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Chemistry Of Cells
Chemistry
• Science that studies the elements, their
compounds, the chemical reactions that occur
between them and the molecular structure of
all matter
Matter
• Anything that takes up space and has mass
• Everything we touch is matter
• Three forms
– Solid
– Liquid
– Gas
Elements
• Substances that can’t be broken down into
another substance by ordinary chemical means
• All matter, living and non-living composed of
elements
• 92% naturally occurring elements
– Differ by properties
Our Elements
• Six elements special to us
– C- carbon
– H- hydrogen
– N- nitrogen
– O- oxygen
– P- phosphorus
– S- sulfur
• Make up 98% of our body weight
Atomic Theory
• Elements consist of tiny particles called
atoms- smallest particle of an element that
displays the properties of the element
Atomic Structure
• Three types of subatomic particles
– Neutrons- no electrical charge
– Protons- positive charge
– Electrons- negatively charge
• Nucleus- center of the atom
– Protons and neutrons located within
– Electrons (e-) move about nucleus
Periodic Table
• Developed as a way to display elements
according to their characteristics
Understanding Chemical Bonds
• Atoms most stable when outer shell is full
• Octet rule- outer shell containing 8 electrons
Compounds
• Substance composed of atoms of two or more
elements that are chemically combined
– Example: NaCl (table salt)
• Compounds form when elements try to
comply to the octet rule
Types of Bonds
• Ionic- forms when 2 atoms are held together
by attraction between opposite charges
– Ions- charged atoms
– Often form salts
• Example: Na+ Cl-
Types of Bonds
• Covalent- two atoms share electrons in order
to have completed outer shell
– Example: oxygen gas (O2)
• Molecule- group of atoms held together by
covalent bonds
Bonds
• Single bond- when two atoms share a single
electron
• Double bond- when each atom shares two
electrons
• Triple bond- when each atom shares three
electrons
Chemical Reactions
• Occur when bonds are formed or broken
causing substances to recombine into
different substances
• Metabolism- all chemical reactions occurring
in the cells of organisms
• Written as follows:
Mixtures and solutions
• Mixture- combination of substances in which
individual components retain their own
properties
– Example: mixing sand and sugar
• Solution- mixture in which one or more
substances (solutes) are distributed evenly in
another substance (solvent)
– Example: adding sugar to ice tea
Acids and Bases
• Acids- substances that dissociate in water
– Release hydrogen ions (H+)
– Example: HCl-hydrochloric acid (stomach)
• Base- substances that take up hydrogen (H+)
ions or release hydroxide (OH-) ions
– Example: NaOH- sodium hydroxide
pH and Its Scale
• pH- way of indicating the number of hydrogen
ions in solutions
• pH scale- used to indicate acidity or basicity of
solutions
– Ranges from 0 to 14
– 7 is neutral
– pH < 7= acid
– pH > 7= base
• Buffer- chemical that keeps pH within normal
limits (example- Tums and Rolaids)
Water’s Importance to Life
• Life began in water
• Single most important molecule on Earth
• Cells are 60-80% water
• Polar molecule- molecule with an unequal distribution
of charge
– Each molecule has a positive end and negative end
• Unique properties
Another Type of Bond
• Hydrogen (H)- weak bond, arises between
slightly positive hydrogen atom of one
molecule and slightly negative atoms of
another molecule
– Example: H2O
– Water molecules attract other water molecules
Properties of Water
• Because of H-bonds
– Can engage in 4 H-bonds
• Properties
– Solvency
– Cohesion and adhesion
– High surface tension
– High heat capacity
– High heat of vaporization
Life Substances
• Carbon has 4 electrons available for bonding
– To be stable it forms 4 covalent bonds
– Can bond with other carbons or with many other elements
– Form straight chains, branched chains, or rings
– Can have almost any number of carbons
– Can form different structure (shapes)
• Isomer- compounds with same chemical formula but different 3-d
structures
Carbohydrates
• Biomolecule composed of carbon, hydrogen
and oxygen (1:2:1 ratio)
• Monosaccharide- simplest type of carb (sugar)
– Glucose and fructose
• Disaccharide- combining of two
monosaccharides
– Glucose and fructose link together to form sucrose
Carbohydrate cont’d
• Polysaccharide- largest, composed of many
monosaccharides
– Starch- branched, energy storage
– Glycogen- highly branched, stores energy in liver
– Cellulose- long chains (like chain link fenece),
forms cell walls of plants and gives them support
Carbohydrates cont’d
• Five- and six-carbon simple sugars are smallest
– Five-carbon: deoxyribose and ribose
– Six-carbon: glucose and fructose
• Functions: energy storage and cell structure
Lipids
• Insoluble in water
• 95% of fats in body are triacylglycerols
• Saturated fat: fatty acids have single covalent
bonds
• Unsaturated fat: fatty acids have one or more
double covalent bonds
• Functions: energy, insulation and protection
Proteins
• Contain carbon, oxygen, hydrogen, nitrogen
and sulfur
• Amino acids are building blocks of proteins
• Functions: energy and structure
• Enzymes: protein catalysts for chemical
reactions
Proteins
• Structure
– Primary: amino acid sequence
– Secondary: determined by hydrogen bonds
– Tertiary: folding caused by interactions within
peptide bonds and sulfur atoms
– Quaternary: determined by spatial relationships
between units
Nucleic Acids
• Deoxyribonucleic acid: genetic material of the
cell (DNA)
• Ribonucleic acid: protein synthesis
– Messenger RNA
– Transfer RNA
• Structure
– DNA: double helical chain
– RNA: single chain
Nucleic Acids
• Nucleic acids are made up of chains of
nucleotides
– Nucleotide: nitrogen base, sugar and phosphate
group
– Nitrogen bases: purines (two) and pyrimidines
(three)
Adenosine Triphosphate
• ATP
• Fuel for cell function and maintenance
• Molecule consists of sugar, adenine, and three
phosphates
– Energy is stored in the second and third phosphates
• Breakdown of glucose provides energy to make
ATP
Enzyme
• Protein that changes rate of chemical
reactions
• Involved in nearly all metabolic processes
– Speed reactions in digestion of food
• Activities of enzymes depend on temp, ionic
conditions, and pH of surroundings