthesis reactions
what is the test for reducing sugars
benedict’s reagent
how to do the benedict’s test
add blue reagent to a sample and heat in a water bath to 75°C - if positive a coloured precipitate will form
what colour will the precipitate be in benedict’s test
least sugar concentration - blue
highest sugar concentration - red
GRADIENT
what is the test for proteins
biuret’s test
how to do the biuret test
add a few drops of potassium hydroxide solution to make it alkaline
add some copper (II) sulfate solution
what are the results of the biuret test
if positive (protein is present) - purple if negative (protein not present) - blue
what is the test for lipids
emulsion test
how to do the emulsion test
shake test substance with ethanol for a minute until it dissolves
pour this solution into water
what are the results of the emulsion test
if present, there will be a milky emulsion as the lipid precipitates out
the more lipids present, the more noticeable the milky colour will be
what is the test for starch
testing with iodine
how to do the iodine test
add iodine solution to a test sample
what are the results of the iodine test
if starch is present - sample turns blue-black
if starch is not present - sample remains browny-orange
what is the process of calorimetry (5 stages)
1) weigh a small amount of food that will combust easily and skewer it on a mounted needle
2) add a set volume of water to a boiling tube that is held with a clamp
3) measure the temperature of the water
4) set fire to the food with a bunsen burner and hold immediately under the tube ; relight and repeat until it will no longer relight
5) measure the temperature of the water again
energy in food formula
energy in food (J) = mass of water (g) x temperature change of water (°C) x 4.2
energy per gram of food formula
energy per gram of food (J/g) = energy in food (J)
————————
mass of food (g)
resolution
how well a microscope can distinguish between two points that are close together
magnification
how many times bigger an object is
total magnification (formula)
eyepiece lens magnification x objective lens magnification
development of microscopes
light microscopes were first developed in the 16th century
they shone light though a specimen allowing us to observe cells and some organelles such as the nucleus
in the 1930s, electron microscopes were developed
they use electrons and have a greater magnification and resolution to allow us to see specimens in greater details
describe how to view a specimen using a light microscope (8)
1) take a thin slice of specimen
2) place a drop fo water on a clean slide and place the specimen on top using a pair of tweezers, use a stain if needed
3) using a mounted needle lower a cover slip over the specimen leaving no air bubble
4) clip the slide to the stage
5) select the lowest power objective lens
6) use the coarse focusing knob to move the stage up to be close to the objective lens then lower until nearly in focus
7) use the fine focusing knob to adjust
8) measure the field of view using a clear ruler
diffusion
the net movement of gas or liquid particles form an area of high concentration to an area of lower concentration
active transport
the movement of particles across a membrane against the concentration gradient using energy
osmosis
the net movement of WATER particles across a PARTIALLY PERMEABLE membrane from an area of high concentration to an area of low concentration
describe the potato-sucrose-osmosis experiment
- prepare sucrose solutions of different concentrations
- use a cork borer to cute potato into similar sized pieces
- group potato cylinders into threes and weigh using a mass balance
- place one group in each solution and leave for at least 40 minutes
- remove and pat dry and then reweigh each group
percentage change formula
(final mass - initial mass / initial mass) x 100
isotonic
the point where the fluid inside the sucrose solution and the potato cylinders
