Comprehensive Biochemistry Study Guide: Macromolecules, Denaturation, and Cellular Energetics

Carbohydrates:
- Primary consumed carbohydrates include glycogen and starch.
- Glycogen is the primary carbohydrate derived from animal sources.
- Sugars can be attached to proteins and lipids.
Fatty Acids:
- A fatty acid is a lipid composed of a very long chain of hydrocarbons, consisting of carbon atoms bound to hydrogen atoms.
- Fatty acid chains can extend up to $20$ carbon atoms in length.
- Carbon atoms form $4$ covalent bonds. In structural representations, hydrogen atoms reside at the end of unlabelled bond lines.

Saturated Fats:
- Carbons within the chain are fully saturated with hydrogen atoms.
- Interior carbons are bound to $2$ hydrogens, while terminal carbons are bound to $3$ hydrogens.
- Saturated fats are not utilized by the human body for functional metabolic needs.
- High dietary consumption of saturated fats is discouraged due to this lack of physiological utility.
Unsaturated Fats:
- Contain carbon-carbon double bonds within the hydrocarbon chain.
- The presence of a double bond reduces the number of bound hydrogens, as carbon cannot exceed $4$ total bonds.
- Monounsaturated fatty acids contain exactly $1$ double bond.
- Polyunsaturated fatty acids contain $2$ double bonds.
- Saturation classifications are designated under the fat section of standard nutrition labels.

Cis vs. Trans Configurations:
- Cis configuration: Hydrogen atoms are located on the same side of the double bond. The body metabolizes fats structured in this arrangement.
- Trans configuration (Trans fats): Hydrogen atoms are located on opposite sides across the double bond.
- The body cannot utilize trans fats for biological processes.
- Unused lipids, specifically trans fats, accumulate directly as adipose tissue.
Triglycerides:
- Represent stored energy within the body.
- Structure consists of a single glycerol backbone linked to $3$ fatty acid chains.
- Glycerol is a $3$ -carbon chain backbone where each individual carbon atom links to a fatty acid chain.

Steroid Structure:
- Defined by a basic four-ring core carbon shape.
- Cholesterol is a specific example of a steroid.
- Variable regions extending off the ring framework or additional double bonds distinguish individual steroid compounds.
Phospholipids:
- Composed of a single phosphate head and $2$ fatty acid tails.
- Phosphate Head:
- Carries a negative electrical charge.
- Charged molecular groups are hydrophilic (water-loving) and dissolve readily in aqueous environments, similar to salt in water.
- Fatty Acid Tails:
- Composed of $2$ fatty acid chains.
- Represent hydrophobic (water-fearing) nonpolar regions.
- This amphipathic structure allows phospholipids to assemble into organized cellular membranes.

Amino Acids:
- Proteins function as the structural and functional workhorses of the body.
- Synthesized from $20$ distinct amino acids.
- Structural features common to all $20$ amino acids:
- An amine group (a nitrogen-containing group, $NH_3$ ).
- A carboxyl group.
- A variable side chain ( $R$ -group) that differs across the $20$ amino acids.
- Amino acid side chains display either hydrophobic or hydrophilic properties.
- Combinations of these $20$ amino acids can form millions of unique proteins.
Protein Conformation:
- Functional activity depends strictly on maintaining the appropriate conformation (three-dimensional shape).
- Loss of three-dimensional structural integrity results in loss of biological function.

Denaturation Definition:
- Process where a protein loses its specific three-dimensional shape, destroying functional specificity and rendering the protein non-functional.
Primary Causes of Denaturation:
- Elevated Temperature:
- High thermal energy disrupts molecular shape.
- Extreme body fevers of $104^\text{o}F$ to $105^\text{o}F$ require immediate medical treatment to prevent systemic protein denaturation.
- Alterations in $pH$ :
- Significant shifts in $pH$ , particularly toward low $pH$ (acidosis), induce protein denaturation.
- Severe acidosis leads to systemic bodily shutdown due to loss of protein function.

Types of Nucleic Acids:
- DNA (Deoxyribonucleic acid): Stores the genetic code.
- RNA (Ribonucleic acid): Reads the genetic code and directs protein synthesis (mRNA decodes DNA).
Nucleotide Components:
- Every nucleotide consists of three subunits:
1. A nitroglycerin base (nitrogen base).
2. A $5$ -carbon sugar (deoxyribose in DNA; thymine/ribose in RNA).
3. A phosphate group (a central phosphorus atom bonded to multiple oxygen atoms).
Subgroups of Nitroglycerin / Nitrogen Bases:
- Purines: Larger base structures consisting of $2$ fused rings. Includes Adenine and Guanine.
- Pyrimidines: Smaller base structures. Includes Cytosine, Uracil (in RNA), and Thymine.
- Two complementary strands of nucleic acids are bound together by hydrogen bonds.

Function of ATP:
- Acts as a nucleotide derivative containing an adenine base.
- Serves as the universal energy currency of the body.
- Required for energy-dependent processes, including active transmembrane transport and muscle contraction.
Mechanism of Energy Release:
- Composed of adenosine bound to $3$ phosphate groups.
- Specific enzymes break the high-energy bond located between the $2\text{nd}$ and $3\text{rd}$ phosphate groups.
- Cleavage of this terminal phosphate bond releases a high yield of free energy to drive cellular processes.

Chemical Cleavage Pathway:
- Breaking the terminal phosphate bond converts Adenosine Triphosphate (ATP) into Adenosine Diphosphate (ADP) and a free inorganic phosphate group.
- ADP contains $2$ phosphate groups ("di-" indicating two).
- General cleavage formula: $\text{ATP} \rightarrow \text{ADP} + \text{Free Phosphate} + \text{Energy}$
- Cleaving the bond between the $2\text{nd}$ and $3\text{rd}$ phosphate groups consistently releases usable energy for physiological activity.