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Carbohydrates

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Carbohydrates

Includes sugars and polymers of sugars
Contain a carbonyl group and many hydroxyl groups

Comprised of C, H, and O

Monosaccharides: simple sugars

Molecular formulas with multiples of the unit CH₂O –important!
Most common is glucose

Nutrients and fuel for cells
Used in cellular respiration
Can serve as building blocks for amino acids, or as monomers for di- and polysaccharides

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Carbohydrates

Disaccharides: two monosaccharides joined together by covalent bonds

Most common is sucrose

Monomers of sucrose: glucose and fructose
Plants transfer carbohydrates from roots to leaves in the form of sucrose (reverse this statement)
Now let’s “break” this molecule.

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Carbohydrates

Polysaccharides: polymer with many sugars joined via dehydration reactions

Storage polysaccharides

Plants store starch (polymer of glucose monomers)

Allows plants to store excess glucose

Animals store glycogen (polymer of glucose)

Stored in liver and muscle cells

Structural polysaccharides

Cellulose: tough substance that forms plant cell walls
Chitin: forms exoskeleton of arthropods

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Practice

You are given an unknown monosaccharide to identify in the lab. The only clue you are given is that it has 4 carbons. You (being an excellent AP bio student) figure out the formula. What is the unknown monosaccharide?
Answer: C4H8O4, Threose

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Proteins

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Formation of a Protein

Amino acid

Peptide

Polypeptide

Protein

small

large

What kind of bond is holding these peptides together?

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Proteins

Protein: molecule consisting of polypeptides (polymers of amino acids) folded into a 3D shape

Comprised of C, H, O, N, and S
Shape determines function

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Amino Acids

Molecules that have an amino group and a carboxyl group

20 different amino acids

Amino group

carboxyl group

R = variable side chain

Unique side chain (R)

General Structure

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Amino Acids

Each amino acid (AA) has a unique side chain

Unique aspects of the AA are based on the side chain’s physical and chemical properties
Side chains can be grouped as:

Nonpolar (hydrophobic)
Polar (hydrophilic)
Charged/ionic (hydrophilic)

Side chains interact, which determine the shape and function of the protein

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Formation of Peptide Bonds

To form a peptide bond the carboxyl group of one AA must be positioned next to the amino group of another AA

Peptide bond

Repetitive backbone

Side chains

Dehydration reaction

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Polypeptides

Polypeptides: many AA linked by peptide bonds

Each polypeptide has a unique sequence of AAs and directionality

Each end is chemically unique
One end is a free amino group (N-terminus)
One end is a free carboxyl group (C-terminus)

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Polypeptides

Remember: SHAPE determines FUNCTION

The sequence of AAs determines the 3D shape

When a polypeptide twists and folds (because of R group interaction) it forms a protein

Quick! Think, pair share

How is the unique sequence of AAs determined for a polypeptide?

Genes

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Functions of Proteins

Function of proteins include:

Antibody-help protect the body from disease
Enzyme- carry out (speed up) chemical reactions or assist in creating new molecules

Messenger- transmit signals (ie hormones)
Structural- provide structure and support

Transport/storage- bind to and carry small atoms and molecules through the body (cell membrane)

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Levels of Protein Structure

Primary

Secondary

Linear chain of AA

Determined via genes
Dictates secondary and tertiary forms

Coils and folds due to hydrogen bonding within the polypeptide backbone

𝛂 helix- hydrogen bonding between every 4th AA

𝛃 pleated sheet- hydrogen bonds between polypeptide chains lying side by side

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Levels of Protein Structure

Tertiary

Quaternary

3D folding due to interactions between the side chains of the AAs

Reinforced by hydrophobic interactions and disulfide bridges of the side chains

The covalent bond formed between sulfur atoms of two cysteine monomers

Association of two or more polypeptides

Found in only some proteins

All four levels of a protein’s structure determine the protein’s function

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Practice

Folding Video Clip
Let’s work on the practice problems!

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Practice

Cystic fibrosis is a serious, life-threatening disease that affects the lungs and digestive system of affected individuals. Mucous builds up in lungs and tissues.

This disease results from the deletion of three nucleotides on the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. This gene codes for a transmembrane protein that regulates ion channels in epithelial tissue.

Provide an explanation for how this deletion could result in cystic fibrosis.

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Nucleic Acids

Topic 6

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Nucleic Acids

Nucleic acids: polymers made of nucleotide monomers

Function to:

Store, transmit and express hereditary information

Two forms:

Deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)

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Components of Nucleic Acids

Nucleotides

Polynucleotides

Nucleic Acids

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Nucleotides & Polynucleotides

Contain at least 3 parts:

Nitrogenous base
Five carbon sugar (pentose)
Phosphate group(s)

In polynucleotides each monomer only has one phosphate group

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Nitrogenous Base

Two types: pyrimidines and purines

Pyrimidines: one ring with 6 atoms

Cytosine
Thymine
Uracil

Only found in DNA

Only found in RNA

Purines: one ring with 6 atoms bonded to one ring with 5 atoms

Adenine
Guanine

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Five Carbon Sugar

A sugar is bonded to the base

In DNA the sugar is deoxyribose

In RNA the sugar is ribose

Deoxyribose

Ribose

Differ in structure and function

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Phosphate Group

A phosphate group is added to the 5’ carbon of the sugar (which is attached to the base) to form a nucleotide

5’ carbon

Nucleoside- portion without phosphate group

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Polynucleotides

Phosphate groups link adjacent nucleotides

Phosphodiester linkage
Directionality

5’ to 3’

Sugar phosphate backbone

5’ phosphate end

Nitrogenous bases

3’ hydroxyl end

The sequence of bases along the DNA or mRNA is unique for each gene

Dictates AA sequence

Dictates primary structure of a protein

Dictates 3D structure of a protein

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DNA

Consists of two polynucleotides

Forms a double helix

Strands are antiparallel
Held together by hydrogen bonds between bases

antiparallel

Cytosine binds to guanine

Adenine binds to thymine

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RNA

Single stranded polynucleotide

Variable in shape

Due to base pairing within RNA

Adenine bonds to uracil
Cytosine bonds to guanine

Remember which sugar is present!

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Practice

You are given a segment of DNA:

5’- CATGTCAAC-3’

What is the complimentary strand?

Answer: 3’-GTACAGTTG-5’

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Lipids

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Lipids

Lipids: class of molecules that do not include true polymers

Generally small in size

Often not considered to be a macromolecule

Lipids are nonpolar-hydrophobic

Types of lipids:

Fats
Phospholipids
Steroids

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Fats

Fats are composed of glycerol and fatty acids

Glycerol: classified as an alcohol (hydroxyl groups)

Fatty acids: long carbon chains (carboxyl group at one end)

3 fatty acids join to a glycerol via ester linkage

Bond between a hydroxyl and carboxyl group

Classified as a saturated fatty acid or an unsaturated fatty acid

Saturated fatty acid: no double bonds between carbons in the carbon chain = more hydrogen (think: saturated with hydrogen)
Unsaturated fatty acid: contains one or more double bonds

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Phospholipids

Major component of cell membranes

Two fatty acids attached to a glycerol and a phosphate

Assemble as a bilayer in H₂O

Tails are hydrophobic
Head is hydrophilic

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Steroids

Lipids that have four fused rings

Unique groups attached to the ring determine the type of steroid

Example: testosterone

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Putting it all together

Fill out this chart with the appropriate responses

Carbohydrates

Carbon, hydrogen, oxygen

monosaccharide

Polysaccharide

Proteins

Carbon, hydrogen, oxygen, nitrogen, sulfur

Amino acids

Polypeptides

Lipids

Carbon, hydrogen, oxygen (phosphorus for phospholipids)

Glycerol and fatty acids

Does not contain true polymers

Nucleic Acids

Carbon, hydrogen, oxygen, nitrogen, phosphorus

Nucleotides

DNA, RNA