Chemistry and biochemistry Flashcards
Definition of chemistry
The science that deals with the composition and properties of substances and various elementary forms of matter (gas, liquid, solid)
Definition of biochemistry
The science concerned with the chemical and physicochemical processes and substances that occur within living organisms
Definition of matter
Everything around us that has mass and occupies space. Atoms make up matter. Atoms are made up of electrons, protons and neutrons.
Definition of an element
Substance made up of just one type of atom - cannot be split into a simpler substance. Elements we know of are in the periodic table.
How many different elements are normally present in the human body?
26
What are the four major elements which account for 96% of the human body?
Oxygen (65%), carbon (18%), hydrogen(10%) and nitrogen (3%).
What is an isotope?
Different versions of the same element due to a different number of neutrons in the nucleus. Does not affect chemical activity, but does change the mass.
Example of an isotope?
Carbon 12 - 6 protons, 6 neutrons
Carbon 14 - 6 protons, 8 neutrons
What causes radioactivity?
Radioactive isotopes - an imbalance of protons and neutrons in the nucleus - too many neutrons, means the element is unstable and will attempt to lose energy in the form of radioactivity.
What diagnostic techniques use radioactive isotopes?
PET Scan
Radiotherapy - radioactive tracers emit gamma rays to target rapidly dividing cells. Also highly damaging to healthy tissues.
Breath test for H. pylori
What is ionic bonding?
One atom gives an electron to another atom creating positive and negative charged ions that are attracted to each other.
What is covalent bonding?
Atoms share electrons.
Explain what is meant by an ‘ion’?
A charged atom that has either gained or lost an electron.
What is the ionisation?
The process of giving up or gaining electrons
What does it mean when an atom has a positive charge?
The atom has given up electrons and so has more protons than electrons eg Ca2+ has donated two electrons.
What does it mean when an atom has a negative charge?
The atom has gained electrons, so it has more electrons than protons.
What is a covalent bond?
When two elements share electrons - they both have the ‘magic number’ they are looking for. Eg H2O
What is a polar bond?
Where electrons are shared unequally. This happens because some atoms have a lot of ‘electron pulling power’.
Why is water known as the ‘universal solvent’?
Unique ability to dissolve anything with polar bonds or ionic compounds and therefore can dissolve more substances than any other liquid. This means wherever water goes it takes along valuable chemicals, minerals and nutrients, such as salt.
What is an electrolyte?
An ionic compound (eg salt) dissolved in water.
What are the seven key electrolytes in the body?
Sodium, potassium, chloride, calcium, magnesium, phosphate and bicarbonate.
Why are electrolytes important?
- conduct electricity, so essential for nerve and muscle function
- water balance as they exert osmotic pressure
- acid-base balance
What is an acid?
A substance that releases a high amount of H+ ions when dissolved in water.
What is a base?
A substance which binds to H+ ions in solution, creating lots of OH-.
What is the optimal pH range?
7.35 - 7.45 optimal for chemical reactions to occur.
What is the best way to measure pH in the body?
Urine and saliva. Ideally would measure tissue pH, but this is very difficult. The blood will always work hard to maintain it’s pH range (through breathing, the kidneys and buffer systems).
What is the ‘collision theory’?
For a chemical reaction to occur there needs to be the opportunity for two molecules to collide.
What is the ‘energy of activation’?
The minimum energy required for a reaction. The higher the energy of the molecules, the faster they move and the greater chance they of colliding/reacting.
What is a catalyst?
Speeds up chemical reactions by lowering the activation energy required. Catalysts the body produces are called enzymes.
What is an ‘anabolic’ reaction, and provide an example?
It is a building reaction, where bonds are formed, for example building protein from amino acids. Energy is required to build bonds.
What is a ‘catabolic’ reaction, and provide an example?
It is when a bond breaks down, for example the break down of food to release energy. In catabolic reactions, energy is released.
What is a ‘hydrolysis reaction’?
When water is the medium responsible for breaking down the molecule.
What is ‘dehydration synthesis’?
When water is formed as the waste product of a reaction. Typically to make a new bond, we remove water. Eg when makes carbohydrates.
What is the formula OH-?
Hydroxide - consists of an oxygen and hydrogen atom held together by a single covalent bond. Acts as a ligand (an ion or molecule that bonds to a metal atom or ion).
What is a ‘buffer system’?
Buffers are substances that maintain the H+ concentration in the body within normal limits. They can bind to H+ and OH- to ensure blood range of 7.35-7.45 is maintained.
What is ‘oxidation’ and ‘reduction’?
Oxidation is losing (OIL) and Reduction is gaining (RIG).
What is a ‘free radical’?
Molecules with an unpaired electron in their outer shell.
Pathologies linked to oxidative damage?
Cancer, atherosclerosis (endothelial damage), fibromyalgia and neurodegenerative diseases.
Causes of oxidative damage?
Natural processes such as cellular metabolism, aerobic respiration and inflammation. But also from the environment, such as pollution, sunlight, strenuous exercise, X-rays, smoking, alcohol.
What is the role of the antioxidant?
Donating an electron to the free radical, enabling them to become stable and harmless. The key to a good antioxidant is that it must be stable once it has given away its electron.
Examples of antioxidants?
Glutathione peroxidase - formed as part of natural metabolic processes to mop up natural free radicals.
Beta-carotene
Vitamin C and E
Quercetin
What is an isomer?
Same chemical formula but different structures.
What is a glycosidic bond?
A bond formed by dehydration synthesis (carbs).
Name the monosaccharides
Glucose, fructose, galactose, deoxyribose and ribose.
Name the disaccharides
Sucrose (table sugar) = fructose + glucose
Lactose = glucose + galactose
Maltose = glucose + glucose
Name the polysaccharides
Starch, glycogen, cellulose (all glucose chains).
What % of starch is amylose and amylopectin?
amylose - 20-25%
amylopectin - 75-80%
What is the difference between amylose and amylopectin?
amylose is a polysaccharide component made from a single chain of glucose units, whereas amylopectin has a branch-like structure.
What is glycogen?
Glycogen is a polysaccharide of glucose which functions as a primary short-term energy store.
Each glycogen molecule contains about 60,000 glucose molecules. Even more branches than amylopectin. Therefore very quick to break down to release energy.
Where is glycogen made and stored?
In the liver and muscles.
Glycogen in the liver used to maintain blood glucose levels.
Glycogen in the muscles can only be used for that particular muscle.
What is cellulose?
Structural material of walls - found in plant cell walls. Units of glucose in a very rigid structure - a flat, ribbon-like structure. Humans lack the enzymes to break these unique bonds. We cannot digest, so offers little in terms of energy.
Therefore it acts as fibre, assisting with the movement of materials through the intestines.
Bacteria feast on it.
What are the functions of carbohydrates?
FAG
Fibre:
- proper bowel function (brushing material through, carrying out toxins/wastes, aiding elimination)
- protects against CVD, colorectal cancer and diabetes
- satiety, can aid weight loss
ATP synthesis:
- primary fuel for energy production
Glycogen synthesis:
- a limited storage form of energy
What are the different enzymes at play in carbohydrate digestion?
Salivary amylase - neutral pH - starts working on ends of glucose chains in starches. Deactivated by stomach acid.
Pancreatic amylase - small intestine - breaks into disaccharide units.
Brush border enzymes - last stage in small intestine.
Note: coeliac disease - brush border can be damaged leading to poor carb digestion. Brush border damage - can lead to diarrhoea and bloating.
What are the functions of triglycerides?
PIES
Protection of body parts and organs
Insulation
Energy source, albeit not as efficient as carbs
Stores excess calorific intake (extra glucose is also turned into triglycerides)
What is a saturated fat?
Contains single covalent bonds between each of the fatty acid carbon atoms. Each carbon atom is saturated by hydrogen.
What is monounsaturated fat?
Fats with one double covalent bond between two carbon atoms.
What is polyunsaturated fat?
Fats that contain fatty acids with more than one covalent bond between two carbon atoms.
What is an Essential Fatty Acid (EFA)?
EFAs are polyunsaturated fatty acids that cannot be constructed within the body and therefore must be obtained from the diet. Two Families of EFAs - Omega-3 and Omega-6.
Name the different types of omega-3 fatty acids?
a-linolenic acid (ALA) - linseeds, walnuts, flaxseeds
Eicosapentaenoic acid (EPA) - oily fish
Docosahexaenoic acid (DHA) - oily fish
Name the different types of omega-6 fatty acids?
Linoleic acid (LA) - sunflower seeds
Gamma linolenic acid (GLA) - evening primrose oil
Arachidonic acid (AA) - meat, diary and eggs
What are the functions of EFAs?
CHILD BAP
Cell membrane integrity
Hemoglobin production
Immune system balance
Lubrication of joints
Digestive enzyme production
Brain - needed for issues/nerve transmission
Allergy prevention
Prostaglandin production
Polyunsaturated fats are prone to becoming free radicals, what three factors cause this?
Heat, light and oxygen.
What is a lipoprotein?
A fat molecule that has been joined to a protein molecule, enabling the lipid to to move around the bloodstream.
What is the structure of a lipoprotein?
Internally - triglycerides and cholesterol. Externally - phospholipids (hydrophilic - enabling them to interact with blood/water).
What organ makes lipoproteins?
Liver.
What is a chylomicron?
A large type of lipoprotein that transports dietary fat from the small intestine to the liver, muscles and adipose tissue.
What is the function of Very Low Density Lipoproteins (VLDL)?
To carry newly synthesised triglycerides from the liver to adipose tissue. If high - a sign of over-eating.
What is the function of Low Density Lipoproteins (LDL)?
Carry cholesterol from the liver to the cells of the body. Needed to repair cells, support cell membranes and make sex/adrenal hormones.
What is the function of High Density Lipoproteins (HDL)?
To collect cholesterol from the body’s tissues, bringing it back to the liver. Balance of LDL and HDL is critical. Problems arise when there is too much LDL to HDL.
Describe the structure of a phospholipid.
Glycerol part + 2 fatty acid chains.
Phosphate head - contains lots of -OH molecules making it polar and water soluble - hydrophilic.
Fatty acid tails - non-polar, only interact with other lipids. Hydrophobic and fat-soluble. Contain both saturated and unsaturated fats. A good balance of these to support a healthy cell membrane - a structure that isn’t too rigid or too fluid.
Because phospholipids are soluble on one side and insoluble on the other, they are known as amphiphatic.
What are steroids?
Lipids formed from cholesterol. Differ in shape from triglycerides - four rings of carbon atoms joined together at the base.
What are sterols?
Steroid bases that contain at -OH group.
One function of steroids?
To produce sex hormones and cortisol.
