Chapter 3 - enzymes only.

Independent variable

the factor that is being deliberately manipulated to determine how it affects the results

Dependent variable

factor that changes due to the changes being made to the dependent variable

Controlled variable

factors kept the same for both the control and experimental groups

Control groups and experimental groups

Experimental Group:
Receives independent variable to see if it causes a change.

Control Group:
does not receives dependent variable and is used for comparison to see if the treatment caused the change.

Validity

The extent to which an experiment tests what it is supposed to test

how to ensure validity

Identify and control for confounding variables (external factors that could interfere with results).

Design the study with a clear distinction between the experimental and control groups. Ensure they are similar in all characteristics, except for independent variable

Use valid instruments and techniques for measuring variables that are accurate and relevant to your hypothesis.

reliability

the extent to which an experiment gives the same result each time it is performed

How to increase reliability

Perform multiple trials and compare the outcomes. If results are consistent, reliability is ensured.

Write a detailed experimental protocol that everyone follows to ensure consistency.

Use calibrated instruments and fixed settings (e.g., time of day for testing, environmental conditions).

Train all researchers thoroughly on the experimental procedure to ensure consistency in how measurements are taken and interpreted. (inter-rater reliability

Accuracy

The extent to which the measurement are correct

How to ensure accuracy

Regularly calibrate instruments and check for maintenance to ensure they measure accurately.

Double-check measurements, and if possible, have another person verify the results.

Use automated data collection methods if available (e.g., using digital thermometers instead of manually recording temperatures).

Keep detailed logs of every aspect of the experiment (e.g., time of testing, environmental conditions) to minimize accidental data distortion.

cross verification (Use more than one method to measure the same thing to ensure accuracy.)

human error + examples + how to avoid

simply a mistake

• incorrectly reading the scale

• spilling liquid before measuring volume

• mistake in calculations

not part of experimental error, should be avoidable with sufficient care and checking

• Double-check measurements

• Use automated tools

• Use consistent units and symbols

random errors

unpredictable errors that can occur in all experiments, because no measurement can be made with absolute precision

• stopwatch might stop a little early or late (not a human error, js a limitation of the timing procedure)

• Temperature or humidity changes might slightly affect measurements

how to avoid

• Repeat measurements

• Use precise instruments

• Control environmental factors

Systematic erros

occur because of the way an experiment is designed or due to problems with equipment

examples

• measuring from the soil instead of the base of the stem, your results will always be off in the same direction.

• A thermometer that always reads 2°C higher than the actual temperature

how to avoid

• Calibrate instruments:

• Follow proper measurement techniques

• Cross-check with different instruments

metabolism

all the chemical reactions that take place in cells and therefore organisms

concerned with maintaining a balance between energy release and energy utilisation

two types of metabolism and what they do

anabolism → type of reaction where small molecules built up into larger ones such as protein synthesis. require energy

catabolism → type of reaction where larger molecules are broken down into smaller ones such as digestion. release energy

nutrient + 6 types

any substance in food that is used for growth, repair, or maintaining a body; that is, any substance required for metabolism

• water

• carbohydrates

• lipids

• proteins

• minerals

• vitamins

organic compounds

molecules that have a carbon chain

also contain number of hydrogen atoms and can include atoms of sulfur, oxygen and nitrogen

carbohydrates: what are they, types, what they contain

main source of energy for cells

glucose (a simple sugar) is used in cellular respiration to release energy

starch (complex carb) broken down into simple sugars

contain atoms of carbon, hydrogen and oxygen (twice as many hydrogen atoms and oxygen atoms)

• monosaccharides

• disaccharides

• polysaccharides

Monosaccharides, disaccharides and polysaccharides

• simple sugars = monosaccharides (glucose, fructose, galactose)

• Two simple sugar molecules bonded togethe = disaccharides (sucrose, maltose, lactose)

• larger carbohydrate molecules formed when simple sugars join together = polysaccharides (glycogen, cellulose, starch)

lipids; what are they, use in cellular respiration,

Large organic molecules made up of fatty acids and glycerol

• broken down to fatty acids and glycerol

• e.g phospholipds

• consists of one molecule of glycerol and one, two or three fatty acid molecules

• most common fat is triglyceride (stored in body, consists of glycerol and three fatty acid molecules

Proteins

• organic compounds that are made up of amino acids

• most important in metabolism: enzymes

• amino acid: molecule that contains amino group and carboxylic group

• peptide bond: two amino acid bonds join together, releasing water molecule

• dipeptides: shorter lengths of amino acids with two amino acids joined

• polypeptides: 10+ amino acids

inorganic compounds

• not based on carbon chain

• most do not contain carbon atoms at all, but those that do (carbon dioxide) only in small amounts

• water, minerals and vitamins

waters use in metabolism

fluid in which other substances are dissolved

some of cells chemical reactions occur in water

some water molecules take part in reaction

mineral use in metabolism

may be part of enzymes

may function as cofactors

may be part of substances such as ATP that are involved in metabolism

vitamin use in metabolism

act as coenzymes for many reactions

activation energy

the energy needed to break the bonds of the reacting particles in a chemical reaction; the energy needed to start a chemical reaction

any given temp, there is certain proportion of particles that have enough energy to satisfy activation energy. proportion will increase when temperature increases

catalysts, how they affect activation energy

chemicals that are able to decrease the amount of energy needed in activiation energy

This means that the activation energy will be lower and more particles will have enough energy to react, making the reaction happen at a faster rate.

enzymes

Enzymes are biological catalysts that are able to speed up chemical reactions by lowering the activation energy.

They are not consumed or altered in the reaction.

substrate

molecules on which an enzyme acts on

enzyme will only combine with one particular substrate and is therefore involved in only one specific reaction. this is because the enzyme and substrate have complementary characterstics (shape and structure)

active site

part of enzyme molecule that combines with the substrate

when combined, called enzyme substrate complex

Lock and Key model

shape of enzyme (key) is always complementary to shape of substrate (lock)

therefore, two will fit exactly to form enzyme-substrate complex

induced-fit model

when enzyme and substrate join, they form weak bonds that cause the shape of the enzyme to change, creating complementary shapes

factors affecting enzyme activity (7)

concentration of enzyme

concentration fo substrate

continual removal of products of reaction

temperature

pH level of medium in which reaction is taking place

co-factors and co-enzymes

enzyme inhibitors

concentration of enzyme (3)

higher concentration of enzyme = faster rate of reaction

why? more enzyme molecules to influence reactants

by regulating type and number of enzymes present, body can control which reactions to occur and the rate at which they proceed

concentration of substrate

higher substrate = increased rate of reaction

why? → more substrate molecules coming into contact with enzyme molecules

but? → increasing substrate beyond a certain concentration will cease to have effect because active sites on enzyme will be fully occupied

continual removal of products of reaction

must be removed continually otherwise rate of reaction will slow due to it becoming more difficult for substrate molecules to make contact with enzyme molecules

temperature

rate of most chemical reactions increases as temp increases

• true for most enzymes but only within limited temp range

• because enzymes are proteins, beyond 45 - 50 degrees, structure changes and become denatured

• temperature at which an enzyme works best is optimum temperature (for most enzymes in the body this is 30-40 degrees)

pH of the medium in which a reaction is taking place

very sensitive to pH of medium in which a reaction is taking place

each enzyme has optimum pH at which it will work most effectively

co-factors

certain ions and non-protein molecules needed before enzymes catalyse a reaction

• change shape of active site so that enzymes can combine with substrate

• no co-factor = intact enzyme molecule, but unable to function

co-enzymes

organic, non-protein molecules that help enzymes catalyze reactions by transferring chemical groups between substrates

no co-enzyme = Failure to bind to the substrate properly, inablity to carry out the chemical reaction needed for the metabolic process

many vitamins, NAD+