B1 - CELL LEVEL SYSTEMS (FULL)

how many chromosomes do humans have in their cells?

46 chromosomes

what is each long molecule of DNA called ?

a chromosome

where do you get chromosomes from ?

you inherit half from your mother and the other half from your father

what are the only organisms that share identical DNA ?

• identical twins

• clones

how is DNA arranged ?

into sections

what is a gene ?

it is where the short sections of DNA code for a characteristic eg eye colour .

what does the code of a gene contain?

it contains specific proteins to be made .

what do particular proteins do to cells ?

it determines the cells function

what does the combination of genes in an organism show ?

it controls how the organism functions and what it looks like .

what is DNA made up of ?

it is made up of 2 strands

how are the DNA strands joined up ?

by bases

what shape is DNA ?

a double helix

what are nucleotides ?

it is when DNA is made of lots of small units which are joined together , making DNA a polymer

why is DNA a polymer ?

it contains multiple monomers (nucleotides)

what is nucleotide made up of ?

a sugar called deoxyribose , a phosphate group and a base

how the two strands of DNA held together?

by the bonds between the bases

how many different nucleotides is there in DNA?

4 different nucleotides

what are the four bases ?

• A = adenine

• T = thymine

• C = cytosine

• G = guanine

what is a complementary base pairing ?

its when the base pairs always bond together in the same formation .

what are the base pairings ?

• a - t

• c - g

why is mRNA made ?

it is made because DNA is too big to leave the nucleus of the cell so a copy of DNA is made called mRNA . ( its like a single strand of DNA)

what does mRNA stand for ?

messenger RNA

what does DNA stand for ?

Deoxyribonucleic Acid

when is mRNA produced ?

its produced in a process called transcription

what is transcription ?

• DNA around gene unzips - both strands separate

• one strand is template

• complementary bases attach to the strand being copied

• eg c - g .forming a strand of mRNA

• when complete mRNA detahces itself from DNA template

• DNA zips back up

what does adenine bind with in mRNA ?

• uracil (U)

where does the mRNA go after transcription ?

• as its small enough to leave the nucleus

• it goes to subcellular structure called ribosomes in the cytoplasm .

• where protein will be made .

what are proteins made of ?

• amino acids

what do different amino acids do ?

the join up together to form different proteins

what does the order of nucleotides in your DNA do ?

determines the type and order of amino acids and this determines which proteins are produced .

what is translation ?

it is where proteins are made

what is the process of translation ?

• mRNA attaches to a ribosome

• ribosomes ‘reads’ nucleotides on the mRNA in groups of three

• each triplet codes for specific amino acid

• ribosome continues to ‘read’ codons adding more amino acids

• amino acids join together

  THIS IS A PROTEIN

what is the name for the group of three nucleotides?

• base triplets

• codons

what does he sequence of amino acids determine ?

how the protein will fold.

what is important to protein function ?

that each type of protein has a specific shape as many types of proteins are produced including enzymes and hormones .

where does protein synthesis occur ?

ribosomes

where are transcription and translation used?

in translation and transcription

what are enzymes ?

• they are made of protein .

• biological catalyst

what is a biological catalyst ?

• this means they speed up a reaction with being used up themselves

• once a reaction is finished they can be used to catalyse the same type of reaction again

give 2 example of what reactions enzymes are involved in your body

• build larger molecules from small ones - such as protein synthesis

• break down larger molecules into smaller ones , such as digestion

what are enzymes made up of ?

• like all proteins it is made up of long chains of amino acids .

• these are folded together to make a specific shape

what is the active site ?

• its where molecules of other substances bind to the enzyme

• which is why the shape of one part of the enzyme is particularly important

what is the substrate ?

• it is the molecule that binds to the enzyme

• when it binds to the active site the substrate fits inside the enzyme

why are enzymes highly specific ?

• it means they can only bind to one type of substrate molecule

• the substrate must fit exactly into the active site

• if it doesn’t the molecule can’t bind

what is the low key hypothesis ?

you can think of enzymes as a lock and the substrate as key . as only one key will fit the lock and be able to open the door .

what is an enzyme - substrate complex?

it is when the substrate binds the enzyme

what happens after enzyme - substrate complex is formed?

• the reaction happens quickly and the products are released from the enzyme

• then the enzyme is prepared then ready to catalyse another reaction

what happens when enzymes are used to build large molecules from smaller one?

• in this reaction two substrate molecules fit next to each other on the enzymes active site

• a bond forms between them to make a larger molecule . the product is then released

what happens when enzymes are used to break down larger molecules into smaller ones?

• in this reaction a large substrate molecules fits into the enzymes active site

• the bond between them breaks and two product molecules are released

what factors affect enzymes ?

• it depends of a number of factors including temperature and PH

• concentration of the enzyme and substrate

what is optimum conditions ?

• it is the conditions that in which an enzyme works best

how does temperature affect enzyme controlled reactions ?

in higher temperature :

• the enzyme and substrate molecules move faster and collide more often

• the higher the temp the faster the reaction

what happens if the temperature becomes too high ?

• the amino acid chain in the protein starts to unravel , changing the shape of the active site

• meaning enzyme is now denatured

• substrate ca no longer bind so rate of reaction decreases

• once all molecules denatured reaction stops

• most denatured enzymes can’t return to their original shape - change is irreversible

how does PH affect enzyme controlled reactions ?

• each enzyme has its optimum pH

• change in pH affects the interaction between amino acids in the chain - may make chain unfol, changing shape of active site - making it denatured

how does the substrate concentration affect enzyme - controlled reactions ?

• general , higher the substrate concentration the faster rate of reaction

• but at certain substrate concentration , all enzyme molecules are bound to the substrate molecules →meaning rate of reaction is at maximum

• if further increase in no of substrate molecules happens it won’t increase rate of reaction as there are no enzymes for them to bind

how does the enzyme concentration affect enzyme - controlled reactions ?

• general - higher the enzyme concentration the faster the rate of reaction

• but is limited by substrate concentration

• if no new substrate molecules are added the reaction will stop

PRACTICAL: Investigating effect of pH on enzyme activity

Add a drop of iodine to each of the wells of a spotting tile

Use a syringe to place 2 cm of amylase into a testtube

Add 1cm of buffer solution (at pH 2)to the testtube using a syringe

Use anothertesttube to add 2 cm of starch solution to the amylase and buffer solution, start the stopwatch whilst mixing using a pipette

Every 10 seconds,transfer a droplet ofthe solution to a new well ofiodine solution (which should turn blue-black)

Repeat this transfer process every 10 seconds unti lthe iodine solution stops turning blue-black (this means the amylase has broken down allthe starch)

Record the time taken fort he reaction to be completed

Repeat the investigation with buffers at different pH values (ranging from pH 3.0 to pH 13.0)

Results of practical investigating effect of pH on enzyme activity

optimum pH = iodine remained orange-brown within the shortest amount oftime ->
enzyme is working at its fastest rate and has digested all the starch
higher orlower pH's = the iodine took a longertime to stop turning
blue-black or continued to turn blue-black forthe entire investigation -> enzymes are starting to become denatured
and as a result are unable to bind with the starch or break it down
- shorter the time taken,the greater the rate of the reaction
Rate = 1 ÷ Time

what do food rich in carbohydrates and fats do ?

provides you with energy to move and stay alive

what do food rich in protein do ?

are used for the growth and repair of body tissues

what is the metabolic rate ?

the rate at which our cells transfer energy from chemical stores in foods

starch is an example of …

a carbohydrate polymer

what is starch synthesised from ?

glucose monomers

what is starch ?

a chemical energy store

what enzyme breaks down carbohydrates ?

carbohydrase

what enzyme breaks down starch ?

amylase

where are carbs broken down in the body?

in your mouth and small intestine

what are proteins formed from ?

amino acids

what does the order of amino acids do ?

it determines the protein that is synthesised

where are proteins broken down in the body?

in your stomach and your small intestine

what are lipids ?

they are fats and oils that you eat

what are lipids good for ?

• a good store of energy

• some animals use it for insulation and buoyancy

what do lipids get synthesised to ?

into three fatty acid molecules and glycerol

where are lipids broken down in the body?

in your small intestine

what do lipase enzymes break down lipids into ?

fatty acids and glycerol

what happens when the food molecules are fully digested ?

they are absorbed into your bloodstream and then travel to the cells that need them

what do food molecules get fully digested into ?

• soluble glucose

• amino acids

• fatty acids

• glycerol

why is energy transferred ?

• so you can move , grow and keep warm

how often does your body transfer energy ?

regularly

do you transfer energy in your sleep ?

• yes otherwise your body wouldn’t be able to function in activities such as keeping your heartbeat

where does your energy come from ?

from the chemical stores in the food you eat

define aerobic respiration

to transfer energy ,glucose reacts with oxygen in a series of chemical reactions

how do you get the oxygen needed for respiration ?

from the air you breathe

what is the word equation for aerobic respiration ?

glucose + oxygen → carbon dioxide + water

what is the chemical equation for aerobic respiration ?

C6H12O6 + 6O2 → 6CO2 +6H2O

what does the aerobic reaction transfer energy from ?

it transfers it from its chemical energy store in glucose to another chemical energy store for all process in the cell

what is the energy store called that process i the cell ?

• ATP(adenosine triphosphate )

what is ATP used by ?

living organisms

what other products are produced during aerobic respiration ?

• carbon dioxide

• water

what is the ATP produced in respiration used for ?

• to synthesise larger molecules from smaller ones to make new cell material .Plants make amino acids from sugars , nitrates and other nutrients .In turn the amino acids form protein

• for movement - animals use ATP to contract muscle cells enabling the organism to move

• to stay warm - when animals surroundings are more coder than they are , they increase their rate of respiration . this transfers more energy by heating , so that they can keep their body at a constant temp

when does respiration occur ?

it occurs all the time in plant and animal cells . it provides the organism with a constant supply of energy

where does respiration take place ?

inside the mitochondria of a cell . each chemical reaction that takes place during respiration is controlled by a specific enzyme .

what does the number of mitochondria tell you ?

it tells you how active a cell is

what kind of reaction is respiration ?

exothermic reaction

what happens during the process of respiration ?

energy is transferred to the surrounding by heat

what happens to your muscles during exercise ?

they need to transfer more energy than normal when they contract . as your heart and breathing rate increase to provide your cells with enough glucose and oxygen for respiration to increase

what happens in strenuous exercise that doesn’t happen in normal exercise

your heat rate can’t increase fast enough to meet the demand

define aerobic respiration ?

you body starts to transfer energy from its chemical store in glucose. the series of chemical reaction doesn’t need oxygen . it allows the body to transfer extra energy for short periods of time.

what is the word equation for anaerobic respiration ?

glucose → lactic acid

in anaerobic reaction what is produced ?

in the reaction glucose isn’t completely broken down . instead poisonous lactic acid is produced