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Edexcel Snab Topic 2
Genes and Health
| Question | Answer |
|---|---|
| How do gases such as oxygen cross the walls of the alveoli in to the blood system. | Through Diffusion. Therefore to supply enough oxygen, gas exchange must be rapid. |
| What helps gas exchange? | Large surface area of the alveoli, Numerous capillaries around the alveoli and Thin walls of the alveoli and capillaries meaing a short distance between the alveolar air and blood in the capillaries. |
| What is the rate of diffusion dependent on? | Surface Area; as it increases the rate of diffusion increases, Concentration gradient; greater the concentration gradient, the faster the diffusion.Thickness of gas exchange surface; thicker the surface, the slower the diffusion. Ensure Rapid diffusion. |
| What is Flick's law? | Rate of Diffusion = SA X Difference in Conc/ Thickness of Gas Exchange Surface. |
| How many different Amino Acids are there? | 20. |
| Draw a structure of the Amino Acid. | [Diagram] |
| What is a Primary Structure? | The sequence of Amino Acids in a polypeptide chain joined by a peptide bond |
| What is a Peptide bond? | A bond between amino acids formed by the loss of water in a condensation reaction. |
| What is Secondary Structure? | Interactions between the Polypeptide chains cause the chain to twist and fold into 3D shape. A-helix/Beta Pleated sheet where within Hydrogen bonding occur; between the C=O and NH; holding the parallel chains. |
| What is Tertiary Structure? | Three Dimensional shape Interaction between R groups Disulphide bond,Hydrogen bonds,Hydrophobic interactions (between R groups), Polar interactions |
| What are the properties of the R group? | They are polar and attract other polar molecules like water therefore Hydrophillic. Some parts are Non-polar therefore Hydrophobic and therefore they are arranged so they face inside of the Protein. |
| Explain how the primary structure determines its three-dimensional(tertiary) structure and its properties. | Primary structure position/sequence of the amino acids / R groups determines the positioning of the bonds / folding Solubility Polar/Hydrophilic on the outside of enzymes / Non polar /Hydrophobic on the inside |
| What is a Quaternary structure? | Two or more polypeptide chains held together by Hydrogen bonds. For example Haemoglobin. |
| What is a conjugated protein? | A protein with another chemical group associated. |
| Name 2 types of proteins. | Globular and Fibrous. |
| What are Globular proteins? | Polypeptide chain folded in compact spherical shape. Soluble, due to Hydrophillic side chains, project from the outside,important in metabolic reactions. 3D shape for binding. E.g. enzymes, membrane proteins, Antibodies, Oxygen transport pigments. |
| What are Fibrous proteins? | Remain in long chains, can be cross linked for strength. Insoluble. Important for structural molecules; E.g. Keratin in skin, Collagen in nails. |
| What is a Phospholipid Bilayer? | Is when all the molecules are arranges so that the Hydrophobic tails are inside the Bilayer. As cells are filled with watery/aqueous cytoplasm and tissue fluid. Avoids Hydrophobic fatty tails being in contact with the water |
| What does the Phospholipid contain? | Phospholipids Phosphate (head) (Two) fatty acid (tails) Glycerol Ester bonds |
| What are the properties of a Phospholipid? | Phosphate is polar and attracts other polar molecules like water. A bilayer will tend to close on itself so that there are no edges with hydrocarbon chains. |
| Why do they form a Bilayer? | Fatty acids/tails} are hydrophobic/non-polar so orientate themselves away from Water Phosphate heads} are hydrophilic /polar so can interact with water / polar environment Cytoplasm / tissue fluid as the polar environment |
| Why do they form a Fluid Mosaic Model? | The Presence of Proteins creates a mosaic like structure also as it allows proteins to move make it fluid. |
| What does a Fluid mosaic model contain? | Proteins, Glycolipids ;Cell Recognition Glycoproteins;Antigens and Receptors Cholestrol;Reduces fluidity by preventing movement of PB, Channel Proteins; Allows substances to move in or out, Phospholipids. |
| What are the 4 different evidence's for the Fluid Mosaic Model. | 1.Protein-Lipid Sandwich 2.Freeze Fracture Membrane 3.Lectin Experiment 4.Mouse Cells |
| What happens if they're are more unsaturated fatty acids? | It would become more fluid, as there are more kinks therefore it prevents them from packing closely together. |
| What is Diffusion? | Net movement of molecules or ions from a region where they are are high concentration to a region of low concentration. Until it has reached an equilibrium. Hydrophobic or small uncharged molecules through PB. Passive. E.g. Carbon Dioxide and Oxygen |
| What is Facilitated Diffusion? | High to Low concentration until equilibrium has reached. Hydrophillic molecules or ions; through a Carrier Protein &Channel Protein. Passive. |
| What is a Channel and Carrier Protein? | Channel: Filled with Water filled pores, different for transporting different molecules. Specific shape that permits the passage of particular ion or molecule. Carrier:Ion/molecule binds to spec site. Protein changes shape and Ion/molecule passes through |
| What is Osmosis? | The net movement of water molecules from a solution with a lower concentration of solute to a solution with a higher concentration of solute through a partially permeable membrane. Passive. |
| What is Active Transport? | When energy is required to change the shape of the carrier protein and move the substance across the membrane against conc grad. Active. Energy comes from respiration in the form of ATP, which changes the shape. |
| What is Exo/Endocytosis? | 1. Release of substances from the cell as vesicles fuse with cell membrane. E.g. Insulin 2. Substances are taken into a cell by the creation of a vesicle, Cell membrane engulfs material. E.g. cholestrol and WBC. Bulk Transport. |
| What happens if they're are excess water? | Detected-Cell Membrane Carrier proteins-pump Na+ Na+ diffuse down conc grad. Into cell-FD-Na channels Inc.in Na in TF,creates pot.difference. + ions in mucus, electrical gradient; Cl ions to move out into TF Increase in Na and Cl,draws water by osmo |
| What happens if they're too little water in the mucus? | Cl+ transported into cell Conc gradient, higher then the outside. CFTR opens Cl ions diffuse out - CFTR channels down conc grad. CFTR (opens) channels block Na channels Build up of Cl- electrical gradient Movement Na and Cl ions draws water out- osmo |
| What is Cystic Fibrosis? | CFTR Channel cannot function properly. Different Amino Acid sequence on defective CFTR protein Change in protein, the role of protein in transporting Cl ions,X move out of cells . Na ions move in, Water X move out of cells osmosis. |
| How does Gene mutation cause a build up of mucus in the respiratory system of a person with cystic fibrosis? | Mucus thicker,thickened mucus X be moved out by cilia/coughing |
| Explain how cystic fibrosis affects the digestive system | Mucus blocks pancreatic duct in pancreas Enzymes X be secreted - small intestine Reduced digestion of food Reduced absorption ,malnutrition/weightloss Self-digestion of pancreatic cells / problems controlling blood sugar level/cysts/Fibroid High met |
| Explain how cystic fibrosis affects gas exchange? | Sticky mucus builds in lungs X be cleared by cilia. Traps dust MO's Risk of lung infections, blocks airways; breathing difficult. Gas exchange in alveoli less efficient-mucus fills alveoli & diffusion pathway longer & so less oxygen gets into the blood. |
| Explain how cystic fibrosis affects reproductive system? | Female have reduced chance - pregnant; mucus plug develops in cervix; stops sperm from reaching egg Males lack vas deferens on both sides; sperm can't leave testes. It can become partially blocked by thick sticky mucus layer; fewer sperm are present. |
| What are Enzymes? | Globular Proteins that act as biological catalysts. Speed up chemical reactions. Three- dimensional shape includes a depression on surface- Active Site; binds to spec substrate. Reduce Activation Energy and remain unchanged. |
| How do Enzymes work? | Lock and Key Theory- Spec molecule can fit into active site. Substrate molecule form temp bonds with Amino acids to produce ASC. Each enzyme will only catalyse one spec reaction; one shape will fit the site. |
| How do Enzymes work? [2] | Induced fit theory- Substrate enters AS, Enzyme molecule changes shape fit's close around substrate. Only specific substrate will induce the change in shape of an enzyme's active site. |
| How do Enzymes work? [3] | Minimum energy -to start reaction;Activation Energy. Enzymes reduce;amount of energy to bring about reaction; allows reactions to occur. |
| How do Enzymes work? [4] | Specific shape of the enzyme's active site and comp structure- Electrically charged groups on surfaces interact. Attraction may distort shape of substrate & assist breaking of bonds and form new bonds.Or acidic side chains-provide condition for reaction. |
| How to measure Rate of reaction? | Determining the quantity of substrate used or the quantity of product formed. Measuring the amount of oxygen given off in a known time. As substrate is used, there are fewer substrate molecules to bind with and therefore slows down. |
| What does DNA contain? | DNA contains the genetic code which dictates all the inherited characteristics of an organism. |
| What is a gene? | Is a sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain. |
| What is a genome? | All the genes in an individual or a species. |
| What does DNA stand for? | Deoxyribonucleic acid. Long chain molecule made up of many units called nucleotides or mononucleotides. |
| What does a mononucleotide contain? | Three molecules linked together by condensation reactions; Deoxyribose, Phosphate group and Organic base. Adenine, Cytosine, Guanine, Thymine. ACGT. |
| What are the two chains of nucleotides held by? | Hydrogen bonds. |
| What is the genetic code? | The sequence of bases in the DNA tells the cell which amino acids to link together to make the protein. |
| What is a triplet code? | Each adjacent group of 3 bases |
| What is RNA? | A copy of the DNA, which can leave the nucleus towards the cytoplasm; to make proteins. |
| What is the difference between DNA and RNA? | RNA- single strand made up of RNA nucleotides. Contains Ribose sugar. Uracil replaces Thymine. RNA has one strand whilst DNA has two. |
| What are the three types of RNA? | Messnger RNA, Transfer RNA and Ribosomal RNA. |
| What is Protein Synthesis? | Transcription and Translation. |
| What is Transciption? | - Takes place in nucleus - DNA double helix unwinds & H bonds break - Free nucleotides line up - Enzyme DNA Polymerase bonds nucleotides together,Phosphodiester bonds form between Deoxyribose & Phosphate group. - Hydrogen bonds link 2 strands togeth |
| What is Transcription? [2] | Used strand is called template strand (antisense) whilst the unused strand is called the Sense strand. Ribonucleotides are paired with complement on template strand; Uracil pairs with Adenine instead of Thymine.The RN are joined up by RNA Polymerase. |
| What is Translation? | - Takes place on Ribosomes - tRNA carrying the Amino Acid has 3 bases called anticodon and these pair with Complementary bases on the mRNS codon. - Joins by Peptide bond. |
| What is DNA Replication? | - DNA double helix unwinds and H bonds break - Free nucleotide line up alongside each DNA strand - Enzyme DNA polymerase linkes adj molecules to form Comp strand. |
| Describe the Process, Meselson and Stahl carried out? | DNA from E-Coli,grown in medium with heavy isotope,15N(Denser)moved to 14N. New nucleotides were light, they allowed bacteria to divide & DNA to replicate. Extracted & centrifuged DNA. Medium DNA, in middle; contains heavy & light nucleotides. |
| What is a mutation? | When genetic code is copied,mistakes can be made in new base sequence.Can be passed onto future generations. If it occurs within a gene & new base triplet that codes for a stop signal or different amino acid; protein formed may be faulty.Genetic Disorder. |
| How is sickle cell anaemia formed? | Mutation in gene;codes for 1 of the polypeptide chains in haemoglobin.mRNA is GUA than GAA. Protein;non-polar AA valine than Glutamic acid. Haemoglobin-less soluble.Oxygen is low,form long fibres;stick together;distorts shape. Half moon cells carry less o |
| What is a mutation? | When genetic code is copied,mistakes can be made in new base sequence.Can be passed onto future generations. If it occurs within a gene & new base triplet that codes for a stop signal or different amino acid; protein formed may be faulty.Genetic Disorder. |
| How is sickle cell anaemia formed? | Mutation in gene;codes for 1 of the polypeptide chains in haemoglobin.mRNA is GUA than GAA. Protein;non-polar AA valine than Glutamic acid. Haemoglobin-less soluble.Oxygen is low,form long fibres;stick together;distorts shape. Half moon cells carry less o |
| What is a locus? | A position of a gene in a chromosome. |
| What is an allele? | A form of an allele. |
| What is Genotype? | g |
| What is Phenotype? | gh |
| What is a Dominant allele? | g |
| What is a Recessive Allele | m |
| What is Monohybrid Inheritance? | Characteristics is controlled by one gene. |
| What is Beta Thalassaemia? | Genetic disease caused by recessive allele of a gene on chromosome 11. |
| What other conditions are caused by single recessive alleles? | Albinism, Phenyketonuria and Sickle Cell Anaemia. |
| What other plant's charcateritic is determined by one gene e.g. whether plants are tall or short, seeds are smooth or wrinkled? | Garden pea. |
| What are the treatments for Cystic Fibrosis? | 1. Medication - Bronchodilators, Antibiotics, DNAase enzymes, Steroids. 2. Diet 3. Digestive Enzyme Supplement 4. Physiotherapy 5. Heart and Lung Transplant |
| Describe the process of Gene therapy. | 1. Normal alleles of the gene are inserted into the target cells, using a virus or liposomes. 2. They are transcribed and translated. 3. Protein is produced in the target cells. |
| Gene Therapy [2] | Using alleles / genes coding for the CFTR protein /channel Introduce the alleles into the cells Lungs /pancreas/reproductive tracts Produce mucus Use a vector, nebuliser or injection Repeated |
| How genes are inserted using viruses? | 1.Virus;DNA sequence(replicates)removed 2.Replaced-normal allele of desired gene + promoter sequence; initiates transcription and translation 3.Viral DNA remains independent in nucleus- Inflammatory Response, headache, fatigue, fever and raised heart ra |
| How genes are inserted using liposomes? | 1.Copy of Normal allele,inserted into a loop of DNA (plasmid) 2.Plasmids combined with liposomes. 3.+ charged head groups of Phospholipids combine with DNA,form a liposome DNA complex 4.Aerosol;nebuliser 5.Fuse with epithelial cells & carry DNA into c |
| Why aren't Germ line therapy not allowed? | As it could affect future generations. |
| How would you test someone with Cystic Fibrosis? | Genetic testing; identifying abnormal gene in the DNA.Where cells are extracted from cheek cells, white blood cells or cells from foetus/embryo. DNA is tested to see if it contains the known base sequences for the mutation. |
| How can Genetic Testing also help? | To identify carriers; where a sample of blood or cells are taken from the mouth; to deteact abnormal alleles in people with the disease. Family history can help and Counselling is offered before and after tetsing and parents can make informed decisions. |
| What is Amniocentesis? | Amniotic fluid removed from amniotic sac of mother Fetal/embryonic cells present in amniotic fluid fetal / embryonic cells needed DNA can be analysed To detect defective gene in sample |
| What is Chorionic Villus Sampling? | Placental tissue removed from womb of mother Fetal cells present in placenta/ placental tissue / chorionic tissue / fetal cells needed DNA can be analysed To detect defective gene(s) in sample |
| Discuss Ethical and Social implications towards Genetic testing? | Right to life Abortion is murder,risk of miscarriage False positive /negative Implications of medical costs Possible problems with {future employment / insurance / what constitutes a serious condition Loss of fetus / Risk to mother Stress to paren |
| What is PIGD? | IVF can test an embryo before it is implanted in the uterus. Cell can be removed from embryo in culture; 8/16 cells. DNA can be analysed. Expensive,fairly unreliable. |
| State 4 ethical frameworks for the genetic screening and abortion. | 1.Rights and duties; human rights,duties and religious teachings. 2.Maximising good (Utilitarian) 3.Making decisions for yourself- Informed consent 4.Leading virtuous life- Virtues and justice. |
| How does Genetic counselling help? | -Help couple understand -Tests available and possible courses of action -Help couple make informed decisions |
| Describe how the structures of the lung is adapted to gas exchange? | -Walls of alveoli,one cell thick -Walls of blood capillaries, one cell thick -Alveoli covered with dense network of capillaries -Concentration gradients maintained by blood flow -Large Surface Area, by Alveoli -Oxygen combines rapidly with Haemoglob |
| What is the significance of the R groups in the folding of the 3D shape? | R group-chemical side chain:different for every amino acid. -POLAR:Electrons shared unevenly,attracts other polar molecules,Hydrophillic.Fold so the polar parts are on the the outside. Non Polar R groups, Hydrophobic;face inside.+ Sulfur, Disulfide bond. |
| Describe the three-dimensional (tertiary) structure of an enzyme | 1.Globular 2.Active site 3.Specific shape of active site 4.Bonds /named bond/interaction between R groups 5.Bond/interaction,disulphide bond, hydrogen bonds, hydrophobic interactions (between R groups) |
| Explain how the primary structure of an enzyme determines its three-dimensional (tertiary) structure and its properties. | -Primary structure position,order of the {amino acids / R groups} / -Type of the {bonds / folding -Shape/properties active site -Interaction of AS & substrates e.g.ESC -Polar/hydrophilic,outside of enzymes/non polar /hydrophobic inside -Solubilit |
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