1.3 Macromolecules

Polymers

Long chains of similar subunits joined by covalent bonds

Composite molecules

Large molecules made up of several distinct subunits

Complex carbohydrates — subunits, bond name

Monomers of glucose

Glycosidic linkage

Triglyceride — subunits, bond name

3 fatty acid, 1 glycerol

Ester linkages

Proteins — subunits, bond name

Monomers of amino acids

Peptide linkage

Nucleic acid — subunits, bond name

Monomers of nucleotides

Phosphodiester bond

Carbohydrates — general info and structure?

• names usually end in -ose (ex. cellulose)

• made up of carbon and water (CH2O)n

Carbohydrates — general functions?

• primary energy source; if available the body chooses carbohydrates to breakdown because it is more faster and efficient compared to fats and proteins

• Has structural building materials such as cellulose and cell walls

• aids in cell communication and cell identification

• components of nucleotides

How to classify carbohydrates

• Number of carbons: 3C=triose, 5C=pentose, and 6C=hexose

• Functional group: Aldoses (terminal carbonyl) and ketoses (non-terminal carbonyl)

• Reducing/non-reducing: reducing sugar acts as a reducing agent and tests positive when interacted with Benedict’s solution

• Number of simple sugars: monosaccharides, disaccharides, polysaccharides

What are monosaccharides?

• single chains or single rings of sugar

• known as simple sugars

• know how to draw pentose!! (ribose vs deoxyribose)

Hexoses

• are stereoisomers (same molecular formula but different shape or arrangement): alpha glucose and beta glucose

• structural isomer (molecular formula): C6H12O6

What is linear glucose?

Linear glucose is an anhydrous form of glucose. When water is added, it will create an alpha or beta arrangement.

Do not need to know how to draw linear glucose.

Properties of Monosaccharides

• highly soluble

• easily transportable in polar solvents

• chemically stable

• high yields of energy from oxidation reactions

Oligosaccharides

• contains 2-10 monosaccharides

• held together by glycosidic linkages

• short chains and disaccharides

• soluble in water

• good for transport

Molecular formula of main disaccharides

C12H22O11

Should’ve been C12H24O12 if following the C:H:O ratio of 1:2:1. However a glycosidic bond was made using dehydration synthesis (removal of H2O)

What type of reaction forms disaccharides?

Dehydration Synthesis

What is the break down of sucrose?

Glucose + fructose

What is the break down of lactose?

Glucose + galactose

What is the break down of maltose?

Glucose + glucose

Need to know how to draw this (two glucoses with glycosidic linkage)

Arrangement of alpha glucose in polysaccharides?

• straight chains

• same orientation

• helical nature

Arrangement of beta glucose in polysaccharides?

• straight chains

• alternating orientation

• facilitates hydrogen bonding (parallel array)

Why do plants need to store glucose if they use photosynthesis for energy?

The sun is not available during the nighttime and we do not want the plants to die during the night so the glucose stored acts as their energy source at night

Amylose (starch) contains what type of linkage? Is it soluble or insoluble?

• 1-4 alpha glycosidic linkages, giving it it’s straight chain nature

• Soluble because the hydroxyl groups are exposed to the water

Amylopectin (starch) contains what type of linkage? Is it soluble or insoluble?

• contains 1-4 alpha glycosidic linkages for straight chain portion and 1-6 alpha glycosidic linkages for the branched portion

• Insoluble because it is massive and highly branched which takes more energy to dissolve in water

Where do humans store excess glucose?

• liver

• muscle cells

• if the brain does not have enough glucose, it sends a message to the liver which releases glucose to hydrolase

What is the most highly branched polysaccharide?

Glycogen (benefits: less soluble, space saving, effective for storage as it’s protected from water)

What type of linkages form in cellulose?

1-4 beta glycosidic linkages. Can tell from alternating carbons (look for sixth carbon)

What does cellulose form?

forms strands called microfibrils which run parallel to each other to form bundles called fibres

Which polysaccharide is an aminopolysaccharide?

Chitin

What is an aminopolysaccharide?

A sugar molecule that has an amino group attached to it (be able to recognize by finding the R group)

Also in cell wall of fungi

Properties of Polysaccharides

• branching and coiling during polymerization ensures that polysaccharides are compact

• the larger they are, the less soluble

• used to mobilize energy stores by removing or adding an alpha glucose

Examples of polysaccharides

• starch

• glycogen

• cellulose

• chitin

Examples of lipids

• triglycerides

• phospholipids

• steroids

• waxes

Properties of lipids

• insoluble in water but soluble in nonpolar substances

• composite molecules (not polymer)

• contains more C-H bonds which means they have more calories than carbs (energy per gram)

Functions of lipids

• maintains cell integrity

• secondary energy source

• insulation and cushioning

• hormones

• food taste

• hydrophobic and dissolves in non polar solvents

Components of monoglyceride

glycerol + 1 fatty acid

Components of diglyceride

Glycerol + 2 fatty acid

Components of triglyceride

Glycerol + 3 fatty acid

Saturated fats

• no double bonds between carbons of the chain

• high melting point

• solid at room temperature

Unsaturated fats

• has one or more double bonds between carbons

• can be cis- or trans-

• lower melting points

• liquid at room temperature

what is the difference between cis- and trans-

Cis- has kinks within its chain and has a similar configuration on both sides while trans- have an opposite arrangement around the kinks

Adipose tissue

Cells that store fat in the form of triglycerides for long term storage.

The amount of triglycerides stored is related to calorie intake vs calories burned

What is brown fat

Brown fat generates heat due to the excess of mitochondria and therefore cellular respiration. Brown fat eventually becomes beige and then white due to hormonal changes. The white fat contains less mitochondria and therefore produces less heat.

Where is white fat located?

• under the skin

• around internal organs

• instead central cavities in bones

Where is brown fat located?

• upper back

• above the clavicle

• around the vertebrae

Are fats and carbs equally efficient at storing energy?

No.

The amount of energy released via cellular respiration per gram of lipids is 2X the amount released per gram of carbohydrates.

Lipids contribute to ½ of body mass by storing as much energy as carbohydrates.

Do fats and carbs equally affect water retention?

• Fat droplets are hydrophobic (do not associate with water) and form pure droplets.

• Glycogen is polar. Each gram of glycogen is associated with about 2 grams of water.

• Triglycerides are most effective in storing energy.

What are phospholipids made of?

• 1 fatty acid

• 3 glycerols

• Choline

• Phosphate

What type of molecule is a phospholipid?

Amphipathic. Know how to draw.

(They also naturally form phospholipid bilayers).

Steroids

• four fused hydrocarbon rings (sharing sides)

• cholesterol is a precursor to other proteins (the body mainly uses cholesterol to create other steroids)

• sterOL → hydroxyl on C3

• sterONE → carbonyl on C3 as a ketone

What steroid is an exception to the naming rule?

Cortisol, the stress hormone

Properties of steroids

• non polar just like other lipids (there are more C-H bonds and not as many O bonds)

• steroids are chemical messengers called hormones

Do steroids pass through the cell membrane?

Yes

• since the cell membrane is mostly non polar, and steroids are also non polar, the membrane allows the steroids to pass through (if they are not too large)

Why does cholesterol not pass through the cell membrane if steroids can pass through?

• most steroids are derived from cholesterol

• cholesterol has a polar hydroxyl group that attaches to the polar region of the membrane and tucks its non polar region within it (so cholesterol sticks out)

• when cholesterol transforms into another steroid like testosterone or cortisol, the polar hydroxyl group is taken away

Purpose of waxes

• repels water (therefore non polar)

• is found on cuticles of plants with varying thickness (for example cacti have thick cuticles to prevent water loss)

Which macromolecule has the greatest range of structures and functions?

Proteins

Functions of proteins

• structural component (collagen)

• transport channels (pump)

• enzyme (RuBisCo, most common enzyme on earth and crucial for photosynthesis)

• systemic transport (hemoglobin)

• blood clotting (fibrin, thromboplastin)

• antibodies (immunoglobulin)

• pigment (retinal)

• hormones (insulin)

• muscle contraction (actin)

• buffer

• toxins

General properties of proteins

• proteins are polymers of amino acids that are joined by peptide bonds and fold into different shapes

• most proteins are 50-200 amino acids long though some can be 10000+

• 20 different amino acids (though there were two more that were recently discovered)

What’s the importance of R-groups?

• the R-groups gives each amino acid its specific properties

• the R-group can be hydrophilic (containing S, O, N) and is polar

• the R-group can be hydrophobic (contains a simple hydrocarbon chain) and is nonpolar

• R-groups can be acidic or basic

• the R-group dictates how amino acids in a polypeptide interact with each other

What are essential amino acids? How many are there?

cannot be synthesized within the body so it must be eaten from food (9)

What are non-essential amino acids? How many are there?

can be made within the body and therefore not really essential (or need to be taken from food) (4)

What are conditionally essential amino acids and how many are there?

not always made within the body but only during specific times for specific reasons (7)

How many different peptides are there? Dipeptides? Tripeptides?

20, 20², 20³ possible amino acids, introducing diversity

What determines the order of the amino acids?

• DNA, though it affects it indirectly through mRNA, which actually makes the protein.

Polypeptide vs protein

A polypeptide is an unbranched chain of amino acids.

A protein is a long chain of amino acids and other components to form a functional protein.