Biology Coursework

• Condensation reaction – two molecules combine and produce a water molecule

• Hydrolysis reaction – this is when water is added to a bond which causes it to break.

• Monosaccharide is a basic monomer and can combine to form a disaccharide or a polysaccharide

• Glucose joined to glucose forms maltose
• Glucose joined to fructose forms sucrose
• Glucose joined to galactose forms lactose

• Alpha glucose has the OH on the bottom and beta glucose has the OH on the top

• Starch is made of a glucose monosaccharide’s linked by glycosidic bonds in a condensation reaction.

• Starch can be used for storage in plants and can be branched for quick enzyme action and it insoluble in water.

• Glycogen is found in animals and is highly branched for quick release of energy and it is insoluble so it is suited for storage

• Cellulose is made of beta glucose and is a polysaccharide cellulose has straight un branched chains

• The parallel chains have hydrogen bonds between them for structural support of cell walls.

• Lipids contain carbon hydrogen and oxygen and they are insoluble in water. The main groups are phospholipids and triglycerides.

• Lipids are used for waterproofing, insulation, energy and protection.

• Triglycerides are made of three fatty acids and one glycerol and each fatty acid forms an ester bond with the glycerol due to a condensation reaction and a hydrolysis reaction would break the bond.

• Triglycerides produce a lot of energy to high ratio of carbon hydrogen bonds and they also have a low mass to energy ratio which is good for storage. They are also non polar which means they aren’t effected by osmosis.

• Phospholipids have 2 fatty acids and one phosphate molecule attached to the glycerol. The phosphate is hydrophilic and the fatty acids are hydrophobic

• The phospholipid Is polar which means it will form a bilayer within cell surface membranes. The hydrophobic end will form a barrier in and out the cell.

• The hydrophilic will hold the surface of the membrane together.

• Phospholipids can form glycolipids in the cell membrane which is used for cell recognition

• Amino acids are basic monomer units, which combine to form polymers called polypeptides. Polypeptides combine to form proteins.

[pic 1]

• H2N = basic amino group
• COOH = acidic group which forms the second part of amino acid
• H = hydrogen atom
• R = different chemical groups which are different in amino acids

• Peptide bonds are made from the H in H2N combining with an OH from COOH group via a condensation reaction. This will form a dipeptide bond

• The primary structure of a protein is the sequence of amino acids found in its polypeptide chains. This sequence determines its properties and shape.

• The secondary structure forms a 3D spiral structure due to the weak hydrogen bonding in the polypeptide chain. Known as an alpha helix

• The tertiary structure is due to the bending and twisting of the polypeptide helix into compact structure. Bonds present are disulfide bond, which are the strongest, then ionic bond and hydrogen bonds.

• The quaternary structure arises from a number of different polypeptide chains and there are non-protein groups in the molecule of protein. The 3D structure affects its functions however the sequence of amino acids would affect its functions in the first place.

• Enzymes are globular proteins and act as catalysts to speed up the rate of a chemical reaction with taking part in it itself. They can be reused so can be used in small amounts.

• Enzymes help to lower the activation energy. Enzymes have an active site made of amino acids. The substrate will combine with the active site to form an enzyme substrate complex.

• Induced fit model suggests the enzyme will mould around the substrate as long as it has generally similar shape. This puts tension on the substrates bonds and distorts them, which lowers the activation energy.

• The lock and key model suggests the substrate will only fit one active site of a particular enzyme. However it is limited as the model suggest the enzyme was rigid and scientist found molecules could form bonds with places other then active site which shows that it can change shape and is not rigid.

• Increasing the temperature gives the more kinetic energy to the enzymes, which means they move faster and collide more frequently. However after the optimum temperature the hydrogen bonds begin to break and the shape of the active site changes.

• The PH is measured y the hydrogen ion concentration and certain PHs will affect the enzyme activity. If the PH is too high it can change the amino acids, which affects the active site so it can combine with the substrate. If it’s a stronger PH it can break the tertiary structure or denature the enzymes and affect the active site shape.

• Drawing a straight line or tangent off the steepest part of the graph does measuring the rate of a reaction. you would pick two point at either end of the tangent and then do the change in Y divided by the change in X.

Miss Robbin revision

• Magnification is how many times larger an object will appear under a microscope.
• Magnification = size of image / size of real object

• Resolution is being able to distinguish between two objects under a microscope.

• Cell fractionation begins by putting the tissue in cold with to reduce enzyme activity and adding buffer solution to control PH and the same water potential to stop the cell from bursting.

• Cells are first homogenised or blended to break the organelles from the cells then homogenate is filtered to remove any complete cells or debris.

• Then the homogenate is placed into a centrifuge and spun around at varying speeds. The heavier organelles will come out at low speeds such as the nuclei then the mitochondria and then the ribosomes. The supernatant is removed to leave the nuclei.

• Electron microscopes have very short wavelengths and therefore show smaller objects. Also electrons are negatively charged and can be focused using electromagnets.

• TEM microscopes work by firing electrons at a specimen and some electrons are absorbed which show up dark and some pass through which are shown as white. This gives an image. Limitations are that it needs to be in a vacuum, complex staining process and specimen must be thin. However it gives 3D images and how magnification.

• The SEM microscopes work by firing electrons on the under side of specimen and the electrons bounce back to form a 3D image due to the contours and pattern of reflective electrons. Produces a 3D image however it has a lower resolution then the TEM.

• To calibrate a eye piece graticule you line the stage micrometre up with the graticule and if the micrometre is 10 units it would equal 40 units on the graticule scale. 1 unit on the micrometre equals 4 on the graticule so you would do 10/4 =2.5 micrometres.

• Nucleus acts as a control centre for the cell and retains the genetic information in the form of DNA and chromosomes. It also produces ribosomes. It consists of a nuclear envelope, which is a double membrane which controls entry in and out of the cell, also has ribosomes on it. Nuclear pores also messenger RNA out of the nucleus. Nucleoplasm, which is a jelly material in the nucleus. Chromosomes with DNA and nucleolus produce RNA ribosomes.

• The mitochondrion has a double membrane for control of material in and out of organelle and the inner membrane is folded in and is known as cristae they provide large surface area for enzymes and proteins to attach for respiration. The matrix contains lipids, proteins ribosomes and DNA that allows the mitochondria to produce its own protein. It also produces energy carrying ATP for metabolically active cells such as the muscle cells or the epithelial cell, which require a lot of energy for the absorption of substances via active transport.

• Chloroplast consists of a double plasma membrane, which is selective of passage in and out of cell. The grana are stacks of disc, which are called thylakoids within them or chlorophyll, which absorbs light. Then the stroma is a fluid filled matrix for synthesis of sugars it also contains starch. Granal membranes give a large surface area for attachment of chlorophyll and enzymes for photosynthesis. The stroma fluid contains enzymes needed to make sugars.  Chlorophyll contains DNA and ribosomes for protein production.

• RER has ribosomes on its surface and is used as a transport pathway for protein through the cell. It also carries out protein synthesis using the ribosomes. SER has no ribosomes and is more tubular it synthesises stores and transports carbohydrates and lipids.

• Golgi apparatus helps to modify proteins and give them non-protein characteristics they are then package and sent to the various other places. The Golgi helps to create lysosomes, manufacture proteins and carbohydrates for glycoproteins, transport modify and store lipids. Secrete enzymes into intestine.

• Lysosomes are produced by the Golgi apparatus and are used to produce enzymes to hydrolyse bacteria. It also digests warn out cells and dead cells. They also release enzymes out side of the cell to destroy material around the cell.

• Ribosomes carry out protein synthesis and are found on many organelles they also have 80s and 70s sizes.

• Cell wall is made of polysaccharide cellulose and is used for structural support of the cell and to stop the cells from bursting when osmosis takes place.

• Vacuoles are memory bound organelles which help to store waste and food temporarily. They also contain amino acids and sugars and they help with structural support.

• A collection of similar cells that perform a specific function is known as a tissue.  An example is epithelial tissue, which lines organs in animals, and either protects them or secretes. Xylem is another example of a tissue.

•  Organs are collections of tissues which work together to perform a particular function for example in the stomach the muscle tissues help to churn and mix contents, epthialal tissue protects the wall, and connective tissues to hold other tissues. For example in plants a leaf is an organ and the xylem and phloem tissue transport stuff, the mesophyll helps with gaseous exchange and the epidermis helps with protection.

• Organ systems are groups of organs, which work together for example in digestion the salivary glands, stomach, pancreas and liver work together. Respiratory system includes the bronchi, trachea and lungs. The circulatory system includes the heart, arteries and veins.

• Bacterial cells have a cell wall, slime capsule for protection, and a cell membrane. Inside the cell it has a cytoplasm and 70s ribosomes. No nucleus just a strand of DNA or plasmids.

Prokaryotic cells have:

• Slime capsule
• No chloroplast
• 70s ribosomes
• no nucleus
• not associated with proteins
• no membrane organelle

Eukaryotic cells:

• Has a nucleus
• Has membrane bound organelles
• No slime capsule
• Has chloroplast
• Associated with DNA
• Ribosomes are 80s

• Viruses are non-living and the DNA only multiplies when in a host cell. They have attachment proteins which inject their nucleic acids into host cell which has instructions for its metabolic rate.

Interphase:

• Cellular activity
• Copying of DNA

Prophase:

• Chromosomes appear and shorten/thicken.
• Centrioles move to opposite poles
• Spindle fibres develop
• Nucleolus disappears

Metaphase:

• The chromosome is made of two chromatids, joined by centromere
• The spindle fibres attach and move them to the equator

Anaphase:

• Centromeres divide into two spindle fibres
• Chromatids are pulled to their poles.
• The energy comes from mitochondria

Telophase and cytokinesis:

• Chromosomes reach poles and disappear leaving chromatid
• Nucleolus reforms
• Spindle fibres disappear.
• Cytoplasm divides leaving two cells.

• Mitosis is needed for growth, repair and reproduction.

Cell division in prokaryotic cells:

• Circular DNA replicates and attaches to cell membrane
• Plasmids replicate
• Cell membrane grows between two DNA molecules
• This causes two daughter cells which contain plasmids/ circular DNA

Cell cycle:

• Interphase resting period
• Nuclear division nucleus divides
• Division of cytoplasm to form tow new cells

• Mitosis is controlled by genes however if there damaged it can lead to uncontrolled growth and cell divisions. This can lead to damaged cells being cloned and forming tumours. Mutated genes can be replicated and for malignant tumours which are dangerous.

• Controlling cancer is done by stopping the cell cycle by preventing DNA from replicating and stopping metaphase stage by messing with spindle fibres.  This stops rapidly dividing cells such hair producing cells, which causes hair loss.

• The cell surface membrane consists of a phospholipid bilayer with a hydrophilic head and a hydrophobic tail. This helps to control the passage of material in and out of the cell while forming a barrier. Proteins are used as channel proteins to allow ions to diffuse across. Also carrier proteins mind to amino acids and change shape to pass across the membrane if it’s to large. Proteins also provide structural support. Cholesterol helps provide structural support and as it is hydrophobic it prevent water leaking as it pulls the lipids closer together. Glycolipids help act as a recognition site for toxins such as cholera. Glycoproteins help act as a recognition site for hormones and help cells join to form tissues.

• Many molecules don’t pass through the surface membrane because they are too large for the protein channels or have the same charge so repel.

• Diffusion is the net movement of particles from a region of high concentration to a region of low concentration.

• Facilitated diffusion is the movement of particles from an area of high concentration to an area of low concentration by a carrier protein or protein channel.

• The net movement of water from an area of high water potential to and area of low water potential through a partially permeable membrane. Water potential is measured in kilo pascals and pure water has a potential of zero. The water will move to the more negative KPa.

• In plant cell if the water potential is higher out side the cell the water will flow into the cell and causes it to swell and become turgid and if it flows out the cell the cell will shrink and become plasmolysed.

• Active transport is the net movement of molecules from an area of low concentration to and area of high concentration using ATP and carrier proteins.

• Increasing the movement across membranes can be done by increasing number of micro villi, increasing number of protein channels and carrier proteins.

• Co transport is when sodium goes from a lumen into a cell by diffusion however it binds to a carrier protein and glucose molecules and goes into the cell. The glucose goes into the blood stream by facilitated diffusion, as there is a lower concentration of glucose in the blood. The sodium is taken by active transports, which requires ATP. The ATP breaks down to DTP to release energy and carry the sodium and carrier protein into the blood.

Calibrating a graticule:

• Start with lowest power object
• The scale on the stage is aligned with micrometre
• Reading is taken from each scale
• For example 100 divisions on eyepiece = 25.9 on the micrometre
• 100 divisions = 1mm
• each division is 1/100 mm = 10 micrometres
• 100 eyepiece div = 25.9 um
• 1 eyepiece div = 259/100um = 2.59um

Experimental tests:

Test for reducing sugars:

• Place 2cm of sample into a test tube
• Add 2cm of benedict’s reagent
• Place in a water bath at 80 for 5 minutes
• Colour change to brick red indicates reducing sugars

Test for non- reducing sugars:

• Carry out the test for reducing sugars
• Add 2cm of HCL to break the glycosidic bonds
• Add sodium hydro carbonate to neutralise the acidic conditions
• Then add Benedict’s reagent and look for a colour change.

Test for starch:

• Add 2cm of sample into a depression spotting tile
• Add 2 drops of iodine solution
• Presence of starch will turn it black or blue.

Test for lipids:

• Add 2cm of sample to 5 cm of ethanol in a grease free tube
• Shake thoroughly to let the lipids dissolve
• Add 5cm of water and shake
• A cloudy shite colour indicates lipids. This is due to the lipids dispersing and the light is refracted as it passes through

Test for proteins (biuret test):

• Add 2cm of sample and 2cm of sodium hydroxide to a test tube
• Add a few drops of dilute copper sulphate solution and mix
• A purple coloration indicates peptide bonds and hence proteins if no proteins the solution stays blue.