Cell Biology:
Cell Compounds and Biological Molecules
Lesson 3 – Carbohydrates and Lipids (Inquiry into Life pg. 31-36)
Today’s Objectives
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Analyze the structure and function of biological molecules in living
systems, including carbohydrates, lipids, proteins, nucleic acids
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Demonstrate a knowledge of dehydration synthesis and hydrolysis
applied to organic monomers and polymers
Differentiate among carbohydrates, lipids, proteins, and nucleic acids with
respect to chemical structure
Recognize the empirical formula of a monosaccharide
List the main functions of carbohydrates
Differentiate among monosaccharides, disaccharides, and polysaccharides
Differentiate among starch, cellulose, and glycogen with respect to
function, type of bonding, and level of branching
Describe the location, structure, and function of the following in the
human body: neutral fats, steroids, phospholipids
Compare saturated and unsaturated fatty acids in terms of molecular
structure
2.4 Organic Molecules
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Always contain:
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Carbon (C) and Hydrogen (H)
A carbon atom may share electrons with another
carbon atom
Can form long carbon chains (below)
Carbon Rings
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Can also form carbon rings when a carbon chain
turns back on itself
Called a ring compound
Functional groups can be attached to carbon
chains or rings
Macromolecules
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Many molecules of life are macromolecules.
(macromolecules contain many molecules joined together)
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Monomers:
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Simple organic molecules that exist individually
Can also be called “unit molecules”
Polymers:
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Large organic molecules form by combining monomers
Macromolecules
Organic Molecules
A meal containing carbohydrates, lipids, and proteins.
Dehydration and Hydrolysis Reactions
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Cells have mechanisms of joining monomers to build
polymers
 Dehydration Reaction:
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an -OH and -H are removed as a water molecule
Hydrolysis Reaction:
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the components of water are added
Dehydration and Hydrolysis Reactions
Dehydration and Hydrolysis Reactions
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Ex) dehydration of glucose
Practice
Pg. 42-43, #12, 17
Organic Molecules
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The 4 main types of organic polymers that we will be
looking at are:
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Carbohydrates
Lipids (fats)
Proteins
Nucleic Acids
All are essential to life
2.5 Carbohydrates
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Some Functions:
 Quick
fuel*
 Short-term energy storage*
 Structure of organisms
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* foremost function
Molecules characterized by presence of the grouping
H-C-OH
Ratio of H to O is 2:1
Monosaccharides
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Simple Carbohydrates
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Monosaccharides are sugars with 3 - 7 carbon atoms
Sugars are vital fuel nutrients for cells
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Pentose refers to a 5-carbon sugar
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All occur as ring structures with the formula C5H10Ox
Hexose refers to a 6-carbon sugar
 Glucose
– found in our blood
 Fructose – found in fruits
 Galactose – found in milk
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All occur as ring structures with the formula C6H12O6
Exact shape of ring differs, as does arrangement of the –H and –OH
groups attached
Monosaccharides - Glucose
Three ways to represent the structure of glucose.
Monosaccharides
GLUCOSE
FRUCTOSE
GALACTOSE
Disaccharides
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Disaccharides contain two bonded monosaccharides
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Have a common formula C12H22O11
Common disaccharides:
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Maltose - two molecules of glucose
Sucrose – one glucose, one fructose
Lactose – one glucose, one galactose
Polysaccharides
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Polysaccharides are long polymers that contain many
glucose subunits.
basic formula (C6H10O5)n
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n= dozens to thousands of glucose units
Three main types:
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Starch is the storage form of glucose in plants.
Glycogen is the storage form of glucose in animals.
Cellulose can be found in the cell walls of plants.
Polysaccharides
Glycogen
Starch
Cellulose
Starch
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Storage form of glucose in
plants
Few side chains of glucose
Linkage between glucose
units are the same
Figure 2.17 pg. 33
Glycogen
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“animal starch” stored in the
liver and muscle tissue
Storage form of glucose in
animals
Many side chains of glucose
Linkage between glucose
units the same
Figure 2.18 pg. 33
Cellulose
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Gives plants its structure
Found in the cell walls of
plants
No side chains of glucose
Different linkages between
glucose units
Fig. 219 pg. 33
Cellulose
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Our digestive system is
unable to digest this
linkage.
Cellulose passes
through our system as
fiber or roughage.
May be important for
good health and
prevention of colon
cancer
Summary of Carbohydrates
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1) Source of short-term energy for all organisms:
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Animals – glycogen
Plants – starch
Energy is released as the carbohydrates are broken
down by hydrolysis
2) Structural molecules in plants - cellulose
Practice
Pg. 42-43, #7, 9, 29
2.6 Lipids
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Include:
 Fats and Oils
 Phospholipids
 Steroids
We eat lipids as part of our food. Our bodies are
capable of producing them as well as metabolizing
them
Next to glucose, fats are the second most important
energy molecule for us
Unfortunately, we store them in adipose (fat) cells
Lipids
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Some functions:
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Long-term energy storage
Insulation against heat loss
Protection of major organs
Primary component of the cell membrane
Molecules also contain carbon, hydrogen, and oxygen
but the H:O ratio is greater than 2:1
Lipids do not dissolve in water (non-polar)
Lipids are electrically neutral
Lipids
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Fats and Oils
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Fats (saturated fats)
Usually of animal origin
 Solid at room temperature
 Fats provide long-term energy storage, insulate
against heat loss, and protect major organs
 Ex.) lard, butter
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Oils (unsaturated fats)
Usually of plant origin
 Liquid at room temperature
 Ex.) vegetable oils
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Formation of Fats
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Fats and oils form when one glycerol molecule
reacts with three fatty acid molecules
A fat molecule is sometimes called a triglyceride
because of its three-part structure
The term neutral fat is sometimes used because the
molecule is non-polar
Neutral Fat Structure
Synthesis and degradation of a fat molecule
Fatty Acids
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Saturated and Unsaturated Fatty Acids
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Fatty acids are hydrocarbon chains that end
with an acidic group -COOH.
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Saturated fatty acids:
 No
double covalent bonds between carbon atoms
 Carbon atoms are “saturated” with as many hydrogen
atoms as they can hold
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Unsaturated fatty acids:
 Have
some double bonds between carbon atoms
(wherever the number of hydrogens is less than two
per carbon atom)
Fatty Acids
Saturated Fatty Acid
Unsaturated Fatty Acid
-COOH acidic group
Carbon double bond
Phospholipids
Phospholipids are a variation of a triglyceride
where one of the 3 fatty acids is replaced with a
phosphate and nitrogen-containing group
 Primary components of cellular membranes
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Phospholipids
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The phosphate group creates a polar region on one
end of the phospholipid
This allows phospholipids to mix with both polar
(hydrophilic) and non-polar (hydrophobic) materials
Phospholipids
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The heads of the
phospholipids are
polar and are said
to be water loving
(hydrophilic)
The tails of the
phospholipids are
non-polar and are
said to be water
fearing
(hydrophobic)
Phospholipid
Structure
Cell Membrane
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The structure of phospholipids make them a very
important part of cells as they form much of the cell
membrane
Steroids
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Assist in protein synthesis
Insoluble in water
All steroids have four adjacent carbon rings.
Examples:
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Cholesterol
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Testosterone
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important part of the cell membrane
Protective cover around nerve fibers
Precursor of sex hormones
Male sex hormone
Estrogen
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Female sex hormone
Structure of Steroids
All steroids have four adjacent carbon rings, but their
attached groups differ. The effects on the body largely
depend on the difference in the attached groups
(shown in blue)
Cholesterol
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Formed by the body and also enters body as a part
of our diet
Important part of the cell membrane and
protective cover around nerve fibers
Cholesterol is important but often results in fatty
deposits inside arteries which narrows the pathway
for blood to the heart
Can result in high blood pressure
Summary of Lipids
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1) Source of long term energy storage
2) Insulate against heat loss
3) Protect internal organs
4) Saturated and Unsaturated fatty acids
5) Include fats and oils, phospholipids, and steroids
Practice
Pg. 42-43, #
15, 28
Review Quiz
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Organic Molecules always contain which elements?
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What reaction joins monomers to form polymers?
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Unit molecules
The unit molecules of carbohydrates are?
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Hydrolysis
Monomers are also known by which name?
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Dehydration synthesis
What reaction breaks down a polymer into monomers?
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C and H
Monosaccharides (such as glucose)
The unit molecules of lipids are?
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Glycerol and 3 fatty acids