L3: Macromolecules

Cells are mostly composed of…

Water and macromolecules.

An organic molecule is a molecule that:

Contains at least one C-H bond.

What are examples of nucleic acids?

DNA and RNA

What are the monomers of DNA?

Deoxyribonucleotides

What are the monomers of RNA?

Ribonucleotides

What is the basic composition of the nucleotides of nucleic acids?

A sugar bonded to a phosphate group and a nitrogenous base.

What’s the sugar in DNA?

Deoxyribose

What’s the sugar in RNA?

Ribose

Ribose and deoxyribose are:

5-Carbon sugars

What’s attached to each carbon in nucleic acids?

• (1’) → Bonded to nitrogenous base

• (2’) —> Bonded to H (deoxyribose) or OH (ribose)

• (3’) —> Bonded to OH

• (4’) —> Important but don’t need to know.

• (5’) —> Bonded to phosphate

What polymers have directionality?

Nucleic acids, proteins, and carbohydrates.

What does polarity mean in regard to monomers?

Different “ends”; different functional groups at different ends of the molecule.

All polar monomers are added in:

The same orientation.

What’s on the 5’ end of nucleic acids?

The phosphate group

What’s on the 3’ end of nucleic acids?

The hydroxyl group bonded to the 3’ carbon.

What bond links nucleic acids?

Covalent phosphodiester bond

Carbohydrates are also known as:

Polysaccharides

What’s a dimer

Two monomers bonded

What bond connects monosaccharides and where?

A glycosidic bond between the 1’ and 4’ carbon.

What are the ends of polysaccharides?

4’ and 1’.

Do lipids have directionality/polarity?

No. They’re structurally diverse.

What linkage forms between the glycerol head and fatty acid tail of lipids?

A covalent ester bond.

What’s the structure of phospholipids?

• Polar head

• Non-polar tail

• Amphipathic

Can hydrophobic molecules still interact with water?

Yes, but relatively weak interactions (e.g. oil droplets still have to touch water; ID-PD)

What are macromolecules?

Larger molecules that are assembled from small repeating subunits.

Macromolecules — Subunits

Polymers — Monomers

Molecules like DNA, RNA, proteins and polysaccharides have directionality or polarity because:

Each end of the molecule has a different functional group

Lipids are chemically diverse molecules that share the property of: 

Being hydrophobic

Where are nucleic acids in prokaryotes?

Nucleoid and Plasmids (DNA); Cytoplasm (RNA)

Where are nucleic acids in eukaryotes?

Nucleus, Mitochondria, and Chloroplast (DNA and RNA); Cytoplasm (RNA)

Examples of carbohydrates?

Starch and cellulose

Where are carbohydrates in prokaryotes and eukaryotes?

• Cell wall: structural support

• Glycoproteins and glycolipids

How does a macromolecule get its directionality?

• Monomers have distinct ends. (polarity)

• Polymerization occurs in one direction, bonding opposite ends of monomers.

• Results in a macromolecule with two distinct ends. (directionality)

How are nucleic acids synthesized?

• Phosphodiester bond forms when 3’ OH attacks the 5’ Phosphate of incoming nucleotide.

• 5’ to 3’

How are carbohydrates synthesized?

• Monosaccharides form a Glycosidic bond via a dehydration synthesis reaction.

  • Hydroxyl groups combine —> water released

How are triglyceride molecules synthesized?

• Hydroxyl groups of glycerol combine with hydroxyl groups of 3 fatty acids: dehydration synthesis

  • Ester bonds

What macromolecule type is ATP?

Nucleic acid

Are carbs energy sources?

Yes.

What’s the backbone of a phospholipid?

Glycerol

Why is polymerization not spontaneous?

Creating polymers means creating more organized states, less entropy, and a positive free energy.

Identify which molecules are generally taken up from growth media versus molecules that are synthesized by cells.

• Bacterial cells need some kind of carbon source* (often a sugar), nitrogen, and minerals.  

• With these things as starting materials, cells can make the various macromolecules (carbohydrates, nucleic acids, proteins, lipids) and they can also produce CO2 via respiration.