Transcript Chapter 2 The Chemistry of Life

CHAPTER 2
THE CHEMISTRY OF
LIFE
Section 2-1
Atom:
•Smallest unit of matter; can’t be broken
down by chemical means.
•Atom has 3 particles: electrons (e-), protons
(p+), neutrons (n).
p+ and n are in nucleus
of the atom
e- orbit nucleus in
different energy levels
Section 2-1
Element:
•Pure substance (sub) made of 1 kind of atom
•Elements differ in # of p+ their atoms
contain
•# of n in atom is often but not always = to #
of p+ in atom
Oxygen atom
Section 2-1
Compound: sub made by joining atoms of 2
or more diff elements
•Atoms can join w/other atoms to form
stable sub
•Force that joins atoms is called a chemical
bond
Section 2-1
Covalent Bonds:
•Form when 2 or more atoms share eMolecule:
•Group of atoms held together by covalent
bonds.
Section 2-1
Hydrogen Bonds:
•In water, shared e- are attracted more
strongly by O nucleus than by H nuclei
•Molecules w/unequal distribution of charge,
such as water, are polar molecules
•Attraction between 2 water molecules is ex
of hydrogen bond—weak chem attraction
between polar molecules
Section 2-1
Ionic Bonds:
•Atom/molecule that gain/lose 1 or more e- is
an ion
•Ions have electrical charge because they
contain unequal # of e-/p+. Ions of opposite
charge interact to form ionic bond
Section 2-2
Importance of Water to LT:
•Many organisms release excess heat
through water evaporation
•This ability to control temp helps cells to
maintain constant internal temp when
external temp changes
•Water helps cells maintain homeostasis!
Section 2-2
Cohesion:
•Attraction between sub of the same kind
•Because of cohesion, water and other
liquids form thin films/drops
•Molecules at surface of water are linked
together by H bonds like a crowd of people
linked by holding hands. This attraction
between water molecules causes surface
tension
Surface tension
Surface tension
Section 2-2
Adhesion:
•Attraction between different substances
•Adhesion causes capillary action, in
which water molecules move upward
through narrow tube, such as stem of a
plant
Section 2-2
Solution:
•Mixture of 1 or more substances evenly
distributed in another substance
•Important substances in the body are
dissolved in blood/other aqueous fluids
•Because these substances dissolve in water,
they easily move w/in and between cells
Section 2-2
Polarity:
•Polarity of water enables many substances
to dissolve in water
•When sodium chloride, NaCl, is dissolved in
water, Na+ and Cl– become surrounded by
water molecules, H2O
Section 2-2
Nonpolar molecules:
•Nonpolar molecules don’t dissolve in water
Inability of nonpolar molecules to dissolve in
polar molecules is important to LT
Shape/function of cell membrane depends on
interaction of polar water w/ nonpolar
membrane molecules
Outside of cell
Inside of cell
Section 2-2
Acids/Bases:
•Compds forming H+ when dissolved in
water are acids
•Compds reduce[H+] in a sol’n are bases
•Many bases form hydroxide ions (OH-)
when dissolved in water
•When acid is added to water, [H+] in sol’n is
↑ above that of pure water
•pH scale (0-14) measures [H+]
Acids
Bases
Section 2-3
Carbohydrates:
•Organic compounds made of C,H,O atoms
in proportion of 1:2:1
•Key source of energy; found in most foods—
fruits, vegetables, grains
Section 2-3
Types of Carbohydrates:
•Building blocks of carbohydrates are single
sugars, monosaccharides, glucose,
C6H12O6, and fructose
•Single sugars such as glucose are major
source of energy in cell
Section 2-3
Disaccharides:
•Double sugar formed by 2 monosaccharides
•Sucrose, table sugar, consists of glucose and
fructose.
Section 2-3
Polysaccharides:
•Starch are chains of 3 or more
monosaccharides
Section 2-3
Lipids:
•Nonpolar molecules not soluble in water;
fats, phospholipids, steroids, waxes
•Fats are lipids that store energy
•Typical fat has 3 fatty acids bonded to a
glycerol molecule
Section 2-3
Saturated/Unsaturated Fats:
•Saturated fatty acid, all C atoms are
bonded to 2 H atoms (except end C is
bonded to 3 H atoms)
•Unsaturated fatty acid, some C atoms are
linked by “double” covalent bond, each w/
only 1 H atom, producing kinks in molecule
Section 2-3
Proteins:
•Molecule formed by amino acids (aa) the
building blocks of proteins
•20 diff aa can form proteins
Section 2-3
Nucleic Acids: (DNA, RNA, ATP)
•Long chain of nucleotides w/ 3 parts:
sugar, base, phosphate group
•DNA, deoxyribonucleic acid, 2 strands
of nucleotides that spiral around each other
•RNA, ribonucleic acid, single strand
Section 2-3
ATP:
•Adenosine triphosphate, single
nucleotide w/energy-storing phosphate gr
•When food molecules are broken down
inside cells, some energy is stored as ATP
ATP
Section 2-4
Energy:
•Ability to move/change matter
•Energy’s in many forms—light, heat,
chemical, mechanical, electrical—can be
converted from 1 form to another
•Energy can be stored/released by chem rxn
Section 2-4
Energy in Chemical Reactions
•Energy is absorbed/released when chemical
bonds are broken and new ones formed
•Metabolism is used to describe all the
chem rxn that occur w/in an organism
Reactant = start with
Product = end with
Section 2-4
Activation Energy (AE):
•Energy needed to start chemical rxn
•AE is a chem “push” that starts chem rxn
•Even in chem rxn that releases energy, AE
must be supplied before rxn can occur
Section 2-4
Enzymes:
•Sub that speed up chemical rxn = catalyst
and can lower AE of the rxn
•Enzymes are proteins that act on a specific
substrate by attaching to the active sites of
the substrate during a chemical rxn
Section 2-4
Enzymes:
Example: amylase assists in the breakdown
of starch to glucose (hydrolysis)
Example: catalase assists in the breakdown
of hydrogen peroxide to water and oxygen
gas
Enzymes in your body probably work best at
98° F or 37° C.
Section 2-4
Factors in Enzyme Activity:
•Factor that ∆ shape of enzyme can affect
enzyme’s activity
•Temp/pH/shape of enzyme can alter
enzymes effectiveness
•Enzymes that are active at any 1 time in a
cell determine what happens in that cell