Cell Chemistry (III)

Functional GroupsPolysaccharides Lipids

KNOW & Be Able to Identify These Functional Groups

Polysaccharides Examples of polysaccharides

Glycogen: In animal cells (meats) Starch: In plant cells Cellulose: In plant cells

Composition of polysaccharides Glucoses (several) joined by covalent bonds

Polysaccharides are POLYMERS of Glucose The bonds between the many glucose molecules

are synthesized by a type of chemical reaction called --- ???

These bonds can be broken by a type of chemical reaction called --- ???

Glycogen: A Polysaccharide

Significance of Polysaccharides in Physiology (I)

Polysaccharides function as stored fuel, in both plant cells and animal cells.

Any excess fuel that is not burned (or --- ?? is stored, first, in the form of glycogen, a polysaccharide, and then in the form of triglycerides (or neutral fats) in adipocytes.

In humans, the organs and tissues rich in glycogen are: Liver cells (Hepatocytes) and muscle cells

In animal cells, there is a limit to the amount of glycogen that can be stored by ---? and ---? When the glycogen storage capacity is filled, all additional fuels are metabolized to triglycerides and stored in fat cells, also called --- ?

Significance of Polysaccharides in Physiology (II)

What is the advantage of storing fuel? When monosaccharides are not available (as in

hours after a meal or during fasting), the cells can --- ?? the polysaccharides/oligosaccharides of the disaccharides to get the monosaccharides.

Fill-in blank spaces with correct term Polysaccharide --??-- Monosaccharides Glycogen --?? ??? What happens to Cellulose consumed by humans

and animals? Can cells burn or --- ?? polysaccharides?

LIPIDS

Fatty acids, triglycerides, phospholipids, steroids and eicosanoids are all examples of lipids.

Significance of lipids: They function as fuels, stored fuel,

structural components of cell membranes and hormones.

Fatty Acids Chemistry

Contain even # of C atoms Most contain 16 to 20 C atom

Examples: Palmitate (C16), Stearate (C18) Oleate (C18, 1db)

Contain a carboxyl group at one end May be classified as:

1) Saturated (meaning??) 2) Unsaturated (meaning ??)

Property: Characterized as amphipathic, meaning that one

small region is ---? While the other region is ---??

Significance of Free Fatty Acids

Free fatty acids (FFAs) are, with Glycerol, building blocks of triglycerides (or fats)

Margarine is a significant dietary source of FFAs

Using dehydration synthesis reaction (or condensation reaction), cells covalently bind three free fatty acids (FFA), one to each C atom of glycerol.

Illustrated in next slide

Synthesis of Triglycerides

Triglyceride Composition & Synthesis

As illustrated in previous slide, a triglyceride consists of: Three FFA covalently bonded to One Glycerol

The FAs are covalently linked by a chemical reaction called ---?

Their chemical property: Hydrophobic

Significance of Triglycerides in Physiology

Triglycerides are “stored fuel”. When hepatocytes and muscle cells can no longer store glycogen, the excess fuel is stored as triglycerides in cells called adipocytes.

Adipocytes form a type of connective tissue called adipose tissue.

There is no limit to the amount of triglyceride that can be stored by this tissue

YOU Should be able to

1. Draw the chemical structure of a FFA2. Be able to tell the difference between

saturated and unsaturated FFA Questions

1. Complete hydrolysis of a triglyceride yields what product/ or products?

2. Complete oxidation of a FFA by cellular respiration yields what product or products?

Triglycerides or triacylglycerols They are commonly known as fats In humans and other vertebrates

triglycerides are stored in adipocytes. Adipocytes are cells that form a type of

connective tissue called adipose tissue

When ---?? storage capacity of --?? and --?? is reached, all excess fuel is stored as triglycerides

Remember that:

Preferred fuels: Monosaccharides When not immediately available cells

hydrolyze polys to get monos When no more monos are available

cells start using free fatty acids (FFA). Fill-in the blank spaces with correct term To get FFAs, cells must --- triglycerides to

--- + ---??

Significance of phospholipids in physiology

They are structural components of all cell membranes

The plasma membrane (PM), the ER, the membranes around the mitochondria and the lysosomes are composed of a phopholipid bilayer (plus cholesterol and proteins)

Phospholipids are amphipathic

Phospholipids:Chemistry

Property: Amphipathic Composition

Glycerol 2 fatty acids Phosphate group “X” group attached to phosphate

Phospholipids are structurally closest to what other lipid ---??

Structure of a Phospholipid and a Steroid

Steroids

CholesterolAndrogens (i.e., testosterone)Estrogens (i.e.,Glucocorticoids (i.e.,Mineralocorticoids

(like Aldosterone)Vitamin D

Significance of Steroids in Physiology

Cholesterol is the classic example of a steroid

It is the starting material for synthesis of androgens-(male hormones), estrogens (female hormones), glucocorticoids, bile acids, bile salts and Vit. D

Chemical property: Amphipathic

Some Questions ?? Assume that this is a gene: ….-5’-ATGCAATCAGTC-….

1. What is the sequence of the complementary strand?2. These two strands would be joined by what bonds

…Assume that the 3-’strand is the gene.1. What is the sequence of the mRNA from that gene?2. How many codons are there in that mRNA?

Write each codon on a separate line in your notes3. What would be the corresponding seqence of the

anticodons?4. Which RNA has anticodons?5. According to the genetic code, what is the AAS of the

peptide from that gene?

The end

Functional groupsPolysaccharidesLipids