Download Option B IB Chemistry Definitions SL

Chemistry: Definitions
Option B – Human Biochemistry - SL
Amino acid:
A compound in which an amino group and a carboxylic acid group are
present. There are 20 aa that occur naturally. Can be polymerized to
form proteins. Exists as a zwitterion at their isoelectric point. All
except glycine can show optical activity.
aa
Amino acids, essential: Aa’s that our body is not able to produce and we need to have them as
nutrients. There are 10 of these.
Amino-acids, non-essential:
Anabolic steroids:
Aa’s that we are able to produce in our body.
All steroids contain characteristic four-ring structure. Have similar
structure to testosterone. Build up muscle.
Anabolic:
Processes in which complex molecules are made from simpler ones, such
as in photosynthesis.
Calorie:
The energy required to raise the temperature of 1g of water by 1C.
Calorific value:
The energy content of food.
Carbohydrates:
Produced by photosynthesis in plants. Used to
1) provide energy;
2) store energy (starch is stored in liver in form of glycogen);
3) precursors for important biological molecules (e.g. they are
components of nucleic acids).
Catabolic:
Processes in which molecules are broken down into simpler ones, such as
aerobic respiration.
Denaturation:
When the three-dimensional conformation of the structure is destroyed,
and the protein becomes biologically inactive. Denaturing agents are:
1) heat;
2) UV-radiation;
3) strong acids and bases;
4) concentrated salt solutions;
5) heavy metals (no, not that kind… examples are Pb, Hg, etc).
Diet:
Well-balanced diet consists of about 60% carbohydrate, 20-30% protein
and 10-20% fat. Should include essential vitamins and fifteen essential
minerals. Amount of food required depends on age, weight, gender, and
daily activity.
Eluent:
The solvent in which the chromatographic paper is placed in paper
chromatography.
Fats:
Solid triglycerides at room temperature. Contain only saturated
carboxylic acid groups. Uses of fats:
1) efficient way to store energy (in adipose tissue);
2) thermal insulation;
3) protection;
4) form part of cell membranes,
5) source of energy (can be oxidized more than carbohydrates).
Fatty acid:
Long chain carboxylic acids.
Feedback mechanism: When a product of a process or a hormone reaches a certain level, it
inhibits (negative feedback) or promotes (+ feedback) a further
response.
Food calorimetry:
Measuring the energy content of food.
Furanose:
Five membered ring containing an oxygen atom, such as in fructose.
Glucose:
A hexose monosaccharide. Form of glucose found in nature is D-glucose,
which can exist in two separate crystalline forms:
1) -D-glucose (OH groups are down, down, up, down; following
carbon chain);
2) -D-glucose (up, down, up down).
Glycosidic link:
C6H12O6
Link between two sugar in a polysaccharide, formed by condensation
reaction.
GM food:
Genetically modified food. Benefits: Improve flavor, nutritional value,
and shelf life. Could incorporate anti-cancer substances. Could make
plant more resistant to disease. Concerns: unpredictable outcome. May
cause antibiotic-resistance. May alter balance of ecosystems.
Hard water:
Contains Mg2+ or Ca2+. Prevents soap from working efficiently as it
reacts with the anion of the soap, producing a precipitated salt.
Hormone, adrenalin:
Responsible for ‘fight or flight’ response (goose bumps, increased
pulse/BP). Produced in adrenal medulla.
Hormone, insulin:
Made up of 51 aa residues. Decreases glucose levels in blood by making
liver absorb glucose in the form of glycogen. Insulin produced in -cells
of Islets of Langerhans.
Hormone, thyroxine: Regulates metabolism. Produced in thyroid gland. Hypothalamus releases
local hormone which tells anterior pituitary to release thyroid SH (+
feedback). TSH tells thyroid glands to release thyroxine (+ feedback).
When the concentration of thyroxin reaches a certain level, a –
feedback is sent to hypothalamus, ceasing production of the local
hormone.
Hormones, sex:
Responsible for development of secondary sexual characteristics. Both
estrogen and testosterone produced in testes (males) and ovaries
(females). They are all steroids  contain characteristic four-ring
structure.
Hormones:
Chemicals produced in glands and transported to specific target cell by
blood stream, and binds to a receptor site on or within the target cell
 produces a specific physiological response. Glands are controlled by
pituitary gland, which in turn is controlled by the hypothalamus.
Hormones act as chemical messengers.
Hydrophilic:
Describing part of molecule that is attracted to water.
Hydrophobic:
Describing part of molecule that repels water.
Iodine number:
Number of grams that reacts completely with 100g of a triglyceride.
The higher the iodine number, the more unsaturated the triglyceride.
The pH value at which an aa exists as a zwitterion.
Isoelectric point:
Lactose:
Disaccharide in which -D-galactose and -D-glucose are joined by
glycosidic link.
Lipids:
Menstrual cycle:
Biological substances that are soluble in non-polar solvents (generally).
Lipases in digestive system degrade lipids.
Pituitary gland releases follicle SH, which travels to ovaries causing
release of estradiol. Two weeks later, – feedback stops release of FSH
and triggers release of luteinizing hormone, which travels to ovaries
and releases progesterone. Progesterone causes egg to be transported
to uterus. If egg is fertilized, it embeds itself on uterine wall and
hormone levels rise dramatically, otherwise hormone levels fall and
menstruation occurs.
Metabolism:
The network of biochemical reactions that supports life.
Micelle:
The particle formed when the hydrophilic tail dissolves in oil or grease.
Ninhydrin:
An organic dye. Causes coloration of aa’s. Used to see how far aa’s have
moved in both paper chromatography and electrophoresis.
Nutrient:
Substances that are required by an organism as food.
Oils:
Liquid triglycerides at room temperature. Contain at least one double
bond, i.e. they are unsaturated. The more unsaturated, the lower the
m.p. due to its inability to pack so closely together  the surface area
decreases  decrease in the van der Waals’ forces between the
molecules. Number of C=C bonds can be determined by addition
reactions with I2. See IODINE NUMBER.
Oral contraceptives: Most common ‘pill’ contains a mixture of estradiol and progesterone 
mimics the high hormonal levels of pregnancy, in turn preventing the
release of more eggs.
PAGE:
Polyacrylamide gel electrophoresis.
Phospholipid:
Form major part of plasma membranes. Phosphate group is hydrophilic
while lipid part is hydrophobic.
Polyunsaturated oils: An oil containing several double bonds.
Protein structure, electrophoresis:Electrophoresis is carried out on a medium called PAGE.
Sample is placed in center of gel, and a potential difference is applied
across it. The movement of the aa depends on the pH of the buffer: at
low pH, the amine group will be protonated, while at high pH, the
carboxylic
acid
is
deprotonated.
At
the
isoelectric
point
–
characteristic for each aa – the aa exists as a zwitterion, and will not
move (charges balanced). When satisfactory separation is complete,
the aa can be sprayed with ninhydrin, and their isoelectric points can
be compared.
Protein structure, paper chromatography:When a piece of chromatographic paper containing a
small sport of the unknown aa is placed in an eluent, the eluent rises up
the paper (capillary action). The different aa’s spread out to different
extents, and move up the paper at different rate.
Proteins:
Large macromolecules of chains of 2-amino acids. Formed by aa’s bonding
to each other by peptide bonds.
1) The primary structure of the proteins is their strict sequence
of aa residues.
2) The secondary structure describes how the chain folds itself
due to intramolecular hydrogen bonding (can be -helix – hydrogen
bonds within single chain, causing spiraling – or -pleated – hydrogen
bonds between chains).
3) The tertiary structure describes overall folding of the chain,
giving the protein its three-dimensional shape (may be due to hydrogen
bonds, van der Waals’, and ionic attraction. Two Cys residues can form
disulphide bridges).
4) The quaternary structure results from the interactions
between separate polypeptide chains.
Uses of proteins:
1) Many are enzymes;
2) can give structure;
3) source of energy;
4) regulation hormones.
Pyranose:
Six-membered monosaccharides such as glucose.
Retention factor:
The ratio of the distance traveled by the sample to the distance
traveled by the solvent in paper chromatography. Each aa has a
specific Rf value.
Saccharide, mono-:
Simple sugars. Empirical formula CH2O. Water soluble. Two families:
1) hydroxyaldehydes (contain aldehyde group and at least 2 OH
groups. Reducing sugars);
2) hydroxyketones (contain ketone group and at least 2 OH
groups. Non-reducing sugars). Monosaccharides containing more than 5
C-atoms can make cyclic molecules.
Saccharide, oligo-:
Containing 2-9 monosaccharides.
Saccharide, poly-:
Polymers of monosaccharides. Formed by condensation reactions,
forming glycosidic links.
Saponification:
The process in which a triglyceride is hydrolyzed, forming soap. Reverse
of esterification.
SH:
Stimulating Hormone.
Soap:
The sodium or potassium salt of the fatty acids produced from the
saponification process. Functions because of hydrophilic head and
hydrophobic tail. The tail dissolves in oil or grease to form a micelle.
Surrounded by hydrophilic heads, which makes it soluble in water.
Starch:
Polymer of -D-glucose. Exists in two forms:
1) amylose (water soluble);
2) amylopectin (water insoluble). Most plants use starch as a
store of carbohydrates.
Structure-function relationship:The structure of a chemical compound is adapted to its
function by evolution.
Sucrose:
Disaccharide in which -D-glucose and -D-fructose are joined by
glycosidic link between the C1 from the glucose and the C2 from the
fructose.
Synthetic detergents: Soap molecules of which the calcium or magnesium salts are soluble 
that they can work well in hard water as well. Cause more pollution than
soaps.
Triglyceride:
Formed from condensation reaction between glycerol and fatty acids.
Vitamin A:
Retinol. Found in cod liver oil, green vegetables and fruit. Fat soluble
despite OH group, due to long hydrocarbon chain. Not broken down
readily by cooking. Aids night vision. Retinol is oxidized to retinal in
body. Retinal combines with
protein opsin to form rhodopsin, the
active agent for converting light signals into electrical signals that
travel along optical nerve to brain. Deficiency  xerophtalmia or
night-blindness.
Vitamin C:
Ascorbic acid. Found in fresh fruit and vegetables. Water soluble.
Involved in biosynthesis of the protein collagen (found in connective
tissue). Deficiency  scurvy.
Vitamin D:
Calciferol. Found in fish liver oils and egg yolk. Can be formed on surface
of skin by UV light reacting with 7-dehydrocholesterol. Involved in
uptake of Ca2+ and PO43+ ions from food, and in formation of bone
structure. Deficiency  rickets.
Vitamins, fat soluble: A, D, E, F and K. Characterized by long non-polar hydrocarbon chains or
rings.
Vitamins, water soluble: C and the 8 B’s. Contain NH or OH groups  has ability to hydrogen
bond to water. Do not accumulate in body.
Vitamins:
Vitamin D is the only vitamin that the body is capable of synthesizing.
Can be defined as: 1) fat soluble or 2) water soluble. Vitamins
containing C=C bonds and OH groups are readily oxidized. Refrigeration
slows this process.
Water equivalent:
The equivalent addition of energy to water as released when burning
1.00g of a food, causing a temperature increase.
Zwitterion:
Ion with + and – charge. Aa’s exist as zwitterion at their isoelectric
point.