Download atoms - St. Clair Schools

Biology
Chapter 2: Chemistry of Life
Matter
• Anything that takes up space and has mass
• Made up of particles called atoms
Atom
• Smallest unit of matter that cannot be broken down by
chemical means
• Made up of protons (positive charge), neutrons (no
charge), electrons (negative charge)
• Equal number of protons and electrons (balance each
other out)
• Combine by sharing
electrons
• Electrons can be anywhere
in cloud but are usually
hang out near nucleus
Element
•
•
•
•
Substance made up of only 1 kind of atom
Periodic table made up of elements
Each element represented by a symbol
Example: copper wire (made up of only
copper therefore it is an element)
Compound
• Substance made of 2 or more different
elements bonded together.
• Represented by a chemical formula such
as HCl, NaOH, CO2
• Chemical formula does not change
• Example: water ( made up of hydrogen
and oxygen)
Atomic Number
• Tells how many electrons that atom has
• # electrons = # protons
Atomic Mass/Weight
• equals the # protons + # neutrons
• # neutrons = atom weight – atomic number
Bonds
• Covalent
• Hydrogen
• Ionic
Covalent
• 2 atoms share electrons between them
• Molecule is a group of atoms held
together by covalent bonds; no electrical
charge
• Examples: H2O, CO, H2, O2
Hydrogen
• Special bond that holds H more strongly to
another atom
• Can be polar (unequal distribution of
electrical charge) or nonpolar (equal
distribution of electrical charge)
• Example: bond between 2 water
molecules
• Weak bond
Ionic
• Atom that gains (-) or loses (+) an electron
(e- ) called an ion
• Atoms like to have stable outer electron
level thus some ions will accept or give up
an electron to become more stable
• Ions of opposite charge are attracted to
each other and form ionic bonds.
• Ionic compound
Na+ + Cl- 
NaCl
Water
• 70% of body made up of H2O
• 2/3 of molecules in body are H2O
molecules
• Cells are made of H2O and surrounded by
H2O
Properties of Water
•
•
Stores heat – heats more slowly & retains heat
longer than many other substances
Bonds to itself & other substances
–
–
–
Attraction between H2O molecules forms thin film at
surface of water to prevent it from stretching or
breaking (known as surface tension)
H2O drops form on plants because of cohesion
(attraction between Substances of same kind)
Adhesion is attraction between different substances
Water Dissolves Many Substances
• Solution is mixture when 1 or more substances are
evenly distributed in another substance (usually H2O)
• Solute = what is dissolved
• Solvent = does the dissolving (liquid)
• Sugars & salt need to “dissolve” or break up before they
can be distributed to your cells
Acids & Bases
• H2O molecules break forming hydrogen ion (H+ ) and a
hydroxide ion (OH- )
• H2O  H+ + OH• Acids are compounds that form H+ when dissolved in
water
• Bases are compounds that reduces the amount H+ in
a solution
• pH scale measures concentration of hydrogen ions in a
solution (range from 0 to 14)
• Pure water has pH value of 7.0 (neutral)
• Acidic solutions have pH below 7.0
• Basic solutions have pH above 7.0
Organic vs. Inorganic
• Organic contain CARBON atoms (typically
bonded to hydrogen, oxygen and other
carbon atoms)
• Inorganic compounds contain elements
other than carbon
4 Types of Organic Compounds
•
•
•
•
Carbohydrates
Lipids
Proteins
Nucleic Acids
Carbohydrates
– Made of C, H, O (proportion 1:2:1)
– Source of energy – found in most food
• monosaccharides or simple sugars (glucose,
fructose)
• disaccharides (sucrose = glucose + fructose)
• polysaccharides (starch, cellulose)
– Polysaccharides act as warehouse for energy
contained in sugars
– Chains of molecules put together
Lipids
– Nonpolar, not soluble (dissolve) in water
– Includes fats, waxes, steroids (cholesterol), and
phospholipids (cell membrane)
– Fats store energy (more than carbs)
– Saturated fats – butter, lard, grease from meat; solid
@ room temp.
– Unsaturated fats – olive oil, some fish oils; liquid @
room temp.
– Trans fatty –
– Cholesterol – not all is bad, body needs some to
make lipid based molecules like steroid hormones
Proteins
–
–
–
–
Chain of amino acids linked together
20 diff. amino acids make up all proteins in your body
Large molecules that fold up into diff. shapes
Some proteins called enzymes promote chemical
reactions
– Collagen – most abundant protein in body; found in
skin, ligaments, tendons
– Other proteins like antibiotics – fight infection
– Protein called hemoglobin carries O2 from lungs to
body tissues
Nucleic Acids
– Long chain of smaller molecules called
nucleotides (three parts: sugar, base,
phosphate group)
– 2 kinds of nucleic acids – DNA and RNA
– DNA – deoxyribonucleic acid; two strands
spiraled around each other (double helix);
stores heredity info.
– RNA – ribonucleic acid; single strand; makes
proteins
ATP
– Adenosine
triphosphate
– Main energy currency
of cells
– Food gets broken
down and energy gets
stored as ATP
– Cells use ATP
(energy) to function
Energy
• All organisms need it
• Has ability to move or change matter
• Can be stored or released by chemical
reactions
• Cells consume fuel (food) because they
need energy to function
• Help organisms maintain homeostasis
Chemical Reactions
• Enzymes increase speed of a
reaction (most are proteins &
end in “ase”)
• Need a certain amount of
energy to get a reaction going
this is called activation energy
(ex. Riding a bike uphill)
• Think of activation energy as
the chemical “push” to start it
• Catalyst speeds up reactions
by lowering the amount of
energy needed to get the
reaction going (NOT ALL
catalysts are enzymes)
Why Do We Need Enzymes?
• Reactions in body are @ body temp –
most would proceed too slowly to maintain
life
• Examples include amylase in saliva
(starch), pepsin in stomach (protein),
tripson in small intestine
How Enzymes Work
•
•
•
•
•
•
•
Enzymes bring key molecules together
Enzymes act only on specific substrates
Substrate – substance the enzyme is going to act upon
An enzyme’s shape determines what it does
Active Site – folds in enzyme where the substrate will fit in
Enzyme & substrate interact to reduce activation energy
When reaction complete, substrate is released (products), & enzyme can be
reused since it is not changed during the process
Factors that Affect Enzyme Activity
• Fever response to
infection – kill bacteria
• High fever is dangerous it
inactivates critical
enzymes at high temps.
• Fever above 105 degrees
F can be fatal
• Change in pH can cause
enzyme to break denatured