Biomolecules

Organic Compounds and Isomers

Organic compounds are molecules primarily composed of carbon and hydrogen, often with other elements. Their structure and bonding allow for a wide diversity of forms and functions in living organisms.

• Methane: The simplest form of carbon compound, consisting of one carbon atom bonded to four hydrogen atoms.

• Ethene: A double-bonded molecule of carbon (C2H4).

• Isomers: Compounds with the same molecular formula but different structural arrangements, resulting in different properties.

• Macromolecules: Large molecules such as carbohydrates, proteins, and nucleic acids.

Polymers and Chemical Reactions

Polymers are large molecules made by linking many small, identical building blocks called monomers. Their formation and breakdown involve specific chemical reactions.

• Polymer: A long molecule composed of repeating monomer units.

• Dehydration Reaction: A chemical reaction in which two molecules are covalently bonded with the removal of water.

• Hydrolysis: A chemical reaction that breaks bonds between two molecules by the addition of water.

Carbohydrates

Carbohydrates are sugars and polymers of sugars, serving as energy sources and structural components in cells.

• Monosaccharides: Simple sugars (e.g., glucose).

• Disaccharides: Two sugars linked together (e.g., sucrose).

• Polysaccharides: Polymers with hundreds to thousands of monosaccharide units joined by glycosidic linkages (e.g., starch, cellulose).

Proteins

Proteins are essential macromolecules that perform a wide range of functions in cells, including catalysis, transport, and structural support.

• Account for more than 50% of the dry mass of most cells.

• Functions: Defense, storage, transport, cellular communication, movement, and structural support.

• Amino acids: Building blocks of proteins, each containing an amino group and a carboxyl group.

• Amino acids differ in their side chains (R groups), which determine their properties.

• Amino acids are linked by peptide bonds.

• Polypeptides: Unbranched polymers ranging in length from a few to more than a thousand monomers.

• Protein: A biologically functional molecule consisting of one or more polypeptides.

Protein Structure

The specific activities of proteins result from their intricate three-dimensional structure.

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Local folding into structures such as alpha helices and beta sheets.

• Tertiary Structure: Overall three-dimensional shape of a polypeptide.

• Quaternary Structure: Association of multiple polypeptide chains.

• Proteins lose their structure due to denaturation.

Cell Structure and Function

Cell Types

Cells are the basic units of life and can be classified into two main types: prokaryotic and eukaryotic.

• Prokaryotic Cells: Found in organisms of the domains Bacteria and Archaea. Lack a nucleus and most organelles.

• Eukaryotic Cells: Found in organisms of the domain Eukarya. Possess a nucleus and membrane-bound organelles.

Cell Membranes and Cytoplasm

The plasma membrane and cytoplasm are fundamental components of all cells, controlling the movement of substances and housing cellular processes.

• Plasma Membrane: Boundary that separates the cell from its surroundings. Structure is a fluid mosaic of phospholipids and proteins.

• Cytoplasm: Contents of the cell bounded by the plasma membrane; in eukaryotes, excludes the nucleus.

• Cytosol: Fluid part of the cytoplasm in which cellular components are suspended.

Genetic Control Center

The nucleus is the genetic control center in eukaryotic cells, containing most of the cell's DNA.

• Nucleus: Contains chromosomes and is separated from the cytoplasm by a nuclear envelope.

• Nucleolus: Site of ribosome synthesis within the nucleus.

Ribosomes

Ribosomes are the sites of protein synthesis in both prokaryotic and eukaryotic cells.

• Composed of ribosomal RNA and proteins.

• Function: Translate genetic information into proteins.

Organelles in Eukaryotic Cells

Eukaryotic cells contain specialized organelles that perform distinct functions.

• Endoplasmic Reticulum (ER): Network of membranes involved in protein and lipid synthesis.

• Endomembrane System: Includes ER, Golgi apparatus, lysosomes, and other organelles that manufacture and distribute cellular products.

• Golgi Apparatus: Receives, refines, stores, and distributes chemical products of the cell.

• Lysosome: Membrane-bound sac containing hydrolytic enzymes for digestion of macromolecules.

• Vacuole: Large vesicle for storage of water, pigments, ions, nutrients, etc.

Transformation of Energy

Cells transform energy through specialized organelles to sustain life processes.

• Mitochondria: Found in almost all eukaryotic cells; site of cellular respiration and ATP synthesis.

• Chloroplasts: Unique to photosynthetic cells of plants and algae; perform photosynthesis.

Endosymbiont Theory

The endosymbiont theory explains the origin of mitochondria and chloroplasts in eukaryotic cells.

• Evidence found in both mitochondria (MT) and chloroplasts (CP).

• Suggests these organelles originated as free-living prokaryotes engulfed by ancestral eukaryotic cells.

Table: Comparison of Prokaryotic and Eukaryotic Cells

Additional info: Expanded explanations and table added for clarity and completeness.