Essential Idea: Compounds of Carbon, Hydrogen and Oxygen Are Used to Supply and Store Energy

Topic 2: Molecular Biology (Student)

Essential Idea: Compounds of carbon, hydrogen and oxygen are used to supply and store energy.

Carbohydrate VS. Lipid Energy
Carbohydrate / Lipid
______term energy storage / ______term energy storage
______in water, so easy to transport around the body / ______in water, so more difficult to transport around the body
Rapidly digested and need less oxygen to release energy- allows for quick burst of energy / Contain more energy per gram than carbs, so less lipids used for same amount of carb. Energy. Need more oxygen to release energy, so energy released slowly.

Ø  2.3 Carbohydrates and lipids

i.  Monosaccharide monomers are linked together by condensation reactions to form disaccharides and polysaccharide polymers.

o  Monosaccharides can be linked together for make larger molecules (disaccharides and polysaccharides); they combine by a process called condensation.

o  During condensation one molecule loses an –OH and the other a –H which join to form H2O. One water molecule is created each time two monomers combine.

o  Condensation is an anabolic process and energy has to be used, ATP supplies the energy.

Reactions
/ Condensation reaction: Two monosaccharides join to form a disaccharide.
Example: Glucose is a monosaccharide that is used to build up large storage molecules (polysaccharides) in plants and animals. In plants, many glucose molecules combine through condensation reactions to form the polysaccharide starch. In animals, glucose molecules are combined to form the polysaccharide glycogen through condensation reactions.
/ Hydrolysis reaction: water is added to split apart the disaccharide or polysaccharide into its components (monosaccharides). This releases energy stored in the bond.
Example: starch and glycogen are broken down into glucose (the energy molecule used in aerobic respiration)

Types of Carbohydrates:

Monosaccharides / Energy molecule used in aerobic respiration, animal
Galactose / Sweetener in foods, used in respiration, animal
Fructose / Fruit sugar, used in respiration, plant
Disaccharides / Maltose / Malt sugar found in barley, consists of 2 glucose molecules, animal
Lactose / Sugar found in milk, animal
Transport sugar found in plants because of its solubility
Polysaccharides / Starch / Storage carbohydrate in plants
Storage carbohydrate in animals. Stored in liver, produced using insulin.
Cellulose / Main structural component in plant cell walls.

*** See journal of structure of these carbohydrates

Application: Structure and function of cellulose and starch in plants and glycogen in humans.

-  Starch, glycogen and cellulose are all made by linking together glucose molecules, but their structure and function are different.

-  Different because there are different types of glucose and linkage.

Glucose
Has 5 –OH groups but only 3 used for linkage. Most common link is with –OH on carbon 1 and –OH on carbon 4. The –OH on carbon 6 is used to form side branches /
The –OH group on carbon atom 1 can point upward or downward (makes it alpha or beta)
è  Alpha is down
è  Beta is up /

-  Cellulose, starch and glycogen are all polysaccharides consisting of long chains of glucose by condensation reactions. They differ in their structure and type of glucose, which leads to different functions.

Carbohydrate
Cellulose / -  Linking of beta-glucose
-  Link carbon atom 1 to carbon atom 4 on different glucose molecules
-  Since –OH on different sides (one up and one down) makes a straight chain.
-  Chains unbranched so form bundles (cellulose microfibrils) with hydrogen bonds linking the cellulose molecules.
-  Very high tensile strength so used I plant cell walls (prevents cells from bursting during osmosis)
- 
Starch / -  Linking of alpha-glucose
-  Link carbon atom 1 to carbon atom 4 on different glucose molecules
-  -OH both point downwards so chain formed is curved.
-  Two forms:
a.  Amylose: chain is unbranched and forms helix
b.  Amylopectin: chain is branched so globular shape
-  Made in plant cells
-  hydrophilic but to large to be soluble in water
-  used to store glucose for energy in plant cells, seeds, leaves, etc.
- 
Glycogen / -  lots of branching, making glycogen compact
-  made by animals and some fungi
-  stored in liver and muscles of humans
-  stores energy in the form of glucose
- 
Starch and Glycogen:
In starch and glycogen it is easy to add extra glucose or remove them at both ends
Neither has a fixed size and glucose molecules can be increased or decreased.

SKILL: Use of molecular visualization software to compare cellulose, starch and glycogen.

o  WORKSHEET

LIPIDS:

Function of lipids:

-  Structure: Phospholipids are a main component of cell membranes

-  Hormonal signaling: Steroids are involved in hormonal signaling (ex. Estrogen, progesterone, testosterone)

-  Insulation: fats in animals can serve as heat insulators while omega-3 fatty acids in the myelin sheath (around neurons) can serve as electrical insulators

-  Protection: Triglycerides may for a tissue layer around many key internal organs and provide protection against physical injury

-  Storage of energy: used as a long-term energy storage source, stored in the body as adipose tissue.

ii.  Fatty acids can be saturated, monosaturated or polysaturated.

o  Lipids are insoluble in water and some are composed of fatty acids monomers

o  Fatty acids are the main component of triglycerides and phospholipids.

o  Fatty acids are non-polar and therefore hydrophobic.

o  Chains consist of covalently bonded carbon with hydrogen, lengths are variable.

o  Saturated fatty acids are all single bonds and are therefore “saturated” with hydrogen.

o  Unsaturated fatty acids contain a double bond or bonds.

o  At one end of chain is an acid area called carboxyl group (-COOH)

Fatty Acids
Generalized structure:

Fatty acids can be saturated or unsaturated

iii. Unsaturated fatty acids can be cis or trans isomers.

o  ______-: hydrogen atoms on same side of the two carbon atoms that are double bonded.

·  There is a bend in chain at double bond

·  Cannot pack together as well

·  Lowers melting point, usually liquid at room temperature (oils)

o  ______-: when hydrogen are on the opposite sides

·  Do not bend

·  Can pack together

·  Higher melting point and are solid at room temperature (margarine)

iv.  Triglycerides are formed by condensation from three fatty acids and one glycerol.

o  Triglycerides include fat in adipose tissue in humans and oil in sunflower seeds.

o  Fats are liquid at body temperature but solid at room temperature.

o  Oils are liquid at both body and room temperature.

o  Triglyceride is made by combining three fatty acids and one glycerol.

o  Each fatty acid is linked by condensation reaction to glycerol, producing 3 water molecules.

o  Bond between fatty acids and glycerol is called ester bond (formed when an acid reacts with –OH group in alcohol) reaction between –COOH group on fatty acid and –OH on the glycerol.

o  Triglycerides used as energy storage, energy released by aerobic cell respiration.

o  They are good heat insulators because don’t conduct heat well (blubber)

Triglycerides

APPLICATION: Lipids are more suitable for long-term energy storage in humans than carbohydrates.

Energy Storage

·  One’s body requires energy to function, more specifically each cell relies on a source of energy to drive the chemical reactions involved in metabolism, growth and other physiological functions

·  Both carbohydrates and lipids (triglycerides) are a major source of energy in animals.

·  Fats contain about twice as much energy as carbohydrates. Each gram of carbohydrates stores about 4 calories of energy, whereas each gram of lipid stores about 9 calories.

·  Therefore, lipids serve as a more compact way to store energy, since it contains more energy per gram than carbohydrates. As a result, your body tends to use fat to store energy over long periods of time and uses carbohydrates to store energy short-term.

·  Glycogen (carb storage) can be quickly into glucose for energy.

·  Triglycerides (fats) contain a glycerol and 3 fatty acids and is stored mainly in the body’s adipose tissue

·  Fats also provide thermal insulation, protection for organs (shock absorber) and hormones

Outline the use of carbohydrates and lipids in energy storage:

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