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162 Cards in this Set

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  • Back
what are 4 things that plant and animal cells have in common?
- nucleus
- cytoplasm
- cell membrane
- mitochondria
what are 3 things that only plant cells have?
- large vacuole
- rigid cell wall
- chloroplasts
what is the function of a nucleus?
contains DNA that controls the actions of the cell
what is the function of cytoplasm?
gel-like substance where most of the chemicals reaction occur
what is the function of a cell membrane?
to allow/prevent certain substances in and out of the cell and to hold everything together
what is the function of the mitochondria?
most of the reaction for respiration are carried out
what is the function of a rigid cell wall in plants?
made of cellulose and gives the cell support
what is the function of the vacuole?
contains cell sap to give the plant volume and in a storage of sugars and salts
what is the function of chloroplasts?
where photosynthesis occurs and contains green pigment known as chlotophyll
what features do bacterial cells have?
-chromosomal DNA
-plasmids
-flagella (sometimes)
-cell wall
- pili
- cell membrane
what is chromosomal DNA and what is the function of it?
it is one long circular string of DNA which contains all the information of the cell for its replication and activities and floats free in the cytoplasm
what is a plasmid and what is the function of it?
a small loop of DNA that are not related to the chromosomal DNA. Contain information for things like drug resistance and can be passed between bacteria
what is a flagellum and what is the function of it?
a long hair like structure that rotated to allow the bacterium to move
what is the function of a cell wall?
to support the cell
what is a pili and what is the function of it?
small 'hairs' on the surface of a bacterium that help with reproduction and cell-to-cell contact
what do microscopes do?
they allow us to see things we can't see with the naked eye
what are the 2 types of microscopes?
light microscopes
electron microscopes
when were light microscopes invented?
1590s
when were electron microscopes invented?
1930's
what do light microscopes allow us to see?
chloroplasts, nuclei, mitochondria
what do electron microscopes allow us to see?
internal structures of mitochondria, chloroplasts and smaller things like plasmids
magnification =
length of image / length of actual object
what is the structure of DNA?
a double helix
what makes up the double helix of DNA?
two strands coiled and joined together by paired bases (chemicals)
how many different bases are there?
4
name the 4 bases
adenine, guanine, thymine, cytosine
which bases pair together?
adenine and thymine
guanine and cytosine
what are the base pairs joined together by?
relatively weak hydrogen bonds
specifically, how many hydrogen bonds join together the base pairs?
2 hydrogen bonds between A-T
3 hydrogen bonds between C-G
what makes up the strands of the DNA?
sugar phosphates
what is a gene?
a section of DNA
what do the sequencing of bases in the gene do?
they code for a certain protein
Who worked out the helical structure of DNA?
Franklin and Wilkins
Who made the model for DNA?
Watson and Crick
how did Franklin and Wilkins work out the helical structure?
they used x ray beams on crystallised DNA and used the reflected patterns to determine the structure
how did Watson and Crick determine a model for DNA?
they used photo's from Franklin and Wilkins and other secondary information from other scientists to create a model
how do cells make proteins?
by stringing certain amino acids together in a certain shape/sequence
how many different amino acids are there to make all the different types of proteins?
20 different amino acids to make thousands of different proteins
what does the order of the different bases tell the cell?
the order of the amino acids
how many bases code for 1 amino acid?
3 bases (a triplet)
e.g. if TAT = tyrosine GCA = alanine then what would be the order of the amino acids of GCA-TAT-TAT-GCA?
alanine-tyrosine-tyrosine-alanine
what else does DNA determine?
which genes are producing and which aren't and therefore which proteins the cell produces
how does this determine what type of cell it is?
if it produces a certain types of proteins, like keratin, then it is only suitable for a certain job, like a skin cell
what is the function of some proteins?
to help make all the things which are not made of proteins from substances sourced from your diet. For example, cell membranes
what makes proteins and where are protein made?
in the cytoplasm by organelles called ribsomes
where is DNA found?
in the nucleus
what has to be done to get the gene information to the ribosome and why?
DNA is too big to take out of the nucleus, so the information is copied as a single strand
what is the molecule which copies and transports the information of the DNA from the nucleus to the ribosome?
mRNA
what is the molecule mRNA?
it is similar to DNA but smaller and shorter and only one strand of bases and acts as a messenger
what is the first stage of protein synthesis?
the two strands of DNA 'unzip'
then the DNA is used as...
...a template for the mRNA which does complementary base pairing with one side of the DNA
what is this step known as?
transcription
what does the mRNA do next?
moves out of the nucleus and joins the ribosome
what happens next?
tRNA molecules brings matching (to the mRNA code) amino acids to the ribosome
what does the ribosomes do with the amino acids?
sticks the amino acids together in the correct sequencing
what is this chain of amino acids called?
a polypeptide (protein)
what is a codon?
a triplet of bases
what is this step known as?
transcription
what does protein synthesis cause?
it means every protein is a specific order of amino acids which shape into a certain form which can be used for a specific job e.g. as a particular enzyme
what is a mutation?
a change in the organism's DNA base sequencing
what can mutations cause?
amino acids to be formed in the wrong order and change the protein's shape and function
what would the change is the shape and function of the protein cause?
a change in characteristics of the organism
are mutations always harmful?
no, they can be harmful, neutral or beneficial
describe how a mutation can be harmful
it could cause a genetic disorder
give an example of a genetic disorder
cystic fibrosis
describe how a mutation can be beneficial
could produce a new/better characteristic that is helpful to the organism
give an example
bacterial plasmids with a mutation which cause a resistance to antibiotics
describe how a mutation can be neutral
some mutations are neither harmful or beneficial
give an example
they do not affect the protein's function
what are enzymes?
proteins that are biological catalysts - speed up useful chemical reactions in the body
without enzymes, what would have to be done to speed up reactions?
raise the temperature
what is bad about this?
it allows bad chemical reactions to speed up too
bodily chemical reactions have to be c______ c______
carefully controlled
what is a catalyst?
a substance that speeds up reactions without being used up or changed during the reaction
where do enzymes work?
inside and outside the cells
what are 3 things enzymes are used for?
-DNA replication
-protein synthesis
-digestion
explain how enzymes are used in DNA replication
they help copy the cell's DNA before it divides during mitosis/meiosis
explain how enzymes are used in protein synthesis
they hold the amino acids in place and form the bonds which hold the amino acids together
explain how enzymes are used in digestion
they help digest the food molecules in the gut. e.g. pepsin helps digest proteins into amino acids
what do chemical reactions usually involve?
chemicals to be joined together or split apart
what is the substrate?
the molecule which is changed during the reaction
what do enzymes have to help catalyse the reaction?
an active site
What is an active site?
the part of the enzyme which joins onto the substrate to catalyse the reaction
what is specific about the active site?
it often only works with 1 substrate
why do they have a high specificity for their substrate?
because for the enzyme to work, the substrate has to fit into the active site
what is the name of this mechanism?
'lock and key'
what 3 things affect the rate of enzyme reactions?
-temperature
-pH level
-concentration of substrate
describe how the temperature effects the rate of enzyme reaction
The higher the temperature, the quicker the rate of reaction because the enzymes have more energy and move quicker and meet substrates to react quicker
however...
...this only works up to a certain temperature because if it gets too hot, the bonds holding the amino acids of the enzymes together will break and the make the enzyme loose it's shape so it can't catalyse it's substrate any longer
what do we call an enzyme that has lost it's shape?
denatured
will it return to it's old shape when it has cooled down?
no
what is the optimum temperature for most human bodily enzymes?
37 degrees C
describe how the pH effects the rate of enzyme reaction
all enzymes have an optimum pH which they function best at but if it is too high or low, the enzyme can become denatured.
what is the optimum pH usually?
pH7
what is an example of an optimum pH?
pepsin works in the stomach and so, its optimum pH is pH 2 acidic)
describe how the concentration of the substrate effects the rate of enzyme reaction
the higher the substrate concentration, the faster the reaction because it is more likely the enzymes will find a substrate to catalyse
however...
...this is only true up to a certain point when enzymes cannot catalyse any more substrate reactions that it is already (all active sites full) and adding more makes no difference
what is the human genome project?
where thousands of scientists collaborated to try to find every single human gene
roughly, how many genes make up human DNA
25,000
what was the benefit of scientist collaborating?
genes were found more quickly and data was made public
what 4 things are good about it?
- predict/prevent diseases
- develop new and better medicines
- accurate diagnosis
- improve forensic science
how can it be used to predict/prevent disease?
-if we new what genes predisposed people to diseases, we could tailor lifestyles to reduce chances
-people with the genes could regularly get checked for the developing disease
-cures could be found
how can it be used to develop new/better medicines?
-possibly develop medicines specially designed for individuals
-knowing how disease effects us on a deeper level means we can design more effective treatment
how can it be used to make accurate diagnoses?
-some disease are hard to test for
-knowing genetic cause means accurate testing is easier
how can it be used to improve forensic science?
-may be able to work out what the person looks like from their DNA at crime scenes
- currently can produce a 'DNA fingerprint'
what 3 things are negative about the human genome project?
-stress increase
-gene-ism
-discrimination (employers/insurers)
how can it cause an increase in stress?
if someone knows they are susceptible to a disease, they will worry all the time about their life
how can it cause gene-ism?
people with genetics of a disease may be encouraged not to have children
how can it cause discrimination, especially from employers and insurers?
life insurance may become impossible to get if they know you will potentially become ill and employers may not want to employ some one who is unreliable owing to disease
how is genetic engineering carried out?
-useful gene 'cut' from one organism using enzymes
-enzymes used to cut open another organism's chromosome open
-enzymes used to insert the useful gene into the cut chromosome
what do we call the organisms that have had a useful gene inserted?
genetically modified (GM) organism
name three uses of genetic engineering to benefit humans
- reducing vitamin A deficiency
- producing human insulin
- increasing crop yeild
describe how it can be used to reduce vitamin a deficiency
-bodies use beta-carotene to make vit. A
-south asia + Africa suffer from vit. A deficiency (causes blindness)
- GM rice (golden rice) has 2 genes in which produce beta-carotene
describe how it can be used to produce human insulin
-human insulin gene inserted into bacteria to produce it
-insulin made quickly and cheaply to treat diabetes
describe how it can be used to increase crop yeild
-GM crops which are now resistant to herbicides
-crop fields sprayed with herbicides and all plants, excluding GM crops, die
-crop yield increased to make more food
what are 3 issues with GM crops?
1. could reduce farmland biodiversity
2. could be unsafe? develop allergies to food?
3. transplanted genes spread to unwanted species e.g. weeds become herbicide resistant
what is mitosis?
the process where new cells are made for growth/repair. One cell divides to make two cells identical to the original cell with nucleuses with the same number of chromosomes as the original cell
are human body cells haploid or diploid?
diploid
what does diploid mean?
two versions of each chromosome (one from mother, one from father)
in a cell that is not dividing, what is the DNA like in the nucleus?
spread out in long strings
what happens if the cell gets a signal to divide?
it copies all its DNA and forms X-shaped chromosomes where each arm is identical to the other
what happens after this?
the chromosomes line up in the centre of the cell
what happens to the chromosomes from here?
the cell fibres pull them apart and each identical arm goes to opposite sides of the cell
then...
...membranes (new nuclei) form around each set of chromosomes
finally...
...the cytoplasm splits and two new diploid cells are formed which are genetically identical
what process is used in asexual reproduction?
mitosis
what are the offspring of asexual reproducers like?
genetically identical to their parents
what are gametes?
sex cells
what are female gametes called?
ova (singular: ovum)
what are male gametes called?
sperm
what happens during sexual reproduction?
the gametes join to form a new cell (a zygote) which later grows to become an organism
are gametes haploid or diploid?
haploid
what does haploid mean?
they only have one copy of each chromosome
why are they haploid?
so that when the two gametes join at fertilisation the cell (zygote) has the right number of chromosomes (diploid)
what is meiosis?
the process that occurs in reproductive organs in which 4 haploid gametes are produced from 1 diploid cell. The resulting cells are not genetically identical.
how does meiosis begin?
the DNA is duplicated to get double the amount of pairs of chromosomes - each arm is identical to the other.
what happens during the first division?
the chromosome pairs (each with copied arms), then line up in the centre of the cell - two by two - and the cell fibres split the pairs apart into two new cells
how does this stage allow variation in the offspring?
each new cell has a mixture of mother and farther chromosome
what happens in the second division?
the cells line up again - singular this time - and the arms are pulled apart by cell fibres into 4 new cells in total
finally...
the nucleus membrane forms around the chromosomes to make 4 haploid gametes
what is a type of asexual reproduction?
cloning
how is an adult cell cloned?
1. take an unfertilised egg cell
2. remove its nucleus (enucleated)
3. take nucleus from adult body (diploid) cell
4. insert nucleus into enucleated egg cell
5. stimulate new cell with electric shock (causes mitosis)
what happens once the new cloned cell undergoes mitosis?
it will form an embryo (ball of cells) and can be implanted into a surrogate mother and will grow into a clone of the original adult body cell
name 3 possible uses of cloning
1. to supply organs for transplants (clone pigs to then use their organs in transplants for humans)
2. study of animal clones to understand embryo development, aging and age-related disorders
3. preserve endangered species
name 3 issues with cloning
1.reduces 'gene pool' - less variation
2. cloned mammals might not live very long
3. cloning process is unreliable and risky
explain how it reducing the 'gene pool' is an issue
clones are closely related and could all be wiped out by the same disease (lacks certain resistance)
give an example of a cloned animal not living as long
Dolly the sheep only lived for 6 years owing to her lung disease and arthritis - her 'true' age was suspected to be older.
explain how the cloning process is unreliable and risky
-it often fails to work
-clones often have genetic issues/defects
-poor immune systems in cloned mammals
what are the cells in an embryo like?
undifferentiated
what are these undifferentiated embryo cells called?
embryonic stem cells
what are stem cells?
cells that are able to divide to produce either more stem cells or different specialised cells
what is the name of the process in which stem cell become specialised?
differentiation
when does differentiation occur?
when an embryo starts to develop into a human body with tissues, organs and systems
what is the difference in differentiation in animals and plants?
animals often lose the ability at a young age but plants continue throughout their life
where can stem cells be found in adults?
only in certain places e.g. bone marrow
what is the issue with stem cells from adults?
they lack versatility and often only work in the same area they were taken from e.g. stem cells taken from the blood will often only differentiate into blood cells
what are stem cells used for?
sometimes used by doctors to cure diseases
what is the other option from adult stem cells?
experimentation with extracting stem cells from early human embryos and differentiating them under certain conditions
what is a future possibility with stem cells?
to be able to grow the cells into new tissues which can then replace those damaged by injury/disease - new cures!
what is the argument against embryonic stem cell research
embryos shouldn't be used for experimentation because the embryos could be a life potentially. New sources of stem cells should be found
what is the argument against this?
people who are already alive are more important that embryos that will probably never be lives and are often unwanted (fertility clinics where many are destroyed)
in some countries, stem cell research is _____ but in the UK it is carried out under _____ __________
banned
strict guidelines