cheat sheet

What is true about caffeine?

• Caffeine is more soluble in boiling water than in cold water, which is why hot water is used to extract it from tea.

• Ethyl acetate is the solvent used to extract caffeine from tea.

• Caffeine moves into the ethyl acetate layer because it is more soluble in ethyl acetate than in water at room temperature.

• The purity of caffeine is determined using melting point analysis and IR spectroscopy.

• The first step of the caffeine extraction experiment is making concentrated tea.

• Caffeine is an alkaloid.

What is true about soaps?

• Soaps are sodium or potassium salts of fatty acids.

• Soaps are produced by saponification (hydrolysis of triglycerides with NaOH or KOH).

• Soap molecules have a nonpolar hydrocarbon tail and a polar ionic carboxylate head.

• Soaps can emulsify grease and oils by forming micelles.

• The hydrophobic tails dissolve in grease, while the hydrophilic heads interact with water.

• Soaps work poorly in hard water because Ca²⁺ and Mg²⁺ ions form insoluble precipitates ("soap scum").

• Soaps are amphipathic (contain both hydrophobic and hydrophilic regions).

Cholesterol belongs to the ____ type of lipids

Steroids

What feature makes a molecule a steroid?

It contains four fused carbon rings (the steroid nucleus).

Identify the polyunsaturated fatty acid from the compounds

Fatty Acid	Double Bonds	Type
Palmitic (16:0)	0	Saturated
Stearic (18:0)	0	Saturated
Myristic (14:0)	0	Saturated
Oleic (18:1)	1	Monounsaturated
Linoleic (18:2)	2	Polyunsaturated
Linolenic (18:3)	3	Polyunsaturated

On Multiple Choice Questions

If you see triglycerides:

• Triolein = 3 oleic acids = monounsaturated

• Tripalmitin = saturated

• Tristearin = saturated

• Trimyristin = saturated

• Trilinolein = 3 linoleic acids = polyunsaturated ✅

This is why the homework question:

Which of the following is a polyunsaturated fat?

A) triolein
B) tripalmitin
C) tristearin
D) trimyristin
E) trilinolein

Answer = E) Trilinolein

If They Show Structures

Count the C=C double bonds in the fatty acid chains:

• 0 double bonds → saturated

• 1 double bond → monounsaturated

• 2 or more double bonds → polyunsaturated

Example:

• CH₃-(CH₂)₇-CH=CH-(CH₂)₇-COOH → 1 double bond → monounsaturated

• CH₃-(CH₂)₄-CH=CH-CH₂-CH=CH-(CH₂)₇-COOH → 2 double bonds → polyunsaturated

Exam Shortcut

For your final, memorize:

Palmitic, stearic, myristic = saturated
Oleic = monounsaturated
Linoleic and linolenic = polyunsaturated

If the answer choices contain linoleic or linolenic, that is usually the polyunsaturated fatty acid your instructor is looking for.

How do you know what fatty acid will be solid at room temperature?

1. More saturated = more likely solid

• No C=C double bonds → straight chains pack tightly → stronger intermolecular forces → higher melting point → solid.

• Example: stearic acid (18:0), palmitic acid (16:0).

2. More double bonds = more likely liquid

• Double bonds (especially cis double bonds) create kinks.

• Kinked chains cannot pack together well.

• Lower melting point → liquid at room temperature.

• Example: oleic acid (18:1) is liquid.

• Linoleic acid (18:2) and linolenic acid (18:3) are even more liquid.

3. Longer carbon chain = more likely solid

For fatty acids with the same number of double bonds:

• More carbons = higher melting point.

• Example:

  • Myristic acid (14:0) < Palmitic acid (16:0) < Stearic acid (18:0)

  • Stearic acid is the most likely to be solid.

---

Exam Shortcut

When comparing fatty acids:

Most solid → Least solid

1. Saturated, longest chain

2. Saturated, shorter chain

3. Monounsaturated (1 double bond)

4. Polyunsaturated (2+ double bonds)

Example:

• Stearic acid (18:0) → solid

• Oleic acid (18:1) → liquid

• Linoleic acid (18:2) → more liquid

• Linolenic acid (18:3) → most liquid

Previous-final style question

"Which fatty acid will be solid at room temperature?"

Look for:
✅ No double bonds
✅ Longest carbon chain

Avoid:
❌ Multiple double bonds
❌ Cis-unsaturated fatty acids

A good rule for your exam:

The more saturated and the longer the chain, the more likely the fatty acid is solid at room temperature. The more double bonds, the more likely it is liquid.

Commercially liquid vegetable oils are converted to solid fats such as margarine by ___

Hydrogenation

___  is the process of hydrogenation of glyceryl tripalmitoleate

Based on the lipids material you've been studying, glyceryl tripalmitoleate contains three palmitoleic acid chains, which are monounsaturated fatty acids (each has one C=C double bond).

Hydrogenation adds H₂ across those double bonds, converting them to single bonds.

So:

Glyceryl tripalmitoleate → glyceryl tripalmitate

The process is called hydrogenation, and the product is glyceryl tripalmitate (a fully saturated triglyceride).

If the exam question is written exactly as:

"___ is the process of hydrogenation of glyceryl tripalmitoleate"

the expected answer is likely:

Glyceryl tripalmitate

This is a classic lipid question your instructor has used before:

• Triolein → hydrogenation → tristearin

• Tripalmitoleate → hydrogenation → tripalmitate

• Trilinolein → hydrogenation → tristearin (if fully hydrogenated)

That's one I'd definitely put on your flashcards.

Glycerophospholipids can interact with other lipids and water because they both contain ___ and ____.

Based on the Chapter 20 lipid material you've been studying, the answer your instructor is most likely looking for is:

hydrophobic regions and hydrophilic regions

or equivalently:

nonpolar regions and polar regions

Why:

• The fatty acid tails are nonpolar (hydrophobic) and interact with other lipids.

• The phosphate-containing head is polar (hydrophilic) and interacts with water.

Flashcard:

Q: Glycerophospholipids can interact with other lipids and water because they contain ______ and ______.
A: Hydrophobic (nonpolar) regions and hydrophilic (polar) regions.

This is a very common final exam question because it explains why glycerophospholipids form cell membranes.

What phospholipids contains fatty acids but not glycerol?

From the material you've been studying in Chapter 20 (lipids), the phospholipid that contains fatty acids but not glycerol is:

Sphingomyelin

• Has a sphingosine backbone instead of glycerol.

• Contains one fatty acid attached to sphingosine.

• Contains a phosphate group and choline.

• It is classified as a sphingophospholipid.

A common exam question is:

What phospholipid contains fatty acids but not glycerol?

Answer: Sphingomyelin

Memory trick:

• Glycerophospholipids → glycerol backbone

• Sphingomyelin → sphingosine backbone (NO glycerol)

This exact question appeared in the list of previous final questions you shared, and sphingomyelin is the answer your instructor is most likely looking for.

What are the products of hydrolysis of glyceryl tripalmitate with HCI?

From the lipid chemistry material you've been studying, hydrolysis of glyceryl tripalmitate (a triglyceride) with HCl and water breaks the three ester bonds.

Reaction:

Glyceryl tripalmitate + 3 H₂O + HCl → Glycerol + 3 Palmitic acid

Products:

1. Glycerol

2. 3 molecules of palmitic acid (hexadecanoic acid)

A common exam answer would be:

→ Glycerol + 3 palmitic acids

Quick exam tip

• Hydrolysis with HCl (acid hydrolysis) → glycerol + fatty acids

• Saponification with NaOH/KOH (base hydrolysis) → glycerol + fatty acid salts (soap)

So if you see glyceryl tripalmitate + HCl, the answer is:

✅ Glycerol + 3 palmitic acid molecules.

In the fluid mosaic module that describes plasma membranes... what bond is this (O-C= O)?

Based on the material you've been studying on lipids and membranes, the bond O–C=O is an ester bond (ester linkage).

The general ester functional group looks like:

R–O–C(=O)–R′

or

   O
   ||
R–O–C–R'

This bond is formed when:

• an alcohol (-OH) reacts with

• a carboxylic acid (-COOH)

and water is removed.

In membrane lipids:

• Glycerophospholipids contain ester bonds linking glycerol to fatty acids.

• During hydrolysis or saponification, these ester bonds are broken.

Flashcard:

Q: In the fluid mosaic model of plasma membranes, what type of bond is represented by O–C=O?
A: Ester bond (ester linkage).

This is a very common exam question in your Chapter 20 membrane/lipid material.

What are the products of saponification of glycerol trimyristate with sodium hydroxide?  

From the lipid material you've been studying, saponification is the base hydrolysis of a triglyceride with NaOH.

Glycerol trimyristate consists of:

• 1 glycerol

• 3 myristic acid chains (14-carbon saturated fatty acid)

When reacted with 3 NaOH, the ester bonds are broken, producing:

Products:

1. Glycerol

2. 3 sodium myristate molecules (the soap)

Reaction:

[
\text{Glycerol trimyristate} + 3\text{ NaOH} \rightarrow \text{Glycerol} + 3\text{ Sodium myristate}
]

Exam answer:

Glycerol and 3 sodium myristate (soap) molecules.

A common exam trick is to distinguish:

• Acid hydrolysis (HCl, H₂O) → glycerol + myristic acid

• Saponification (NaOH) → glycerol + sodium myristate

For your final, memorize this pattern:

Reaction	Products
Hydrolysis with HCl	Glycerol + fatty acids
Saponification with NaOH	Glycerol + sodium salts of fatty acids (soap)

So for glycerol trimyristate + NaOH → glycerol + 3 sodium myristate. ✅

How do you know what can not form hydrogen bonds with water?

Based on the Chapter 19 protein material you've been studying, your teacher is likely testing a very simple rule:

A molecule can form hydrogen bonds with water if it has:

• Oxygen (O) attached to H or with lone pairs (–OH, C=O)

• Nitrogen (N) attached to H or with lone pairs (–NH, –NH₂)

A molecule generally cannot form hydrogen bonds with water if it contains only:

• Carbon (C)

• Hydrogen (H)

Examples that cannot hydrogen bond with water:

• Alkanes (hexane, propane)

• Fatty acid hydrocarbon tails

• Steroids that lack O or N groups

Quick exam shortcut

Ask yourself:

Does the molecule have an O or N?

• Yes → can usually hydrogen bond with water.

• No → cannot hydrogen bond with water.

Examples from your exam topics

✅ Can hydrogen bond with water

• Alcohols (–OH)

• Amines (–NH₂)

• Amides (–CONH–)

• Amino acids

• Proteins

• Carbohydrates

❌ Cannot hydrogen bond with water

• Hydrocarbon chains of fatty acids

• Saturated fats (the long carbon tails)

• Cholesterol's hydrocarbon rings except at its one –OH group

• Pure alkanes

For multiple-choice questions, the answer is often the structure that has only C and H atoms and no O or N. That's usually the quickest way to spot the molecule that cannot hydrogen bond with water.

When 2 polypeptide chains combine to form an active protein the structure level is ___.

The answer is quaternary structure.

• Primary = amino acid sequence

• Secondary = alpha helix and beta-pleated sheet

• Tertiary = 3D folding of a single polypeptide chain

• Quaternary = two or more polypeptide chains combine to form an active protein

This wording ("2 polypeptide chains combine to form an active protein") is the classic definition of quaternary structure from Chapter 19.

Flashcard:

Q: When 2 polypeptide chains combine to form an active protein, what level of protein structure is formed?
A: Quaternary structure.

Diethylamine and HCI react to produce ____

Diethylamine ((CH_3CH_2)_2NH) reacts with HCl in an acid-base reaction to form the ammonium salt:

[
(CH_3CH_2)_2NH + HCl \rightarrow (CH_3CH_2)_2NH_2^+Cl^-
]

Answer: diethylammonium chloride

This follows the pattern from your amines chapter:

• amine + HCl → ammonium chloride salt

• methylamine → methylammonium chloride

• diethylamine → diethylammonium chloride ✅

Amines are ___

Based on the Chapter 18 material you've been studying:

Amines are derivatives of ammonia (NH₃) in which one or more hydrogen atoms are replaced by alkyl or aryl groups.

Short version for a fill-in-the-blank:

Amines are derivatives of ammonia.

If your teacher is using the exact wording from the textbook/slides, that's the answer most often expected.

Immuglobus is classifies as ____ protein.

How many amino acids will you get from hydrolysis of a peptide heltip?

Nicotine, caffeine, codeine, and morphine are examples of ___

What heterocyclic ring is found in DNA?

What is the common name?

What are the rules for determining the highest boiling point?

How can you tell what compound is a tertiary amine?

The amide formed in reaction of benzoic acid and ethylamine is…

What is the reaction for the acid hydrolysis of N-methylpropanmite with NaOH?

What amino acids are also neurotransmitters?

IUPAC name? ()

What is the amide formed in the reaction of propunoic acid and I-Butanimine

The amino alcohol choline is a quaternary ammonium with a ___ charge on the nitrogen (does it have an acid or polar base? Is it hydrophobic or hydrophilic?)

The following amino acid R group chain is -ch2-ch(-ch3)

(does it have an acid or polar base? Is it hydrophobic or hydrophilic?)

Amino acids have ami - de/ne and ____ functional groups

Amylase, the protein the … would be classified as ___ protein.

In a typical amino acid at physiological pH, the carboxylate is ___. (+ or -. Soluble?)

In a peptide Trp-Tro-gly-phe, the N-terminal amino acid is ___?, all the tripeptides that can be formed from one molecule each of glycine, valine, and asparagine? What shows?

Denaturation of a protein…A peptide bond has __ functional group? 

What is a primary protein structure?

Which R group is likely to be found in a hydrophobic area of the tertiary structure of a protein?

What type of interaction in 2 groups of tertiary structure of a protein -CH2 -Sh and HS - CH2-) 

How do you name a peptide?