Lipids & Nucleic Acids

Lipids: Basic Information• Lipids are defined as

groups of molecules that are insoluble in water.

– Fats (triglycerides), oils, waxes, and steroids.

– Long chains of CH2 units

–Molecules are nonpolar

Phospholipids

• Special types of lipid• form the core of all biological

membranes.

Types of LipidsType Organismal Use Human Uses

Fats Long-term energy storage & thermal insulation in animals

Butter lard

Oils Long-term energy storage in plants and their seeds

Cooking oils

Phospholipids Component of plasma membrane No-stick pan spray

Steroids Component of plasma membrane; hormones

Medicines

Waxes Wear resistance; retain water polishes

Lipids are hydrophobic• Lipids repel

water.• Ex. The cuticle of

plants is waxy. The waxy covering makes the plant water proof and minimizes water loss.

Building Blocks of Lipids• One glycerol-alcohol• Three fatty acid chains

Fats and Oils (triglycerides)

• Fats and oils consist of a glycerol molecule with three attached fatty acids (triglyceride / triglycerol).– Saturated fats - all internal carbon atoms are

bonded to at least two hydrogen atoms–usually a solid at room temperature

– Unsaturated fats - at least one double bond between successive carbon atoms• Polyunsaturated - contains more than one

double bond–usually liquid at room

temperature

Fats as Energy Storage Molecules

• Fats, on average, yield about 9 kcal per gram versus 4 kcal per gram for carbohydrates.– Animal fats are saturated while most plant

fats are unsaturated.• Consumption of excess carbohydrates leads to

conversion into starch, glycogen, or fats for future use.

Triglycerides

Saturated vs. unsaturated fatty acids

Which fats are best?

• Unsaturated with one double bond can help lower cholestrol• Examples-olive and canola

• Saturated or hydrogenated are considered unhealthy and should be consumed in limited quanities

Cis and Trans

Hydrogenated Fats

• Hydrogenation is used to add hydrogens to unsaturated fats and make them more solid. If a fat is FULLY saturated, it becomes solid, like candle wax. If it is PARTIALLY saturated (the same as partially hydrogenated) the result is a semi-solid, like margarine.

Steroids• Steroid hormones are crucial substances for

the proper function of the body. They mediate a wide variety of vital physiological functions ranging from anti-inflammatory agents to regulating events during pregnancy.

• They are synthesized and secreted into the bloodstream by endocrine glands such as the adrenal cortex and the gonads (ovary and testis).

• Skeleton made of four fused carbon rings• Cholesterol is a steroid

as well as the foundation for other steroids.

Waxes Long-chain fatty acid

bonded to a long-chain alcohol

• High melting point

• Waterproof

• Resistant to degradation

• Why do you wax a car?

Waxes

Phospholipids

Phospholipids• Derived from triglycerides

– Glycerol backbone– Two fatty acids attached instead of three– Third fatty acid replaced by phosphate group

• The fatty acids are nonpolar and hydrophobic• The phosphate group is polar and hydrophilic

• Molecules self arrange when placed in water

– Polar phosphate “heads” next to water

– Nonpolar fatty acid tails” overlap and exclude water

– Spontaneously form double layer & a sphere

Phospholipid Structure• Phospholipid

molecules have one end which is attracted to water while the other is repelled by it. The fatty acid end is not attracted to water and is called hydrophobic. At the other end of the molecule the phosphate group is attracted to water, it is said to be hydrophilic.

Hydrophobic Tail

Hydrophilic Head

Phospholipids Form Membranes

Nucleic Acids

Nucleic Acids

• Deoxyribonucleic Acid (DNA)– Encodes information used to assemble

proteins.• Ribonucleic Acid (RNA)– Reads DNA-encoded information to

direct protein synthesis.

Adenosine triphosphate (ATP)– Provides energy

Nucleic Acid Structure• Nucleic acids are composed of long

polymers of repeating subunits, nucleotides - the monomer.– five-carbon sugar– phosphate– nitrogenous base• purines

– adenine and guanine

• pyrimidines– cytosine, thymine, and uracil

Nucleic Acid Structure

• DNA exists as double-stranded molecules.– Genetic info. - coded for by the order of

the nucleotides.– double helix– complementary base pairing• hydrogen bonding • base pairing: A-T, C-G

• RNA exists as a single stand.– contains ribose instead of deoxyribose– contains uracil in place of thymine

Nucleotides

•No•Yes•Helix•Interprets genetic info; protein synthesis•Heredity; cellular control center•Function•Cell nucleus and cytoplasm•Chromosomes of cell nucleus•Where

Comparison of DNA & RNA

•Mostly single stranded•Double-stranded; Pairing across strands•Strands

•Cytosine, guanine;•adenine, uracil

•Cytosine, guanine;adenine, thymine•Bases

•Ribose•Deoxyribose•Sugar

•RNA•DNA•Feature

Structure of DNA

RNA Structure

DNA RNA Protein

Other Nucleic Acids

• ATP (adenosine triphosphate) is composed of adenine, ribose, and three phosphates

• In cells, one phosphate bond is hydrolyzed – Yields:

– The molecule ADP (adenosine diphosphate)

– An inorganic phosphate molecule pi

– Energy

• Other energy sources used to put ADP and pi back together again

ATP