Biochemistry Chapter 6

Atoms and their interactions

Elements Substances that cannot be broken down into simpler chemical substances 90 naturally occurring  25 essential to life

Carbon (C), hydrogen (H), oxygen (O), and nitrogen (N)  96% of human body Trace elements  present in small amounts Iron, magnesium, iodine

Atoms Smallest particle of an element that has the characteristics of that element Nucleus  central portion Protons  positive charge Neutrons  no charge

Atoms cont. Electron cloud surrounds the nucleus Negative charge Travel in energy levels 1 st level  2e- 2 nd level  8e- 3 rd level  8e- (18e- total) Most atoms have equal numbers of protons and electrons  no net charge

Isotopes Atoms of the same element containing different numbers of neutrons Effects mass only (not charge) Some are unstable  radioactive

Carbon 12  6p and 6n Carbon 14  6 p and 8n

Compounds and bonding

Compound Composed of atoms of 2 or more different elements that are chemically combined Water  H 2 O Bonding occurs between atoms to reach stability Stability = outermost energy level is full

Covalent bonding  sharing e- H 2 O: O  6e- in 2 nd level H  1e- in 1 st level Most compounds in living organisms have covalent bonds  strong

Ionic bonding  gaining or losing e- Produces ions  charged particles NaCl: Na  1e- in 3 rd level Cl  7e- in 3 rd level

Chemical reactions Breaking and forming bonds Atoms are rearranged to form new substances Metabolism  all the chemical reactions in an organism

Chemical reactions cont. Represented by chemical equations 2H 2 + O 2  2H 2 O 2H 2 + O 2 are the reactants 2H 2 O is the product The numbers of each atom must be = on each side of the equation

Mixtures and solutions

Mixture Combination of substances that each retain their own properties Can easily be separated Salt and pepper

Solution 1 or more substances (solutes) are distributed equally in another (solvent) Cannot easily be separated Kool-Aid  sugar dissolved in water

Acids and bases The pH scale

Water and diffusion

The importance of water Essential for most life processes Universal solvent Means of transport

Polarity  unequal distribution of charge e- not shared equally  positive and negative ends to a molecule Polar molecules attract other polar molecules and ions (opposites attract)

Polarity continued Form weak hydrogen bonds Cohesion  water molecules stick together Adhesion  water sticks to other molecules Capillary action  water creeps up thin tubes

Water resists temperature changes Requires a lot of heat to increase water temperature Insulator  helps maintain homeostasis Expands when freezes  ice is less dense that water and floats

Diffusion Movement of particles from an area of high concentration to an area of lower concentration Due to random movement of all molecules  slow Continues until equilibrium is reached  equal concentration on each side

Diffusion Demonstration ure/lecnotes/lecgraphics/diffusion2.gif

Diffusion cont. Concentration gradient  difference in concentration No energy required to move with the gradient

Rate is affected by Concentration  higher concentration of molecules = faster diffusion Temperature  higher temperatures = faster diffusion Pressure  higher pressure = faster diffusion

Life substances

Role of carbon  organic compounds (C-H bonds) Can form 4 different bonds  versatile Straight chains, branched chains, rings Any number of C atoms  infinite number of structures Isomer  same formula, different structures

Role of carbon cont. Polymers  long chains of repeating units Made from smaller molecules bonded together by the removal of water  dehydration synthesis Hydrolysis  breaking apart polymers by adding water

Opposite Reactions Dehydration SynthesisHydrolysis

Carbohydrates  C:H:O in a 1:2:1 ratio Used to store and release energy Monosaccharides  simple sugars Building blocks of carbs Glucose  C 6 H 12 O 6

Forms of glucose Linear (dry) formRing (dissolved) form

Disaccharides  2 monosaccharides linked together Glucose + glucose  maltose

Carbs cont. Polysaccharides  polymers of monosaccharides Used for food storage Starch (plants), glycogen (animals), and cellulose

Lipids  CHO Less O than carbs Used for energy storage, insulation, protection, cell membrane components

Nonpolar  insoluble in water Building blocks  3 fatty acids and 1 glycerol molecule Fats, oils, and waxes

Lipids cont. Saturated fats  C-C bonds are single Maximum amount of H Solid at room temperature Increase cholesterol levels  cardiovascular disease

Unsaturated fats  some C-C double bonds Liquid at room temperature Plant products Hydrogenation  converting unsaturated to saturated by adding hydrogen

Proteins  CHON Used for tissue structure and cell metabolism Building blocks  amino acids Humans need 20 different amino acids Held together by peptide bonds

Proteins cont. Number and order of amino acids determines the protein Each protein has a specific 3-D shape Shape determines function Denaturation  changing the shape of a protein impairs it’s function

Proteins cont. Enzymes  protein catalysts that change the rates of chemical reactions, but are not changed themselves Most reactions will not occur without enzymes Highly specific  1 enzyme per substrate Lock and key model  enzyme and substrate fit together precisely to form an enzyme-substrate complex

Proteins cont. Factors affecting enzyme action: Concentrations of enzyme and substrate Temperature  37 o C (human body temp.) pH of environment Homeostasis must be maintained in order for enzymes to function

Nucleic acids  DNA and RNA Store cellular information in code form Building blocks  nucleotides 5-C sugar Nitrogenous base Phosphate group

Nucleic acids cont. DNA  deoxyribonucleic acid Double helix structure  Watson and Crick Sugar is deoxyribose Bases: cytosine, guanine, adenine, thymine RNA  ribonucleic acid Single strand Sugar is ribose Bases: cytosine, guanine, adenine, uracil