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Unit 3
The Chemistry of
Living Things
(“Biochemistry”)
1
Atoms
• “atom” means “can’t be cut” – coined by
Greeks 2500 years ago.
• The atom is the smallest functional unit of
an element.
• Atoms are made of: (see next slide)
Slide 2.1
Atoms are made of
• Protons: positive charge, in nucleus, are heavy,
“p+”
• Neutrons: no charge, in nucleus, are heavy,
“n0”
• Electrons: negative charge, outside nucleus
“electron cloud”, very light (1/1840 of a
proton or neutron), “e-”
Only copy red diagram in upper
left. No caption needed.
Charges in an Atom
• The + charge on a proton is equal to the charge on an electron.
• Atoms are neutral (have no overall charge)
• Therefore, the # of protons = # electrons in an
atom.
Atomic number
– determines the identity of the atom.
– It tells us the number of protons in the atom.
– It also tells us the number of electrons (b/c an
atom is neutral in charge.)
– Ex: atomic number of carbon, C = 6
– Question: how many protons? How many
electrons? How many neutrons?
Slide62.2
ELECTRONS
• Electrons are in constant motion around the
nucleus.
• e-s in the highest occupied level are called
valence e-s.
14
BONDING:
• (Definition) atoms combining to form
molecules
• It occurs when valence electrons rearrange
themselves
– There are 2 ways to get the e-’s you need.
Sharing electrons (COVALENT BONDING)
Gain/lose electrons (IONIC BONDING)
.
172.3
Slide
COVALENT
BONDS
18
IONIC BONDS
Formation of SALT, NaCl
19
The Most Common Elements in
Living Things
•
•
•
•
•
•
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
Sulfur
20
Elements of Living Organisms
(DON’T COPY)
Table 2.2
212.5
Slide
Life Depends on Water
IMPORTANT FACTS ABOUT WATER
• Water molecules are polar (they have slight
electrical charges, like little magnets)
o Biological solvent-ex: K+ for muscle contraction
o Hydrogen bonds make it expand when frozen
(animals in lakes can survive winter)
o Water is liquid at body temperature
o Water can absorb and hold heat energy
o Water helps regulate body temperature
222.6
Slide
Properties of Water
(b/c of hydrogen bonding)
1. Cohesion- attraction between molecules of
the same substance. (water-water attraction)
Examples
– Drops of water
– Surface tension (Fig 2-8 p 41 of text)
23
Properties of Water
(b/c of hydrogen bonding)
2. Adhesion-attraction btwn molecules of
different substances (water-other substance
attraction)
Examples
– Capillary action-water drawn up a tube
– “Meniscus”= the curve shape water has when in a
tube
24
Water forms Important Mixtures
• Solutions
• (DEFINITION) when a substance dissolves in
water
• Ex: Salt-water.
• NaCl is pulled apart into IONS by the water.
25
Water forms Important Mixtures
(cont.)
• Suspensions
• Material does NOT dissolve, but separates into
small pieces that remain floating
• Ex: blood w/red blood cells
26
ACIDS & BASES
• Water can form ions too!
• H2O 
+
H
+
OH
• When by itself, water makes equal
amounts of H+ + OH27
ACIDS & BASES (cont.)
• Some things cause water to release many H+
ions. These are acids.
• Some things cause water to release many OHions. These are bases.
• pH is a measure of the H+ concentration in a
solution.
28
The pH Scale
Figure 2.10
Slide29
2.10
BUFFERS
(DON’T WRITE THIS) Remember homeostasis?
WRITE THIS:
• All living things need to maintain a stable pH.
– Humans need a pH between 6.5 & 7.5
– Otherwise, chemical reactions get messed up.
• They do this through buffers: weak acids or bases that
prevent sharp, sudden changes in pH
– Ex: ______ for an upset stomach. It absorbs extra H+ ions.
30
(Section 3): Carbon “Organic”
Compounds
• Why is carbon so special?
• Carbon has 4 valence electrons,
• Allows it to bond to many other things at
once.
• Pix of organic compounds important to living
things
31
Section
3:
Carbon
(Organic)
Carbon is the building block of living things:
Compounds of Living Organisms
•
•
•
•
Is 18% of human body by weight
Forms four covalent bonds
Can form single or double bonds
Can build micro- or macromolecules (big
chains)
Slide 2.11
Carbon Can Bond in Many Ways
Don’t Copy Diagrams. Leave room for 2-3 sentences.
Figure 2.12
Slide33
2.12
1: Carbohydrates
MADE OF: C, H, O
(don’t copy diagrams)
FUNCTION: energy & structure
Figure 2.14
Slide 2.15
Types of Carbohydrates
1. Sugars: short chains of
– Monosaccharides- 1 sugar ring
Ex: glucose, galactose
– Disaccharides-2 attached sugar rings
Ex: sucrose, fructose, lactose
2. Polysaccharides: thousands of
monosaccharides
joined in chains and branches
– Starch: made in plants; stores energy
– Glycogen: made in animals; stores energy
– Cellulose: undigestible polysaccharide made in
plants for structural support
Slide 2.16
2: Lipids
Lipids:Made
Insoluble
in
Water
of: C,H,(O)
Function: energy storage, waterproof coverings
TYPES OF LIPIDS
• Triglycerides: energy storage molecules
– Fatty acids: saturated and unsaturated
• Phospholipids: cell membranes
• Steroids: carbon-based ring structures
– Cholesterol: used in making estrogen and
testosterone
Slide36
2.17
Proteins: Complex Structures
Proteins
Contructed of Amino Acids
• Made of: C,H, O, N
• Function: building materials, enzymes
• Structure
– Made of monomers called amino acids
– The instructions for building proteins are in DNA
Slide 2.18
Copy only bottom diagram &
leave room for examples
Don’t copy,
but Leave
room for
examples
Hemoglobin (4 protein
strands held together)
Don’t copy,
but Leave
room for
examples
Enzyme Function
Enzymes:
– are proteins
– function as catalysts (something that speeds up
chem rxns)
– facilitate chemical reactions
• Lower the activation energy (energy required to start a rxn.)
The function of an enzyme is dependent on:
– temperature
– pH
– ion concentration
– presence of inhibitors
Slide41
2.19
Enzyme Action
42
Structure and Function of Nucleic
Acids
• Functions
– Store genetic information
– Provide information used in making proteins
• Structure
– Nucleotides consist of a phosphate group, a sugar,
and a nitrogenous base
– DNA structure is a double helix: two associated
strands of nucleic acids
– RNA is a single-stranded molecule
Slide43
2.20
Nucleic Acids
Structure
of DNA and RNA
• DNA: double-stranded
– Sugar: deoxyribose
– Nitrogenous bases: adenine, thymine, cytosine,
guanine
– Pairing: adenine-thymine and cytosine-guanine
• RNA: single-stranded
– Sugar: ribose
– Nitrogenous bases: adenine, uracil, cytosine,
guanine
– Pairing: adenine-uracil, cytosine-guanine
.
Slide44
2.21
Structure and Function of
Adenosine Triphosphate (ATP)
Copy diagram
on right,
Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
Figure 2.25
Slide 2.22