Cell Chemistry (III) Functional Groups Polysaccharides 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 FFA 2.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 Cholesterol Androgens (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 notes 3.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 groups Polysaccharides Lipids