Download Lipids, Proteins, and Nucleic Acids

Lipids
Background Info:
Elements
Ratio of elements
C, H, O (just like carbs)
-Large numbers of Cs and Hs and few Os
-H:O ratio is greater than 2:1
Monomers
USUALLY glycerol + fatty acids but not always
Polymers
fats, phospholipids, wax, steroids
Bonds
Main functions
1.
2.
3.
4.
5.
6.
Important fact(s)
excess energy storage (store 2x energy of
carbs) and long term energy storage
insulation – keep organisms warm
padding (protects internal organs) and shape
vitamin storage
structural part of cell membranes
chemical messengers (hormones)
NONPOLAR and therefore HYDROPHOBIC
Lipid monomers
 Usually glycerol and fatty acid chains
– linked together in condensation reactions
– water also forms
Lipid monomers cont:
Glycerol structure
 Glycerol--3 carbon
chain
– Alcohol
**alcohols often
have -ol ending
Lipid monomers cont:
Fatty acid general structure
 Fatty acid chain
– hydrocarbon (C and H)
with a fatty acid
(carboxyl group
-COOH) attached
 R represents the
R in structural formulas
stands for a varying structure
or “side chain”
hydrocarbon chain
which can vary
Lipid monomers cont:
More on Fatty Acid Structure
 Fatty acids are unbranched C chains with
two ends:
– carboxyl (-COOH) end
• polar and hydrophilic
– hydrocarbon end
• nonpolar and hydrophobic
carboxyl end
hydrocarbon end
Examples of fatty acids
 Lipids aren’t quite as simple as carbs. Most
lipids are made of glycerol and fatty acids;
however, you will see some aren’t. So why
are these oddballs still considered lipids?
– They’re nonpolar and hydrophobic!
Complex Lipids (lipid polymers)
 4 kinds
1. fats: monoglycerides, diglycerides, and
triglycerides
2. phospholipids
3. wax
4. steroids
 divided according to structure
 all formed in condensation reactions; water
is also produced!
FATS
 Can be monoglycerides, diglycerides, or
triglycerides depending on the # of fatty
acids
1. Fats - Triglycerides
glycerol + 3 fatty acid chains
• “tri” refers to 3 fatty acids
 Monoglycerides = glycerol + 1 fatty acid
 Diglycerides = glycerol + 2 fatty acids
Triglycerides structure
 glycerol + 3 fatty acids
 saturated or
unsaturated
 How many monomers
are joining?
 How many water
molecules will form?
Condensation of a triglyceride
 Fats can be saturated or unsaturated
– These words refer to the fatty acid chains
specifically but often the entire fats is described
as “saturated fat” or “unsaturated fat”
Unsaturated Fatty Acid
(aka unsaturated fat)
 Hydrocarbon portion has one or more double or triple




bonds (so C is not bonded to the max # of atoms)
chain is bent due to double or triple bonds
found in plants
liquid at room temperature
Don’t increase cholesterol ; exps. : olive oil, soybean oil
Double bond causes bend in chain
Saturated Fatty Acid
(aka saturated fat)
 all single bonds in hydrocarbon chain (so all C
atoms are bonded to four other atoms)
 Chains are straight due to single bonds
 found in animals
 solid at room temperature
 increase cholesterol; cause atherosclerosis
(plaques in arteries) that can lead to heart attacks
and strokes
 Exps: lard, tropical oils (coconut, palm), butter,
cream, cheese
Saturated fatty acids
Saturated vs. Unsaturated Fat
Summary
Unsaturated Fats
Saturated Fats
Bonds in H-C
contain C-C double or
triple bonds
all single C-C bonds
Chain is ___ due to ___
bent; double/triple bonds
straight; single bonds
Found in
plants
animals
State at room temp
liquid
solid
Effect on cholesterol
no effect
increase
Exps.
olive oil, corn oil,
soybean oil
cream, butter, lard,
cheese, tropical oils
Hydrogenation
 The process of converting naturally
unsaturated oils into saturated ones through
the forced addition of hydrogens.
 Gets rid of double/triple bonds to create a
solid, straight chained fat
– makes an unsaturated fat saturated!
 Peanut butter and margarine
2. Phospholipids
 Almost like a
triglyceride except a
phosphate group
replaces one fatty acid
chain
 Glycerol + 2 FA chains
+ 1 phosphate group
 Head-phosphate-polar
 Tail-FA chain-nonpolar
Triglyceride vs. Phospholipid
General structure
glycerol + 3 fatty acids
triglyceride + water
glycerol + 2 fatty acids + phosphate
phospholipid + water
Phospholipid Models
Phospholipid
bilayer (aka cell
membrane)
Phospholipid
representation
Space filling
model
Structural formula
 We use a shorthand for phospholipids.
 Draw a circle with two squiggly lines
coming from it.
Head: phosphate
(and glycerol) polar
Tails: FA chains nonpolar
Cell membrane
 Phospholipids form the cell membrane
 Act as a barrier between the internal and
external environment
 Also called a phospholipid bilayer because
it’s made of two layers of phospholipids!
 How many monomers join to form a
phospholipid? How many water molecules
will form?
Cell Membrane
3. Waxes
 Long fatty acid chain + an alcohol
 long FA chain makes it very waterproof
 Plants use waxes as coating--cuticle--to
keep from drying out
 Animals use wax as protection against
microorganisms—ears
 How many monomers join to form wax?
How many water molecules are formed?
4. STEROIDS
 Four fused carbon
rings
 3 six sided, 1five
sided, and an R group
(variety)
 No glycerol or fatty
acid
 Nonpolar property
makes them a lipid