AQA AS Biology unit1
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| Oesophagus | Carries food from the mouth to the stomach, made up of a thick muscular wall
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| Stomach | Thick muscular sac, which stores and digests food, especially proteins
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| Small Intestine | Long muscular tube that further digests food by enzymes, and absorbs the products of digestion into the bloodstream
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| Large Intestine | Absorbs water, meaning food becomes drier and thicker, and forms faeces
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| Rectum | Final section of intestines, where faeces are stored before being periodically egested
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| Salivary glands | Pass secretions of amylase via a duct into the mouth
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| Pancreas | Large gland situated below stomach, which produces pancreatic juice, containing proteases, lipases and amylase
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| Physical breakdown | Breaks down molecules to increase surface area, and to make ingestion possible
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| Chemical digestion | Large, insoluble molecules are broken down into small, soluble molecules by enzymes
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| Hydrolysis | Splitting up molecules by adding water to chemical bond that hold them together
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| Hydrolases | Enzymes that function by hydrolysis
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| Carbohydrases | Break down carbohydrates, ultimately to monosaccharides
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| Lipases | Break down lipids into glycerol and fatty acids
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| Proteases | Break down protein, ultimately to amino acids
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| Assimilation | Small molecules are absorbed from small intestine into blood and taken to parts of the body where they are built into large molecules that are incorporated into body tissue or used in processes in the body
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| Carbohydrates | Carbon molecules combined with water
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| Monosaccharide | A basic carbohydrate monomer - sweet tasting, solubel sunstance with formula (CH2O)n
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| Disaccharide | A pair of monosaccharides
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| Polysaccharide | A chain of saccharides
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| Reducing sugar | A sugar that can donate electrons to another chemical (eg Benedict's reagent)
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| Benedict's reagent | alkaline solution of copper (II) sulfate
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| Maltose | Glucose+Glucose
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| Sucrose | Glucose+Fructose
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| Lactose | Glucose+Galactose
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| Condensation reaction | A molecule of water is formed (removed from reactants) as a result of the reaction
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| Glycosidic bond | A bond that forms between saccharides
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| Starch | A polysaccharide formed by linking of between 200-100,000 glucose molecules, found in many parts of plants in the form of small granules/grains
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| Amylase | Hydrolyses starch to give maltose
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| Maltase | Produced by epithelial lining, hydrolyses maltose to give glucose
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| Sucrase | Produced by epithelial lining, hydrolyses sucrose
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| Lactase | Produced by epithelial lining, hydrolyses lactose
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| Lactose intolerance | Do not produce enough lactase and cannot digest lactose. Reaches large intestine and is broken down by microorganisms which causes bloating, nausea, cramps and diarrhoea
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| Amino acids | Basic monomer units that combine to make a polymer called a polypeptide
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| Polypeptide | Polymer made up of amino acids linked by peptide bonds
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| Dipeptide | Two amino acids combined
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| Peptide bond | Bond formed between amino acids
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| Primary structure | The sequence of 100s of amino acids in a polypeptide chain, which determines the ulimate shape of a protein and hence it structure
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| Secondary structure | positive -NH groups and negative -C=O groups on either side of peptide bonds readily form hydrogen bonds, causing coils and pleats in the polypeptide chain (eg alpha helices, beta pleated sheets)
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| Tertiary structure | Secondary structure is twisted and folded even more to give a complex and unique 3D structure, held together by disulfide bridges, ionic bonds, hydrogen bonds, and hydrophobic interactions and Van der Waals
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| Quaternary structure | Large proteins can form complex molecules containing a number of individual polypeptide chains, along with other non protein (prosthetic) groups
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| Globular proteins | (eg enzymes, haemoglobin) are roughly spherical in shape and have metabolic functions
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| Fibrous proteins | (eg collagen) have structural functions, and form long chains which run parrallel to each other. Linked by cross bridges, so form very stable molecules
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| Enzymes | Globular proteins which act as catalysts for biochemical reactions
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| Activation energy | minimum amount of initial energy needed to 'kick start' a reaction
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| Active site | A small, hollow depression made up of relatively few amino acids within the muchh larger enzyme molecule, where the enzyme substrate complex is formed
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| Substrate | Molecule on which an enzyme acts
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| Enzyme-substrate complex | Formed when an enzyme and substrate come together, held in place by bonds which temporarily form between amino acids on the active site and groups on the substrate
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| Lock and key model | Proposes that just as one key fits one specific lock, one substrate fits one specific enzyme
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| Induced fit model | Proposes that enzymes are flexible and change shape slightly to fit the profile of a substrate (like a glove and hand), which distorts the bonds of the substrate and lowers activation energy
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| Competitive inhibitors | Have a molecular shape similar to the substrate, so are complementary to the active site. They therefore compete for available active sites, so increasing substrate concentration decreases effects
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| Non competitive inhibitors | Attach themselves to the enzyme at an allosteric site which changes that shape of the active site, so do not directly compete with substrate, meaning that a change in its concentration has no effect.
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| End-product inhibition | To keep a steady level of a particular chemical in a cell, the same chemical acts as an inhibitor to an enzyme at the start of the reaction.
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| Microscope | An instrument which magnifies the image of an object
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| Max resolution of a light microscope | 0.2 micrometres
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| Max resolution of an electron microscope | 0.1 nanometres
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| Magification= … | size of image/size of object
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| Resolution | Minimum distance apart that two objects have to be in order to appear as two separate items
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| Cell fractionation | Process where cells are broken up and the different organelles they contain are seperated out in order to study their structure and function
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| Homogenation | Cells are broken up by a homogeniser that releases the organelles from the cell. The resultant homogenate is filtered to remove complete cells and large pieces of debris
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| Ultracentrifugation | The process by which fragments in the filtered homogenate are separated in an ultacentrifuge, which spins homogenate round at a very high speed to create a centrifugal force
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| Transmission electron microscope | Electron gun that produces a beam of electrons that penetrates specimen from below, focussed by a condensor electromagnet. Produces an image on a screen that can be photographed to give a photomicrograph. Resolution of 0.1nm
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| Scanning electron microscope | Directs beam of electrons from above, passed across specimen in a regular pattern and are scattered depending on contours. Computer image of specimen built from electrons/secondary electrons produced. Resolution of 20nm.
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| Ultrastructure | Internal structure of a cell that is specific to its job
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| Nucleus | Is the control centre of the cell as it prouces mRNA and therefore protein synthesis. Retains genetic material of the cell in the form of DNA/chromosones. Manufactures ribosomal RNA and assembles ribosomes. 10-20 um
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| Nuclear envelope | Double membrane - outer memebrane is continuous with ER and has ribosomes on surface. Controls what comes in/goes out of nucleus, and reactions taking place within it.
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| Nuclear pores | Let large material such as RNA out of the nucleus. Around 3000, 40-100nm in diameter
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| Nucleoplasm | Granular, jelly like substance that makes up the bulk of the nucleus
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| Chromatin | DNA found within the nucleoplasm. Is the form that chromosones take when not dividing.
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| Nucleolus | Small, spherical, within the nucleoplasm. Manufactures ribosomal RNA and assembles ribosomes
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| Mitochondria | Rod shaped, 1-10um in length. Site of certain stages of respiration - Krebs cycle, oxidative phosphorylation pathway. Responsible for production of energy carrier molecule ATP from carbohydrates
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| Cristae | Extensions of the inner memebrane of mitochondria that increase surface area for attachment of enzymes involved in respiration
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| Matrix | Semi rigid material in the mitochondria that contains proteins, lipids, DNA for protein production as well as enzymes for respiration
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| Endoplasmic reticulum | A system of sheet like membranes that spread through the cytoplasm and enclose flattened sacs called cisternae
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| Rough ER | Has ribosomes on outer surface. Provides a large surface area for protein and glycoprotein synthesis, and provides a pathway for transport of material though the cell (especially proteins)
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| Smooth ER | Is more tubular than RER, and lacks ribosomes. Synthesises, stores and transports lipids and fats
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| Golgi apparatus | A stack of membranes that make up cisternae. Adds carbohydrate to protein to form glycoprotein, secretes carbohydrates, produces secretory enzymes, modifies, stores and transports lipids, and forms lysosomes.
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| Vesicles | Small, rounded, hollow structures regularly pinched off from ends of cisternae of the Golgi. Move to the cell surface, where they fuse with the membrane and release their contents.
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| Lysosomes | Formed when vesicles contain proteases and lipases. Break down material ingested by phagocytic cells, release enzymes to the outside of the cell to destroy material around it (exocytosis), digest organelles to reuse useful chemicals, and perform autolysis
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| Ribosomes | Small, cytoplasmic granules found in all cells. 80S type are 25nm in diameter and are found in eukaryotic, 70S are slighly smaller and prokaryotic. Have 2 subunits that contain ribosomal RNA and protein. Are the active site of protein synthesis
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| Lipids | Substances that contain carbon, hydrogen and oxygen with a smaller proportion of O+C to H than carbohydrates. Insoluble in water but soluble in organic solvents such as alcohol and acetone. Main groups are triglycerides, phospholipids and waxes
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| Tryglycerides | A molecule of glycerol combined with 3 fatty acids by an ester bond
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| Saturated fat | Formed by fatty acid chains with no double carbon bonds
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| Monounsaturated fat | Formed by fatty acid chains with one double carbon bond
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| Polyunsaturated fat | Formed by fatty acid chains with many double carbon bonds
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| Phospholipid | A molecule of glycerol combined with 2 fatty acids and a phosphate group
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| Hydrophilic | Water loving' - interacts with water
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| Hydrophobic | Water hating' - will orient away from water
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| Polar molecules | Molecules that have two ends which behave differently to one another (eg phospholipids)
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| Extrinsic proteins | Occur either side of the phospholipid bilayer, and give mechanical support to the cell, helping it adhere together, or act as cell receptors for molecules such as hormones, in conjunction with glycolipids
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| Intrinsic proteins | Completely span the phospholipid bilayer. Act as carriers to transport water soluble materials , large materials or ions across membrane, or are enzymes.
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| Fluid mosaic model | Fluid: phospholipid molecules can move relative to one another, giving the membrane a constantly changing structure. Mosaic: proteins vary in shape, size and pattern in the same way as mosaic tiles.
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| Diffusion | Net movement of particles or ions from a region of higher concentration to a region of lower concentration.
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| Fick's law | Diffusion is proportional to: surface area x difference in concentration / length of diffusion path
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| Channel proteins | Form water filled channels in the phospholipid bilayer that allow water soluble molecules (ions) to diffuse through
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| Carrier proteins | Bind to a specific molecule (eg glucose) which causes a change in shape, and the molecule is released to the other side.
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| Osmosis | Passage of water from an area of higher water potential to an area of lower water potential through a partially permeable membrane
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| Water potential | The pressure created by water molecules, measured in kPa. Pure water has the highest water potential of 0.
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| Active transport | Movement of molecules or ions in/out of a cell, from a region of lower to higher concentration using energy carrier molecules
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| Sodium-potassium pump | Carrier protein that allows sodum to be secreted while potassium is absorbed
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| Villi | Imm finger like projections in the intestinal wall that increase surface area, are thinly walled, and have a good blood supply which can carry away absorbed materials and maintain a diffusion gradient.
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| Bacterial cell wall | Is made of peptidoglycan, a polymer of peptides and polysaccharides. Is a physical barrier which excludes certain substances and protects against mechanical damage
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| Capsule | Made of mucilaginous slime, and protects bacteria from other cells by enabling them to stick together
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| Flagella | Occur in certain types of bacteria. Their rigid corkscrew shape and rotating base enable them to spin through fluids
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| Bacterial DNA | Is circular and possesses genetic information for replication of bacterial cells
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| Plasmids | Are small, circular pieces of DNA that reproduce seperately. Possess genes that enable bacteria to survive in adverse conditions (eg produce enzymes that break down antibiotics). Are used as vectors to replicate genetic information in genetic engineering.
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| Oral rehydration therapy | Method used to treat cholera and other diarrhoeal diseases, involves using a sodium glucose pump to reduce water potential in intestinal epithelium, stopping rapid water loss.
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| Ribcage | a bony box that can be moved by the intercostal muscles, enabling the lungs to be ventialted by a tidal stream of air that ensures constant replenishment
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| Lungs | a pair of lobed structures, made up of a series of highly branched tubules called bronchioles, ending in tiny air sacs called alveoli
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| Trachea | Flexible airway supported by rings of cartialge that stop collapse when air pressure inside falls. Walls are made of muscle lined with goblet cells (produce muscus) and ciliated epithelium (cilia move mucus up trachea to the throat)
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| Bronchi | Two divisions of the trachea, one for each lung. Have a similar structure of goblet cells and cilia. Larger bronchi supported by cartilage which decreases as they get smaller
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| Bronchioles | Braching divisions of the bronchi, with muscular epithelial walls that expand and contract to control air flow in and out of alveoli
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| Alveoli | Air sacs at the end of the bronchioles, contain collagen and elastic fibres which allow expansion and contraction. Membrane is the gas exchange surface.
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| Inspiration | The active process of breathing in: external intercostals contract, diaphragm moves downwards, thorax volume increases which decreases pressure and allows flow of air into lungs
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| Expiration | The largely passive process of breathing out: internal intercostals contract, diaphragm moves upwards, thorax volume decreases which increases air pressure and allows flow of air out of lungs
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| Tidal volume | Volume of air taken in on one breath, measured in dm3
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| Ventilation rate | Number of breaths taken per minute, measured in min-1
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| Pulmonary ventilation | Total volume of air moved into lungs in one minute, dm3min-1 (ventilation rate x tidal volume)
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| Cause of pulmonary tuberculosis | Mycobacterium tuberculosis/bovis
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| Symptoms of pulmonary tuberculosis | Cough, tiredness, loss of appetite, fever, coughing uo blood
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| Transmission of pulmonary tuberculosis | Spread through air by droplets - breathing, talking, laughing, coughing. Close contact - friends, family, colleagues
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| Course of infection of pulmonary tuberculosis | bacteria grow and divide in upper lungs, inflammation of lymph nodes - primary infection. Post primary TB - bacteria destroy lung tissue - cavities and scars - cough up tissue.
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| Pulmonary fibrosis | Scars form on lung epithlium - becomes thickened, lengthening diffusion pathway, lengthening volume of air lungs can contain. Elasticity of lungs also reduced, meaning air cannot be expulsed as quickly.
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| Effects of pulmonary fibrosis | Shortness of breath, chronic, dry cough, pain and discmofort in chest, weakness and fatigue
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| Asthma | A localised allergic reaction, triggered by certain allergens, air pollutants, cold air, exercise, anxiety that causes production of histamine, inflaming lungs and constricting bronchi(oles)
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| Symptoms of asthma | Difficulty in breathing, wheezing sound when breathing, tight feeling in chest, coughing
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| Emphysema | Developed by one in 5 smokers, causes elastin in lungs to be permenantly stretched so lungs cannot force out alveolar air, and alvelar surface area to be reduced, reducing gas exchange
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| Symptoms | Shortness of breath, chronic cough, bluish skin colouration
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| Atrium | Is thinly walled and elastic - stretches as it collects blood. Only has to pump blood the short distance to the ventricle
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| Ventricle | has a thicker muscular wall and has to pump blood further - to the lungs/rest of body
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| Aorta | Artery connected to left ventricle, carries blood to whole body except lungs
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| Vena Cava | Vein connected to right atrium, brings deoxygenated blood back to right atrium
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| Pulmonary artery | Artery connected to right ventricle, carries deoxygenated blood to lungs
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| Pulmonary vein | Vein connected to left atrium, carries oxygenated blood to heart
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| Diastole | relaxation of the heart: blood returns to atria, AV valves open and it flows into ventricles, closing semi lunar valves
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| Atrial systole | contraction of atria, forcing blood into ventricles, while ventricular walls are relaxed
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| Ventricular systole | When ventricles have filled, their walls simultaneously contract, forcing AV valves to shut and SL valves to open, pushing blood into arteries
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| Atrioventricular valves | located between ventricles and atria, prevent backflow of blood when pressure in ventricles is greater than in atria, meaning blood moves to arteries
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| Semi Lunar valves | located in aorta and pulmonary artery, preventing backflow of blood into ventricles when the recoil action of their elastic walls creates a greater pressure in vessels than ventricles.
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| Pocket valves | occur in veins, meaning blood will flow to the heart rather than away when veins are squeezed
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| Cardiac output | volume of blood pumped by the volume of blood pumped by one ventricle of the heart in one minute, measured in dm3min-1. heart rate x strokevolume
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| Heart rate | rate at which heart beats
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| Stroke volume | volume of blood pumped out at each beat
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| myogenic | where muscular contraction is initiated within the muscle itself rather than by outside nervous impulses (which are neurogenic)
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| Sino atrial node | a group of cells in the wall of the right atrium which provide the initial stimulus for the cardiac cycle. Has a rhythm of stimulation that determines heartbeat (so is known as the pacemaker)
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| Atrioventricular septum | non conductive tissue that prevents the electrical impulse from crossing from the atria to the ventricles during the cardiac cycle
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| Atrioventricular node | Lies between the atria and the ventricles. Holds the wave of electricity for around 0.1s during the cardiac cycle to allow blood to travel from the atria -> ventricles
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| Bundle of His | muscular fibres that pass between the two ventricles
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| Purkinje fibres | located at the base of the ventricles where the BOH brnaches into smaller fibres. Releases a wave of electricity that is transmitted to them which causes ventricular systole
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| ECG | Electrocardiogram - shows electrical activity of the heart
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| Atheroma | A fatty deposit in the arterial wall, caused by accumulation of white blood cells that have taken up low density lipoproteins - made up of cholesterol, fibres, and dead muscle cells
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| Thrombosis | caused when atheroma breaks through the endothelium of the blood vessel, forming a rough surface which restricts smooth flow of blood, which then clots
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| Aneurysm | Atheromas can weaken the arterial wall, which swells into a balloon like, blood filled structure. These frequently burst.
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| Cerebrovascular accident | a brain aneurysm, or stroke
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| Myocardial infarction | Reduced supply of oxygen to myocardium, resulting from arterial blockage. Means heart may stop beating/will be damaged. Also known as a heart attack.
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| High Density Lipoproteins | Remove cholesterol from tissues, transport to liver for excretion. Help protect arteries against heart disease
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| Low Density Lipoproteins | transport cholesterol from liver to tissues, including artery walls, which they infiltrate, leading to development of atheroma
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| Non Specific Defence Mechanisms | do not distinguish between pathogens, but respond to all in the same way. Take the form of a barrier to entry or phagocytosis
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| Specific defence mechanisms | distinguish between different pathogens meaning response is less rapid but provides longer lasting immunity. Either involve T lymphocytes in a cell mediated response, or B lymphocytes in a humoral response.
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