B1: Cell-level systems Flashcards
eukaryotic cell
-membrane bound organelles
-complex and relatively large from 10-100 micrometres.
-plant and animal cells are examples of this
prokaryotic cells
-do not contain membrane bound organelles;instead their genetic material floats in the cytoplasm.
-simple cells with sizes of 1-100 micrometres
-bacterial cells are example of this
nucleus
-contains genetic information needed to make proteins
-controls activities of the cell
mitochondria
site of aerobic respiration
cytoplasm
-jelly-like substance
-site of chemical reactions in the cell
cell membrane
selective barrier which controls what goes in and out of the cell
what does a plant cell have that an animal cell doesnt
chloroplast- contains chlorophyll which is needed for photosynthesis
vacuole-contains cell sap and also keeps the cell rigid,keeping the cell upright
cell wall-cellulose structure and makes the cell rigid and supports the cell.
what are bacteria
-smallest living bacteria
-unicellular organisms
-can carry out 7 life processes
-1 micrometre in size
examples of prokaryotes
E.COLI-causes food poisioning
STREPTOCOCCUS-causes sore throats
STREPTOMYCES-used to make an antibiotic for the soil.
what structures do all prok cells have
-cell membrane
-cell wall
-genetic material
extra prok structures
-flagella-tail like structures all cells to move through liquids
-pili-tiny hairlike structures that enable cells to attatch to structures and are also used to transfer genetic material between bacteria
-slime capsule-layer outside the cell wall that protects a bacterium from drying out and from poisonous substances.Also helps bacteria to stick to smooth substances.
plasmid-circular ring of DNA used to store extra genes.Where anti biotic resistance genes are normally found.
what is a light microscope
-used to observe small structures in detail
-passes light through an object placed on a stage ],then through two glass lenses-the objective and eyepiece .These magnify the object, so when you view it through the eyepiece you can see it in more detail
to observe cells under a microscope
1) move stage to its lowest position
2)select the objective lens with lowest magnification
3)place slide with cells on stage
4)raise stage to highest position making sure it does not touch the lens
5)lower stage slowly using coarse focus knob until you see the object
6)turn the fine focus knob slowly until your object comes into clear focus
7) to see cells in greater detail, switch to a higher magnification objective lens without moving stage. Use FINE FOCUS KNOB to bring the object into clear focus again
total magnification formula
total magnification=eyepiece lens maginfication X Objective lens magnification
t,l,o
why are cells stained
makes them easier to observe
common stains
methylene blue-nucleus of an animal cell
iodine-plan cell nuclei
crystal violet-stains bacterial cell walls
how to apply a stain
1)place the cells on a glass slide
2) add drop of stain
3)place coverslip on top
4)tap the coverslip with a pencil to remove air bubbles
what is resolution
the smallest distance between two points that can be seen as separate entities
electron microscope
-uses electrons instead of light to prodcue an image.
-The greater resolution is achieved by using high-energy electrons as the light source
-
two types of electron microscope
TEM(transmission electron microscope)-produce the most magnified image by sending a beam of electrons pass a thin sample of the surface of the specimem.Beam focuses to produce an image
SEM(scanning electron microscope)-produces a 3D image of a surface.Sends a beam of electrons accross the surface of a specimen.These collect to produce an image
comparisons of the two types of microscopes
-light is cheap to buy and operate,electron is expensive
-light is small and portbale,electron is large and difficult to move
-light is simple prepare,electron is not
-in light natural colour can been seen unless stains used,in electron it is black and white until false colour added
-in light,speciemns can be living or dead,in electron specimen must be dead
-electron has higher resolution
-
development of electron microscopy
-has allowed scientists to see the detail within subcellular structures.
-for e.g.TEM showed chloropyll is stored in flattened membranes within a choroplast.
chromosome
long strand of DNA-most people have 46 in each cell. 23 pairs-one from mother,one from father
genes
short sections of DNA that code for a characteristic.contains code for specific proteins to be made.
structure of DNA
-polymer
-made of nucleotides(sugar phosphate base)
-made up of two strands joined by bases and twisted together to form a double helix shape.
The four bases
A-T
C-G
what is a base pair
when a base from on strand bonds with another to hold the strands of DNA together
what is mRNA
-messenger RNA
-A copy of DNA made as DNA is too bif to leave the nucleus
transciption
-DNA around a gene unzips so both strands are separated.One strand acts as a template
-complemenatry bases attacth to the strand being copied-this forms a strand of mRNA.no thymine,so bases called uracil(u)binds with adenine.
-when complete the strand will detatch itself and the DNA will zip up.
-mRNA is small enough to move out the nucleus to ribosmomes in the cytoplasm,where proteins will be made
what are proteins made from
amino acids
what determines the proteins that are produced
The order of nucleotides in your DNA determines the type and the order of amino acids,and this determines which proteins are produced.
translation
-mRNA attaches to a ribosome
-the ribosome reads the nucleotides in 3’s(codons)-each codon codes for a specififc amino acid
-ribosome continues to read the triplet code,adding more and more amino acids
-these join togeteher forming a protein
what does the sequence of amino acid determine
-How the protein will unfold.
-each type of protein has a specific shape.this is important for protein function
what are enzymes
biological catalysts-speed up reactions without being used up themselves
what do enzymes do
-build larger molecules from smaller one -protein syntheisis
-break down larger molecules into smaller ones-digestion
what is the active site
where molecules of other substances bind to the enzyme
substrate
molecule binds to the enzyme
why can an enzyme only bind to one type of substrate molecule
enzymes are highly specific and if it does not fit,the molecule will not bind
lock and key hypothesis
once the key(substrate) will fit the lock and be able to open the door(enzyme)
after the enzymatic reaction:
when the substate binds to the enzyme,an enzyme-substrate complex is formed.
reaction happens qucikly and products are released from the enzyme
how does temp afftect enzyme reaction
increase-molecules and ezyme moce faster and collide more often,until goes beyond optimum and denatures
PH affect on enzymatic reatic
each enzyme has a optimum ph and changing it affects the interactions between amino acids in a chain.This may make the enzyme unfold,changing the shape of the active site.The enzyme becomes denatured
substrate and enzyme concentration affect on enzyme reactions
both increase=increase rate until no other enzyme/substrates to bind with and reaction stops
metabolic rate
speed at which cells transfer energy from its chemical stores in food
high metabolic rate=more food needed to eat
what are carbohydrates
-polymers
-made from smaller carbohydrate molecules.
-carbohrdrayse enzymes break down carbohydrates.
-Enzyme that breaks down starch is amylase
proteins
-polymers
-formed from amino acids
order of amino acids joined determines the protein that is made
-protease breaks down protein into amino acids
lipids
-fats and oils
-made from glycerol and fatty acids
-used for energy,booyancy and insulation.
-lipase enzymes break down lipids into fatty acids and glycerol
what happens once food molecules are fully digested
absorbed into bloodstream and travel to the cells that need them
aerobic respiration
glucose reacts with oxygen to transfer chemical energy from food to make energy(ATP)
What is ATP used for
-to synthesise larger molecules from snaller ones to make new cell material
for movement-ATP is used for muscle contraction enabling the organism to move
to stay warm-when it is cold,they increase rate of respiration.This transfers more energy by heating so that they can keep their body at a constant temperature
when does respiration happen
-all the time in plant and animal cells-to provide a constant supply of energy
-takes place in the mitochondria.Each chemical reaction that takes place during respiration is controlled by a specific enzyme
what does the number of mitochondria in a cell tell you
-how active the cell is
-cells that need a lot of energy(muscle cells) will have a high amount of mitochondria to carry out the reactions
what type of reaction is respiration
-exothermic-energy is transferred to the surroundings by heating
equation for respiration
C6H1206+602–>6CO2+6H20
how does anaerobic respiration occur
during strenuous exercise,your heart cannot increase fast enough to meet the demand of oxygen needed so your body starts to trnafer energy from its chemical store in glucose by anaerobic respiration
what does ana resp allow
the body to transfer extra energy for short periods of time
word equation for anaeorbic respiration
glucose–>lactic acid
glucose is not completely broken down,instead poisonous lactic acid is produced
why does the body normally respire aerobically
-produces more ATP molecules per glucose molecule and has a greater yield as glucose is fully broken down here
-lactic acid can cause cramp and when built up,can cause pain and the muscles stop contracting.Known as fatigue
oxygen debt
The amount of oxygen required to remove the lactic acid, and replace the body’s reserves of oxygen
fermentation
when anaerobic respiration in microorgansims and plant cells produces ethanol and carbon dioxide instead of lactic acid
equation for fermentation
glucose–>ethanol+carbon dioxide
C6H1206+2C2H50H+ 2CO2
what organisms carry out photsynthesis and why
producers as most do not catch their own food.They use this to grow,in turn increasing their biomass
to make food plants have to take in…
carbon dioxide-diffuses from the air into the plant from the stomata
water-enters the roots from the soil through the root hair cells by osmosis
what do the reactants in ph do
co2 and water react together to make glucose which the plants as a food source
oxygen is also produced,some used by plant in respiration.The rest is released into the environment
equation for ph
carbon dioxide+water–>glucose+oxygen
where does photosynthesis occur
inside the plant’s chloroplasts.This means most happens in stem,but a small amount in stem
what happens
light transfers energy from the sun to chlorophyll,where co2 and h20 react to make glucose that stores energy within its chemical boncds
stage 1(light dependent)
energy transferred from light splits water molecules into oxygen gas and hydrogen ions
stage 2(light dependent)
-co2 gas combines with hydrogen ions to make glucose
what type of reaction is photosynthesis
endothermic-energy must be transferred from the surroundings to keep it going
phototropism
growing towards the light
photometer
an instrument for measuring light intensity
photoconductive
a material whose resistance decreases when it absorbs light
what happens to glucose produced
respiration
- converted into sugar molecules eg. fructose, sucrose
- starch, food store
- cellulose, to form cell walls
- ( + nitrogen ) proteins, for growth and repair
- fats & oils, food store and growth
how can we test a plant to see if it photosynthesises
test it for starch because if a plant is unable to photosynthesise, it doesn’t produce starch
photosynthesis test:
starch
1 take leaf you’re going to test
2 place in beaker with boiling water to kill it
3 place leaf (using forceps) into boiling tube with boiling water to remove all chlorophyll
4 wash leaf with water to remove ethanol and soften leaf and spread on white tile
5 add a few drops of iodine solution onto leaf
if starch present, iodine will turn from yellow-brown to blue-black
photosynthesis test:
chlorophyll
1 place destarched variegated plant in sunlight
2 leave for several hours
3 test one of its leaves for starch
photosynthesis test:
light
1 take a destarched plant and cover one of its leaves with black card or tin foil
2 light cannot reach the covered area
3 place plant in sunlight for several hours
4 remove card and test leaf for starch
photosynthesis test:
carbon dioxide
1 take a destarched plant
2 place it in a polythene bag
3 add a pot of soda lime (a chemical that absorbs carbon dioxide and water vapour)
4 place plant in sunlight for several hours
5 test a leaf for starch
photosynthesis test:
showing oxygen is given off
1 place an upturned test tube above an aquatic plant such as pondweed (Elodea)
2 put apparatus in light
3 leave for a while
4 lift test tube off of apparatus (keeping it upside-down)
5 place glowing splint inside tube
if oxygen is present, splint will relight
formula for rate
rate=1/time taken for measurement to occur
limiting factor meaning
A limiting factor is a condition, that when in shortage, slows down the rate of a reaction
Factors affecting photosynthesis
- temperature
- light intensity
- carbon dioxide concentration
light intensity affect on photosynthesis
higher light=higher rate of photosynthesis until it reaches its maximum point.In very low levels or light,or no light-photosynthesis stops completely
Co2 affect on photosynthesis
- a reactant of photosynthesis so increase co2=faster rate of reaction.Atmosphere only has 0.04% co2 so is most commonly limiting factor
-farmers use articifical methods to increase co2 level e.g. greenhouses.This increases rate of photosynthesis
temp affect on photosynthesis
photosynthesis is a series on enzyme-controlled reactions,so increasing the temperature will increase the enzymatic activity,hence increasing rate of reaction.However,if the temperature is too high,the enzymes will denature and reactions will stop
how can you measure rate of photosynthesis
By measuring how much oxygen or glucose a plant makes in a given time,
also by measuring rate of phsynts by calculating the increase of biomass in a given time, as glucose is used to produce new cells
