Transcript Chapter 3

CHAPTER 3
THE MOLECULES OF CELLS
Carbon: The Organic Element
• Compounds that are
synthesized by cells and contain
carbon are organic
• So what is inorganic?
•Why are carbon compounds so
prevalent?
• 4 valence electron configuration
• completes shell by sharing 4
• the 4 electron orbitals are
shaped like teardrops
• this forms a 3-D tetrahedron
C
Hydrocarbons
• organic molecules consisting of only
hydrogen and carbon
• The molecules’ chain of carbon atoms
is called the carbon skeleton
• Ex: methane, ethane, propane
Isomer – compounds with the same
molecular formula but different structure
Functional Groups
- Attachments replace one or more of
the H on the C skeleton
1. Hydroxyl Group
• H bonded to O (-OH or HO-)
•Polar
•Known as alcohols
Carbonyl Group
• C double bonded to O
(-CO) C=O
•Compounds are called aldehydes
when –CO is at the end of the chain
•Compounds are called ketones when
–CO is in the middle
(Chain must have at least 3
carbons when finished)
Carboxyl Group
• O double bonded to C which is
also bonded to a hydroxyl
group,…forms carboxylic acids
• -COOH
Amino Group
• N bonded with 2 H (-NH2)
• Forms compounds called
amines
• The amino group acts like a
base
Amino Acids
•Amino acid combines an amino
group with a carboxyl group
Phosphate Group
•P bonded w/4 oxygen atoms
(-OPO3)
*Used in energy
transfer
(ATP)
Macromolecules
Polymer – a large molecule consisting
of similar or identical subunits strung
together
Monomers - subunits
Making a Polymer
• Dehydration synthesis – monomers
linked together by the removal of
water
• One monomer loses a hydroxyl (-OH),
the other loses a hydrogen (H)
• One H2O molecule must be removed
for every link in the chain of
monomers
Breaking a Polymer
• Hydrolysis – the reverse of
dehydration synthesis (adding water)
• It breaks the molecule by using H2O
Hydrolysis
Hydrolysis
break a bond while
adding water
break a bond while
adding water
Carbohydrates
Monosaccharides
• Simple sugars with a molecular
formula in multiples of CH2O
ex:C6H12O6
• Carbons in the chain each have
an –OH group bonded to them;
except one which is bonded to
form a carbonyl group
• sugar is either an aldehyde or a
ketone depending on the location
of the carbonyl group (p. 37 Fig B)
Are these
properly
identified?
• monosaccharides are major
nutrients for cells
Disaccharides
• double sugars (2 monomers)
• 2 monosaccharides joined by
glycosidic linkage – 1 monomer gives
up a H from a hydroxyl group and the
other gives up an entire hydroxyl group
• bond formed by
dehydration
synthesis ex:
p. 38
Polysaccharides
--contain a few hundred to a few
thousand monosaccharides linked
together
Storage polysaccharides – are
hydrolyzed as needed to provide
sugar for the cell
2 Storage Types
Starch – in plants – consists of
many glucose molecules
Glycogen – in animals – stored in
the livers and muscles
2 Structural Types
- serve as building materials
for structures protecting cells
Cellulose – the major component of the
tough walls enclosing plant cells (fiber
for humans)
- enzymes that digest starch are unable
to hydrolyzed the linkages here
(exception: cows & termites)
Chitin – structural polysaccharides are
used by arthropods
to build their
exoskeletons
Lipids
(hydrophobic – water fearing)
Fats
- large molecules composed of
glycerol and fatty acids
Glycerol – an alcohol w/3 carbons,
each w/a hydroxyl group
Fatty acids – have long carbon
chains (p. 79)
What are the two
kinds of fats?
Fatty Acids
-One end has a –COOH head
-Other end is a long hydrocarbon tail
-Insoluble in water
-Can be linked to glycerol by
dehydration
synthesis
-Ester linkage
bond
-triglyceride can be
made this way –
3 fatty acids and a
gylcerol
-vary in length and # &
location of double bonds
Triglyceride-unsaturated
Saturated – no double
bonds in the tail of the
molecule (animal fats –
solid at room
temperature), causes
plaque build up in arteries
Transfats – unsaturated fat
that has been converted to
saturated by adding
hydrogen
Unsaturated – have one or more double
bonds in the tail (plant fats – liquid at
room temperature)
•Major function of
fats is energy
storage (more
than twice as
much as sugar)
•Stored in adipose
cells
•Cells shrink and
swell
Phospholipid
•Structurally related to fats in structure,
but only have 2 fatty acids
•Third carbon of glycerol is joined to a
phosphate group (p. 79)
•The major component of cell
membranes (phospholipid bilayer)
Waxes
• Have one fatty acid linked to an
alcohol & are more hydrophobic than
fats
• Used as water-resistant coatings on
surfaces of fruits, leaves, and insects
Steroids
• Are lipids w/ a carbon skeleton
consisting of 4 fused rings
• Cholesterol – precursor from which
most other steroids are made
• Are all steroids bad?
No! Cancer treatments, poison ivy
Anabolic Steroids – synthetic variants of
testosterone, indiscriminate usage can
cause liver damage, cancer, infertility,
aggressive behavior and reduced sex
drive
Natural
Synthetic
Proteins
-structural, storage, enzyme (biological
catalyst)
-Made up of amino acids
Amino Acids (aa)
--Building blocks of proteins
--There are 20 amino acids that make
trillions of different proteins
--Consist of an asymmetric carbon
bonded to 4 different covalent
partners
•C (alpha carbon) bonds to a H, a carboxyl
group, an amino group, and a variable
group (chemical group) called the R group
or side chain
Polypeptide Chains= many aa’s joined
by peptide bonds
--2 amino acids can be joined by
dehydration synthesis forming a peptide
bond (p. 43)
Protein Conformation
• A protein consists of one or
more polypeptide chains twisted
in a 3-D shape or conformation
•When a cell makes a polypeptide,
the chain folds spontaneously into
its conformation
Levels of Protein Structure
Primary – is the protein’s unique
sequence of aa’s (one aa change in
hemoglobin causes sickle cell)
Secondary – describes how the
primary structure is folded into it’s
conformation (looks like spring coils
or pleated folds) *this results from H
bonding between peptides
Tertiary – describes additional, less
regular contortions of the molecule
(its 3-D shape)
-caused by hydrophobic
interactions, H bonds, ionic bonds,
etc.
-Disulfide bridges reinforce
conformation
Quaternary – results from the
relationship (bonding interactions)
between subunits – each polypeptide
chain is a subunit
Denaturation
What is this?
What causes denaturation?
Nucleic Acids
• Polynucleotides – another name
for nucleic acid, phosphodiester
linkages (phosphate and sugar)
join monomers
• RNA and DNA are made up of
monomers called nucleotides –
contains 3 parts: nitrogenous
base, a sugar, & a phosphate
group (sugar-phosphate
backbone)
RNA & DNA
• Ribonucleic acid • Deoxyribonucleic
acid
• Has the sugar
ribose
• Has the sugar
(pentose=5-C)
deoxyribose
(pentose=5-C)
• Adenine,
Guanine, Uracil, • Adenine,
Cytosine
Guanine,
Thymine,
Cytosine
Who all played a part in
discovering the double helix?
-Watson, Crick, Franklin, Wilkins
-consists of 2 polynucleotide chains
that spiral
-Genes are specific stretches of DNA
that program the aa sequences
(primary structure) of proteins
Watson
Crick
Wilkins
Franklin
How do base pairings ALWAYS
occur?
Adenine – Thymine
Guanine - Cytosine