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AQA AS & A-Level Biology (Year 1) Section 1: What are biological molecules? molecules made and used by living organisms e.g. Carbohydrates, Proteins, Lipids, DNA, ATP, Water, Inorganic Ions What are the functions of carbohydrates? energy source (glucose in respiration) energy store (starch in plants, glycogen in animals) structure (cellulose in cell wall of plants) What are the building blocks for carbohydrates called? monosaccharides Example of monosaccharides? glucose (alpha and beta), galactose, fructose Formula for monosaccharides? C 6 H 12 O 6 (isomers = same formula but different arrangement) Difference between alpha and beta glucose? on Carbon 1, alpha glucose has a OH group on the bottom and beta glucose has a OH group on the top How are monosaccharides joined together? condensation reaction (removing water) – between 2 OH groups Bond in carbohydrate? glycosidic bond Example of disaccharides? glucose + glucose = maltose, glucose + galactose = lactose, glucose + fructose = sucrose Formula for disaccharides? C 12 H 22 O 11 How are polymers separated? hydrolysis (add water) What is a polysaccharide? many monosacharrides joined by condensation reaction/glycosidic bonds Example of polysaccharides? Amylose (long chain of alpha glucose) which makes starch/glycogen Cellulose (long chain of beta glucose) which makes cell wall in plants What are Polysaccharides? carbohydrates made of a long chain of monosaccharides joined by condensation reaction/glycosidic bonds 3 examples: Starch, Glycogen, Cellulose Starch & Glycogen used as Energy Stores (starch in plants, glycogen in animals), they are made out of many alpha glucose which are used for respiration Cellulose used to form Cell Wall in Plants, made out of many beta glucose Properties of Starch and Glycogen as energy stores? Insoluble = do not affect water potential of the cell, do not diffuse out of the cell Coiled/Branched = compact, more can fit into a cell Branched/Chained = glucose removed from the end Structure of Cellulose? β-glucose arranged in a straight chain (each alternative β-glucose is rotated 180 degrees) = cellulose straight
chain many cellulose chains are cross linked by hydrogen bonds to form microfibrils many microfibrils are cross linked to form marcrofibrils forms structure of cell wall strong material (prevents plant cell from bursting or shrinking) Test for starch? add iodine, turns blue/black Test for reducing sugar? heat with benedicts, turns brick red Test for non-reducing sugar? heat with benedicts – no change therefore, add dilute hydrochloric acid (hydrolyses glycosidic bond) then add sodium hydrogencarbonate (neutralises solution) heat with benedict - turns brick red What are 2 types of proteins? Globular and Fibrous What are globular proteins? soluble proteins with a specific 3D shape e.g. enzymes, hormones, antibodies, haemoglobin What are fibrous proteins? strong/insoluble/inflexible material e.g. collagen and keratin What are the building blocks for proteins? amino acids Structure of amino acid? central carbon, carboxyl group to the right (COOH), amine group to the left (NH2), hydrogen above and R group below How do amino acids differ? have different R groups e.g. glycine has a hydrogen in its R group – simplest amino acid How are amino acids joined together? by condensation reaction between the carboxyl group of one and amine group of another, leaves a bond between carbon & nitrogen (called a peptide bond) forming a dipeptide Define primary, secondary, tertiary, quaternary structure? Primary = sequence of AA, polypeptide chain (held by peptide bonds) Secondary = the primary structure (polypeptide chain) coils to form a helix, held by hydrogen bonds Tertiary = secondary structure folds again to form final 3d shape, held together by hydrogen/ionic/disulfide bonds Quaternary = made of more then one polypeptide chain Examples of quaternary structure proteins? collagen (3 chains), antibodies (3 chains), haemoglobin (4 chains) Structure of collagen? strong material, used to build tendons/ligaments/connective tissues primary structure mainly made up of glycine (simplest amino acid) secondary structure forms a tight coil (not much branching due to glycine) tertiary structure coils again quaternary structure made from 3 tertiary structures wrapped around each other like rope = a collagen molecule
Structure of triglyceride? made of 1 glycerol and 3 fatty acids joined by condensation reaction, ester bonds bond is COOC there are 2 types of triglycerides: saturated fat and unsaturated fat Saturated vs Unsaturated Fat? Saturated = has no carbon double bonds in the R group of the fatty acid Unsaturated = has carbon double bonds in the R group of the fatty acid Structure of phospholipid? made of 1 glycerol, 2 fatty acids and 1 phosphate phosphate forms a hydrophillic head, fatty acids form hydrophobic tails forms a phospholipid bilayer, basic structure of membranes What are Nucleic Acids? Polymers made from Nucleotides (2 types = DNA and RNA) What is DNA? DeoxyriboNucleic Acid found in all organisms (animals, plants, microorganisms) carries genes genes = section of DNA that codes for a protein all organisms are built of proteins Building block of DNA? DNA nucleotide (made of phosphate, deoxyribose sugar, nitrogenous base) 4 types of nucleotides (each has a different base, either Adenine/Thymine/Cytosine/Guanine) DNA structure? DNA Double Helix join nucleotides by condensation reaction between sugar and phosphate to form a polynucleotide join 2 polynucleotides by hydrogen bond between the bases A joins with T, C joins with G (complementary base pairing) produces double strand then coil double strand into Double Helix Properties of DNA Structure? Double Stranded = makes DNA more stable & 2 strands act as templates in semi-conservative replication Coil into Helix = more compact Sugar-phosphate backbone = protects bases (bases code for protein) Hydrogen bonds between bases = weak, so double strand separates more easily for semi-conservative replication Complementary Base Pairing = ensures identical copies of DNA made by semi-conservative replication DNA Replication? occurs in interphase before mitosis & meiosis occurs by semi-conservative replication Describe Semi-Conservative Replication?
DNA double strand separate and act as templates, producing 2 identical copies of the DNA, each has half the original strand and half the new strand process: DNA Helicase breaks hydrogen bonds between the complementary bases double strand separates, leaves 2 template stands free complementary nucleotides bind to exposed bases on template strands (A to T, C to G) DNA Polymerase joins the sugar-phosphate backbone of the new strand Evidence for SCR? Replicating Bacterial DNA in 2 types of Nitrogen Isotopes, 15N and 14N 15N = heavy isotope 14N = light isotope Nitrogen found in nitrogenous bases of DNA Bacterial DNA made from 15N will have a Heavy Density Bacterial DNA made from 14N will have a Light Density Experiment = Bacterial DNA made of 15N is replicated in an environment of 14N – produces DNA molecules with half 15/half 14 (semi-conservative replication, original strand = 15N & new strand = 14N), therefore, DNA molecule has medium density What is RNA? RiboNucleic Acid 2 types (mRNA and tRNA) mRNA = messenger RNA tRNA = transfer RNA both single stranded both made of RNA Nucleotides (phosphate, ribose sugar, nitrogenous bases - AUCG) What is ATP? Adenosine Triphosphate (Energy Carrier Molecule – delivers energy for life processes) Structure of ATP? Adenosine Triphosphate made from 1 adenosine and 3 phosphates formation: ADP + Pi (+ energy used) = ATP condensation reaction using ATP Synthase carries energy in its bonds breakdown: ATP = ADP + Pi (+ energy released) hydrolysis reaction using ATP Hydrolase releases energy from its bonds What makes ATP a good deliverer of energy? immediate source = need to only break one bond (plus bond is weak) manageable source = releases small amount of energy Uses of ATP (releases energy) in organisms? protein synthesis organelle synthesis DNA replication cell division (mitosis) active transport metabolic reactions movement maintaining body temperature
Sexual Reproduction in Animals & Some Plants Asexual Reproduction in Microorganisms & Some Plants Sexual Reproduction uses 2 parents (each provides a gamete which fuse to form a zygote, zygote develops into organism) Asexual Reproduction uses 1 parent to produce genetically identical offspring How does a Zygote develop into an Organism? Zygote is a stem cell stem cell = undifferentiated/unspecialised cell, can form any type of cell zygote divides by mitosis to make many stem cells each stem cell differentiates into specialised cell each specialised cell divides by mitosis to make many copies and form a tissue different tissues join to form an organ different organs join to form an organ system this is surrounded by the Body Define a tissue, organ and organ system? tissue = a group of specialised cells organ = made of different tissues organ system = different organs working together What is an Animal Cell made of? Organelles (nucleus, endoplasmic reticulum, golgi body, lysosomes, mitochondria, ribosomes) – all have membrane except the ribosomes Cytoplasm (site of chemical reaction) Cell Membrane (holds cell contents together, controls what enters/leaves cell, cell signalling) Structure of Nucleus? contains DNA (made of genes, genes code for making proteins) DNA wrapped around histones to form Chromatin nucleus has a double membrane, called Nuclear Envelope, which contains pores at centre of nucleus is Nucleolus – produces mRNA (copy of a gene) rest of nucleus made of Nucleoplasm (contains the DNA/chromatin) Endoplasmic Reticulum? 2 types = Rough and Smooth Rough Endoplasmic Reticulum has ribosomes on it, makes proteins Smooth Endoplasmic Reticulum has no ribosomes on it, makes lipids/carbohydrates Golgi body? modifies and packages proteins packages them into vesicles for transport digestive enzymes are placed into lysosomes (vesicles with membranes around them) Mitochondria? site of respiration, releases energy, produces ATP (energy carrier molecule) has a double membrane, inner membrane folded into Cristae (increases surface area for enzymes of respiration) middle portion called Matrix Ribosomes? attached to RER site of protein synthesis
What is a Plant Cell made of? Organelles (nucleus, endoplasmic reticulum, golgi body, lysosomes, mitochondria, chloroplast, vacuole, ribosomes) – all have membrane except the ribosomes Cytoplasm (site of chemical reaction) Cell Membrane (holds cell contents together, controls what enters/leaves cell, cell signalling) Cell Wall (made of cellulose, prevents cell from bursting or shrinking) Structure of chloroplast? organelle for photosynthesis has double membrane contains discs called thylakoids thylakoids contain chlorophyll stack of thylakoids called granum thylakoids surrounded by a fluid called stroma Vacuole? Surrounded by a membrane called a tonoplast, contains Cell Sap (water, sugar, minerals) What is Bacteria made of? No nucleus – loose DNA in the form of a single loop and plasmid No membrane bound organelles: smaller ribosomes, mesosomes – infolding of cell membrane for respiration Cytoplasm Cell Membrane & Cell Wall (made of peptidoglycan/murein) some have a Capsule (reduce water loss, protect from phagocytosis) and Flagella (movement) What is Virus made of? DNA or RNA (if RNA, also has a enzyme called reverse transcriptase to turn RNA into DNA) Protein Coat called Capsid and Lipid Coat Attachment proteins on outside (infects host cells by attaching using their attachment protein, send in their DNA which uses the cell to make the viruses components and uses the cell membrane to make the viruses lipid coat, hence, producing copies of the virus and destroying the host cell) What is a Chromosome? DNA in coiled form formed during interphase of cell division (mitosis/meiosis) in Animals/Plants made of 2 identical/sister chromatids joined by a centromere carries 2 copies of the same DNA molecule What is a homologous pair of chromosomes? a pair of chromosomes: 1 maternal (from mother)/1 paternal (from father) carries same genes but different alleles – there are 23 pairs in humans What is Cell Division? formation of new cells in multicellular organisms (animals & plants) 2 methods = mitosis & meiosis mitosis = produces genetically identical cells for growth & repair of tissues meiosis = produces genetically different haploid cells as gametes for sexual reproduction What does Mitosis (cell cycle) produce?
levels/depth Resolution? minimum distance at which 2 very close objects can be distinguished Which has higher resolution? TEM > SEM > LM Why does electron microscopes have a higher resolution? Electron microscope uses electrons which have a shorter wavelength (light microscope uses light which has a large wavelength) Difference between TEM and SEM? in Transmission the electrons pass through the specimen, in Scanning the electrons bounce off the specimen's surface Advantage and Disadvantage of TEM? Advantage = highest magnification and highest resolution Disadvantage = works in a vacuum so can only observe dead specimens, specimen needs to be thin, black and white image, 2D image, artefacts Advantage and Disadvantage of SEM? Advantage = produces 3D image Disadvantage = works in a vacuum so can only observe dead specimens, black and white image, artefacts Cell Fractionation? Breakdown tissue into cells (cut, pestle & mortar) add cold/isotonic/buffer solution ( cold = reduce enzyme activity, isotonic = same water potential so organelle does not shrink or burst, buffer = maintains constant pH ) homogenate – breaks open cells releasing organelles filter = removes large debris and intact cells centrifuge – spin at low speed, largest organelle builds at bottom (nucleus), leaves supernatant, spin at higher speed, next heaviest organelle forms at bottom (chloroplast or mitochondria) ( organelle by size: nucleus, chloroplast, mitochondria, endoplasmic reticulum/golgi body/lysosomes, ribosomes ) Simple vs Facilitated Diffusion? Simple = molecules move directly through the phospholipid bilayer Facilitated = molecules pass through transport proteins (large use carrier, charged use channel) Factors that affect rate of diffusion? surface area (increase = increase rate of diffusion) concentration gradient (increase = increase rate of diffusion) thickness (decrease = decrease diffusion distance = increase rate of diffusion) temperature (increase = increase kinetic energy = molecules move faster = increase rate of diffusion) size of molecules (smaller molecules = increase rate of diffusion) What is Ficks Law? (Surface Area x Concentration Gradient)/Thickness Define Osmosis? movement of water molecules from an area of high water potential to an area of low water potential through a partially permeable membrane Which liquid has the highest water potential? distilled/pure water has a value of 0kPa lower water potential by adding solutes (makes water potential negative)
water moves from less negative water potential (e.g. - 35 kPa) to more negative water potential (e.g. - 75 kPa) Surround animal cell with pure water? swells and burst (water enters by osmosis) Surround plant cell with pure water? swells but does not burst cell wall prevents it from bursting made of cellulose – strong material the cell is Turgid Surround animal cell with concentrated sugar/salt solution? shrinks (water leaves by osmosis) Surround plant cell with concentrated sugar/salt solution? water leaves by osmosis cell wall prevents cell from shrinking, keeps it rigid the protoplast (cell membrane plus contents) shrink the cell is Plasmolysed Define Active Transport? movement of molecules from an area of low concentration to an area of high concentration using ATP and carrier proteins (against concentration gradient) Describe the process of active transport? molecules (in area of low concentration) bind to carrier protein ATP breaksdown to ADP, Pi and Energy the Pi and Energy cause the carrier protein to change shape carrier protein releases molecules on opposite side (in area of high concentration) the carrier protein releases the attached Pi to return to its original shape Adaptations of SI? folded to form Villus (large surface area) cells lining SI have Microvilli (large surface area) wall of SI is thin (short diffusion distance) rich blood supply (maintains concentration gradient) cells lining SI have transport proteins and mitochondria Active Transport of Glucose in SI? sodium ions are actively transported from the cells lining the SI into the blood lowers the sodium ion concentration in the cell therefore sodium ions move from the lumen of the SI into the cell this pulls in glucose via a cotransport protein therefore glucose builds up in the cell and moves into the blood by diffusion What is a pathogen? a disease causing micro-organism e.g. bacteria, virus, fungi bacteria cause disease by producing toxins virus cause disease by dividing in cells causing them to burst Body's defence against pathogens? I, Barriers (prevents pathogens entering the body) II, Phagocytes (perform phagocytosis and stimulate specific response) III, Specific Response (uses lymphocytes to produce memory cells and antibodies)
How does activity immunity occur? naturally = by primary infection, artificially = by vaccination How does passive immunity occur? naturally = from mother to baby (placenta or breast milk), artificially = by injection Successful Vaccination Programme? produce suitable vaccine (effective – make memory cells, does not cause disease, no major side effects, low cost, easily produced/transported/stored/administered) herd immunity What is herd immunity? when a large proportion of the population is vaccinated, therefore most people will be immune, only a few will not be a immune, increases chance of non-immune person coming into contact with immune person, so the pathogen has no where to go, so it dies out Problems with Vaccination Programmes? vaccine does not work (dead form ineffective, pathogen hides from immune system) vaccine not safe (no weak/inactive form, causes major side effects) many strains of pathogen cannot achieve herd immunity (logistic of vaccinating large proportion) antigenic variability What is antigenic variability? the pathogen mutates, the antigen changes shape, so the memory cells no longer complementary – do not recognise the pathogen, therefore the pathogen can reharm What is a monoclonal antibody? one type of antibody, complementary to one type of antigen, made by one type of plasma cell What are monoclonal antibodies used for? identify specific antigens or antibodies in person's blood, or pregnancy tests How do monoclonal antibodies identify specific antigens in the blood? e.g. identify PSA antigen made by prostate cancer place monoclonal antibodies complementary to PSA antigen on test plate add person's blood to test plate if PSA antigen is present in the blood, it will bind to the monoclonal antibodies then a 2nd^ set of monoclonal antibodies with an enzyme attached is added if the PSA antigen is present, this 2nd^ set will bind to it if the PSA antigen is not present, this 2nd^ set will not bind the test plate is then washed if PSA antigen is present, 2nd^ set of monoclonal antibodies will attach, this will not be washed away, so the enzyme will be present if PSA antigen not present, 2nd^ set of monoclonal antibodies will not attach, this will be washed away, so enzyme also washed away a colourless substrate is then added, if the enzyme is present it will breakdown the substrate causing a colour change, if the enzyme is not present there will be no colour change therefore: colour change occurs = enzyme present/PSA antigen is present, no colour change = no enzyme present/no PSA antigen is present How do monoclonal antibodies identify specific antibodies in the blood? e.g. identify TB antibodies in the blood place antigen complementary to TB antibodies on test plate add person's blood to test plate if TB antibodies are present in blood, they will bind to the antigen then a set of monoclonal antibodies (with an enzyme attached) complementary to the TB antibodies are added
if the TB antibodies are present, the monoclonal antibodies will attach if the TB antibodies are not present, the monoclonal antibodies will not attach the test plate is then washed if the TB antibodies are present, the monoclonal antibodies will attach, this will not be washed away, so the enzyme will be present if the TB antibodies are not present, the monoclonal antibodies will not attach, this will be washed away, so the enzyme will be washed away a colourless substrate is then added, if the enzyme is present it will breakdown the substrate causing a colour change, if the enzyme is not present there will be no colour change therefore: colour change occurs = enzyme present/TB antibody is present, no colour change = no enzyme present/no TB antibody is present How are monoclonal antibodies used in pregnancy testing? Pregnant Women produce HCG Hormone in their Urine Test Strip has 3 parts to it (1st: start contains antibodies complementary to HCG, 2nd: middle contains antibodies complementary to HCG-Antibody complex, 3 rd: end contains antibodies complementary to HCG Antibodies) if woman is pregnant, HCG in the urine binds to antibodies on 1st^ part forming a HCG-Antibody complex, the HCG-Antibody complex then binds to antibodies on the 2nd^ part forming a blue line (positive result), HCG Antibodies also bind to 3rd^ part as a control if woman is not pregnant, no HCG in urine so nothing binds to HCG Antibodies in 1st^ part, so nothing binds to antibodies in 2nd^ part leaving no blue line (negative result), the HCG Antibodies still bind to 3rd part for the control What is HIV/AIDs? HIV = Human Immunodeficiency Virus AIDs = Acquired Immunodeficiency Syndrome HIV is the Pathogen, AIDs is the Infectious Disease HIV is spread by fluid to fluid contact (unprotected sexual intercourse, sharing needles, mother to child via placenta or breast feeding) HIV damages and destroys T Helper Cells, therefore person no longer produces Immune Response and has no defence to against pathogens/infections = AIDs With AIDs, individual at risk from all sorts of pathogens/infections called Opportunistic Infections Section 3: How do Microorganisms Obtain Nutrients & Remove Waste? by exchange via their surface nutrients (e.g. glucose, oxygen) move in by diffusion via their surface waste (e.g. carbon dioxide) move out by diffusion via their surface Why are Microorganisms able to perform exchange via their surface? have a large surface area to volume ratio have a short diffusion distance have low demand Why can't Animals/Plants perform exchange via their surface? have a small surface area to volume ratio multicellular (large diffusion distance and high demand) impermeable surface (prevent pathogens entering and reduce water loss) therefore, require specialised Exchange & Transport systems exchange system = increases rate of diffusion of nutrients in and wastes out
(occurs when surrounded by noxious gases – reduces amount reaching alveoli) lining made of goblet cells and ciliated epithelial cells Adaptation of alveoli? millions of tiny alveoli that are folded (large surface area) thin wall/one cell thick/squamous epithelial cells (short diffusion distance) elastic tissue in wall (stretches when breathing in to increase surface area, recoils when breathing out to push the air out) ventilation maintains concentration gradient (high oxygen, low carbon dioxide) Adaptation of capillaries? millions of tiny capillaries (large surface area) thin wall/one cell thick/squamous epithelial cells (short diffusion distance) narrow lumen (increases diffusion time, decreases diffusion distance) circulation maintains concentration gradient (low oxygen, high carbon dioxide) How O 2 moves from the alveoli to the capillaries? by simple diffusion passing thru the alveolar epithelium and capillary epithelium
How CO 2 moves from capillaries to the alveoli? by simple diffusion passing thru the
capillary epithelium and alveoli epithelium
Describe the process of Breathing/Ventilation? Breathing In/Inhalation = external intercostal muscles contract (rib cage moves up and out) & diaphragm contracts (flattens), therefore increase in volume in chest and decrease in pressure, so air moves in Breathing Out/Exhalation = external intercostal muscle relax (rib cage moves down and in) & diaphragm relaxes (back to dome shape), therefore decrease in volume in chest and increase in pressure, so air pushed out (aided by elastic recoil in the alveoli) Formula for Pulmonary Ventilation? PV = tidal volume x ventilation rate tidal volume = volume of air breathed in/out in one breath ventilation rate = number of breaths per minute Pulmonary Ventilation = volume of air breathed in/out per minute Function of Intestines? s ite of exchange of digested nutrients in mammals What is Digestion? Breakdown of Large Insoluble Molecules into Small Soluble Molecules (so they can move into the blood and then into the body cells) Starch/Glycogen (Carbohydrates) into Glucose by Amylase (Salivary in mouth, Pancreatic in small intestine) and Maltase/Lactase/Sucrase (on lining of small intestine) Proteins into Amino Acids by Endopeptidase/Exopeptidase/Dipeptidase (Endopeptidase in stomach, Exopeptidase in small intestine, Dipeptidase on lining of small intestine) Lipids into Monoglyceride and 2 Fatty Acids by Lipase (in small intestine) What do Intestine Absorb? Small Intestine absorbs small soluble nutrients (glucose, amino acids, monoglyceride and fatty acid, vitamins and minerals) Large Intestine absorbs water Why do Humans/Mammals require a Specialised Transport System? multicellular organisms therefore have large diffusion distances and high demand need a transport system to deliver nutrients and remove waste from all cells
transport system in humans/mammals called Circulatory System Circulatory System made of heart, blood vessels, blood (heart pumps blood, blood vessels carry blood, blood carries nutrients/waste) Why is the transport system in mammals called a double circulatory system? the heart pumps twice, the blood goes through the heart twice – generates enough pressure to supply all body cells Why is the transport system in mammals called a closed circulatory system? blood is transported in blood vessels – helps to maintain pressure and redirect blood flow Layout of Circulatory System? heart pumps blood which is carried in arteries which flow into arterioles which flow into capillaries which then are carried in venules then veins back to the heart Artery to Arterioles to Capillaries to Venules to Veins Artery/Arterioles carry blood away from the heart (arterioles are small arteries) Capillaries are the site of exchange (nutrients out, waste in) Veins/Venules return blood back to the heart (venules are small veins) Heart? job is to pump blood around the body (delivers nutrients to cells and remove waste) made of 4 muscular chambers (2 atria, 2 ventricles) atria pumps blood to ventricles, ventricles pump blood out of heart (R to lungs, L to body) ventricles thicker then atria (has to pump blood further) left ventricle has a thicker muscular wall then right ventricle, therefore has stronger contractions, so can generate higher pressure and pump the blood further around the body Blood vessels of the heart? artery takes blood away from the heart, vein returns blood to the heart Vena Cava supplies R atrium (with deoxygenated blood from body) Pulmonary Vein supplies L atrium (with oxygenated blood from lungs) R ventricle supplies Pulmonary Artery (deoxygenated blood to lungs) L ventricle supplies Aorta (oxygenated blood to body) Job of valves in heart? Ensure one way flow of blood, no backflow (blood flows from atria to ventricles to arteries) 2 sets of valves: Atrio-ventricular Valve & Semi-lunar Valve AV valve = between atria and ventricles SL valve = between ventricles and arteries When are AV valves open or closed? Open = pressure in atria greater then pressure in ventricles, Closed = pressure in ventricles greater then pressure in atria When are SL valves open or closed? Open = pressure in ventricles greater then pressure in arteries, Closed = pressure in arteries greater then pressure in ventricles Describe the processes of the cardiac cycle? Filling Stage = atria relaxed, ventricles relaxed, AV valve open, SL valve closed Atria Contracts = the SAN located in the R atrium initiates the heart beat and sends the impulse across
exception 2 = Hepatic Portal Vein carries deoxygenated blood from digestive system to liver (for filtering) Function of Arteries/Arterioles? carry blood away from the heart so should be able to withstand high blood pressures & maintain high blood pressures Structure of Arteries/Arterioles? narrow lumen = maintains pressure lining made of squamous epithelial cells = smooth lining to reduce friction thick wall = withstand pressure elastic tissue in wall, ventricles contract – elastic tissue stretches to withstand pressure ventricles relax – elastic tissue recoils to maintain pressure and smooth out flow smooth muscle in wall (particularly in arterioles), smooth muscle contracts – lumen narrows and arteriole constricts smooth muscle relaxes – lumen widens and arteriole dilates collagen in wall prevents artery from tearing Function of Veins/Venules? return blood back to the heart, the blood is under low pressure Structure of Veins/Venules? wide lumen = ease of blood flow lining made of squamous epithelial cells = smooth lining to reduce friction thin wall = vein can be squashed by skeletal muscle pushing blood back to the heart valves in lumen = prevents backflow of blood Function of Capillaries? site of exchange 3 locations, With Alveoli, takes in O 2 and removes CO 2 With Microvilli, takes in glucose/amino acids/monoglyceride and fatty acids/vitamins/minerals With All Cells, deliver nutrients and remove waste Adaptation of Capillaries? many small capillaries = large surface area thin wall, one cell thick, squamous epithelial cells = short diffusion distance pores between cells = allows fluid to move in and out narrow lumen = increase diffusion time and decrease diffusion distance Content of Blood? main component = Plasma (fluid) plasma carries, Cells = red blood cells, white blood cells, platelets Solutes = nutrients, waste, protein How does exchange occur between Capillaries & All Cells? by mass flow fluid moves out of the blood in the capillaries carrying the nutrients fluid moves back into blood in the capillaries carrying the waste (fluid in the blood called plasma, fluid surrounding cells called tissue fluid, fluid in lymph system called lymph)
How is tissue fluid formed and returned to circulatory system? at the start of the capillary (arterial end) there is a build up hydrostatic pressure this pushes fluid out of the capillary via the pores the fluid carries the nutrients with it the fluid surrounds the cells, this is called tissue fluid at the finish of the capillary (venous end) the fluid moves back in by osmosis the capillary has low water potential due to the presence of proteins (too large to move out of capillaries) any excess tissue fluid is picked up by the lymph system and deposited in the vena cava Why does high blood pressure cause accumulation of tissue fluid? increases hydrostatic pressure, so more tissue fluid is formed – not as much can be returned to the circulatory system Why does diet low in protein cause accumulation of tissue fluid? the water potential in the capillary is not as low as normal, so not as much fluid can move back into the capillary by osmosis Blood Pressure changes along the Circulatory System? Arteries = - highest pressure (connects directly with heart/ventricles)
- pressure fluctuates (increases when ventricles contract which causes the elastic tissue to stretch, decreases when ventricles relax which causes the elastic tissue to recoil)
- overall decrease in pressure due to friction Arterioles = large decrease in pressure due to increase in total cross-sectional area (ensures pressure is not to high to damage capillaries) Capillaries = pressure here is called hydrostatic pressure (decreases due to a loss in fluid) Venules/Veins = blood under low pressure Job of Red Blood Cells? found in humans/mammals (animals) carries haemoglobin haemoglobin carries oxygen Structure of Haemoglobin? globular protein (soluble & specific 3d shape) quaternary structure made of 4 polypeptide chains (2α, 2β) each chain carries a haem group each haem group carries Fe2+ each Fe2+^ carries an O 2 therefore, each haemoglobin carries 4 lots of O 2 Job of Haemoglobin? load oxygen in the lungs and deliver it to the respiring tissues What is Affinity? the level of attraction haemoglobin has to oxygen (high affinity = strong attraction, low affinity = weak attraction) Role of haemoglobin in oxygen transport? haemoglobin has High Affinity in the lungs – due to high partial pressure of oxygen and low partial
