Transcript Lipids - Pima Community College

Lecture 8
Lipids
Page 43-47
Lipids
Lipid
• Hydrophobic organic molecule
– Usually composed of C, H, O
– High ratio of H to O
– Have more calories per gram vs. carbohydrates
– Variable in structure vs. other macromolecules
– 5 main types:
• Fatty acids
• Phosopholipids
• steroids
triglycerides
eicosaniods
Lipids
• Contain C, H, and O, but the proportion of
oxygen in lipids is less than in carbohydrates
• Examples:
– Neutral fats or triglycerides
– Phospholipids
– Steroids
– Eicosanoids
Fatty Acids
• “fa”
• 4-24 carbon atoms in a chain
• Carboxyl group at one end and a methyl
group at the other
3.8 Fats are lipids that are mostly energy-storage
molecules
• Lipids are water insoluble (hydrophobic, or water
fearing) compounds that are important in energy
storage
– They contain twice as much energy as a polysaccharide
• Fats are lipids made from glycerol and fatty acids
Copyright © 2009 Pearson Education, Inc.
3.8 Fats are lipids that are mostly energy-storage
molecules
• Fatty acids link to glycerol by a dehydration
reaction
– A fat contains one glycerol linked to three fatty acids
– Fats are often called triglycerides because of their
structure
Animation: Fats
Copyright © 2009 Pearson Education, Inc.
Glycerol
Fatty acid
Neutral Fats (Triglycerides)
• Composed of three fatty acids bonded to a
glycerol molecule
Figure 2.15a
3.8 Fats are lipids that are mostly energy-storage
molecules
• Some fatty acids contain double bonds
– This causes kinks or bends in the carbon chain
because the maximum number of hydrogen atoms
cannot bond to the carbons at the double bond
– These compounds are called unsaturated fats
because they have fewer than the maximum
number of hydrogens
– Fats with the maximum number of hydrogens are called
saturated fats
Copyright © 2009 Pearson Education, Inc.
Fatty Acids
• Saturated= contains no double bonds
• Unsaturated = contains double bonds
• Monounsaturated = contain ONE double
bond
• Polyunsaturated = contain MANY double
bonds
• Essential fatty acids = cannot be
synthesized by the human body
– Must be obtained from the diet
• Remember:
– Unsaturated molecules can also be drawn in
chemical shorthand showing carbon atoms and
bonds
Types
• Oil = liquid at room temp
• Fat = solid at room temp
• Animal fats = saturated ~ usually saturated,
solid at room temp
– Lard, butter
• Polyunsaturated fats = plant origin, usually
liquid at room temp
– Oils (olive, peanut, corn, vegetable, sunflower)
Other Lipids
• Phospholipids – modified triglycerides with
two fatty acid groups and a phosphorus group
Figure 2.15b
3.9 Phospholipids and steroids are important lipids with a variety of
functions
• Phospholipids are structurally similar to fats and
are an important component of all cells
– For example, they are a major part of cell
membranes, in which they cluster into a bilayer of
phospholipids
– The hydrophilic heads are in contact with the water
of the environment and the internal part of the cell
– The hydrophobic tails band in the center of the
bilayer
– They are called Amphipathic
Copyright © 2009 Pearson Education, Inc.
Hydrophilic
heads
Water
Hydrophobic
tails
Water
Phospholipids
• Most
important
function:
structural
foundation of
the cell
membrane
– Phospholipid
bilayer
Steroids
• Lipids with 17 carbon atoms arranged in 4
rings
• Cholesterol = “parent” steroid which all
others are synthesized from
3.9 Phospholipids and steroids are important lipids with
a variety of functions
• Steroids are lipids composed of fused ring
structures
– Cholesterol is an example of a steroid that plays a
significant role in the structure of the cell membrane
– In addition, cholesterol is the compound from which
we synthesize sex hormones
Copyright © 2009 Pearson Education, Inc.
Cholesterol
Normal artery and vein
Atherosclerosis
3.10 CONNECTION: Anabolic steroids pose health risks
• Anabolic steroids are synthetic variants of
testosterone that can cause a buildup of muscle
and bone mass
– They can be sold as prescription drugs and used to treat
certain diseases
– They may also be abused with serious consequences,
such as liver damage that can lead to cancer
Copyright © 2009 Pearson Education, Inc.
Other Lipids
• Steroids – flat molecules with four interlocking
hydrocarbon rings
• Eicosanoids – 20-carbon fatty acids found in
cell membranes
Figure 2.15c
Table 2.2.1
Table 2.2.2
Representative Lipids Found in the
Body
• Neutral fats – found in subcutaneous tissue
and around organs
• Phospholipids – chief component of cell
membranes
• Steroids – cholesterol, bile salts, vitamin D, sex
hormones, and adrenal cortical hormones
Representative Lipids Found in the
Body
• Fat-soluble vitamins – vitamins A, E, and K
• Eicosanoids – prostaglandins, leukotrienes,
and thromboxanes
• Lipoproteins – transport fatty acids and
cholesterol in the bloodstream
Thank you