Barrons SAT Biology - Chapter 4 Biochemistry
|Six characteristics of water|| 1. High specific heat|
2. High heat of evaporation
3. High adhesion properties
4. Universal solvent of all polar and ionic substances
5. Strong cohesion tension - molecules stick together
6. Ice floats - water is more dense
|Covalent bonds are two types|| Nonpolar covalent - balanced. Electrons are shared equally by same atoms. H+H=H₂|
Polar covalent - unbalanced. Electrons are shared unequally by different atoms. H₂O
|Polar-Polar Attraction||Strong attraction between molecules of a polar bond. The negative end of one polar bond strongly attracts the positive end of another polar bond. H₂O is highly polar.|
| Hydrogen Bonding|
Two important hydrogen bonding functions are...
| 1. Keeps the two strands of DNA bonded together, forming a double helix|
2. Causes water molecules to stick together
/ \ / \
H⁺ H⁺ H⁺ H⁺
|Nonpolar Molecules||Have the weakest attractions, called van der Waals. Ex: CO₂ O=C=O shares double nonpolar bonds and is very balanced.|
|pH||The measure of acidity and alkalinity of a solution. Less than 7 is acidic, greater than 7 is alkaline, or basic. 7 is neutral.|
|pH of stomach acid||2|
|pH of milk||6.5|
|pH of blood||7.4|
|internal pH of most living cells||close to 7|
|How is pH regulated in the body||Buffers - they absorb excess and give needed hydrogen ions for a pH 7 balance|
|Most important buffer in human blood||bicarbonate ion - HCO₃⁻|
|Organic compounds. Name the four types||Organic compounds are compounds that contain carbon. Carbohydrates, lipids, proteins, nucleic acids|
|Carbohydrates consist of what three elements||carbon, hydrogen, oxygen.|
|Name the three important details of carbohydrates and name the three classes|| 1. Supply quick energy|
2. one gram of carbs will release 4 calories when burned
3. dietary sources are starches
4. three classes: monosaccharides, disaccharides, polysaccharides
Have chemical formula of C₆H₁₂O₆. Examples are glucose, galactose, and fructose which are all isomers of each other but have different physical and chemical properties. Image: structural formula of glucose
C₁₂H₂₂O₁₁ - Consist of two monosaccharides joined by a process called dehydration synthesis.
|Dehydration Synthesis|| Process where water is removed to put two smaller molecules together. Monosaccharide+Monosaccharide=Disaccharide and water|
C₆H₁₂O₆ + C₆H₁₂O₆ = C₁₂H₂₂O₁₁ and H₂O
|Hydrolysis|| The breakdown of a compound. it occurs during digestion and is the reverse of dehydration synthesis. |
Sucrose + Water -> Glucose + Fructose
|Polysaccharides||Polymers of carbohydrates. They are formed by many monosaccharides joined together by dehydration synthesis.|
|Four important Polysaccharides - 2 in Plants and 2 in Animals|| Found in plants: cellulose and starch|
Found in animals: chitin and glycogen
|Cellulose||A polysaccharide that makes up plant cell walls|
|Starch||A polysaccharide - the way plants store carbohydrates|
|Chitin||makes up the exoskeleten in anthropods and cell walls of mushrooms|
|Glycogen||A polysaccharide - "Animal starch"; in humans this is stored in the liver and skeletal muscle|
|Lipids are...||Fats, oils and waxes. Structurally, most consist of one glycerol and three fatty acids.|
An alcohol. It bonds with 3 fatty acids to form a lipid.
|Fatty Acids (describe structure and give the two types)||A fatty acid chain is a hydrocarbon chain with a carboxyl group (COOH) at one end. Types are saturated and unsaturated|
|Saturated Fatty Acids|| |
Mostly from animals. Solid at room temps; linked to heart disease. Saturated fatty acids contain only single bonds between atoms and have a carboxyl group (COOH) on the end.
|Unsaturated Fatty Acids|| |
Extracted from plants; liquid at room temps; considered good dietary fats; have at least one double bond between carbon atoms in the hydrocarbon chain so they have fewer hydrogen atoms, and have a carboxyl group (COOH) on the end.
|Lipids - 3 Functions|| 1. Energy storage - 1 gram of lipid releases 9 calories of energy|
2. Structural - Phospholipids are a major component of the cell membrane
3. Endocrine- Some are hormones
|Proteins are...||Polymers or polypeptides consisting of amino acids joined by peptide bonds. They consist of the elements SPCOHN.|
|Characteristics of Proteins|| 1. Responsible for growth and repair. |
2. Dietary sources are animal foods and plants (beans, nuts).
3. One gram burned in caloriemeter releases 4 calories.
4. Enzymes are proteins
|Amino Acids|| |
The building blocks of protein. There are 20 different amino acids. Humans produce 10. The others are supplied by food. Amino acids consist of a carboxyl group, an anime group, and a variable (R), all attached to a central atom. The R group differs with each amino acid
|Peptide bond|| |
covalent bond formed between amino acids.
|Protein Structure - name the four levels|
Primary - the sequence of amino acids in the chain
Secondary - the hydrogen bonding within the molecule
Tertiary - the 3D shape - this determines how it functions. When a protein/enzyme denatures from high heat or adverse pH its tertiary structure is altered and cannot be repaired so it cannot function.
Quaternary - proteins that consist of more than one polypeptide chain. EG - Hemoglobin is quaternary because it has four chains
Large proteins that regulate metabolism by acting as catalysts. They speed up reactions by lowering the energy of activation (Ea); They are reused and not degraded. They work on chemicals called substrates. and are specific so they alter their shape for substrate to fit.
|Naming enzymes||Named after their substrate with -ase suffix. Eg: Enzyme hydrolizes sucrose is sucrase; Enzyme that hydrolyzes lactose is lactase (necessary for digestion of dairy)|
|Enzymes function with the assistance of ...||cofactors (minerals) or coenzymes (vitamins)|
|Enzymes and temperature|| |
If body temp rises above 40C enzymes will stop functioning
|Enzymes and pH|| |
Each enzyme has an optimal pH. Some acidic, some alkaline. Each are at optimal pH in he middle of their range. Gastric enzyme - active at low pH when mixed with stomach acid. Intestinal enzyme amylase active in alkaline (high) pH
|pH compared with Molarity||A solution of pH 1 is 10 times more acidic than one of pH 2, 100 times more than pH 3, 1000 times more than pH4. Each pH value increases by 10.|
|Nucleic Acids||DNA - deoxyribonucleic acid and RNA - ribonucleic acid. They carry hereditary information.|
|Describe nucleic acids||They are polymers (chains of repeating units) of nucleotides. A single nucleotide consists of a phosphate, a 5-carbon sugar (either deoxyribose or ribose) and a nitrogen base.|
|The bases of DNA are...|| |
adenine, cytosine, guanine, and thymine
|The bases of RNA are...||adenine, cytosine, guanine, and uracil|
|Prions||Infectious proteins that cause disease. it is a misfolded version of a protein normally found in the brains of mammals. If it gets into a normal brain it causes all normal proteins to misfold in the same way.|