Exam 4
Exam 4 Outline
CH 105 Spring 2026
Materials Required
- Bring a pencil.
- All other materials must be left at the front of the classroom in an unsecured area.
- All cell phones must be turned off during the exam.
Chapter 20: Carbohydrates
1) Classification of Carbohydrates by Size and Functional Group
- Functional Groups:
- Aldehyde
- Ketone
- By Size:
- 3 Carbons:
- Aldotriose
- Ketotriose
- 4 Carbons:
- Aldotetrose
- Ketotetrose
- 5 Carbons:
- Aldopentose
- Ketopentose
- 6 Carbons:
- Aldohexose
- Ketohexose
2) Chirality
a) Chiral means "handed"; it has a nonsuperimposable mirror image.
b) Enantiomers: Pairs of non-superimposable mirror images.
c) Superimposable mirror images are identical compounds.
3) Chirality Centers
- Tetrahedral carbons bonded to four different groups are chirality centers.
4) Fischer Projections
- Understand the structural representation of carbohydrates in Fischer Projections.
5) Labeling Fischer Projections for Monosaccharides
a) Determine the D- or L-isomer by:
- Looking at the chiral carbon furthest from the carbonyl group.
- Hydroxyl group on the right indicates D; on the left indicates L.
b) Enantiomers of a sugar switch configuration at every chiral carbon.
6) Structures of Common Monosaccharides
- Know Fischer Projections and Haworth structures for:
- Glucose
- Galactose
- Fructose
- Ribose
7) Haworth Structures
a) For cyclic hemiacetals of monosaccharides:
- Drawings viewed edge-on.
b) Ability to draw a molecule in its Haworth structure.
c) Identify glycosidic bonds/linkages and name them.
d) Anomeric Carbon Configuration:
- When –OH (–OR) group = down, it is α (alpha).
- When –OH (–OR) group = up, it is β (beta).
8) Conversion Between Fischer and Haworth Structures
- Draw Fischer Projection from Haworth structure and vice versa.
9) Disaccharides and Polysaccharides
- Disaccharides: Know constituent sugars and types of glycosidic bonds:
- Maltose: D-glucose + D-glucose (α-1,4-glycosidic bond).
- Lactose: D-galactose + D-glucose (β-1,4-glycosidic bond).
- Sucrose: D-glucose + D-fructose (α, β-1,2-glycosidic bonds).
10) Hydrolysis of Disaccharides to Monosaccharides
11) Polysaccharides:
- Know constituent sugars, types of glycosidic bonds, and their geometry:
- Amylose (starch): Straight chain of glucose joined by α-1,4-glycosidic bonds.
- Amylopectin: Branched chains of glucose joined by α-1,4-glycosidic bonds (straight runs) and α-1,6-glycosidic bonds (branches).
- Cellulose: Straight chain of glucose joined by β-1,4-glycosidic bonds.
Chapter 21: Amino Acids, Proteins & Enzymes
1) Chirality in Amino Acids
a) Carbons bonded to four different groups can form chiral stereoisomers that are nonsuperimposable mirror images.
b) Recognize chiral carbons in organic structures; identify chiral atoms.
2) Amino Acids
a) Building blocks of proteins.
b) Contain both carboxylic acid (–COOH) and amino (–NH2) groups attached to the same carbon (alpha carbon).
c) Structures of eleven essential amino acids to know:
- Glycine
- Alanine
- Histidine
- Cysteine
- Glutamic acid/glutamate
- Lysine
- Valine
- Serine
- Glutamine
- Methionine
- Tyrosine
3) Zwitterionic Form of Amino Acids
- Typically, amino acids form zwitterions represented as (+H3N–CHR–COO–).
- Isoelectric Point (pI): The pH at which charges exactly balance, yielding a net charge of zero.
- At pH below pI:
- –COO– becomes –COOH (net positive charge).
- At pH above pI:
- –NH3+ becomes –NH2 (net negative charge).
- Ability to predict amino acid structure at specific pH if pI is provided.
4) Formation of Peptide Bonds
a) Peptide bonds form between –COOH and –NH2 of two amino acids, creating dipeptides.
b) Three amino acids linked yield tripeptides, etc.
c) Polypeptides are formed by linking several amino acids in a linear chain.
d) Proteins are large polypeptides.
5) Folding of Polypeptide Chains
a) Correct folding is essential for biological function.
b) Four levels of protein structure:
i. Primary Structure:
1. Sequence of amino acids in peptide chain (e.g., Ala—Leu—Cys—Met).
ii. Secondary Structure:
1. 3D arrangements (e.g., alpha helix, beta pleated sheet) maintained by hydrogen bonds between backbone groups.
iii. Tertiary Structure:
1. Folding of secondary structural elements, maintained by side-chain interactions:
- Hydrogen bonds
- Salt bridges
- Hydrophobic interactions
- Disulfide bonds (covalent).
iv. Quaternary Structure:
1. Combination of multiple tertiary subunits, each an individual polypeptide, maintained similarly as tertiary structure.
6) Common Proteins
a) Water Insoluble (Fibrous):
- Keratin (e.g., skin, wool, feathers, fingernails, silk).
- Collagen (e.g., animal hide, cornea, tendons, bone).
b) Water Soluble (Globular):
- Hemoglobin (carries oxygen).
- Myoglobin (carries oxygen).
- Enzymes.
7) Disruption of Protein Structures
a) Lack of structural integrity leads to loss of function.
b) Hydrolysis of peptide bonds yields small peptides and eventually amino acids, destroying the primary structure.
c) Denaturation:
- Disruption of interactions that support secondary, tertiary, and quaternary protein structures by:
1. Heat
2. Acids & bases (disrupt hydrogen bonds)
3. Organic compounds (disrupt hydrophobic interactions)
4. Mechanical agitation.
8) Enzymes
- Enzymes are proteins that catalyze chemical reactions in biological systems, reducing the activation energy required.
- Enzyme Action:
i. Active site: area of the protein where reaction occurs.
ii. Steps of enzyme action:
1. Substrate binds to the active site to form an enzyme-substrate complex.
2. Reaction occurs within the complex.
3. Products are released from the active site.
4. Cycle repeats.
iii. Lock-and-Key Model: Active site has a rigid shape (lock) that matches the substrate shape (key).
iv. Induced-Fit Model: Active site is flexible and adapts to the substrate’s shape.
- Enzyme Inhibition: Reduction in enzyme activity due to the presence of an inhibitor.
i. Competitive Inhibition:
- Inhibitor reversibly binds to the active site, blocking substrate access.
ii. Noncompetitive Inhibition:
- Inhibitor binds to a remote area, changing protein conformation and altering the active site.
iii. Irreversible Inhibition:
- Inhibitor permanently binds to the active site and prevents substrate access.
Chapter 23: Metabolism and Energy Production
1) Biochemical Reactions (Metabolism)
a) CATABOLISM: Larger molecules are broken down into smaller molecules plus energy.
b) ANABOLISM: Smaller molecules are combined to form larger molecules using energy.
2) Stages of Biological Energy Production
a) Stage 1: Digestion:
- Occurs in mouth, stomach, small intestines; breaks larger molecules into smaller constituents:
- Proteins → amino acids (catalyzed by pepsin).
- Carbohydrates → simple sugars (catalyzed by amylase).
- Lipids → fatty acids (catalyzed by lipase).
b) Stage 2: Acetyl-SCoA Production:
i. Coenzyme A features an alkylthiol group; it activates acyl groups (such as acetyl, ).
ii. Acetyl-SCoA is a major product of glycolysis, fatty acid oxidation, and certain amino acid catabolism.
c) Stage 3: Citric Acid Cycle:
- Oxidizes acetyl carbons to CO2 and produces reduced coenzymes:
- NAD+/NADH
- FAD/FADH2.
d) Stage 4: ATP Production:
- The electron transport chain reduces O2 to H2O, generating ATP:
- ATP structure: composed of ribose, adenine (base), and triphosphate group.
- The primary energy carrier for biochemical reactions.
- Hydrolysis of ATP to ADP releases 7.3 kcal/mol and makes other biochemical reactions favorable.
3) Citric Acid Cycle (Krebs Cycle)
- Utilizes acetyl-CoA from glycolysis to create reduced electron carriers (NADH & FADH2), CO2, and some ATP (as GTP).
- Net Reaction (Simplified):
- Acetyl-CoA → 3 NADH + FADH2 + GTP + 2 CO2.
4) Electron Transport Chain (Mitochondria)
- Utilizes energy stored in reduced electron carriers to generate ATP:
- Rough outline of reaction (unbalanced):
- .
- Synthesis of ATP:
- Protons are pumped across an impermeable membrane.
- Excess protons on one side represent potential energy.
- ATP synthase uses this energy from protons moving back across the membrane to synthesize ATP from ADP.
Chapter 24: Carbohydrate, Lipid & Protein Metabolism (Sections 24.1-24.6 only)
1) Common Enzyme Types in Metabolism
- Carboxylase: Addition of carboxylate (–COO¯).
- Decarboxylase: Removal of CO2.
- Dehydrogenase: Removal of two H atoms.
- Isomerase: Conversion from one isomer to another.
- Kinase: Transfer of phosphate group.
- Hydrolase: Addition of H2O.
2) Glycolysis
- Anaerobic catabolism of glucose (6 carbons).
- Forms 2 pyruvates (3 carbons each), 2 ATP, and 2 NADH.
- Net Reaction for Glycolysis:
- .
3) Fates of Pyruvate
- Aerobic:
- .
- Anaerobic:
- .
- Fermentation:
- .
4) Overall ATP Production from Glucose = 32 ATP
- From Glycolysis: 7 ATP (2 directly + 5 from NADH (2.5 ATP each)).
- From Pyruvate: 5 ATP (from NADH).
- From Citric Acid Cycle: 20 ATP (2 from GTP + 18 from NADH & FADH2 (1.5 ATP each)).
5) The Cori Cycle
- Glucose is the primary energy source for some tissues, especially the brain.
- Glycolysis represents the catabolic conversion of glucose to pyruvate (in cells).
- Gluconeogenesis represents the anabolic conversion of pyruvate to glucose (in the liver).