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BTEC Unit 3 Applied Science Questions And Answers
What is a hypothesis?
- a hypothesis is defined as an educated guess
What is a null hypothesis?
- null means zero. so a null hypothesis states that two variables are not related.
why when making a hypothesis should it be aimed to be quantifiable
- this is because markers will award more more marks for being more precise and in more detail
what is the meaning of independent variable
- an independent variable is something that you change within an experiment
- for eg. the light intensity.
what is the meaning of dependent variable
- a dependent variable is something that you can measure within an experiment
- for. eg. the growth of plants.
what is the meaning of control variable
- a control variable is something that is kept the same within a experiment
- for eg. the enzyme used to measure the effect on pH
what does it mean if one variable is dependent on another
- for eg. the growth of a crop is dependent on the type of fertiliser used in the soil.
revise A5 part of specification
what happenes if there is an anomalous result in a set of values and how do we spot one.
- it is spotted by looking out of place
- for eg. 2,2,3,19,3,2 --> 19 is the anomaly as it doesn't fit in with the values
- x1 = mean from 1st set of data
- x2 = mean from 2nd set of data
- n = number of items
AD
how do we calculate standard deviation (on new casio calc) method
- home
- statistics
- 2-variable
- input data
- press exe
- 2 var results
- 2nd to last = SD
what are t-tests
- a type of statistical test
- a test which shows if there a significant difference between two sets shown mathematically
- if the t value is less the critical value the null hypothesis cannot be rejected
how do you calculate the critical value
- using the degrees of freedom
- the number of measurements made - 2
how do you calculate the t-value
- x1 & x2 = mean from 1st & 2nd set
- s1 & s2 = standard deviation from 1st & 2nd set
- n1 & n2 = number of items from 1st & 2nd set
what is a chi-squared test
- a chi squared test is a type of statical test which is used to confirm a null hypothesis
- it uses the observed and expected value
how do you calculate the chi squared value
- a chi square value is obtained by using a formula.
- choosing an appropriate graph/charts/tables
- correct plotting/labelling/scales
what are amino acids
- amino acids are monomers
- many amino acids join together to form a protein
AD
what are amino acids made up of
- carbon, hydrogen, oxygen, nitrogen (sometimes sulphur)
what is the amino group
what is the difference between polypeptide and dipeptide
- dipeptide are 2 amino acids joined together by a peptide together
- polypeptide are many amino acids joined by peptide bonds
how do you identify the R group in an amino acid
- the normal amino acid group contains an amino group
- H-N-H
- it also contains a carboxylic acid group
- COOH
- the one isn't one of these two is the R group
which two substances are formed when two amino acid molecules are joined toegther
where in the cell do amino acids joins together to form a protein
- they join together at the ribosomes
- this is because in the ribosomes protein synthesis occurs
what is hydrolysis
- long, straight chain
- the specific sequence of amino acids determines the structure and function of the protein
how are secondary proteins structured
- made up of a chain of amino acids
- which are folded to produce a n alpha, heliex or beta pleated sheet
- this structure is held together by hydrogen bonds
how are tertiary proteins structured
- made up of a chain of amino acids
- which are folded into secondary structures where they are further folded into specific tertiary structures
- this structure is held together by {
why are tertiary globular structures soluble in water
- the R groups are polar meaning they are attracted to water
- so that means they dissolve
why are teritary fibrous protein structures not soluble in water
- they are insoluble in water because they are non polar meaning they arent attracted to water so they won't dissolve
- examples include: - keratin, collagen
what are quaternary structures of protein
- two or more polypeptides joined together
- haemoglobin --> type of protein found in red blood cells
- made up of four polypeptides
- antibodies --> fight off infections also made up of four polypeptides
What is denaturation?
- a structural change in a protein that results in a loss of its biological properties
what happens when denaturation occurs of proteins
- H2 and ionic bonds break
- shape changes
- and we know that proteins are made in the ribosomes
what do enzymes do to a reaction
- biological catalysts
- they speed up the rate of reaction by lowering activation energy
what is meant by the activation energy
- the minimum amount of energy required for a reaction to take place
how do enzymes work
- enzymes have a specific structure
- the active site shape is also specific
- only complementary structures bind to the active site
- forming an e-s complex
- bonds in the substrate become hydrolysed
- products are then released
describe the lock and key model
- the enzyme and the substrate have specific complementary geometric shapes that fit exactly into one another
describe an induced fit model
- substrate and active site shapes are not complementary
- active site changes shape and becomes complementary to substrate
explain why lipase only breaks down fat
- lipase has an active site
- the active site has a specific shape
- only fats are complementary to the shape
what happens to the pH if lipids are digested
- lipids are digested to produce fatty acids
- fatty acids then lower the pH
in an example the pH in a test tube decreased until it didn't and remained the same value why is this
- all the lipids were used up
how does the collision theory help explain the denaturation of enzymes at high temperatures
-the kinetic energy gets too high
- this causes vibrations that disrupt hydrogen bonds holding - - the enzyme's tertiary structure
- the active site changes shape (denaturation)
- now, even if substrate collides with enzyme:
- it won't bind—wrong shape
- so no reaction occurs, despite frequent collisions
first practical - enzymes in action
.....
what are enzyme reactions affected by
- temp
- pH
- concentration of substrate
what happens when the temperature is too high
- as the temp increases the ROR increases -> more ke, more colisions, more e-s form
- at 38 degrees it reaches optimum temperature
- if the temp increases past optimum the ROR decreases -> high temp. causes hydrogen/ionic in enzyme to break
- active site changes shape and substrate is no longer complementary to active site so they do not bind
what are the variables for this experiment
- independent = temp
- dependent = ROR
- control = conc of enzyme./ optimum pH
- repeat experiment
factors affecting enzyme function question (temp)
- at low temp reaction rate is slow because there aren't as many frequent, succesful collisions due to there being little kinetic energy
- at the optimum the rate of reaction is fast and there are frequent successful collisions occurring
- at high temp the rate begins to decrease because bonds start to break and the active site changes shape so the enzyme is no longer complementary to the substrate so it can't fit
how do you determine if starch is still present
- due to the iodine solution
- if there is any starch the parts will remain blue/black
what are the variables for this experiment (pH)
- independent = pH
- dependent = diameter of clear zone
- control = optimum temp
factors affecting enzyme activity question (pH)
- at a low pH the rate of reaction is low. It is high around the enzyme's optimal pH and then decreases as the pH above the optimal pH.
what happens as substrate concentration increases
- as substrate concentration increases the rate of reaction increases rapidly --> more and more substrate binding to active site
- at very high substrate the rate of reaction becomes constant---> enzyme number is fixed and all active sites are occupied with substrate
- enzymes then become the limiting factor
what are the variables in this experiment (conc)
- independent = substrate concentration
- dependent = rate of reaction
- control = optimum pH
optimum temp
why is a control experiment performed
- it is done to prove that the result gained are due to the enzyme
- the same experiment ; however a boiled/denatured is enzyme is used
investigate how temperature, pH, or substrate concentration affects enzyme activity.
- set up each water bath (e.g. 20°C, 30°C, 40°C, etc.)
- add starch to a test tube and amylase to another separate test tube
- place them both in the water for 5 minutes
- take them and mix them and start timer
- time how long until a colour change is observed
- repeat and calculate mean
