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Chapter 2 The Chemical Level of Organization

Cellulose) structural component of many plants, is a polysaccharide that our bodies cannot digest
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Most starches are
manufactured by plants
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G
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Muscle cells make and store glycogen

2-10
Lipids) (lipose,fat )contain carbon, hydrogen, and oxygen, and the carbon-to-hydrogen is near 1:2
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Most lipids are insoluble in water, but special transport
mechanisms carry them into the bloodstream
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Lipids deposits are energy reserves the provide 2x as much energy as carbohydrates do, gram
for gram
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Fatty acids have very limited solubility in water
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Eicosanoids) are lipida derived from arachidonic acid, a fatty acid the must be absorbed in
the diet because the body cannot synthesis it
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Chapter 2 The Chemical Level of Organization
Prostaglandins-- are short chains of fatty acids in which 5 of the carbon atoms are joined in a ring
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Virtually all tissues synthesize and respond to them
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Those released in the uterus help trigger the start of labor contractions
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Those that are produced in part of the
body and have an effect on distant parts are called hormones
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Glycerides) are the result of being attached to a modified simple sugar, glycerol, through a
similar reaction to dehydration synthesis
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Subsequent reactions can yield a diglyceride (glycerol+2fatty acids) and then a triglyceride
( glycerol+3fatty acids)
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Energy source: Fat deposits in specialized sites of the body represent a significant energy
reserve
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Insulation: Heat loss across a layer of lipids is only about ⅓ of the heat loss through other
tissues
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Protection: A fat deposit around a delicate organ such as a kidney provides a cushion that
protects against bumps or jolts
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The steroid Cholesterole and related steroids are important for several reasons:

➔ The outer boundary of all animal cells, called a plasma membrane, contains cholesterol
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➔ Steroid hormones are involved in the regulation of sexual function; Examples include the sex
hormones, estrogen and testosterone
➔ Steroid hormones are important in the regulation of tissue metabolism and mineral balance
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The
liver produces bile salts and secretes them in bile
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Phospholipids and Glycolipids) are structurally related, and our cells can synthesize both
types of lipids, primarily from fatty acids
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Cholesterol, phospholipids, and glycolipids are called structural lipids; they help form and maintain
intracellular structures called membranes
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For example, the plasma
membrane surrounding each cell is composed primarily of phospholipids
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They account for 20% of total body weight
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Proteins carry out a variety of essential functions, which we classify in 7 major categories
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Structural proteins 3D framework for the body
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❖ Movement
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❖ Transport
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❖ Buffering
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❖ Metabolic regulation
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❖ Coordination and Control
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❖ Defense
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Example protect against environmental haz-

ards, antibodies help fight infection and disease (immune response)
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Chapter 2 The Chemical Level of Organization

Protein structure
Amino acids) are proteins consisting of long chains of organic molecules
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Peptides) a covalent bond between the carboxyl group of 1 amino acid and the amino group of
another
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Polypeptides of 100 amino acids or more are usually called proteins
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Primary structure
2
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Tertiary structure
4
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▪ Fibrous proteins form extended sheets or strands
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▪

Globular proteins are compact, generally rounded, and soluble in water
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Chapter 2 The Chemical Level of Organization

Protein Shape and Function
The shape of a protein determines its functional characteristics, and the sequence of amino
acids ultimately determines its shape
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Enzyme Function
Enzymes are among the most important of all the body’s proteins
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This
region is called the Active site (a groove or pocket)

All enzymes share 3 basic characteristics:
1
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Each enzyme catalyzes only 1 type of reaction, a characteristic called Specificity
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2
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The rate of an enzymatic reaction is directly linked to the concentrations of
substrate molecules and enzymes
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Higher concentration = more frequent encounters-----resulting in cycling at top speed
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Regulation
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Without a cofactor, the enzyme is intact but nonfunctional
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Effects of Temperature and pH on Enzyme Function
Each enzyme works best at specific temps and pH values
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Denaturation) is a change in tertiary or quaternary structure that makes it nonfunctional
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Chapter 2 The Chemical Level of Organization

Glycoproteins and Proteoglycans
Glycoproteins and Proteoglycans are combinations of protein and carbohydrate molecules
Glycoproteins) large proteins with small carbohydrate groups attached
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Glycoproteins play a major role in identifying normal from abnormal cells and they are also important
in the immune response
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Proteoglycans) are large polysaccharide molecules linked by polypeptide chains that bind
adjacent cells together, and give tissue fluids a syrupy consistency
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Nucleotides) the individual subunits of a chain
Each nucleotide has 3 parts
1
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a phosphate group and
3
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1
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Transfer DNA (tDNA) transfer RNA 3
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Complementary base pairs) name given to combinations of adenine-thynine (A-T) and
cytosine-guanine (C-G)

Complementary strands) the name given for the 2 nucleotide chains of the DNA molecule

2-13
ATP is a high-energy compound used by cells
To perform their vital functions, cells must use energy, which they obtain by breaking down organic
substrates (catabolism)
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Generally, these bonds bind phosphate group to an organic molecule
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Most high energy compounds are derived from nucleotides
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(Example…phosphate + phosphate=diphosphate or a phosphate + ADP= ATP

The requirements of high-energy bonds are:
1) A phosphate group
2) Enzymes capable of catalyzing the reactions involved, and
3) Suitable organic substrates to which the phosphate can be added

The most important such substrate is the nucleotide adenosine (AMP), which already contains
1 phosphate group
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The conversion of ADP to ATP is the most important method of storing energy in our cells
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ATP is our most abundant high-energy compound
Example ADP + phosphate group + energy ↔ ATP + H2O

Adenosine triphosphatase (ATTPase)) an enzyme required to perform hydrolytic
breakdown of ATP to ADP

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