Topic 1 Biology Flashcards
What are the 5 key properties of water?
- Important metabolite
- Important solvent
- High specific heat capacity
- High specific latent heat
- Cohesion and Adhesion
Why is water an important metabolite?
- It is present within hydrolysis or condensation.
Why is water an important solvent?
- Water is a polar molecule and can therefore interact with other charged ions or polar molecules.
Why does water have a relatively high specific heat capacity?
- Due to hydrogen bonding, it takes a lot of energy to change the temperature of water.
Why does water have a large latent heat of vaporisation?
- It takes a lot of energy to break hydrogen bonds and change liquid water into a gas.
Why is water very cohesive and adhesive?
- Water is cohesive as water forms hydrogen bonds with itself.
- Water is adhesive as water forms hydrogen bonds with other materials.
Why is water being a good solvent useful?
- Many ions and molecules can dissolve in it.
- Provides a stable environment for aqueous organisms.
Why is water having a high specific heat capacity important?
- Water doesn’t experience rapid changes in temperature and acts as a buffer to sudden changes in temperature.
How do aquatic and terrestrial organisms benefit from a high specific heat capacity?
Aquatic - Can live in a thermally-stable environment where their enzymes can stay at optimum temperature.
Terrestrial - Can maintain a constant body temperature.
Why is having a large latent heat of vaporisation?
- Allows water to be an excellent coolant.
Why is cohesion and adhesion important?
- Cohesion allows water to create surface tension when in contant with the air.
- E.G sweat forming droplets which evaporate to cool an organism.
Overall Exam Question:
Explain five properties that make water important for organisms.
1) Water has a high latent heat of vaporisation providing a cooling effect.
2) Water has a high specific heat capacity allowing the buffering of temperature.
3) Water is a good solvent allowing metabolic reactions to occur.
4) Water is a good metabolite, being essential in condensation and hydrolysis reactions.
5) Water has strong cohesion which supports columns of water in plants.
What are 3 features of the non-specific immune system?
- The response is immediate.
- The response is the same for all pathogens.
- The response involves physical barriers and phagocytosis.
What are 3 features of the specific immune system?
- The response is slower.
- The response is specific to each pathogen.
- The response involves lymphocytes.
What must lymphocytes be able to do?
- Distinguish between self and non-self material.
What are the proteins on the surface of cell membranes that are able to detect foreign material called?
- Antigens.
What is a phagocyte?
- A type of white blood cell which carries out phagocytosis.
What is phagocytosis?
- Mechanism by which cells engulf a pathogens to form a vesicle.
Outline phagocytosis in 6 steps…
1) Phagocyte is attracted to a foreign chemical left behind
2) Phagocyte attaches to chemicals on the surface pf the pathogen via receptors.
3) Cytoplasm of the phagocytes moves around the pathogen and engulfs it causing a phagosome to be produced.
4) A lysosome fuses with a phagosome, releasing lyzozymes enzymes into phagosomes.
5) Lyzozymes hydrolyse the pathogen.
6) Phagocyte presents pathogen’s antigens on its surface.
What are 3 features of T lymphocytes?
- Made in the bone marrow.
- Matured in the thymus gland.
- Involved in the cell mediated response.
What are 3 features of B lymphocytes?
- Made in the bone marrow.
- Matured in the bone marrow.
- Involved in the humoural response.
Outline the cell-mediated response in 4 steps…
1) Phagocytosis occurs
2) Phagocyte presents antigens on its surface.
3) T helper cells bind to the antigen via specific T-cell receptors.
4) The binding activates T helper cells to divide rapidly by mitosis.
What cells do T helper cells produce?
- Memory B cells
- Stimulate phagocytes to engulf pathogens by phagocytosis
- B cells
- Cytotoxic T cells.
What is the role of cytotoxic T cells?
- To kill abnormal cells and body cells infected by pathogens.
How do cytotoxic T cells kill abnormal cells?
- By producing perforin, a type of protein.
- Perforin makes holes in the membrane allowing full permeability causing cells to die.
What is an antibody?
- A protein produced by B lymphocytes in response to the presence of the antigen.
Outline the humoural response in 7 steps…
1) Surface antigens of an invading pathogen are taken in by endocytosis.
2) B cells process antigens and present them on cells.
3) T helper cells attach to receptors on the APC B cell to activate it.
4) B cells divides by mitosis (clonal selection) to produce plasma cells.
5) Plasma cells are produced which create antibodies specific to the antigen on the pathogen’s surface.
6) Antibody-antigen complex is formed causing agglutination, making it easier for phagocytes to engulf pathogens.
7) B cells form memory cells which can rapidly divide into plasma cells.
Why is the secondary response more efficient than the primary response?
- Secondary response allows antibodies to be produced at a faster rate.
- Memory B cells can divide rapidly into plasma cells that produce specific antibodies to the antigen.
What is a vaccine?
- The injection of an inactive pathogen which stimulates an immune response against a pathogen.
Why are vaccines important?
- Vaccines stimulate memory cell production against a disease for the future.
What is herd immunity?
- Herd immunity occurs when a large portion of a population becomes immune to a disease, either through vaccination or prior infection.
- thereby reducing its spread and protecting those who are not immune.
What is antigenic variability?
- Antigenic variability is the ability of pathogens to alter their surface proteins to evade detection by the host’s immune system.
What is active immunity?
- Active immunity is the protection against disease developed by an individual’s immune system after exposure to a pathogen or through vaccination.
What is passive immunity?
- Passive immunity is the temporary protection against disease gained by receiving antibodies from another source, such as maternal antibodies or antibody injections, without the immune system generating its own response.
Why does DNA replicate before mitosis and meiosis?
DNA replicates itself to ensure that daughter cells have all the genetic information to produce enzymes and proteins.
What does semi-conservative replication mean?
Molecule will contain an original strand a new strand.
Why is semi-conservative replication important?
Ensures genetic continuity
Outline the steps of semi-conservative replication
1) DNA helicase breaks hydrogen bonds between bases on two strands of DNA causing the helix to unwind.
2) Original strands act as templates for new strands, free floating DNA nucleotides are attracted to their complementary bases on each original strand.
3) DNA polymerase catalyses condensation reactions which join the nucleotides of the new strands together by phosphodiester bonds causing hydrogen bonds to form between the bases between original and new strands.
Which scientists determined semi-conservative replication?
Meselsen and Stahl
How did scientists prove semi-conservative replication?
1) Bacteria grown on heavy 15N nitrogen forming heavier DNA.
2) Placed in lighter 14N nitrogen conditions causing an intermediate density because of 15N and 14N.
3) Replicated in 14 N again so lighter and intermediate density DNA are incorporated.
What is the role of DNA and RNA?
DNA - holds genetic information in all living organism.
RNA - Transfers genetic information from DNA to ribosomes
What are DNA molecules called?
Polynucleotides
What are the components of DNA and RNA?
Phosphate group, nitrogenous base, ribose sugar
What are the base pairings for DNA and RNA?
DNA - A-T C-G
RNA - A-U C-G
How are polynucleotides joined together?
Condensation reaction between two nucleotides that forms a phosphodiester bond.
What are the bonds that join nucleotides together?
Phosphodiester bonds
What is the chain of sugars and phosphates called?
Sugar-phosphate backbone
What direction do DNA strands move?
- Anti parallel direction
How does the structure of DNA link to its function?
1) Weak hydrogen bonds between 2 DNA polynucleotides can separate easily during DNA replication.
2) DNA is a very large molecule, so can carry lots of genetic information.
3) Base pairs are protected by the sugar-phosphate backbone so are able to pair to free bases via complementary base pairing.
How are bases joined together?
- Via hydrogen bonding
What are monomers?
- Smaller units from which larger molecules are made
What are polymers?
- Larger units of monomers joined together
What are 3 examples of monomers?
- Monosaccharides, amino acids, nucleotides
What is a condensation reaction?
- The reaction which joins 2 molecules together via a chemical bond and involving the removal of water.
What is a hydrolysis reaction?
- The breaking of the chemical bond between 2 molecules and the addition of a molecule of water.
What are carbohydrates made from?
- Carbon, hydrogen and oxygen.
What monomers are carbohydrates made from?
- Glucose, galactose and fructose
What is an isomer?
- Molecule with the same molecular form but a different structural form.
What are disaccharides?
- Formed from the combination of 2 monosaccharides.
How is maltose formed?
- By condensation reaction of glucose and glucose
How is lactose formed?
- By condensation reaction of glucose and galactose.
How is sucrose formed?
- By condensation of glucose and fructose.
What are polysaccharides?
- molecules formed by the condensation reaction between many monosaccharides.
What are the characteristics of starch?
- Main carbohydrate store in plants.
- Formed by the condensation of alpha glucose.
- Alpha glucose can be synthesised into amylose and amylopectin.
What are the propoerties of amylose and amylopectin?
- Unbranched, helical for amylose
- Branched polymer of alpha glucose for amylopectin
How does starch structure relate to function?
- Starch is compact due to the helical structure of amylose meaning lots of glucose is stored in a small place, therefore being an efficient energy sotre.
- Due to the branches of amylopectin, enzymes can have a higher rate of activity.
- Starch is insoluble and doesn’t affect water potential.
What are the characteristics of glycogen?
- The main carbohydrate store in animals.
- Same structure as amylopectin, just with more branches.
- Many branches allow an increase in the number of points where enzymes can attach, so many glucose monomers can be released rapidly.
- It is very compact which means lots of glucose is stored in a small space.
What are the characteristics of cellulose?
- Long, unbranches chains of beta glucose
- Forms a straight chain.
- These chains run in parallel to each other and are linkeed by hydrogen bonds to form microfibrils.
- Parallel groups of microfibrils are called fibres.
How do you test for a reducing sugar?
- Using benedict’s reagant
- Heat in a water bath that has been brought to boil
- Will form a brick red precipitate when reducing sugar is present.
How do you test for a non-reducing sugar?
- Add benedict’s and test for a reducing sugar.
- if the sugar was not reducing then we add an acid to catalyse a condensation reaction, then dilute HCL and heat in a water bath, bringing it to a boil.
- Add sodium hydrogen carbonate to neutralise.
How do you test for starch?
- Using iodine dissolved in potassium iodide solution.
- Solution should change from brown to blue/black.
