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Headstart Revision Program VCE Biology Unit 3 Exam Revision

Session 1. Area of Study 1 – Molecules of Life

The chemical nature of the cell

Synthesis of biomacromolecules

Biomacromolecules are the big molecules involved in the biochemical processes of

organisms involved in communication within and between cells, transforming energy and

translating and transferring genetic information. These include complex carbohydrates

like starch, lipids, proteins and deoxyribonucleic acid.

Autotrophs (organisms that synthesise their own energy) are able to synthesise their

own macromolecules from inorganic molecules. For instance, when green plants make

glucose through the process of photosynthesis they combine two inorganic molecules –

carbon dioxide and water with light in the presence of a catalyst (chlorophyll) to make

glucose (an organic molecule) and oxygen. Some autotrophs use a chemosynthetic

process to achieve similar outcomes.

light energy

6CO2 + 12H2O C6H1206 + 6H20 + 6O2

chlorophyll

Heterotrophs are organisms that must consume other organisms to synthesise

macromolecules. That is they consume organic matter which is digested in specialised

organs to reduce the molecules to glucose and other simple sugars, amino acids and

lipids so that they can then be used to build new macromolecules.

The structure and function of carbohydrates

Organisms use carbohydrates as an energy source and for structural components of

cells. Two examples are glucose which is a simple sugar used to provide energy to the

cell for various processes and cellulose which is found in the wall of cells, giving the cell

structure. Carbohydrates are grouped into three main types – monosaccharides

(simple sugars), disaccharides (such as sucrose which bonds two monosaccharides

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StarchGlucose


together) and polysaccharides (such as starch which are many monosaccharides

and/or disaccharides bonded together).

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The structure and function of lipids

Lipids are a diverse group of molecules

which include fats, oils and steroids. They

are used for energy storage, as the

structural component of membranes and for

biological functions (eg. transmission of

chemical signals between cells). Lipids are

classified based on their relationship with

water. Some are hydrophobic as they

posses no polar regions on the molecule

and won’t dissolve in water. Some do

posses polar regions, will therefore dissolve

in water and are known as hydrophilic and

others have a hydrophobic and hydrophilic

region and are referred to as amphipathic.

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The structure and function of DNA and RNA

DNA is a large protein found in the nucleus of eukaryotic cells and in the cytoplasm of

prokaryotic cells. It is comprised of nucleotides, which in turn are comprised of a five

carbon sugar, a negatively charged phosphate group, and a Nitrogen containing base

(there are four types: Adenine, Thymine, Guanine and Cytosine). The molecule is

comprised of two long chains of nucleotides which join by hydrogen bonds between the

N-bases which twists the molecule into its distinctive double helix shape.

DNA contains the codes for all the proteins made by a cell. These proteins are

responsible for movement, structure, biochemical reactions, transport, poisons,

immunoglobins, neurotransmitters, hormones and cell surface receptors.

RNA is used to transmit the information contained in the DNA and construct the proteins

coded for by DNA. RNA is different to DNA by containing one strand of nucleotides,

having one less oxygen atom in the ribose sugar and the base Uracil replaces Thymine.

Protein Synthesis

Transcription is the process by which the DNA strands are unzipped, either for the full

length of the strand, or just for the segment coding for a protein and copied into mRNA.

1. RNA polymerase attaches to a region of DNA and unwinds the double

stranded DNA and exposes the bases of the template strand.

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Deoxyribonucleic Acid

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2. The base sequence of the DNA template guides the building of a

complementary copy of the mRNA sequence.

3. The result is a single-stranded molecule called pre-mRNA.

4. The introns are removed to produce mRNA

5. The final mRNA molecule is chemically capped and a poly-A tail added to

produce the operational mRNA.

Before the pre mRNA leaves the nucleus it undergoes a number of modifications to

become mRNA. A methylated cap (a modified guanine nucleotide that has a methyl and

phosphate group bonded to it) is added to the 5’ end as soon as the mRNA leaves the

DNA template.

The Introns are removed by RNA splicing. The introns are regions of base sequences

not translated into amino acid sequences (non-coding regions of DNA). Exons are the

coding regions that contain the information for protein formation.

Translation

The mRNA passes through the nuclear membrane into the cytoplasm and attaches to

sub-microscopic organelles known as ribosomes. Amino acids are brought to the

ribosome by tRNA which corresponds to the triplet code on the mRNA.

The Amino Acids are joined together at the ribosome to make a protein.

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Comparison of DNA and RNA

DNA RNASugar unit Deoxyribose OxyriboseNitrogen bases A, T, G, C A, U, G, CDouble/single stranded Double SingleLocation Nucleus Mostly Cytoplasm

The outcome of transcription and translation is a functional protein.

DNA complimentary strand ATG GTC GCC GGC AGA TGA (not copied)DNA template strand TAC CAG CGG CCG TCT ACT (copied)mRNA AUG GUC GCC GGC AGA UGAtRNA UAC CAG CGG CCG UCU ACUamino acid sequence Start, Val, Ala, Gly, Arg, Stop (a very short protein)

Genetic Code

The main features of the genetic code are:

Pieces of information in the genetic code consist of triplets or three-base

sequences.

The code is non-overlapping (bases are read three at a time).

The code is universal (same in all organisms, except a few protozoa and

bacteria).

The code is said to be redundant or degenerate since, more than one triplet of

bases codes for one particular amino acid.

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The information encoded in DNA are instructions to assemble amino acid sub-

units into proteins

The information is unambiguous (one codon codes for only one amino acid)

The information also includes a START instruction and a STOP instruction

The proteome

The proteome is a term used to describe the complete set of proteins produced by a

particular cell.

Almost everything that occurs in the cell relies on proteins. Proteins consist of large

complex molecules made by combining the 20 different amino acids in different

sequences. This occurs at the ribosomes under instruction from information held in the

DNA of the nucleus. Proteins are used for movement of cells and organisms, to provide

structure, strength and protection, act as enzymes to catalyse reactions, carry molecules

from one location to another and across membranes, as hormones to stimulate or inhibit

cell processes, label cells as self, neurotransmitters, immunoglobins, and poisons or

toxins to defend the organism against predators or pathogens.

Plants are able to make their own amino acids, but animals must consume amino acids

from other organisms.

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Protein

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Cell organelles

Plasma membrane

The plasma membrane or cellular membrane is made up of two layers of

phospholipids. Each molecule has a hydrophilic head facing outward and a

hydrophobic tail facing into the centre of the membrane. It can be described as partially,

selectively or differentially permeable as it allows some molecules to cross by diffusion

and bars the passage of other molecules.

Small hydrophobic molecules such as oxygen, carbon dioxide and nitrogen pass through

as do small uncharged polar molecules such as water, ethanol and glycerol. Various

ions and larger uncharged polar molecules such as amino acids, nucleotides and

glucose are able to cross the membrane via channels in the membrane with the

assistance of transport proteins.

Osmosis/Diffusion

Diffusion is the movement of molecules of a substance from an area of high

concentration of that substance to an area of low concentration. This is easily achieved

by gases not contained within a vessel and for solids such as salts and sugars dissolved

in water. In organisms this takes place across partially permeable membranes.

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Osmosis refers to the movement of water molecules. They will move from an area of

low concentration of a dissolved substance such as sugar to an area of high

concentration of that dissolved substance. This is important to organisms for the

movement of water and other substances into and out of cells. There are three

conditions to consider.

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Isotonic. The surrounding

fluid and the cellular fluid are

of equal concentration.

Molecules will move in both

directions, but there will be

no change in concentration

either side of the cellular

membrane.

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Facilitated Diffusion

Some molecules required by a cell are either to large to move by diffusion across the

membrane or the cell already has a high concentration of the substance but requires

more and must move it against the concentration gradient.

Carrier proteins – some proteins have a specific site to which certain other molecules

can bind. These then cross the membrane taking the molecule with them.

Channel proteins – there are pores in the membrane which are water filled and allow

certain hydrophilic substances to pass through.

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Hypotonic. When cells are

surrounded by a solution of lower

concentration to the cellular fluid

then water will diffuse into the cell.

This can be a problem as the cell

will swell and possible burst. Plant

cells have a cell wall that partially

protects the cell from this and plant

cells have mechanisms which

regulate and control the

concentration of cell fluids.

Hypertonic. If the cell is

surrounded by a solution with a

higher concentration than the

cellular fluid, then water will leave

the cell by diffusion. This can lead

to cells drying out. We say they

have become desiccated.

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This is referred to as Active Transport. It is thought that energy is provided to carrier

proteins to bring substances through the protein channels. Cells in which active transport

regularly takes place generally have many mitochondria.

Endoplasmic Reticulum (ER)

The rough ER (ER associated with ribosomes) is responsible for the production of

membrane proteins and proteins to be secreted from the cell. Smooth ER are

responsible for the production of phospholipids and cholesterol.

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Nucleus

Is the one of the most easily viewed

structures in eukaryotic cells. It contains the

information that controls the production of

proteins by the cell – DNA.

Ribosomes

Ribosomes are extremely small molecules that

can be found attached to the Endoplasmic

Reticulum or free floating in the cytosol. There are

lots of them as they have a very important role to

play translating the code from the DNA into

proteins.

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Vesicles

Vesicles are membrane bound organelles that are associated with transport of

biomolecules within the cell. Lysosomes are a special class of vesicles that contain

digestive enzymes which break down all the major classes of biomacromolecules. They

help the cell by recycling materials and removing potentially hazardous wastes.

The nature of biochemical processes

Enzymes as organic catalysts

Enzymes are a protein based molecule, created by the organism, that act as catalysts in

chemical processes within cells and the organism generally. Enzymes have an active

site which binds with one specific substrate or family of molecules. Enzymes work within

given ranges of temperature and pH. Below that temperature the enzyme can’t work or

works slowly, but if the enzyme is held at a temperature above that normal range then

the active site can be damaged and the enzyme can no longer do its work – it is said to

be denatured. Enzymes are also denatured when the enzyme is exposed to pH values

either side of the enzymes normal range.

In animals, enzymes have a specific task to perform. They are generally produced in

endocrine glands and secreted into the blood or lymph systems where they make there

way to the target cell. In this way they are specific, slow to act but usually have a

prolonged effect. In plants, cells are responsible for production of enzymes. These

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Golgi Apparatus

Once the cell has produced protein and

lipid molecules they have to be

packaged and delivered elsewhere. The

Golgi Apparatus (also described as a

Golgi body or Golgi complex) is

responsible for packaging these

molecules and transporting them around

the cell or to the membrane.

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enzymes move slowly through the phloem or are excreted as gases. They are less

specific in their function and also have long lasting effects.

Energy requirements of cells

The term metabolism is used to describe the complete set of biochemical reactions that

take place in the organism.

Catabolic Reactions

These are reactions that break down complex molecules into simpler molecules. The

most important of these in a biochemical sense is cellular respiration.

C6H12O6 + 6O2 6CO2 + 6H20 + energy as 36 - 38 molecules of ATP

In Cellular Respiration glucose is used by almost all organisms as the primary source of

energy for cellular metabolism. To release the energy in glucose requires the cell to

break down the glucose into ATP and other by-products which include water and carbon

dioxide. This takes place in the cytosol and the mitochondria of cells.

The first step is called Glycolysis. This part takes place in the cytosol. The glucose is

broken done into 2 molecules of ATP, 2 molecules of NADH and 2 molecules of

pyruvate. If the process stopped here we would describe this as anaerobic respiration (in

the absence of oxygen) and poisonous by-products could build up and damage the cell.

However, if oxygen is present then a biochemical process known as Krebs cycle takes

place within the cristae (inner folded membrane) of the mitochondria. In Krebs cycle the

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2 pyruvate molecules are broken down to release 6 molecules of carbon dioxide, 2 units

of ATP, 6 molecules of NADH and 2 of FADH2. These enter the electron transport system and are broken down to release a further 32 – 34 molecules of ATP.

Anabolic Reactions

These are reactions that build up complex molecules from more simple molecules. The

most important of these in a biochemical sense is photosynthesis.

light energy

6CO2 + 12H2O C6H1206 + 6H20 + 6O2

chlorophyll

Photosynthesis (phs) takes place in specialised organelles known as chloroplasts,

which contain chlorophyll. The chloroplast consists of two main structures – the stroma

and thylakoid membranes consisting of flat, sac-like structures called grana where the

first stage of phs takes place - the light dependent stage.

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The light energy is absorbed by different pigments. The electrons within the molecule

become energised. This energy is used to split water into H+, electrons and oxygen gas

which is released as a by product. The electrons pass along a chain of molecules giving

off energy which is used to pump protons into the thylakoid space and results in the

production of ATP (adenosine triphosphate). ATP is used to make sugar molecules.

NADP is used to transport spent electrons and excess protons to the stroma for the

second stage of phs.

The light independent stage uses the ATP produced in the grana and the excess protons

and electrons carried by the NADP to combine with carbon dioxide to form a sugar

molecule. This process is described by the Calvin-Benson cycle. Carbon fixation

requires carbon dioxide to be attached to ribulose biphosphate, forming an unstable 6

Carbon compound. This splits to two 3 Carbon compounds. NADP donates H+ ions to

form 3 Carbon sugar phosphate molecules – some exit the cycle to be used by the plant

to form more complex carbohydrates and some remains in the cycle to make new

ribulose biphosphate.

Applications of molecular biology in medicine

In the past 20 or 30 years there have been major advances in the design of drugs and

the diagnosis of disease based on our developing understanding of the cell, its

processes and in particular the structure and function of proteins.

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Kidney dialysis was an early development based on this knowledge. Having learnt how

the kidney uses diffusion to remove wastes from the blood a machine was constructed to

mimic this function. The blood was removed from the patient, filtered through partially

permeable membranes to remove water, glucose, lipids, amino acids, oxygen, carbon

dioxide, and urea using diffusion and then the blood was returned to the patient with the

useful materials such as water, glucose, lipids, amino acids and oxygen added.

Since then we have been able to use our knowledge of the biochemistry of the body to

many wonderful procedures and develop drugs. Such as the development of Relenza.

Relenza is an Australian made drug which binds to a protein on the surface of the

influenza virus and prevents the virus from causing any harm. Similar research is being

conducted across the globe to try to find treatments for many diseases including Bird Flu

and HIV.

There are many examples of the use of our knowledge of the cell and its processes

which the examiners could use in your exam. It is important to not become distracted by

the example, but to look carefully at the information presented and use your knowledge

of these concepts to answer the questions asked.

Homework1. List 5 concepts from this section of the course and display these in your home

(bedroom, fridge door, toilet wall etc).

2. Create a poem about one of the important concepts that you are having difficulty understanding.

3. Create flash cards for all the glossary words for this section of the course.

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VCAA 2008

Question 1A process occurring at structure W in this plant cell would beA. packaging of molecules.B. aerobic respiration.C. protein synthesis.D. DNA replication.

Question 2In this plant cell, the light-dependent reactions of photosynthesis occur in structureA. N.B. M.C. Q.D. P.

Question 4The four main types of biomacromolecules in a cell areA. monomers, polymers, DNA and RNA.B. proteins, carbohydrates, DNA and RNA.C. nucleic acids, proteins, carbohydrates and lipids.D. monosaccharides, disaccharides, polysaccharides and proteins.

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Question 5The enzyme maltase catalyses the breakdown of maltose into glucose. Maltase was added to a tube containing a solution of maltose in water and incubated at 37°C. The amount of glucose produced was monitored over a period of time. No maltose remained at the end. The graph showing the change in glucose concentration in the tube is

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Question 6The following graph shows the relationship between light intensity and net oxygen uptake or output by a particular green plant.

At a light intensity of 10 unitsA. the rate of photosynthesis is zero.B. the rate of aerobic respiration is zero.C. oxygen produced by photosynthesis is equal to the oxygen used by aerobic respiration.D. oxygen produced by photosynthesis is equal to twice the oxygen used by aerobic respiration.

Question 7Glycogen isA. a polysaccharide found in animal cells.B. an energy-storing lipid molecule.C. a molecule in which plants store sugars.D. a polysaccharide found in plant cell walls.

Question 8Lipids characteristicallyA. are hydrophobic.B. catalyse reactions.C. have a low energy content.D. are information-storage molecules.

Question 12Insulin is a complex protein that is said to have a quaternary structure.This means that insulinA. cannot be denatured.B. lacks disulphide bridges.C. contains all the known amino acids.D. has more than one polypeptide chain.

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Question 15Facilitated diffusion is a form of cell transport thatA. moves oxygen and carbon dioxide across membranes.B. occurs against a concentration gradient.C. requires specific protein channels.D. uses energy supplied by ATP.

Question 18Sucrose (cane sugar) is a disaccharide used by plants as a transport molecule. Sucrose is formed in the following reaction

With reference to this process it can be stated thatA. glucose and fructose are polysaccharides.B. the production of sucrose is an endergonic reaction.C. sucrose is a reactant and glucose is a product of the reaction.D. a molecule of fructose contains more stored energy than a molecule of sucrose.

Question 19Activation energy in a biological reactionA. increases in the presence of an enzyme.B. increases with an increase in temperature.C. is the energy required to start the reaction.D. is involved in the formation of complex molecules only.

Question 20Materials are constantly exchanged between a cell and its surroundings. The ease with which a molecule passes through a plasma membrane can be represented by a permeability coefficient.The graph below shows the permeability coefficients for a range of molecules plotted against their solubility in oil (lipid).

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From the graph you can conclude thatA. water is more lipid-soluble than alcohol.B. a cell gets rid of urea more slowly than excess water.C. drugs like alcohol and codeine enter cells more slowly than ethylene glycol.D. ethylene glycol passes through the plasma membrane more easily than diethylurea.

Question 1The diagram below shows a cross section of part of the plasma membrane of a typical mammalian cell. The substances labelled X and Y are about to be transported across the membrane in the directions shown by the arrows ( ).

i. Structure AChemical compositionExplain how the chemical composition of structure A facilitates its role.ii. Structure BChemical compositionExplain how the chemical composition of structure B facilitates its role.1 + 1 = 2 marks

Question 2There are structural differences between molecules of DNA and RNA.a. Outline two of these differences by completing the following table.

b. Name one kind of RNA and state its function.Type of RNAFunction1 mark

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Proteins may be classified as fibrous or globular depending on their 3-dimensional shape.In fibrous proteins, the polypeptide chains are arranged in parallel to form long fibres or sheets. In globular proteins, the polypeptide chains are folded into compact spherical or globular shapes.c. Name the subunit of a polypeptide.1 markKeratin, found in fingernails and claws, is an example of a fibrous protein.d. Name another example of a fibrous protein and briefly outline its function.1 marke. Describe a distinctive property of a fibrous protein and explain how this property is due to the arrangementof its polypeptides.1 markTotal 6 marks

Question 3The following diagrams showGraph one The rate of photosynthesis in a green plant at different wavelengths of lightGraph two The estimated absorption of the different wavelengths of light by the different plantpigments

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a. Explain why the graph showing the rate of photosynthesis has approximately the same shape as the absorption graphs of the plant pigments.1 mark

The following diagram shows a simplified representation of the first stage of photosynthesis.

b. i. Name one input item that X could represent.ii. Name one output item that Y could represent.1 + 1 = 2 marksThe breakdown of glucose in aerobic respiration can be represented by the simplified equation

c. What is the energy yield per molecule of glucose as a result of aerobic respiration?1 markThe breakdown of glucose in aerobic respiration can also be represented as occurring in three particular stages as indicated below.

d. i. Within a cell, where does the electron transport stage of aerobic respiration occur?ii. Describe what happens during the electron transport stage. In your answer include the name ofproduct Z.1 + 2 = 3 marksTotal 7 marks

VCAA 2007

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Question 1A polysaccharide that can be made in some animal cells isA. starch.B. pectin.C. glycogen.D. cellulose.

Question 2Liposomes are found in the cytosol and are formed from a double layer of phospholipid molecules identical to those found in plasma membranes. Liposomes can also be manufactured and used to carry medicinal drugs into cells.Examine the following diagram.

It is reasonable to expect thatA. drug 1 is lipophilic.B. drug 2 is water soluble.C. the interior of the liposome is aqueous.D. liposome-based membranes have a rigid structure.Question 4A protein-based Þ bre could be constructed from repeated monomers ofA. C5H13N4COOHB. CH3(CH2)nCOOHC. Cx(H2O)yD. C6H5COClQuestion 7A student was asked to identify differences between the overall processes of photosynthesis and aerobic respirationin eukaryotic cells. The student prepared the table below to outline the differences.The only correct comparison listed by the student is

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Question 8During periods of strenuous exercise or prolonged fasting, glycogen stored in liver and muscle cells is depleted. All glucose in the blood and cells may be completely depleted as well. If this occurs, the compound that is next most accessible for use in glycolysis isA. lipid.B. DNA.C. starch.D. protein.

Question 9The following diagram represents a nucleotide with subunits X, Y and Z.

This nucleotide could be identified as a monomer of DNA but not RNA ifA. X is ribose.B. Z is thymine.C. Y is phosphate.D. Z paired with cytosine.Question 11A haemoglobin molecule is composed of four protein (globin) chains each attached to an iron-containing haem group. Two are identical alpha chains and two are identical beta chains. The following diagram is a stylised representation of a haemoglobin molecule.

A haemoglobin molecule would be classified as having aA. primary protein structure.B. secondary protein structure.C. tertiary protein structure.D. quaternary protein structure.

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Question 14Nitrosomonas europa is a species of bacteria that obtains its energy by oxidising ammonium ions to nitrite ions.

It is reasonable to argue thatA. the reaction is anaerobic.B. the reaction is endergonic.C. no heat is produced in this reaction.D. ATP is produced as a result of this reaction.Question 19Myosin is a protein consisting of six chains and is the main component of some muscle Þ laments.It would be reasonable to classify myosin as aA. contractile protein.B. hormonal protein.C. globular protein.D. storage protein.

Question 20Cell organelles and membranes that are involved in the transport of biomolecules from inside a cell to outside a cell includeA. ribosomes.B. microtubules.C. membranes that form vesicles during endocytosis.D. secretory vesicles that bud off from the Golgi complex.

Question 3Many living cells produce hydrogen peroxide as a by-product of some metabolic reactions. Hydrogen peroxide is a poisonous substance for these cells and is immediately decomposed into water and oxygen by an enzyme called catalase.The reaction is represented by the equation

a. Which is the substrate in this chemical reaction?1 markThe activity of catalase in humans was tested across a number of different temperatures and the results graphed. The results are shown below.

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Catalase is found in many plants, including carrots.

A student predicted that if a temperature graph was prepared for carrot catalase activity, the optimal temperature would be expected to be much lower than that shown by catalase from humans.b. Do you agree or disagree with the student’s prediction? Explain the reason for your choice.1 markc. Describe (or outline) an experiment you would carry out with pieces of carrot to test the accuracy of the student’s prediction. Hydrogen peroxide is available as a 3% in water solution.Explain fully what results would support or negate the student’s prediction.3 marksTotal 5 marksQuestion 4The bird’s-nest fern, Alocasia marcrorhizza, usually grows in deeply shaded rainforests and has dark green fronds. Sometimes it is found in open, sunny locations by roadsides where it tends to have lighter coloured fronds.Two bird’s-nest ferns, one from each of the two habitats described above, were examined. A sample of cells from a frond of each of the ferns was collected.

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These cells were examined under an electron microscope and a typical chloroplast from each habitat (deeply shaded rainforest and sunny location) was drawn. These drawings are shown below.

a. Which of the labelled parts, X, Y or Z, absorb light energy? Name the part.1 markb. Which drawing, A or B, shows a chloroplast from the rainforest habitat? Explain the reason for your choice in terms of the relationship between structure and function.2 marksc. Name the process by which the chemical reactants for the light-dependent reactions of photosynthesis enter a chloroplast.1 markChloroplasts contain large numbers of ribosomes.d. Explain the importance of the presence of these ribosomes.1 markIt is now widely accepted by biologists that chloroplasts and mitochondria were once independent prokaryotic organisms which came to live symbiotically inside larger eukaryotic cells. This idea is known as the endosymbiotic theory.e. Name one structural feature of chloroplasts or mitochondria and outline how it supports the endosymbiotic theory for the origin of these organelles.1 markThe simplified diagram below summarises the light-independent reactions (Calvin cycle) of photosynthesis.

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f. Name reactant Q.1 markYou will note that during the light-independent reactions many energy-carrier molecules of NADPH and ATP are used.g. What is the source of these energy carriers?1 markh. What is compound P?1 markTotal 9 marksQuestion 6During digestion, large molecules are broken down into their constituent monomers (subunits).a. Complete the table below.

b. Explain how a monosaccharide enters an epithelial cell.1 markc. For what purpose would a cell use a lipid monomer?1 markd. Part of the sequence of a DNA strand responsible for the production of an amino-acid chain is shown.Below it, write the complementary DNA base sequence.

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e. What does G in AGC stand for?1 markTotal 6 marks

Question 7Chromosomes are DNA structures in the nucleus of a cell. The ends of chromosomes are called telomeres

Some changes in the DNA of these telomeres can trigger the development of cancer.Scientists are working to detect these changes in telomeres at an early stage of their development.a. Outline one advantage of being able to detect early changes in telomere DNA.1 markOne normal sequence of DNA in a particular telomere was AATCGTCCAGGG. On examination of the telomeres of one patient this sequence was found to have changed to AACCGTCCTGGG. The doctor examined the relationship between a DNA sequence and amino acids that could be expected. He used the following table to obtain information.

b. Is the doctor likely to be concerned or not concerned about the change in the telomere DNA of this patient? Explain your answer.1 markc. Name one application of molecular biology in medicine that you have studied this year and outline the significance of its use. Name of applicationSignificance2 marksTotal 4 marks

VCAA 2006

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Question 1Starch is a polysaccharide. Other polysaccharides synthesised by organisms includeA. lactose.B. sucrose.C. glucose.D. glycogen.

Question 2Anabolic reactions, also called endergonic reactions, includeA. glycolysis.B. Kreb’s cycle.C. photosynthesis.D. protein digestion.

Question 3The protein chymotrypsin is derived from a parent molecule, chymotrypsinogen.Cell organelles that are essential for the production of chymotrypsinogen includeA. ribosomes.B. microtubules.C. cell membrane.D. Golgi apparatus.

Question 4Molecules found in an animal cell membrane includeA. chitin.B. cellulose.C. cholesterol.D. nucleotides.

Question 5The formula that represents a protein is compoundA. C18H32O2B. C58H114PNO8C. C600H1000O500D. C708H1130N180O224S4

Question 6The chloroplast is the organelle responsible for photosynthesis in eukaryotic cells.In chloroplastsA. the light independent reactions require water as the initial reactant.B. the light independent reactions occur in the inner membrane area.C. the final product of the light reaction is glucose.D. the light reactions occur in the grana.

Question 11There are 4 polypeptide chains in a human haemoglobin molecule. The monomers in a small section of each of the 4 chains is shown.chain 1 … leu-ser-pro-ala-asp-lys-thr-asn-val-lys ...

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chain 2 … leu-thr-pro-glu-glu-lys-ser-ala-val-thr …chain 3 … leu-ser-pro-ala-asp-lys-thr-asn-val-lys ...chain 4 … leu-thr-pro-glu-glu-lys-ser-ala-val-thr …Consider the sections of the chains shown.The information given suggests thatA. each of the chains is the result of the same DNA sequence.B. each total chain contains the same number of monomers.C. adjacent monomers are linked by a peptide bond.D. each monomer is specified by a nucleotide.

Question 13The following data represents a small section of a sequence of bases of a nucleic acid taken from an animal cell. … G C U C G U U …From this data it is reasonable to assume that the seven basesA. would lead to the production of a chain of seven amino acids.B. would be complementary to the sequence C G T G C T T.C. must contain the sugar ribose.D. would be from DNA.

Question 15Consider the following diagram that is a summary of an important biochemical process.

The product, X, in this biochemical process isA. ADP.B. a polymer.C. an amino acid.D. a monosaccharide.

Question 17The packaging and transport of biomolecules within a cell involves theirA. distribution through a series of microfilaments.B. transport by Golgi apparatus to the endoplasmic reticulum.C. movement from the ribosomes into the endoplasmic reticulum.D. transport from the plasma membrane into the cytosol by secretory vesicles.

Question 19Bacteria such as Thermus aquaticus live in hot springs where temperatures are around 90°C. The most likely reason that the bacteria are able to carry out their metabolic functions in this environment is that the bacteriaA. have enzymes with a high optimal temperature.B. can lower the temperature of the cellular environment.C. use compounds other than enzymes to catalyse reactions.D. have enzymes other than proteins that do not respond to changes in temperature.

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Question 18The following image shows a portion of an electron photomicrograph of a chloroplast.Light-dependent reactions occur in region P and the Calvin cycle reactions occur in region Q.Considering events that occur in a chloroplast during photosynthesis it is reasonable to claim that

A. oxygen is an input to reactions at P.B. carbon dioxide is an input to reactions at Q.C. chlorophyll is essential for reactions that occur at Q.D. ADP produced during the events at P is used by events at Q.

Question 20Phospholipids are built from lipids and phosphate. They are found in plasma membranes.The diagram that most closely resembles the arrangement of phospholipids in a plasma membrane is

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Question 42,4-dinitrophenol is a chemical that is toxic to mitochondria. When added to mitochondria this chemical allows electron transport to occur but prevents the phosphorylation of ADP to ATP. The chemical achieves this by breaking the essential link between electron transport and ATP synthesis. This toxin causes mitochondria to produce heat instead of ATP. The greater the amount of toxin added, the quicker is its action.a. If mitochondria are poisoned with 2,4-dinitrophenol by what process could a plant cell produce more ATP? 1 mark

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b. Where in the mitochondria does electron transport and ATP production occur? 1 mark

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A researcher wanted to study cellular respiration in insect cells. She cultured some muscle cells from the common field cricket, Teleogryllus oceanicus, then studied the effects of adding 2,4-dinitrophenol to these cells. An agricultural company may want to fund this research.c. Give one reason why an agricultural company might want to fund research on the effects of this toxin on field crickets. 1 mark

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The experiment is summarised in the table below. Temperature observations in each trial were made at equal time intervals.

d. In terms of energy production, why did the temperature go up in trial 1 and not in the control? 1 mark

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e. Explain why the temperature went down after the fifth observation in trial 1. 1 mark

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f. Trial 2 had twice the concentration of 2,4-dinitrophenol added. Complete the table by writing in temperatures in the spaces provided to predict the trend. 2 marks

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Another researcher suggested adding pyruvate to the cells to cancel out the effects of this toxin.g. Explain what effect adding pyruvate would have on cancelling out the effect of this toxin. 1 mark

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