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tentatively explains somthing observed (proposes an answer to a question - suggest a possible explanation)
*MUST BE TESTABLE AND FALSIFIABLE*
Who found the stricture of DNA?
Watson & Crick
What are the components of scientific investigation?
- 1) Ask a question (must be testable - not subjective eg pretty, smart)
- 2) Develop a hypothesis
- 3) Design an experiment to test the hypothesis (experimental design)
- 4) Make a prediction
- 5) Conduct experiment
What is involved in Experimental Design?
- 1)Determine All Variables
- a. Dependent Variable
- b. Independent Variable
- c. Controlled Variables
- 2)Develop a procedure
- a. Level of Treatment
- b. Replication
- c. Control
measured, counted, or observed in response to the experimental conditions
experimental condition which is manipulated to test the hypothesis
*most important variable by which to text the hypothesis*
The variables that must be kept consistant during the experiment
sequence of steps to be performed for the experiment
Level of Treatment
value set for the independent variable (specifically amount used for the test)
in some experiments there is no level of treatment
procedure should be repeated several times, providing consistant results
Control (control treatment)
Hold the same (placebo)
the indenpendent variable is held at established level or omitted. Allows scientist to decide if the effect is really due to the indepentent variable.
If/ then statement
If the hypothesis is true/ then the results of the experiment will be....
qualitative - subjective - quality such at pretty or smart cannot be measured by science
quantatative - objective - data - measurable
growth at the same rate - two body parts grow at the same rate. Proportions between body parts remain constant as the organism grows.
growth at different rates - parts of an organism grow at different rates
what axis is the independent variable on?
x axis - horizontal
what axis is the dependent variable on?
y axis - vertical
Components of a graph
- 1) Title - clearly tells what graph is about - goes BELOW the graph - Cap first work and period at the end.
- 2) Key - what the different lines or dots represent
- 3) X axis labeled - (indedendent variable) what measured and measurement used (oC, cm, mm)
- 4) Y axis labeled - (dependent variable) what measured and measurement used
- 5) line of best fit (optional) dont connect the dots
If time is involved in an experiment - what variable is it (normally)?
independent - x axis
In Lab 1 what was the formula to find the ratio?
Height/ Body Part = ratio
In lab 1, what was the independent variable? what was the dependent variable?
Independent was the body part (head circumference)
Dependent was the ratio H/BP
What is another name for graphs?
What are the primary functions of tables and figures (graphs)?
1. Help you analyze and interpret your results
2. Enhance the clarity with which you present the work to your reader
What are the guidelines for making a table?
- 1. All values of the same kind should read down the column
- 2. Column headings should include unit of measure (if appropricate)
- 3. Title - should be clear and concise - Goes at the TOP of the table - cap first word and important words...no period
- 4. Include replication if appropriate
Show changes in the quantity of the chosen variable and emphisize the rise and fall of values over their range. ( use to present continuous data)
- 1. plot data as seperate points
- 2. use line of best fit (normally) - only connect points when emphesizing changes in the independent (x) variable
- 3. If more than one set of data - use different colors and include a key
Used for data that represents separate or discontinuous groups or non-numerical categories
Histograms are bar graphs in which the values on the x axis are numbered but grouped together.
What is the essential feature of science that makes it different from other ways of understanding the natural world?
Science assumes that boilogical systems are understandable and can be explained by fundamental rules or laws
Long chains of amino acids (monomer)
How many different amino acids are there?
How are amino acids joined?
Peptide bond which is created by dehydration synthesis
bilogical catalyst - a compound that speeds up a chemical reaction without being used up or altered in the reaction.
speed up the reaction by lowering the activation energy necessary for the reaction to occur
Without enzymes most reactions could not happen quickly enough
Do all enzymes have the same shape?
Each enzyme must have it own specific shape
Each enzyme can only hold a particular substrate
Enzymes hold reactants in a particular configuration so that a reaction can occur (lock and Key model)
What is an enzyme made of?
Enzymes are proteins that are highly specific in function
the material that the catalyst (enzyme) acts upon
the substrate is modified during the reaction to form a new product
part of the enzyme that binds the substrate (forming the enzyme-substrate complex)
bond of enzyme and substrate
after the enzyme had done it work the complex disassociates into enzyme and product (or products)
What factors are enzyme activity influenced by?
environmental factors such as pH & temperature - can change the three-dimensional shape of the enzyme and alter its rate of activity
enzymes in the human body are designed to work at pH 7 and about 37oC
Chemicals that must bind to the enzyme for it to be active (binds and changes it shape)
example - perms - solution dosent work until activator is applied
nonprotein substances that bind to the active site of an enzyme and are essential for the enzyme to work
organic (biological materials) that are needed for the enzyme to function properly
many vitamins are coenzymes - if the body is deficient in a certain vitamin then enzymes that need that vitamin will not work right
chemicals that shut off enzyme activity
compeditive and noncompeditive inhibitors
compete with the normal substrate for the active site
adding more substrate can overwelm the compeditive inhibiter and cause it not to work
Antifreeze and alcohol
binds to some other part of the enzyme - changes the shape (configuration) of the enzyme
AChE inhibitors - (pestcides causes enzyme processos of insect body to not be able to work)
Two ways to measure enzyme activity
1. Determine rate of disappearance of the substrate
2. determine rate of appearance of the product
Describe process of enzyme activity
- 1. a substrate or substrates bind to the active siteof the enzyme
- 2. forming the enzyme-substrate complex
- 3. which then disassociates into enzyme and product or products
Enzymes can bind substrates together or break them apart
what suffix denotes enzyme?
enzyme that in the presence of oxygen, causes the removal of electrons and hydrogens from catechol (compound in plant cells). Catechol is converted to benzoquinone (pigment product) and water.
Catechol + 1/2 O2 →Catechol oxidase→ Benzoquinone + H2O
this reactions is what causes fruits and vegetables to turn brown when exposed to air
In lab 4 what was the inhibitor that was used?
how does it work?
PTU - phenylthiourea
to be active Catechol oxidase required copper as a cofactor. PTU combines with the copper in the catechol oxidase and inhibits its enzymatic activity
- enzyme in the saliva of many animals, including humans
- breaks up starch (polysaccharide) into maltose (disaccaride)
How does starch react when treated with I2KI?
- Starch turns purple
- Malose does not react to I2KI
Rate of disappearance
allows quantatative measure of reaction rate by watching how quickly starch disappears when treated with the enzyme amylase
take an aliquot (sample) of enzyme and dilute it with an equal amount of water (1:1) Take an aliquot of the dilutution and add to an equal amount of water (1:3) and so on (1:7), (1:15), (1:31)
In the rate of disappearance experiments why is the data graphed in reverse order?
The deaction rate (the dependent variable) was measured as time of starch disappearance - the highest values indicate the slowest reaction time
Influence of Enzyme concentration on the rate of starch digestion
- Independent - Enzyme concentration
- Dependent - Reaction rate (time of starch disappearance)
- As the enzyme amylase concentration is resuced, reaction times get slower and slower until there is no reaction because there is not enough amylase
Effect of pH on amylase activity
- Independnet - pH
- dependent - Recation rate (in seconds)
- Each enzyme has a pH range that it works best at (pH can affect the three-dimensional shape of the the enzyme). Amylase works best at pH near 7 and slower at lower and higher pH (bell shaped graph)
Effect of temperature on chemical reactions
chemical reactions accelerate as temp rises - increased temp speeds up motion of molecule
10o rise in temp will result in two to three fold increase in reaction
Effect of Temperature on Amylase Activity
- Independent - Temperature
- Dependent - Reaction Rate
- Enzyme have an optimal temp that they work best at. Amylase works best near 37oC. It does not work at 4o or 80o (bell shaped graph)
- High Temperature can cause the integrity of the protein to be permanently denatured.