A&P - 2.5 Organic Compounds Essential to Human Functioning

organic compound

• organic molecules possess carbon and are formed from covalent bonds

• organic compounds are polymers (a large molecule - macromolecule) made from many covalently bonded monomers

types of organic compounds

• carbohydrates

• lipids / fats

• proteins

• nucleic acids

carbohydrate

• most abundant compounds of life

• molecule composed of carbon, hydrogen, and oxygen

• referred to as saccharides (sugars)

• three forms are important in the body:

  • monosaccharides

  • disaccharides

  • polysaccharides

monosaccharide

• monomer of carbohydrates (simplest carbohydrates (sugars))

• five monosaccharides are important in the body:

  • glucose (body uses mostly glucose)

  • fructose

  • galactose

  • ribose

  • deoxyribose

disaccharide

• made up of two monomers (pair of monosaccharides - simplest short-chain carbohydrates)

• bonded by dehydration synthesis

• three disaccharides are important to humans:

  • lactose - formed by monosaccharides glucose and galactose bonding

  • sucrose - formed by monosaccharides glucose and fructose bonding

  • maltose - formed by two glucose monosaccharides bonding

polysaccharide

• polymers that are straight or branched chains that can consist of hundreds to thousands of monosaccharides (complex carbohydrates)

• bonded by dehydration synthesis

• three polysaccharides are important to the body:

  • starch - polymer of glucose, energy storage in plant-based foods that is digestible by humans

  • glycogen - polymer of glucose, energy storage in cells of liver, muscle, brain, uterus, vagina

  • cellulose - primary component of the cell wall of green plants, is the component of plant food referred to as “fiber”, not digestible

lipids

• nonpolar organic compounds built from hydrocarbons

• hydrophobic

• will not dissolve in polar solution (ie: water)

• will dissolve in nonpolar solutions (ie: alcohol)

primary types of lipids in humans

• fatty acids

• triglycerides

• phospholipids

• Fat -soluble vitamins

• steroids

fatty acids

• long carbon chains with hydrogen atoms attached

• serve as energy sources and are absorbed from food or synthesized with body cells

• end of carbon chain is the head it always bears a carboxylic acid group (COOH) - head is hydrophilic

• carbon chain is called the hydrocarbon tail - tail is hydrophobic, so fatty acids have limited solubility

saturated fatty acids

• saturated fatty acid chains are straight

• only single carbon-carbon bonds in their tail

unsaturated fatty acids

• unsaturated fatty acid chains are kinked

• one or more double bonds between the carbons in the fatty acids permit “kinks” in the tails

• unsaturated ones are bad for us because we can’t break these down as well, so they remain in our blood stream too long and start to clog our arteries

triglycerides

• three fatty acid chains bonded to a glycerol molecule via dehydration synthesis - with the help of enzymes as these are crucial for the synthesis of triglycerides

• stored in fat cells

• provide energy for the body, store excess calories, help regulate body temperature (insulation)

phospholipid

• lipid compound in which a phosphate group is combined with a diglyceride (glycerol with just two fatty acid chains attached)

• composed of two fatty acid chains (nonpolar “tail”), glycerol (backbone), and phosphate group (polar “head”)

• tails are hydrophobic but the heads are hydrophilic

• main structural materials of plasma membranes where they arrange in bilayers

steroid

• four interlocking hydrocarbon rings (steroid nucleus) bonded to a variety of other atoms and molecules

• broader class of compounds

• sterols are a specific subgroup within that class

  • to be classified as a sterol, a steroid must have a hydroxyl (-OH) group attached to third carbon of its four ring core structure

  • all sterols are steroids, but not all steroids are sterols

cholesterol

• type of steroid/sterol that makes the most important contribution to human structure and function (the “parent” steroid from which other steroids are synthesized)

• important for nervous system function and structural integrity of all cell membranes

  • 15% from diet

  • 85% internally synthesized (mostly in liver)

other steroids

• cortisol

• progesterone

• estrogen

• testosterone

prostaglandins

lipid compound derived from unsaturated fatty acid chains in cell membranes that act as hormone-like substances in the body and are important in regulating several body processes

proteins

• building blocks (monomer unit) of proteins are amino acids (therefore proteins are polymers of amino acids)

• organic compounds

amino acids

• small organic molecules that all have a central carbon with an alkaline amino group (nitrogen group: -NH₂) and an acidic carboxyl group (-COOH)

• they also have a R group but that is different for each amino acid

• 20 different amino acids

peptide bonds

• special name for covalent bond

• amino acids are bound together through peptide bonds (peptide meaning protein) during dehydration synthesis

• peptide bonds are between amino of one AA to the carboxyl group of the next AA

shape of proteins

determined by the sequence of amino acids it is made of

the different protein shapes

the function of the protein determines how much modification it must undergo

• primary structure

• secondary structure

• tertiary structure

• quaternary structure

primary structure

sequence of amino acids (which is encoded in the genes) that make up the polypeptide chain

• DNA just codes for the primary structure of proteins - meaning the sequence of amino acids is determined by DNA and is unique for each kind of protein

secondary structure

• take form as alpha-helix (spring-like shape) or a beta-pleated sheet (pleated, ribbon-like shape) that is the result of hydrogen bonds

• hydrogen bonds between amino acids (between slightly negative carboxyl group and slightly positive amino group) in different regions of the original polypeptide strand

tertiary shape

• result of further folding and bonding of the secondary structure due to (hydrophobic-hydrophilic) interactions among R groups along the polypeptide chain

• folding of proteins into globular and fibrous shapes

globular proteins

compact tertiary structure for proteins within cell membrane and proteins that move freely in body fluids

fibrous proteins

slender filaments suited for roles in muscle contraction and strengthening of skin and hair

quaternary shape

result of interactions between two or more tertiary subunits (twisting of two or more polypeptide chains) - due to ionic bonds and hydrophobic-hydrophilic interactions

• occurs only in some proteins

• example: hemoglobin (has four peptide chains) - protein in red blood cells which transports oxygen to body tissues

denaturation

change in the structure (shape) of a molecule through physical or chemical means

• denatured proteins lose their functional shape and are no longer able to carry out their jobs (changes shape so different function)

functions of proteins

• recognition and protection

• movement

• cell adhesion

• enzymes

recognition and protection

• glycoproteins are important for immune recognition

• antibodies are proteins!! (pieces of protein floating around in your blood)

movement

motor proteins - molecules with the ability to change shape repeatedly

cell adhesion

• proteins bind cells together

  • example: sperm to egg

• keeps tissues from falling apart

enzymes

proteins that function as biological catalysts

• accelerate the rate of a chemical reaction by lowering the amount of energy required to start the reaction (activation energy)

all enzymes are proteins, but not all proteins are enzymes

enzymatic reaction

1. substrates approach active sites on enzyme

2. when substrates bind to the enzymes this is when the reaction starts (this occurs on regions of the enzyme known as active sites), substrates form a product

3. enzyme then release the product, and resumes its original shape

substrate

substance enzyme acts upon (reactant in an enzymatic reaction)

active site

a groove or pocket where substrate bind and undergo a chemical reaction

• spot on protein (enzyme) that substrate binds to

• bonding sites for the substrates

naming convention

named for substrate with -ase as the suffix

• example: amylase enzyme digest starch (amylose)

• -ose as the suffix means sugar and -ase as the suffix means it’s an enzyme

nucleotide

• organic compound important to human structure and function

• nucleotides can be assembled into nucleic acids (DNA or RNA) or the energy compound adenosine triphosphate (ATP)

components of nucleotides

• nitrogenous base: purines and pyrimidines (single or double carbon-nitrogen ring)

• sugar (monosaccharide): deoxyribose or ribose

• one or more phosphate group

purine

• nitrogen-containing base with a double structure

  • adenine (A) and guanine (G)

pyrimidine

• nitrogen-containing base with a single ring structure

  • cytosine (C), thymine (T) found only in DNA, or uracil (U) found only in RNA

complimentary base pairing

• occurs between one purine and one pyrimidine

  • adenine always binds to thymine (or uracil in the formation of RNA) with two hydrogen bonds

  • cytosine always binds to guanine with three hydrogen bonds

components of nucleotide ATP

• best known nucleotide

  • adenine (nitrogenous base)

  • ribose (sugar)

  • phosphate groups (3)

adenosine triphosphate (ATP)

• ATP = “energy currency” of the cell

  • when you need energy, or even just sitting and doing nothing you are burning ATP which keeps you alive

• holds energy in phosphate bonds

  • second and third phosphate groups have high energy bonds

  • most energy transfers to and from ATP involve adding or removing the third phosphate

  • ATP converted to ADP + P + energy (synthesis reaction)

• when bonds are broken, energy can be released for physiological reactions

• GTP (guanosine triphosphate) is similar to ATP, but has a guanine base instead of adenine

phosphorylation

addition of one or more phosphate groups to an organic compound

• example: adding a phosphate group to ADP results in ATP

uses for ATP

• muscle contraction

• ciliary beating

• active transport

• synthesis reactions

• etc.

nucleic acids

• polymers of nucleotides

• nucleic acids differ in their type of pentose sugar: deoxyribonucleic acid (DNA) contains deoxyribose, while ribonucleic acid (RNA) contains ribose

DNA (deoxyribonucleic acid)

• contains millions of nucleotides

• constitutes genes (stores genetic information)

  • instructions for synthesizing proteins

RNA (ribonucleic acid)

• three types: messenger RNA (mRNA), ribosomal RNA, (rRNA), transfer RNA (tRNA)

• 70 to 10,000 nucleotides long

• carries out genetic instruction for synthesizing proteins

  • DNA (two strands) is too big so it can’t leave the nucleus but RNA (one strand) is smaller so it can, so it copies the genetic instruction from the DNA and then brings it out of the nucleus to another part of the cell to assemble proteins

• assembles amino acids in right order to produce proteins

summary of DNA and RNA structural differences

• DNA

  • sugar is deoxyribose

  • bases include A, T, C, and G

  • double-stranded (double helix), two strands attach via hydrogen bonds between the bases of the component nucleotides

• RNA

  • sugar is ribose

  • bases include A, U, C, and G

  • single-stranded