Comprehensive Biology Review: Biochemistry, Cell Biology, and Molecular Genetics

Biochemistry: Organic Macromolecules and Enzyme Activity

All four organic macromolecules are carbon-based and consist of polymers constructed from smaller units known as monomers. Carbohydrates occupy a central role in energy storage; their monomers are identified as menesacarides, while their complex polymer forms are known as polysacarides. The primary carbohydrate used by all cells for immediate energy is glueese. In plants, this sugar may be polymerized into Starch for storage, whereas in animals, it is stored as glycogen. Additionally, plants utilize the carbohydrate Cellulase to construct their structural cell walls. Lipids are composed of monomers consisting of fatty acid and glycerol, which can be polymerized into triglysirides. These molecules serve three vital biological functions: long-term energy storage, insulation, and protection. A specific type of lipid known as a phospholipid constitutes the fundamental structure of the cell membrane in all cells.

Proteins are composed of monomers called amino acids, which link together to form polymers known as poly peptides. Proteins serve diverse specialized roles within organisms; for instance, the protein insulin is essential for maintaining blood glucose homeostasis, while the protein hemoglobin is responsible for the transport of oxygen within the body. A specialized category of proteins known as enzyme acts to speed up chemical reactions by lowering the required activation energy. However, the functionality of proteins is highly dependent on their environment; in conditions involving high temperatures or abnormal pH levels, proteins undergo a process called denature, where they lose their shape and function. Finally, nucleic acids, which include DNA and RNA, are composed of monomers called nucleotides. Both types of nucleic acids are utilized by cells to store and execute the genetic code necessary for protein synthesis.

Cellular Organization: Prokaryotic and Eukaryotic Structures

Cells are categorized into two primary types based on their complexity and internal organization. Any prokaryote is characterized as a small, simple cell that contains circular DNA and lacks a nucleus. In contrast, any Eukaryote is larger and more complex, featuring a nucleus and various membrane-bound organelles. The structural and functional components of these cells include:

1. Membrane: A semipermeable boundary that controls the transport of materials entering and exiting the cell.

2. nucleus: The structure that protects eukaryotic DNA.

3. ribosomes: The sites where protein synthesis occurs.

4. Mitocondria: The organelle that performs aerobic cellular respiration to generate $ATP$.

5. Cell wall: A structure providing support and protection for plant and fungi cells, typically made of cellulose*.

6. Chloroplast: The organelle responsible for performing photosynthesis.

7. vacuole: A membrane-bound sac used for the storage of materials such as water and food.

8. rough er: The location for some ribosomes, distinct from those found in the cytoplasm.

9. Smooth er: The site where lipids are synthesized.

10. golgi: The organelle that packages, ships, and sorts materials within the cell.

11. 1430801: A component that contains enzymes specifically involved in waste disposal.

12. flagella: A protein tail used for cell movement.

13. Cillia: Short protein hairs used for cell movement.

14. Cytoplasm: The watery filling that occupies the interior of the cell.

Bioenergetic Processes: Photosynthesis and Cellular Respiration

Plant cells facilitate the process of photosynthesis to convert inorganic materials into organic energy. During this process, they utilize the reactants $CO_2$ and water, combined with the energy harvested from sunlight, to produce glucose (a carbohydrate) and oxygen. To effectively absorb solar energy, plants utilize a specific chemical pigment known as Chlorophyll. The overarching function of photosynthesis is the transformation of Solar energy into Chemical energy. Following the production of energy-rich molecules, cells must produce $ATP$ through the process of respiration. While most respiration is aerobic, some cells perform respiration in the absence of oxygen, a process known as anarobic respiration or firmintation.

Cellular Homeostasis: Passive and Active Transport Mechanisms

Cells maintain a stable internal environment, or homeostasis, by strictly regulating the transport of materials across the Cell membrane. Passive transport occurs without the expenditure of energy. When solute molecules move across the membrane following the gradient from a high to a low concentration, the process is called diffusion. The specific diffusion of water (acting as a solvent) across the membrane is termed Osmosis. When the concentrations of substances are equal on both sides of the membrane, the cell has reached a state of equallibra.

In instances where materials must move against the concentration gradient, cells utilize active transport, which requires the use of the energy molecule $ATP$. This often involves the use of protein Pumps to move materials from a low concentration to a high concentration. Additionally, cells can transport larger quantities of materials by enclosing them in small membrane sacs called vesicles. These vesicles are capable of fusing with the cell membrane to facilitate the movement of materials into or out of the cell.

Molecular Genetics: Nucleic Acid Structure and Protein Synthesis

Nucleic acids, specifically DNA and RNA, serve as the repository for genetic instructions used by cells to produce proteins. The monomers of these acids, nucleotides, are composed of three distinct parts: a 5-carbon sugar (which is deoxyribose in DNA and ribose in RNA), a Phosphate group, and one of 5 different bases. In DNA, these building blocks are organized into a double helix structure where the bases are secured by hydregen bends. These bases pair in a specific pattern, with $A$ pairing with $T$ and $C$ pairing with $G$.

The process of creating proteins begins with transcription, which occurs in the nucleus of eukaryotes. During this stage, the sequence of bases in the DNA serves as a template to create an mRNA copy. A critical distinction in this process is that the $T$ base (thymine) found in DNA is replaced with Ureacil in the mRNA strand. Once transcription is complete, the mRNA transcript is transported to the ribosome. At the ribosome, translation occurs: the mRNA is read in groups of three bases known as a codon. Each codon codes for a specific amino acid that will be incorporated into the final protein, also referred to as a polypeptide (the polymer name). Another form of nucleic acid, RNA, is responsible for delivering the correct amino acids to the ribosome during translation. Any change in the DNA sequence is known as a mutation, which can lead to significant changes in the coding and functionality of the final protein product.