Paper 1 recall Flashcards
What is the test for reducing sugars and what are some examples of reducing sugars?
Add Benedict’s reagent (copper sulphate- blue) to 2cm^3 solution of food and heat for 5 minutes to form a red insoluble precipitate (copper oxide)
All monosaccharides and some disaccharides (maltose)
What is the test for a non-reducing sugar?
Carry out reducing sugar test and if negative: add 2cm^3 of food solution to dil HCl and boil for 5 minutes, add NaOH to neutralise and test pH with litmus paper (must be alkaline), re-test with Benedict’s and orange-brown solution should form for positive test
What is the test for starch?
Place 2cm^3 of the sample being tested into a test tube, add 2 drops of iodine solution and shake, positive test will show blue-black colour
What are the features of starch?
May be branched or unbranched
Unbranched are wound into tight coil
What are the features of glycogen?
Shorter chains than starch and more highly branched
Why is glycogen more suitable storage for animals than starch?
More highly branched for enzymes to act simultaneously for respiration and animals have a higher metabolic rate so need rapid glucose release
How does the cellulose cell wall prevent the cell from bursting?
Exerts an inward pressure that stops any further influx of water, the rigidity allows cells to align for larger surface areas for photosynthesis
What are the roles of lipids?
Cell membranes, source of energy, waterproofing, insulation and protection
What are the properties of triglycerides?
High ratio of energy storing carbon-hydrogen bonds to carbon atoms, low mass to energy ratio, large, non-polar, high ration of hydrogen to oxygen meaning the release water
What is the test for lipids?
2cm^3 of food solution add 5cm^3 of ethanol and shake thoroughly, add 5cm^3 water and allow shake gently, a milky-white emulsion appears for positive test
What is the secondary structure of proteins?
The positive charge of NH group and negative charge of C=O causes weak hydrogen bonds to form that create alpha helix or beta pleated sheet
How are ionic bonds formed in tertiary structure of proteins?
Formed between carboxyl and amino groups that aren’t involved in peptide bonds, they are relatively strong but easily broken by change in pH
What is the test for proteins?
Add Biuret reagent and a purple solution indicated positive test
What is the induced fit model for enzyme action?
The proximity of the substrate leads to a change in the enzyme shape that forms the functional active site, when the enzyme changes shape it puts a certain strain on bonds in the substrate, lowering the activation energy
What are the two ways changes in pH can alter how enzymes work?
Alters the charges on amino acids and breaking of ionic bonds in the tertiary structure
Why is DNA stable?
Phosphodiester backbone protects the more chemically reactive bases inside the double helix and hydrogen bonds between bases form bridges C-G forms 3 so the more C-G : A-T the more stable
How is ATP used by an organism?
Metabolic processes, movement, active transport, secretion and activation of molecules (glycolysis)
What are the features of water?
Dipole, hydrogen bonds, high specific heat capacity, high latent heat of vaporisation, high cohesion and surface tension in water
What are the importances of water?
Metabolite, raw material, hydrolysis, physiological solvent for O2, control of temperature, transparent for photosynthesis in water
What are some inorganic ions and what are their functions?
Fe2+ in haem, PO4 3- in ATP and DNA, H+ in determining pH and Na+ in co-transport
What are the 3 conditions for solutions used in cell fractionation?
Cold- reduce enzyme activity
Same water potential- prevent bursting organelles
Buffered- maintain pH for organelle structure
What are the steps in cell fractionation?
Homogenation: cell placed in homogeniser to release organelles, then the homogenate is filtered to remove debris and whole cells
Ultracentrifugation: spun in centrifuge at lowe speed and organelles form pellets from high to low mass as speed increases, supernatant removed and transferred to new tube before spinning again
What are the limitations of TEM?
Difficult to prepare specimen for resolution, may destroy the specimen, vacuum, must be dead, complex staining must be thin, artefacts may be present in the photomicrograph
How does SEM work?
All limitations of TEM, only it forms 3D images from computer analysis as the electron scatter and bounce of specimen surface, this has a lower resolving power then TEM
What does the nucleolus do?
Manufactures rRNA and assembles the ribosomes, there may be more than one nucleolus in each nucleus
What are the functions of RER?
Large SA for the synthesis of proteins and glycoproteins and provide a pathway for the transport of materials, especially proteins throughout the cell
What are the functions of the SER?
Synthesise, store and transport lipids and carbohydrates
What are the functions of the Golgi apparatus?
Add carbs to proteins to form glycoproteins, produce secretory enzymes, secrete carbohydrates for cell walls, transport, modify and store lipids and form lysosomes
When are lysosomes formed?
When Golgi apparatus vesicles contain proteases and lipases and lysozymes
What are the functions of lysosomes?
Hydrolyse ingested phagocytic material, release enzymes outside cell, digest worn-out organelles and autolysis
What are the cell walls of algae, fungi and bacteria made up of?
Algae- cellulose and/or glycoproteins
Fungi- chitin, glycan and glycoproteins
Bacteria- murein
What is the tonoplast and what does it contain?
The single membrane around a vacuole and a solution of mineral salts, sugars, amino acids, wastes and sometimes pigments
What’s the structure of mitochondria?
Double membrane with the inner folding to form cristae, to provide a large SA for enzyme attachment, the matrix is the rest of the mitochondria and consists of the proteins, lipids, ribosomes, DNA and many respiration enzymes
What’s the structure of chloroplasts?
Double plasma membrane, grana are stacks of thylakoids containing chlorophyll, some are joined by extensions, the stroma is the fluid-filled matrix where the second stage of photosynthesis happens, starch grains can be found here
What are the features of prokaryotic cells?
No nucleus, no histones, may contain plasmids, no membrane-bound organelles, smaller ribosomes, murein cell wall, may contain outer mucilaginous layer called capsule
What’s the structure of general viruses?
Nucleic acids contained within a protein capsid
What happens in prophase of mitosis?
Centrioles move to opposite poles of the cell and spindle fibres develop, spanning the whole cell to form the spindle apparatus, nuclear envelope breaks down and chromosomes are left free and drawn to the equator by
spindle fibres attached to centromere
What happens in metaphase of mitosis?
Chromosomes are seen as two chromatids joined by centromere, they arrange across the equator of the cell
What happens in anaphase of mitosis?
Centromeres divide into two, spindle fibres pull the individual chromatids rapidly towards their respective poles and they’re now considered chromosomes
What happens in telophase and cytokinesis?
Chromosomes become longer and thinner, disappearing altogether, leaving chromatin, spindle fibres disintegrate and nuclear envelope and nucleolus reform, cytoplasm divides
Why may proteins be embedded in the membrane but not span across it?
To provide mechanical support, or act as cell receptors for molecules such as hormones
What are the functions of cholesterol in membranes?
Reduce lateral movement by pulling together fatty acid tails, make the membrane less fluid at high temp and prevent leakage of water and dissolved ions from the cell as they are very hydrophobic
What are the functions of glycolipids?
Act as recognition sites, help maintain the stability of the membrane and helps attach to other one and so form tissue
What are the functions of glycoproteins?
Act as recognition sites, help cells to attach to one another and form tissues and allows cells to recognise one another e.g. lymphocytes
How do protein channels control the entry and exit of substances?
Particular ions bond with the protein causing changes in shape, it is always open at one end and closed at the other
How can the rate of movement across membranes be increased?
Microvilli
Increase the number of protein channels and carrier proteins in a given area of membrane
Why is co-transport an indirect form of active transport?
The concentration gradient of sodium ions drives the movement, rather than ATP
What cells must an immune system be able to recognise?
Pathogens, non-self material, toxins and abnormal body cells such as cancer
How do lymphocytes recognise cells belonging to the body in foetus?
Foetus rarely become infected as they are protected by the placenta, lymphocytes within the foetus collide constantly with other cells, meaning they collide exclusively with own body cells, complimentary lymphocytes either die or are suppressed
How do lymphocytes recognise cells belonging to the body in adults?
Once produced in the bone marrow, they initially encounter self anit-gens and any that show immune response under controlled cell death (apoptosis) before they can differentiate
What are B lymphocytes?
Mature in the Bone marrow, associated with humoural immunity (antigens) in bodily fluids or ‘humour’ such as blood plasma