VCE BIOLOGY UNIT 3VCE BIOLOGY UNIT 3EXAM REVISIONEXAM REVISION

Gary Simpson Gary Simpson

ContentsContents

• Area of Study 1 – Molecules of LifeArea of Study 1 – Molecules of Life

• Past Exam QuestionsPast Exam Questions

• Area of Study 2 – Detecting and RespondingArea of Study 2 – Detecting and Responding

• Past Exam QuestionsPast Exam Questions

• Don’t forget the Exam is on Tuesday 8 June from 9.00am to 10.45am..

Area of Study 1 – Molecules of Area of Study 1 – Molecules of LifeLifeThe chemical nature of the cellThe chemical nature of the cell• Biomacromolecules are the big molecules Biomacromolecules are the big molecules

involved in the biomechanical processes of involved in the biomechanical processes of organisms.organisms.

• Autotrophs – organisms able to synthesise Autotrophs – organisms able to synthesise their own organic macromolecules from their own organic macromolecules from inorganic molecules, either by photosynthesis inorganic molecules, either by photosynthesis or chemosynthesis.or chemosynthesis.

• Heterotrophs – organisms that must consume Heterotrophs – organisms that must consume other organisms to synthesise other organisms to synthesise macromoleculesmacromolecules

Structure and Function of Structure and Function of CarbohydratesCarbohydrates

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

The structure and function of The structure and function of lipidslipids

• Lipids are a diverse Lipids are a diverse group of molecules group of molecules which include fats, which include fats, oils and steroids. oils and steroids. Used for energy Used for energy storage, cell storage, cell membranes and membranes and transmission of transmission of chemical signals.chemical signals.

Structure and function of DNA Structure and function of DNA and RNAand RNA• DNA is a large protein DNA is a large protein

found in the nucleus of found in the nucleus of eukaryotic cells and the eukaryotic cells and the cytoplasm of prokaryotic cytoplasm of prokaryotic cells. DNA contains the cells. DNA contains the codes for all the proteins codes for all the proteins made by a cell.made by a cell.

• RNA is used to transmit RNA is used to transmit the information the information contained in the DNA and contained in the DNA and construct the proteins construct the proteins coded for by the DNAcoded for by the DNA

Protein SynthesisProtein Synthesis

• Transcription – occurs in the nucleus. Section of DNA unzipped and Transcription – occurs in the nucleus. Section of DNA unzipped and copied onto mRNAcopied onto mRNA

• Translation – mRNA moves to the ribosome. tRNA bring amino Translation – mRNA moves to the ribosome. tRNA bring amino acids to the ribosome based on sequence of nucleotides (read as a acids to the ribosome based on sequence of nucleotides (read as a triplet)triplet)

• Proteins are formed by the amino acids joining together into a Proteins are formed by the amino acids joining together into a chain.chain.

Genetic CodeGenetic Code• Pieces of information in the code based on triplets of nucleotidesPieces of information in the code based on triplets of nucleotides• Code is non-overlappingCode is non-overlapping• Code is universalCode is universal• Code is said to be redundant or degenerate as more than one Code is said to be redundant or degenerate as more than one

triplet can code for the same amino acidtriplet can code for the same amino acid• Code contains instructions to assemble amino acids sub-unitsCode contains instructions to assemble amino acids sub-units• Information is unambiguousInformation is unambiguous• Always includes a START and a STOP instructionAlways includes a START and a STOP instruction

The proteomeThe proteome

• The proteome is a term used to The proteome is a term used to describe the complete set of proteins describe the complete set of proteins produced by a particular cell.produced by a particular cell.

• Almost everything that occurs in the Almost everything that occurs in the cell relies on proteins. cell relies on proteins.

• All the proteins are made from All the proteins are made from combinations of just 20 amino acids.combinations of just 20 amino acids.

Cell OrganellesCell Organelles

• Plasma MembranePlasma Membrane

• The plasma The plasma membrane or cellular membrane or cellular membrane is made membrane is made up of two layers of up of two layers of phospholipids. phospholipids.

• They control what They control what leaves and enters leaves and enters the cell.the cell.

Movement of MoleculesMovement of Molecules• Diffusion/OsmosisDiffusion/Osmosis

• Diffusion is the movement of molecules of a Diffusion is the movement of molecules of a substance from an area of high concentration substance from an area of high concentration of that substance to an area of low of that substance to an area of low concentration.concentration.

• Osmosis is the movement of water from an Osmosis is the movement of water from an area of low concentration of a dissolved area of low concentration of a dissolved substance to an area of high concentration of substance to an area of high concentration of that dissolved substance.that dissolved substance.

Movement of MoleculesMovement of Molecules

• IsotonicIsotonic

• HypotonicHypotonic

• HypertonicHypertonic

Movement of MoleculesMovement of Molecules

• Facilitated DiffusionFacilitated Diffusion

• Some molecules required by the cell are Some molecules required by the cell are either too large to move by diffusion or the either too large to move by diffusion or the cell already has a high concentration of the cell already has a high concentration of the molecule, so diffusion won’t take place.molecule, so diffusion won’t take place.

• Energy is required to move these Energy is required to move these molecules across the membrane using molecules across the membrane using either carrier proteins or channel proteins – either carrier proteins or channel proteins – this is known as active transport.this is known as active transport.

Cell OrganellesCell Organelles

• NucleusNucleus

• The nucleus The nucleus contains the DNA contains the DNA which contains the which contains the information that information that controls the controls the production of production of proteins by the proteins by the cell.cell.

Cell OrganellesCell Organelles

• RibosomesRibosomes

• Ribosomes are extremely small Ribosomes are extremely small molecules that play an important role molecules that play an important role in translating the code from the DNA in translating the code from the DNA into proteins.into proteins.

Cell OrganellesCell Organelles

• Golgi ApparatusGolgi Apparatus

• The Golgi Apparatus The Golgi Apparatus is responsible for is responsible for packaging these packaging these molecules and molecules and transporting them transporting them around the cell or to around the cell or to the membrane.the membrane.

Cell OrganellesCell Organelles• Endoplasmic ReticulumEndoplasmic Reticulum• Rough ER (with ribosomes Rough ER (with ribosomes

attached) is responsible for attached) is responsible for production of membrane proteins production of membrane proteins and proteins secreted from the cell. and proteins secreted from the cell.

• Smooth ER are responsible for the Smooth ER are responsible for the production of phosopholipids and production of phosopholipids and cholesterol.cholesterol.

Cell OrganellesCell Organelles

• VesiclesVesicles

• These are membrane bound These are membrane bound organelles that are associated with organelles that are associated with the transport of biomolecules within the transport of biomolecules within the cell.the cell.

EnzymesEnzymes

• Enzymes are protein based molecules that Enzymes are protein based molecules that act as catalysts in chemical processes within act as catalysts in chemical processes within cells.cells.

• They operate best within given ranges of They operate best within given ranges of temperature and pH.temperature and pH.

• Outside those preferred ranges the enzyme Outside those preferred ranges the enzyme either stops working or becomes denatured – either stops working or becomes denatured – the active site is changed and no longer the active site is changed and no longer matches the substrate that the enzyme works matches the substrate that the enzyme works upon.upon.

MetabolismMetabolismCatabolic ReactionsCatabolic Reactions• These reactions break down complex These reactions break down complex

molecules into simpler molecules.molecules into simpler molecules.• Cellular Respiration is the most important Cellular Respiration is the most important

of these, breaking down glucose to release of these, breaking down glucose to release energy.energy.

• This occurs first in the cytosol and then is This occurs first in the cytosol and then is finished within the mitochondria.finished within the mitochondria.

MetabolismMetabolismAnabolic ReactionsAnabolic Reactions• These reactions build up complex These reactions build up complex

molecules from more simple molecules.molecules from more simple molecules.• Photosynthesis is the most important of Photosynthesis is the most important of

these making glucose to store energy from these making glucose to store energy from carbon dioxide and water.carbon dioxide and water.

• This occurs in the chloroplasts of green This occurs in the chloroplasts of green plants.plants.

Applications of Molecular Applications of Molecular BiologyBiology

• There are many applications of There are many applications of molecular biology.molecular biology.

• Difficult to study for – rather you need Difficult to study for – rather you need to be prepared to analyse situations to to be prepared to analyse situations to explain how the molecular biology is explain how the molecular biology is being used in a particular application.being used in a particular application.

• No useful questions for this in past No useful questions for this in past papers.papers.

Area of Study 2 – Detecting and Area of Study 2 – Detecting and RespondingResponding Signal TransductionSignal Transduction• Organisms need to be able to detect and respond to Organisms need to be able to detect and respond to

changes in the external and internal environment.changes in the external and internal environment.• There are five principles to communication:There are five principles to communication:

– a signal is produced (by production of a signalling molecule in a signal is produced (by production of a signalling molecule in a cell)a cell)

– the signal is detected (by a receptor protein on the target cell)the signal is detected (by a receptor protein on the target cell)– the signal is transferred until it reaches its target – the signal is transferred until it reaches its target –

transduction (through the cell)transduction (through the cell)– a response is made to the signal (the cell responds to the a response is made to the signal (the cell responds to the

signal)signal)– the signal is switched off after the response is made (the the signal is switched off after the response is made (the

signalling cell switches off production of the signalling signalling cell switches off production of the signalling molecule).molecule).

• These principles can be applied to external signals These principles can be applied to external signals and to internal signals of the organism and the cells.and to internal signals of the organism and the cells.

Coordination and RegulationCoordination and Regulation

• Organisms need to be able to detect and Organisms need to be able to detect and respond to changes in their external and respond to changes in their external and internal environment.internal environment.

• Receive external information with Receive external information with chemoreceptors, mechanoreceptors, chemoreceptors, mechanoreceptors, photoreceptors, thermoreceptors and pain photoreceptors, thermoreceptors and pain receptors (collectively known as receptors (collectively known as exteroreceptors).exteroreceptors).

• Receive internal information from Receive internal information from interoceptors which measure changes in interoceptors which measure changes in temperature, water content, blood sugar temperature, water content, blood sugar etc throughout the body.etc throughout the body.

HomeostasisHomeostasisThe abilityThe ability of an organism to maintain a of an organism to maintain a relatively stable internal environment.relatively stable internal environment.• Stimulus-response model. A stimulus is Stimulus-response model. A stimulus is

received by a receptor which passes the received by a receptor which passes the information to a central processing unit information to a central processing unit which analyses the information and send a which analyses the information and send a message to an effector which causes a message to an effector which causes a response.response.

• Negative feedback. The response to the Negative feedback. The response to the stimulus is the opposite to the stimulus.stimulus is the opposite to the stimulus.

• Positive feedback. The response to the Positive feedback. The response to the stimulus is in the same direction as the stimulus is in the same direction as the stimulus, reinforcing the stimulus. stimulus, reinforcing the stimulus.

Nervous SystemNervous SystemThis comprises two parts – the central This comprises two parts – the central nervous system and the peripheral nervous nervous system and the peripheral nervous system. This is a system of nerves found system. This is a system of nerves found throughout the body.throughout the body.The response to a stimulus is quick, but the The response to a stimulus is quick, but the effect is generally short lived.effect is generally short lived.

Endocrine SystemsEndocrine Systems

Both plants and animals use chemical messengers, called hormones, to respond to changes within the internal environment. The response time is slow as the hormone needs to move through the blood system or along phloem, but the response is felt for a long period of time.

Cellular CommunicationCellular Communication

• Cells need to communicate within Cells need to communicate within the cytosol to control cellular the cytosol to control cellular processes eg. The reading of DNA processes eg. The reading of DNA sequences to create proteinssequences to create proteins

• Cells communicate with each other Cells communicate with each other to regulate growth and development to regulate growth and development and responses to external stimuli eg. and responses to external stimuli eg. The presence of pathogensThe presence of pathogens

Plant HormonesPlant Hormones

• Plant hormones regulate growth, Plant hormones regulate growth, development and reproduction and development and reproduction and respond to changes in the external and respond to changes in the external and internal environment of the organism.internal environment of the organism.

• AuxinsAuxins• CytokininsCytokinins• GibberellinsGibberellins• Abscisic AcidAbscisic Acid• EthyleneEthylene

Detecting Self and Non-self Detecting Self and Non-self MoleculesMolecules

Disease is defined as any change that Disease is defined as any change that impairs the function of an individual. impairs the function of an individual. Infectious disease is caused by Infectious disease is caused by organisms known as pathogens.organisms known as pathogens.

• BacteriaBacteria

• VirusVirus

• ViroidViroid

• PrionPrion

• Eukaryotic organismsEukaryotic organisms

Lymphatic systemLymphatic system

• The lymphatic system The lymphatic system consists of the bone consists of the bone marrow, thymus gland, marrow, thymus gland, lymph nodes, mucous lymph nodes, mucous tissues, spleen and tissues, spleen and many vessels which many vessels which transports lymphocytes transports lymphocytes and removes foreign and removes foreign material from the body.material from the body.

Non-specific immunityNon-specific immunity

• The immune system recognises foreign The immune system recognises foreign material from body tissues by recognising material from body tissues by recognising proteins embedded in the cell membrane.proteins embedded in the cell membrane.

• The first line of defence is the bodies The first line of defence is the bodies surfaces – skin, digestive system, respiratory, surfaces – skin, digestive system, respiratory, urinary and reproductive system.urinary and reproductive system.

• The second line of defence is the phagocytes The second line of defence is the phagocytes – these white blood cells simply engulf all – these white blood cells simply engulf all objects that do not have self markers.objects that do not have self markers.

Specific immunitySpecific immunity• If a pathogen gets past the first two If a pathogen gets past the first two

lines of defence then two things lines of defence then two things may occur.may occur.

Humoral responseHumoral response• B lymphocytes recognise the B lymphocytes recognise the

pathogen as non-self and releases pathogen as non-self and releases antibodies to bind with the active antibodies to bind with the active sites on the pathogens.sites on the pathogens.

Cell-mediated responseCell-mediated response• T lymphocytes do not produce T lymphocytes do not produce

antibodies, rather they either antibodies, rather they either recognise antigens and stimulate B recognise antigens and stimulate B cells or kill body cells infected with cells or kill body cells infected with viruses.viruses.

Disorders of the immune Disorders of the immune systemsystem• Allergies tend to be exaggerated responses Allergies tend to be exaggerated responses

of the immune system to relatively harmless of the immune system to relatively harmless substances. An allergic response sees the substances. An allergic response sees the Mast cells and Basophil cells releasing Mast cells and Basophil cells releasing histamines causing swelling and histamines causing swelling and inflammation.inflammation.

• Auto-immune diseases such as multiple Auto-immune diseases such as multiple sclerosis occur when the immune system sclerosis occur when the immune system does not recognise self cells and starts to does not recognise self cells and starts to attack and destroy them.attack and destroy them.

Acquired ImmunityAcquired Immunity

• Organisms gain immunity to disease by Organisms gain immunity to disease by learning to recognise the antigens of learning to recognise the antigens of pathogens. Humans have learnt to mimic pathogens. Humans have learnt to mimic this response by using dead or attenuated this response by using dead or attenuated organisms.organisms.

• It is also possible to gain immunity by It is also possible to gain immunity by giving a person another’s antibodies. This giving a person another’s antibodies. This occurs when nursing mothers feed their occurs when nursing mothers feed their babies.babies.

Barriers to infection in Barriers to infection in plantsplants• Physical – the thick bark of stems and Physical – the thick bark of stems and

trunks, and hairs and thick waxy cuticle trunks, and hairs and thick waxy cuticle on the leaves prevents infection.on the leaves prevents infection.

• Chemical – wounds are filled with resin, Chemical – wounds are filled with resin, infected leaves and branches are shed infected leaves and branches are shed and enzymes and antibiotics are and enzymes and antibiotics are secreted to destroy or deter secreted to destroy or deter pathogens.pathogens.