molecular biology 1 - student notes 2015 · pdf filetopic 2 – molecular biology !! 1 !...
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MOLECULAR BIOLOGY
TOPIC 2
2.1 – MOLECULES TO METABOLISM ............................. 1 2.2 – WATER ..................................................................... 2 2.3 – CARBOHYDRATES & LIPIDS .................................. 7 2.4 – PROTEINS .............................................................. 15 2.5 – ENZYMES ............................................................... 22
SAMPLE QUESTIONS .................................................... 30
TOPIC 2 – MOLECULAR BIOLOGY
1
2.1 – MOLECULES TO METABOLISM
MOLECULAR BIOLOGY
CARBON COMPOUNDS
• Molecular biology explains ______________________________ in terms of the
_____________________ substances involved. • Molecular biologists would identify the __________________ in a _____________________
_____________________ and break down each step into its _____________________. • This has allowed us to better understand the processes of cellular respiration and
photosynthesis. • But there is still a lot that we don’t understand about organic molecules and how they act in
the body.
• Carbon is the backbone of every _____________________ molecule. • Carbon atoms can __________________________________________________________
allowing a diversity of stable compounds to exist.
• Covalent bonds are _____________________. • This allows _____________________, _____________________ molecules to be formed.
− eg. Titin protein (contains 539,000 atoms) found within contractile unit of muscle fibres • Life is based on carbon compounds. • These include:
− _____________________ − _____________________ − _____________________ and − __________________________________________
• You need to be able to draw molecular diagrams these compounds:
− inc. glucose, ribose, a saturated fatty acid and a generalized amino acid • You need to be able to identify biochemicals such as sugars, lipids or amino acids from
molecular diagrams.
2
CARBOHYDRATES
• Identify: monosaccharides and disaccharides
− _______________________: Glucose, galactose, fructose − _______________________: Lactose, maltose, sucrose − _______________________: Cellulose, glycogen, starch
• Draw: the ring forms of D-ribose, alpha–D-glucose and beta-D-glucose
3
LIPIDS
• Draw: a saturated fatty acid
− Saturated fatty acid:
no double bonds eg. stearic acid
− Unsaturated fatty acid: double bonds eg. linoleic acid
− Generalised fatty acid:
• Identify: lipids
− _______________________: fats, oils, phospholipids and steroids
4
PROTEINS
• Draw: a generalised amino acid
− a central _____________________ atom − 4 side groups:
− the _____________________ group (-NH2) − the _________________________________________ group (-COOH) − an _____________________ − the _____________________ – R standing for “the rest”
• Identify: proteins or parts of polypeptides, linked with a peptide bond
− _______________________
− _______________________
− _______________________
5
CONDENSATION & HYDROLYSIS
Condensation reaction: • __________________________________________ from two _____________________ to
form a _____________________
• __________________________________________ • Also known as _____________________ reactions • Also known as _____________________ reactions • Require _____________________ and _____________________ Hydrolysis reaction: • __________________________________________ can break _____________________
and _____________________ back into _____________________
• __________________________________________ • Also known as _____________________ reactions • Require enzymes but _____________________ _____________________
6
CONDENSATION & HYDROLYSIS
METABOLISM
•
• Most _____________________ use most _____________________. • Each _____________________ in each pathway is controlled by a specific
_____________________. • Metabolism is the _____________________ of all of the pathways used in a particular cell.
1
UREA & VITALISM
• Urea as an example of a compound that is produced by living organisms but can also
be artificially synthesized • Urea is an _____________________ chemical compound. • It is essentially the _____________________ produced by
the body after __________________________________________. • Naturally, the compound is produced when the _______________
breaks down _____________________ or _____________________, and _____________________.
• The average person excretes ~______ of urea per day, mostly through ____________, but a small amount in ____________.
• ________________________ of urea can be created in liquid or solid form, and is often an ingredient found in _____________________, animal feed, and diuretics.
Falsification of theories with one theory being superseded by another • The artificial synthesis of urea helped
___________________________________________.
• Vitalism is the theory that living organisms are fundamentally different from non-living entities
because they contain some __________________________________________ or are governed by __________________________________________ than are inanimate things.
• Vitalists would theorise that:
• The synthesis of urea by __________________________________________ in 1828 therefore falsified this statement.
• Vitalism is no longer a generally accepted idea. • Complete relevant practice Qs beginning on Page 30
2
2.2 – WATER
STRUCTUREOF WATER
• Chemical formula: ___________________ • Made up of ___________________ & ___________________ • ___________________ bonds exist between the atoms • Oxygen nucleus is ___________________ & _____________________________________
than the hydrogen nuclei. This ___________________ the ___________________ pair in the covalent bond ___________________ to the oxygen
• This means that water molecules are ___________________ – as one part is ___________________ ___________________ ___________________ than the other
• This means that water molecules can ___________________ each other
• ____________________ ____________________ form between the molecules
3
PROPERTIES OF WATER
Theories can be used to explain natural phenomena • The theory that hydrogen bonds form between water molecules
explains the properties of water
• Properties of water to be covered:
− _____________________ properties − _____________________ properties − _____________________ properties − _____________________ properties
Cohesion and adhesion: • Water molecules are strongly cohesive
− ie. they _____________________ to _______________________________________ • They also adhesive
− ie. they _____________________ to _______________________________________ that are _____________________ or _____________________
• _____________________ of water molecule allows it to _____________________ _____________________ _____________________ with substances
• _____________________ _____________________ _____________________ & allows small _____________________ to be able to _____________________ on water
• Allows water to be _____________________ _____________________ _____________________ in plants
Thermal properties: • Water has a high ___________________________________________________________
− ie. it takes a lot of energy to _____________________ the _____________________ of water
• Water has a high ___________________________________________________________ − ie. it takes a lot of energy to _____________________ it to a
_____________________ • Water has a high ___________________________________________________________
− ie. it needs to _____________________ a lot of energy to _____________________ • _____________________ _____________________ _____________________ requires
_____________________ _____________________ _____________________ to break • This allows lakes to _____________________ lots of heat energy &
____________________ _____________________ _____________________ for _____________________ organisms.
4
PROPERTIES OF WATER
• This is also used by animals and plants as a _____________________. • Plants use heat from their leaves for _____________________, thus preventing
_____________________. • This is also true of animals, who use the evaporation of _____________________ to
remove heat from the body. • The blood is also _____________________. This means that _____________________
blood can be _____________________ to other parts in order to cool them down. • Thermal properties – water vs methane:
− The key difference between water and methane is their _____________________. − Methane has __________________________________________, only covalent. − As a result, _____________________ _____________________ is needed to
separate its molecules from each other. − This causes the differences in their physical properties, particularly their thermal
properties.
Solvent properties: • Water can _____________________ many organic and inorganic substances that have
_____________________ or _____________________ regions. • Polar attraction of large quantities of water can _____________________
_____________________ _____________________: − _____________________ ions will become surround by the
_____________________ _____________________ _____________________ region of the water molecules
− _____________________ ions will become surround by the _____________________ _____________________ _____________________
5
PROPERTIES OF WATER
region of the water molecules • Water is often called the _____________________ _____________________ because of
how well it can act to dissolve substances.
• Watch this: http://www.juntadeandalucia.es/averroes/manuales/materiales_tic/biomoleculas/dissolve.swf
• _____________________ _____________________ _____________________ _____________________ in _____________________ of water.
• Water in cells _____________________ the _____________________ /_____________________ for these reactions.
• Substances that are _____________________ can therefore be _____________________ _____________________ around an organism and be brought into/out of the cells by _____________________.
• All substances that _____________________ in water are _____________________ − eg. _____________________ - its positive and negative regions make it polar and
soluble • All substances that __________________________ in water are _____________________
− eg. Oil
6
MODE OF TRANSPORT THROUGH BLOOD
Glucose • _____________________ molecule • Freely _____________________ • Carried by the _____________________ _____________________ Oxygen • _____________________ molecule • _____________________ in water due to its _____________________ • _____________________ of oxygen _____________________ at
__________________________________________ • Carried by _____________________ protein
in __________________________________________ − has _____________________ oxygen binding sites
Cholesterol • _____________________ (=lipid) • _____________________ molecules • Carried by _____________________
complexes in the blood plasma Fats • __________________________________________ Hydrophobic molecules • Carried by _____________________
complexes in the blood plasma Sodium chloride (salt) • _____________________ molecule
(_____________________) • Freely _____________________ • Carried by the _____________________
_____________________ as _____________________
• Complete relevant practice Qs beginning on Page 31
7
2.3 – CARBOHYDRATES & LIPIDS
MONOSACCHARIDES
Examples Details Example use in plants
Example use in animals
Glucose
• C6H12O6 • hexose sugar • 5C form the ring, with the 6
th corner taken by
oxygen
Galactose
• C6H12O6 • hexose sugar • same as glucose but one set of side chains are reversed
Fructose • C6H12O6 • pentose sugar
Monosaccs à disaccs: • _____________________ reaction • _____________________ is removed • _____________________ _____________________ formed
8
DISACCHARIDES
glucose + glucose à _____________________ + water
glucose + galactose à _____________________ + water
glucose + fructose à _____________________ + water
Examples Details Example use in plants
Example use in animals
Maltose • C12H22O11 • glucose dimer
Lactose • C12H22O11 • glucose and
galactose
Sucrose • C12H22O11 • table sugar • glucose and fructose
Monosaccs/disaccs à polysaccs: • _____________________ reaction • Water is removed (no. of water = ______________________________________________) • Glycosidic bonds formed • Often _____________________ and may be _____________________
• Examples:
− _____________________ – used as an _____________________ _____________________ molecule in _____________________
− _____________________ – used as an energy storage molecule in _____________________
− _____________________ – _____________________ _____________________ of _____________________ cell _____________________
9
POLYSACCHARIDES
Cellulose:
• Function: structural component of plant cell walls • Structure:
− Made of _____________________ molecules linked together − _____________________ reactions link C1 of one glucose to C4 of the next − The molecule is a _____________________ chain (not curvy) − The molecule is _____________________ − Cellulose can _____________________ to itself through _____________________
_____________________ à forming _____________________ _____________________ with a _____________________ _____________________ _____________________
− It’s this strength that allows the cell wall to _____________________ _____________________ _____________________.
Starch:
• Function: used as an energy storage molecule in plants • Structure:
− Made of _____________________ molecules linked together − _____________________ reactions link C1 of one glucose to C4 of the next − The molecule is a _____________________ chain (not straight) − Starch is _____________________, but are _____________________ due to their
_____________________ − There are two forms of starch:
§ _____________________ – contains only C1-C4 bonds and forms linear helices
10
POLYSACCHARIDES
§ _____________________ – also contains C1-C6 bonds, which causes branching
Glycogen:
• Function: used as an energy storage molecule in plants • Structure:
− Made of repeating _____________________ molecules linked together − _____________________ reactions link C1 of one glucose to C4 of the next and
potentially C1 to C6. − The molecule is a _____________________ − Hydrophilic but _____________________ – therefore does not upset the
_____________________ _____________________ of the cells
11
MOLECULAR VISUALISATION SOFTWARE
• Go here: http://www.biotopics.co.uk/jsmol/
12
HEALTH CLAIMS ABOUT LIPIDS
• _____________________ _____________________ could be involved • All fatty acids are _____________________ in _____________________ • _____________________ of fat in the diet linked to an _____________________________
of _____________________ • _____________________ link between diets high in _____________________ and
_____________________ • Link between low levels of _____________________ _____________________ fatty acids
and affected brain and nerve development Evaluation of evidence and the methods used to obtain the evidence for health claims made about lipids. • Evaluation =
−
• Evidence =
• Strengths? − Has a positive or negative _____________________ been determined? − Has the _____________________ _____________________ or
_____________________ _____________________ of the difference between the two means tested?
− Has the _____________________ of data been considered?
• Limitations? − What was the _____________________ of “health” being tested? − What was the __________________________________________? − Was the sample _____________________ of the _____________________
_____________________? − Was the data gathered from human or _____________________________________? − Was it a _____________________ study? − What _____________________ were used to gather the data?
13
LIPIDS FOR LONG-TERM ENERGY STORAGE
Functions of lipids include: • S_____________________: phospholipids in cell membranes • H_____________________ _____________________:
steroid hormones are lipids (eg. oestrogen) • I_____________________: fat is an insulator; lipids also insulate neurons • P_____________________: fats protect internal organs from damage • S_____________________ of _____________________: fats can be used as a
_____________________ energy storage source • Carbohydrates and lipids contain a lot of _____________________
_____________________ and can be used for energy _____________________ • Lipids _______________________________________________________________ so
they are more suitable for long-term storage • These lipids are stored as _____________________ in _____________________
_____________________ (cf. Topic 1) under the skin and around organs, including the _____________________.
• Lipids release __________________________________________ than sugars (or proteins).
• Lipids are therefore _____________________ than sugars of equal yield: − Lipids add ________ as much to body mass as sugars − Glycogen is _________________________________________ (b/c it’s soluble), while
fats are not
• Why use glycogen at all???? − Breakdown of sugars is much _____________________, making them
_____________________ for _____________________ energy storage − Sugars are _____________________ in water (cf. ___________________________),
making them _________________________________________ to sites of use − Glucose can be used aerobically (with O2) or anaerobically (without O2) but fats
_____________________________________________________________________
14
BODY MASS INDEX (BMI) CALCULATION
• Body Mass Index (BMI) is a __________________________________________ to identify
potential weight issues. • It is should be used _______________________________ with other measures, such as:
− a _____________________ _____________________ test − _____________________ evaluations − _____________________ assessments and − _____________________ _____________________
• BMI is calculated in the same way for kids and adults. • Units for BMI = _____________________, • You can also use a BMI chart to assess BMI
• An alternative method uses a
_____________________: − Draw a line between the weight and weight. − It will cross a third axis, a BMI scale.
• Complete relevant practice Qs beginning
on Page 33
15
2.4 – PROTEINS POLYPEPTIDES
ESSENTIAL AMINO ACIDS
• Amino acids are linked together by
_____________________ to form polypeptides. • The bonds formed are _____________________. • The bonds formed are _____________________
bonds. • The bonds form in the _____________________.
• There are ____ essential amino acids found in polypeptides synthesised by the ribosomes. • The source of these amino acids would be the absorbed products of __________________.
16
POLYPEPTIDE SYNTHESIS
• Ribosomes are the molecules (structures)
within cells that _____________________ the _____________________ of __________________________________.
• There are _____________________
possibilities for polypeptides • ______ amino acids ___________________________ or _____________________ or
_____________________ • A ______ amino acid peptide has 1,280,000,000 possible combinations. • Some polypeptides (eg. ________________) are __________________________________
in length!
• The sequence of amino acids is coded for by _____________________.
• DNA stored in the _____________________ is read and “_____________________” into an _____________________.
• This RNA message (___________) can leave the nucleus and head to the _____________________.
• Here, the instructions contained within the message are “_____________________” into a _____________________.
• Each amino acid has unique properties. − side chains can be polar/non-polar, hydrophilic/hydrophobic, acidic/basic, etc
• The properties of each amino acid influence how a _____________________ will be able
to _____________________ up into a _____________________. • There are _______ levels of structure in proteins:
− _____________________ structure − _____________________ structure − _____________________ structure ß _____________________ − _____________________ structure
17
PROTEIN STRUCTURE
• Primary (1˚) structure:
− _____________________ _____________________
− Involves _____________________ _____________________
• Secondary (2˚) structure: − Repeating local structures − Generally found in
_____________________ proteins − These include:
o _____________________: peptide chain wound into a helix
o ___________________________: peptide strands lie in a plane
• Tertiary (3˚) structure:
− Single protein _____________________ into a _____________________
− Generally form _____________________ proteins
− Important for _____________________ of the protein
• Quaternary (4˚) structure: − Two or more polypeptide chains _____________________ together − eg. Hemoglobin _____________________ becoming haemoglobin
18
PROTEIN STRUCTURE
• Proteins can be separated into two groups based on their _____________________:
FIBROUS PROTEINS GLOBULAR PROTEINS
SOLUBILITY
SHAPE
SENSITIVTY TO CHANGES
ROLE
EXAMPLES
19
PROTEIN FUNCTION
• Proteins have a variety of uses in organisms:
− _____________________ – speeds up chemical reactions – ____________________ − _____________________ _____________________ − _____________________ – give animal cells their shape − _____________________ _____________________ – provide strength –
_____________________ − _____________________ _____________________ − _____________________ of _____________________ and
_____________________ − _____________________ _____________________ − _____________________ _____________________ − _____________________ – _____________________ − _____________________ – binding sites in membranes and cytoplasm for hormones,
neurotransmitters, tastes, smells and receptors for light – _____________________ − _____________________ of _____________________ − _____________________ – _______________________________
Rubisco: • Full name = ribulose bisphosphate carboxylase • It is an _____________________ involved in
_____________________ • It “______________”_____________________
from a _____________________ state to one able to be _____________________ by the plant.
Insulin: • It is a _____________________ involved in ______________________________________
levels in the blood within narrow limits. • It is secreted by the _____________________
in the _____________________. • Insulin signals the liver cells to
______________________________ and convert it to _________________.
• This takes it out of the _____________________.
• Not produced by people with _____________________.
•
20
PROTEIN FUNCTION
Immunoglobulins: • Also known as _____________________ • Produced by the _____________________ in response
to the presence of an _____________________ • The _____________________ of the protein is
_____________________________ allowing them to respond to a _________________ of _____________________.
• They also _____________________ other immune cells to help _____________________ the pathogen once it has been identified.
Rhodopsin: • A _____________________ that can _____________________ • _____________________. • Found in _____________________ within the
_____________________ at the back of the eye. • The absorption of light causes a _____________________
and _____________________ change to the molecule. • This results in a _______________________________________
being sent to the _____________________. • Rods work well in even _____________________, and are
responsible for _____________________ vision.
Collagen: • A __________________________________________ protein. • Forms a _______________________________________ in skin
and in the blood vessel walls that _________________________________________.
• Gives tendons, ligaments, skin and blood vessel walls their _____________________. • Forms part of teeth and bones, ________________________________________________.
Spider silk: • _____________________ proteins • Spiders can produce different types of silk with different
_____________________ for different _____________________. • Some of the silk is comparable to _____________________ in regards
to its _____________________ _____________________.
21
PROTEOME
PROTEIN DENATURATION
• Every individual has a _____________________ _____________________. • Proteome:
• The proteome is a function of both the organism’s _____________________ (genes) and _____________________ _____________________.
• Environmental factors such as _____________________, _____________________, etc can affect a cell’s activities − eg. DNA methylation can stop
translation of a protein!
• Epigenetics:
• Watch this: https://youtu.be/kp1bZEUgqVI
• _____________________ _____________________ or ____________________________
(_____________________) can cause _____________________ of proteins. • Denaturation affects the _____________________ holding the _____________________,
_____________________ and _____________________ structures together. • This will result in an _____________________ loss of _____________________ and
therefore _____________________. • eg. Cooking an egg denatures its proteins, causing them to harden
• Complete relevant practice Qs beginning on Page 34
22
2.5 – ENZYMES
ENZYME BASICS
• _____________________ _____________________,
which _____________________ the _____________ of chemical _____________________ without becoming a part of the _____________________
• Enzymes are _____________________ proteins
with a _____________________ shape. • Without enzymes, chemical reactions _____________________ _____________________
_____________________. • Enzymes work by _____________________ the _____________________
_____________________ needed for a reaction. • Many enzyme names end in _____________________
− eg. amylase, lipase, sucrase, lactase, catalase • Active site:
• The active sites are _____________________:
− ie. enzymes are designed to “fit” the shape of their substrate • This is known as the ________________________________________________________ • The active site is simply a _____________________ on the surface of the enzyme
23
ENZYME-SUBSTRATE SPECIFICITY
Lock and key model • Active site and substrate _____________________ each other in terms of both
_____________________ and _____________________ _____________________ (e.g. opposite charges).
• Binding to the active site brings the substrate into close _____________________ _____________________, creating an ____________________-_____________________ _____________________.
• The enzyme _____________________ the _____________________ of the _____________________ into a _____________________ (or products), creating an _____________________-_____________________ _____________________.
• As the enzyme is ___________________________ in the reaction, it can continue to work once the product is completed.
Induced fit model • The lock and key model of enzyme action does not fully explain enzyme activity. • There are some enzymes that are capable of _____________________
_____________________ reactions − eg. some _____________________ have quite a broad specificity
• The Induced Fit Model proposes that the _______________________________________ the substrate precisely ______________________________________________________.
As the substrate binds to the active site, the _____________________ _____________________ _____________________ to better fit the substrate.
24
ENZYME-SUBSTRATE SPECIFICITY
ENZYME CATALYSIS
• As the substrate binds to the active site, the _____________________
_____________________ _____________________ to better fit the substrate. • This _____________________ the _____________________ in the substrate, thus
_____________________ the _____________________ _____________________ required for the reaction.
• Catalysis involves _____________________ _____________________ and the
_____________________ of _____________________ with the ____________________. • Collisions between the free moving enzymes and substrates are the result of
_____________________ _____________________. • Successful collisions will _____________________ the active site and substrate correctly,
allowing _____________________ to occur.
• Go here: http://kscience.co.uk/animations/model.swf
25
ENZYME DENATURATION
FACTORS AFFECTING ENZYME ACTIVITY
• Enzymes, like all proteins, can become _____________________. • Denaturation is usually _____________________. • Can be caused by _____________________ _____________________ and
__________________________________________ • Denaturation ____________________________ holding the _____________________ of a
protein together à resulting in loss of _____________________
26
FACTORS AFFECTING ENZYME ACTIVITY
Temperature • Low temps result in _____________________ _____________________
_____________________ for the _____________________ of a reaction to be achieved • Increasing the temp will increase the _____________________ and
_____________________ of both _____________________ and _____________________, resulting in higher enzyme activity
• This is because a _____________________ _____________________ _____________________ will result in __________________________________________ _____________________ between enzyme and substrate
• At an _____________________ temp, the _____________________ of enzyme activity will be at its _____________________
• Higher temps will _____________________ _____________________ _____________________, as the thermal energy _____________________ the _____________________ bonds holding the enzyme together
• This causes the _____________________ (particularly the _____________________) to __________________________________________, resulting in a loss of enzyme _____________________ (_____________________)
pH • Changing the pH will alter the _____________________
of the enzyme, which in turn will change _____________________ and may change the _____________________ of the molecule
• Changing the shape or charge of the active site will diminish its ability to _____________ to the substrate, _________________________________ _____________________
• Enzymes have an _____________________ pH
27
FACTORS AFFECTING ENZYME ACTIVITY
ENZYME IMMOBILISATION
Substrate concentration • Increasing substrate concentration will increase enzyme activity • More substrate means there is an increased _____________________ of enzyme and
substrate _____________________ and _____________________ • So more _____________________ will be formed in a _____________________ period. • After a certain point, the rate of reaction will _____________________________________
despite further increases to substrate concentration, because as the environment has become _____________________ with substrate and ______________________________ are in use
TEMPERATURE pH
SUBSTRATATE CONCENTRATION
Too low
Too high
Immobilised enzymes are widely used in industry. • Methods:
− Aggregations of enzymes bonded together − Attached to a surface – eg. glass − Entrapped in gels – eg. _____________________
• Advantages:
− Enzyme is not dissolved – so concentration of substrate can be increased − Enzymes can be _____________________ many times, saving time and money − Collection of products is straight forward − ________________________________________________ to changing temp and pH
• Examples:
− Used for medical diagnostic tests − Used for food production – eg. __________________________________________
28
PRODUCTION OF LACTOSE-FREE MILK
• _____________________ of adult humans are lactose intolerant • They have lost the ability to _____________________ _____________________ in
_____________________ _____________________ after early childhood. • A _____________________ _____________________ allows lactase production to
continue through to adulthood. • It is the _____________________ of this _____________________ that results in lactose
intolerance.
• Ingestion of milk will lead to _________________________________________________ & _____________________.
• The food industry has produced lactose-free milk. • Use _____________________ enzyme to break down _____________________ into
_____________________ and _____________________. • Milk tastes _____________________ but will not cause reaction in lactose-intolerant adults.
• Steps:
1. Lactase is _____________________ (from __________________ or __________________)
2. Lactase is ______________ to an __________________ substance (such as _____________________ beads)
3. Milk passed over _____________________ enzymes becomes lactose-free
• Other uses:
− Source of milk for lactose-intolerant individuals − Increases the sweetness of milk, thus
_____________________ the need for _____________________ _____________________
− _____________________ the _____________________ of ice-creams
− _____________________ the _____________________ time for _____________________ or _____________________
• Complete relevant practice Qs beginning on Page 34
29
EXPERIMENTAL DESIGN
• Catalase is an enzyme that catalyses the conversion of hydrogen peroxide into water and
oxygen.
• Choose a research question and design an experiment to be run in class.
• Possible research Qs: − What is the effect of substrate concentration? − What is the effect of temperature? − What is the effect of pH? − Does the source of catalase influence the rate of reaction?
• Things you must consider about your IV: − How are you going to vary your IV across a sufficient range? − What units will you be measuring your IV in? − Have you selected concentrations of chemicals that are safe to handle?
• Things you must consider about measuring your DV: − Measuring increase of product or disappearance of substrate? − Direct or indirect measurement? (eg. concentration or product or change in pH) − Units and uncertainty of equipment? − Time period needed? − How many repeats are needed?
• Things you must consider about designing a fair test:
− What else could affect your DV? − How/why would they affect your DV? − How could you eliminate or reduce their influence on the DV? − Do you need to monitor them throughout to be sure that they were controlled? − Is there anything that was beyond your control? − Safety and ethics of your method and equipment?
•
30
SAMPLE QUESTIONS
MOLECULES TO METABOLISM
Q1 State the number of covalent bonds formed by a carbon atom. ______________
Q2 Define anabolism.
Q3 What is meant by the term ‘dimer’?
Q4 Which describes these molecules correctly?
A. I = ribose; II = amino acid B. I = glucose; II = amino acid C. I = ribose; II = fatty acid D. I = glucose; II = fatty acid
Q5 What is meant by the term ‘dimer’?
A. Glucose and galactose are examples of monosaccharides. State one other example of a monosaccharide. (1) ____________________________
B. The equation below shows the production of glucose and galactose from lactose.
i. There are several different types of carbohydrate. State which type of carbohydrate lactose is. (1) ____________________________
ii. State the type of chemical reaction that occurs when lactose is digested into glucose and galactose. (1) ____________________________
31
WATER
Q1 Which diagram represents the polarity
of a water molecule?
Q2 Which diagram best illustrates the interactions between water molecules?
32
WATER
Q3 Explain how the properties of water are significant to living organisms. [9] ......................................................................................................................................
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33
CARBOHYDRATES & LIPIDS
Q1 A woman has a mass of 72kg and a height of 1.69m.
a. Calculate her BMI. b. Deduce the body mass status of this man using
the table. c. Outline the relationship between height and BMI
for a fixed body mass. Q2 A man has a height of 150cm and a BMI of 40.
a. Calculate the minimum amount of body mass he must lost to reach normal body mass status. Show your working.
b. Suggest 2 ways in which the man could reduce his body mass. Q3 What is the difference between galactose and lactose?
A. Lactose is a disaccharide and galactose is a monosaccharide. B. Lactose is the product of anaerobic respiration in humans and galactose is the
product of anaerobic respiration in yeast. C. Lactose is an enzyme and galactose is a hormone. D. Galactose is a sugar found in milk but lactose is not found in milk.
Q4 What chemical is shown in the diagram below?
A. Saturated fatty acid B. Cis-monounsaturated fatty acid C. Trans-monounsaturated fatty acid D. Polyunsaturated fatty acid
34
PROTEINS
ENZYMES
Q1 Which best describes the tertiary structure of a protein?
A. The interaction of polypeptide subunits and prosthetic groups B. Interactions forming hydrogen bonds between the amino acids C. The sequence of amino acids in the polypeptide chain D. The structure formed from interactions between the amino acid side groups
Q1 The graph below shows the effect of substrate concentration on enzyme activity. What
conclusion can be drawn about section X of the graph?
Which best describes the tertiary structure of a protein? A. The enzyme has started to denature and the reaction slows down. B. The reaction has finished and the substrate has been used up. C. The enzyme is saturated and is working at its maximum reaction rate. D. Some of the enzyme has been consumed and the reaction has reached a plateau.
Q2 Which of the following will cause an enzyme to permanently lose its properties?
I. Hydrolysis II. Freezing to –20°C III. Dissolving it in water
A. I only B. II only C. I and II only D. I and III only
35
ENZYMES
Q3 Discuss factors that affect enzyme activity. [9] ......................................................................................................................................
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