Topic 1 - Genes And Enzymes Flashcards
What do animal and plant cells BOTH have and the purposes?
Nucleus- controls cell and contains all the DNA
Cytoplasm - gel like substance where most of the chemical reactions take place.
Cell membrane- holds the cell together and controls what goes in and out
Mithochondria- this is where the reactions for respiration take place
Ribosomes- where proteins are made
Organelles that only the plant cells have?
Rigid cell wall- made of cellulose and gives the cell support
Large vacuole- contains cell sap, helps the cell keep its shape.
Chloroplasts- where photosynthesis occurs because it holds chlorophyll
Bacteria cell organelles?
Chromosomal DNA- controls the cells activities and replication, no nucleus so floats free
Plasmid DNA- contain genes for things like drug resistance and can be passed between bacteria
Flagellum- long hair like structure that rotates to make the bacteria move
Cell is supported by a cell wall
Magnification formula
Length of image divided by length of specimen
What are the base pairs?
Adenine and thymine
Guanine and cytosine
Describe the shape of DNA
Double helix
Has two strands held together by chemicals called bases
Bases are linked by weak hydrogen bonds
What is a gene?
A section of DNA
Who and how discovered shape of DNA
Rosalind Franklin and Maurice Wilkins discovered shape by bouncing beams of xrays off crystallised DNA and looking at the patterns the xrays formed
James Watson and Francis crick used idea that amount of a + t is equal to amount of c+g to create a model showing the structure
Practical to extract DNA from cells
Chop onion
Put in beaker of detergent and salt
Detergent breaks down cell membranes, salt will make the DNA stick together
Beaker in 60°c water bath for 15minutes to denature enzymes that could break down the DNA
Beaker in ice to stop DNA from breaking down
Put in blender to break down cell walls and release DNA
Cool then filter
Add ice cold alcohol
DNA will come out of solution as its not soluble with the alcohol
What does a gene contain?
The instructions to make a specific protein
What are three bases called and what do they do?
A codon codes for one amino acid
How does protein synthesis work?
Instructions need to get out of the nucleus
The DNA unzips
DNA is used as a template to make the mRNA
They use uracil instead of thymine. The mRNA is complementary to the DNA strand it’s based off. Once the mRNA is made, it’s called transcription.
The mRNA molecule moves out of the nucleus through the nuclear pore and joins with the ribosome. The ribosome reads the bases in a codon (three bases) tRNA is an anticodon. This is called translation. There’s one tRNA for each codon. The tRNA brings the appropriate amino acids in the right order to the ribosome. Ribosome links together the amino acids in the order given by mRNA to form a polypeptide (protein)
What can mutations be!
Harmful- could cause a genetic disorder like cystic fibrosis or cancer
Beneficial- produce new characteristics that is beneficial to the organism e.g natural selection
Neutral- neither harmful nor beneficial
What are enzymes?
Biological catalysts they’re made of proteins
What is a catalyst
A substance which increases the speed of a reaction without being changed or used up in the reaction.
What can enzymes be used for?
DNA replication
Protein synthesis
Digestion
What is the substrate
The molecule being catalysed by the enzyme
What is the active site of an enzyme?
The part that binds to the substrate to catalyse the reaction
Enzymes only work on one substrate, what does this mean?
They have a high specificity for their substrate.
Explain the lock and key theory
The substrate fits into its matching enzyme like a key fits into a lock. If the substrate doesn’t match the active site then the reaction won’t be catalysed
What’s the experiment for rate of enzyme controlled reactions
Use amylase as the enzyme and starch as the substrate. Mix the amylase and starch together then take regular drops of the solution and put it into a spotting tile whilst timing. Add iodine solution, if it’s blue or black starch is still present. Record the time the solution no longer turns blue or black. You can have different factors affecting the reaction.
What are the variables for the experiment?
Temperature- put test tubes into water bath at different temps
PH- pH buffers
Substrate concentration- vary conc. Of starch solution
Temp results
Best around 37°c as body temp. To high enzyme denatures too low substrates lose energy and don’t collide with the enzymes. Increases with temp up to 37 because substrates gain energy and collide more.
pH results
Each enzyme works in a different place so each enzyme has a different optimum pH. E,g stomach enzymes like acidic (HCL) too high or too low from the optimum means denaturing
