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