AQA AS Level Biology Unit 1 Why do we calculate ratios or percentages with data? for easier comparison, because different groups have different starting numbers/masses Why do we take a large sample size? more representative, findings not due to chance Why do we take random samples? avoid bias Why do we take repeats? identify anomalous results and calculate a reliable mean Why do we have controls? to see that what we are testing (e.g. drug) is causing the effect How do we treat control groups? treat exactly the same but do not give the drug, give a placebo Evaluate the conclusion?  compare the conclusion wording to the data wording  correlation does not mean causation, other factors may been involved  sample size unknown  no repeats  no controls  length of study unknown  then answers specific to the data (use common sense) What are biological molecules? molecules made and used by living organisms e.g. Carbohydrates, Proteins, Lipids 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 H O (isomers = same formula but different arrangement) 6 12 6 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 BTC (2014-2015) Formula for disaccharides? C H O 12 22 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 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 How is starch digested?  Salivary Amylase in the mouth and Pancreatic Amylase in the SI breaks the starch into maltose  Maltase on the lining of the SI breaksdown the maltose into glucose How is sucrose digested? sucrase on the lining of the SI breaks it down into glucose and fructose How is lactose digested? lactase on lining of the SI breaks it down into glucose and galactose What is lactose intolerance? person does not have the lactase enzyme Symptoms of lactose intolerance?  Diarrhoea and Flatulence  diarrhoea – undigested lactose lowers water potential of the lumen of the SI, so water enters the lumen by osmosis, = watery faeces  flatulence – undigested lactose enters the LI, broken down by micro-organisms, releasing gas 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 BTC (2014-2015) 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  many of these collagen molecules make the tendons/ligaments/connective tissues Test for protein? add biuret, turns purple What is an enzyme? a biological catalyst (substance that speeds up the rate of reaction without being used up – lowers activation energy) What makes an enzyme specific? has a specific active site shape, only complementary substrates can bind to the active site to form enzyme-substrate complexes Lock and Key Model vs Induced Fit Model?  LK = active site shape is rigid, only exactly complementary substrates can bind to form ES complexes  IF = active site changes shape, the substrate binds to the active site – the active site changes shape so the substrate fits exactly forming an ES complex BTC (2014-2015) Affect of substrate concentration on enzyme activity?  increase substrate concentration, increases chance of successful collisions, increase chance of forming an ES complex, increase rate of reaction  this continues until all the enzyme's active sites are full/saturated = maximum rate of reaction Affect of temperature on enzyme activity?  as temperature increases  the kinetic energy increases  the molecules move faster  increase chance of successful collisions  increase chance of forming ES complex  increase rate of reaction  carries on till optimum  after optimum  bonds in tertiary structure break  lose active site shape  substrate no longer complementary  cant form ES complexes  enzyme denatured Affect of pH on enzyme activity? if change pH away from optimum, bonds in tertiary structure break, lose active site shape, no longer form ES complex, enzyme denatured Competitive vs Non-Competitive Inhibitors?  Competitive = a substance with a similar shape to the substrate and a complementary shape to the enzyme's active site, binds to the active site, blocking it, preventing ES complexes from forming  Non-Competitive = a substance that binds to another site on the enzyme other then the active site, causes the active site to change shape, so less ES complexes can form Competitive vs Non-Competitive Inhibitors? increase substrate concentration to excess (very high concentration) – with competitive inhibitor maximum rate of reaction will be reached, with non-competitive inhibitor maximum rate of reaction cannot be reached 2 types of microscopes? Light and Electron (transmission and scanning) How to judge a microscope? by Magnification and Resolution Magnification? how much larger the image size is compared to the actual size Which has higher magnification? TEM > SEM > LM Formula for magnification? magnification = image size/actual size BTC (2014-2015) Conversion? 1 mm = 1000 micrometre. 1 mm = 1,000,000 nanometre Why can organelles appear different in images? viewed from different angles and at different 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) Eukaryotic vs Prokaryotic?  Eukaryotic = animal/plant cell, has membrane bound organelles (nucleus, endoplasmic reticulum, golgi body, lysosome, mitochondra)  Prokaryotic = bacteria, has no membrane bound organelles BTC (2014-2015) 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 are the 3 types of Lipids?  Triglycerides (fat for energy store, insulation, protection of organs)  Phopholipids (to make membranes)  Cholesterol (for membrane stability and make hormones) BTC (2014-2015) 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 Where are Membranes found?  around organelles (membrane bound organelles) = to hold organelles contents together, control what enter/leaves organelles  around cells (cell surface membranes) = to hold cell contents together, control what enters/leaves cell, cell signalling Basic structure of a membrane?  made of a phospholipid bilayer (a double layer of phospholipids)  hydrophilic heads face water/fluid  hydrophobic tails face towards each other, protected from water/fluid Additional structures in membranes? Proteins, Carbohydrates, Cholesterol Role of proteins in the membrane?  Extrinsic and Intrinsic  extrinsic = found in one layer  intrinsic = found in both layers – forms transport proteins (carrier and channel) Role of carbohydrates in the membrane? form Glycoprotein and Glycolipid (if carbohydrate attaches to protein or lipid) – acts as receptors to hormones in cell signalling Role of cholesterol in the membrane? sits between the phospholipids in the bilayer, provides membrane stability Why are membranes defined as having a Fluid-Mosaic Model? fluid = describes the phospholipids in the bilayer – flexible, mosaic = describes the appearance of the proteins BTC (2014-2015) Define Diffusion? net movement of molecules from an area of high concentration to an area of low concentration until equilibrium is reached (down the concentration gradient) 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 BTC (2014-2015) 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 Structure of Bacteria?  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)  some have a Capsule (reduce water loss, protect from phagocytosis) and Flagella (movement) Cause of Cholera?  involves a bacteria called Vibrio Cholerae entering the SI  the bacteria produces toxins which cause the cells lining the SI to release Chloride ions into the lumen of the SI  this lowers the water potential of the lumen  so water enters the lumen by osmosis leading to diarrhoea (watery faeces) BTC (2014-2015) Treatment for Cholera?  ORT (Oral Rehydration Therapy)  contains Sodium ions – absorbed by cells lining the SI lowering the water potential of the cells so they absorb water by osmosis  contains Glucose – provides energy (given in the form of starch, as starch is insoluble)  contains Potassium ions – increases appetite Function of Lungs? site of gas exchange (oxygen into blood – used in cells for respiration, carbon dioxide out of the blood – toxic waste product of respiration) What is Lungs made up of? Trachea, Bronchi, Bronchioles, Alveoli (+ capillaries) Function of trachea, bronchi, bronchioles? transport of air and filter air, (bronchioles also controls amount of air reaching alveoli) Structure of trachea/bronchi?  wall made of c-shaped cartilage  cartilage is strong so trachea/bronchi do not collapse  cartilage is c-shaped to give flexibility  lining made of goblet cells and ciliated epithelial cells  goblet cells make mucus, which traps pathogens/particles  ciliated epithelial cells have cilia, which pushes mucus up and out of lungs Structure of bronchioles?  wall made of smooth muscle  smooth muscle contracts, lumen narrows, bronchiole constricts  (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) BTC (2014-2015)