Biomolecules and Cell Structure Overview

Triglycerides (Fats)

Composed of glycerol linked to three fatty acids; serve as a major energy storage form.

Unsaturated Fats

Contain one or more double bonds; liquid at room temperature.

Protein Structure Levels

Primary, Secondary, Tertiary, and Quaternary structures; each level determines the protein's shape and function.

Nucleic Acids

Include DNA and RNA, store and transmit genetic information, composed of nucleotides.

Mitochondria

Site of cellular respiration, generating ATP; possess double membrane and own DNA.

Cytoskeleton

Dynamic network of fibers organizing cell structure and activities, crucial for maintaining cell shape and enabling cell motility.

Cell Junctions

Tight Junctions, Desmosomes, and Gap Junctions; facilitate cell-cell adhesion, communication, and transport.

Diffusion

The movement of substances from an area of high concentration to an area of low concentration.

Facilitated Transport

The process of substance movement across membranes with the help of specific transport proteins.

Biomolecules

Essential for life, classified into five main groups: Water, Lipids, Carbohydrates, Proteins, Nucleic Acids.

Water

Polar molecule with partial positive charges on hydrogen atoms and a partial negative charge on the oxygen atom; forms hydrogen bonds with other water molecules and polar substances.

Hydrophilic vs. Hydrophobic Substances

Hydrophilic substances dissolve readily in water (e.g., glucose), while hydrophobic substances (e.g., lipids) do not dissolve in water.

Condensation Reactions

Formation of polymers by releasing water.

Hydrolysis Reactions

Breaking down of polymers into monomers by adding water.

Phospholipids

Contain two fatty acids, a glycerol backbone, and a phosphate group; have both hydrophilic and hydrophobic regions, forming cell membranes.

Saturated Fats

No double bonds between carbon atoms; solid at room temperature.

Monosaccharides

Simple sugars like glucose, providing quick energy.

Disaccharides

Formed from two monosaccharides (e.g., sucrose).

Polysaccharides

Long chains of monosaccharides, including Starch, Glycogen, and Cellulose.

Amino Acid Structure

Contain an amino group, a carboxyl group, and a variable R-group (side chain).

Prokaryotic Cells

Cells lacking a membrane-bound nucleus, simpler in structure, with a single circular chromosome and plasmids; examples include bacteria and archaea.

Eukaryotic Cells

Cells with membrane-bound organelles, larger and more complex than prokaryotic cells, including nucleus, mitochondria, and ER.

Plasma Membrane

Phospholipid bilayer critical for maintaining homeostasis, transport, and structural integrity of the cell.

Nucleus

Enclosed by a nuclear envelope, contains chromosomes organized into chromatin, and nucleolus for ribosomal RNA synthesis.

Endomembrane System

Includes Rough and Smooth ER, Golgi Apparatus, Lysosomes, and Peroxisomes; involved in protein synthesis, modification, and transport.

Active Transport

The energy-requiring process of moving substances against their concentration gradient.

Endocytosis

The process by which cells engulf large molecules by wrapping the cell membrane around them.

Exocytosis

The process of expelling large molecules from the cell by vesicles fusing with the cell membrane.

Cilia

Microtubule-based structures involved in cell motility.

Flagella

Microtubule-based structures involved in cell motility.

Transcription

The process of transcribing DNA into RNA, specifically mRNA.

Translation

The process of translating mRNA into proteins at the ribosomes.

Ribosomes

Molecular machines responsible for protein synthesis in cells.

Selective Permeability

The property of membranes to allow certain molecules to pass through while restricting others.

Passive Transport

Movement of molecules down their concentration gradient without the input of energy.

Osmosis

The diffusion of water through a selectively permeable membrane.

Integral Proteins

Proteins that span the membrane and are involved in transport.

Peripheral Proteins

Proteins bound to the surface of the membrane, contributing to signaling and support.

Membrane Fluidity

The flexibility of the membrane influenced by temperature and fatty acid composition.

Lateral Movement

The side-to-side movement of lipids and proteins within the membrane.

Ion Transport

The movement of ions across membranes through electrochemical gradients.

Resting Membrane Potential

The electrical charge difference across the plasma membrane of a neuron at rest.

Cell Division

The process by which cells replicate and divide to form new cells.

Mitosis

The process of cell division resulting in two identical daughter cells.

DNA Replication

The duplication of the entire genome during the S-phase of the cell cycle.

Chromosome

A long DNA molecule coiled around histone proteins, forming chromatin.

Sister Chromatids

Identical copies of a chromosome, held together at the centromere.

Centromere

The region of the chromosome where sister chromatids are joined.

Mitotic Spindle

Microtubule structure responsible for separating chromosomes during mitosis.

Cyclin/Cdk Complex

Proteins that regulate the progression of the cell cycle.

DNA

Serves as the genetic material, containing the instructions for all biological processes.

Nucleotide composition

Composed of a deoxyribose sugar, a phosphate group, and four nitrogenous bases (Adenine, Thymine, Cytosine, and Guanine).

Polymerization

Nucleotides link via phosphodiester bonds between the 3' carbon of one nucleotide and the 5' carbon of the next, resulting in a sugar-phosphate backbone.

Antiparallel strands

DNA consists of two strands that run in opposite directions (5' →3' and 3' →5').

Double Helix

DNA consists of two complementary strands twisted into a double helix.

Semi-conservative replication

Each new DNA molecule consists of one original (parent) strand and one newly synthesized (daughter) strand.

Replication Fork

A Y-shaped region where the DNA is split into two separate strands for replication.

Leading Strand

Synthesized continuously in the 5' to 3' direction towards the replication fork.

Lagging Strand

Synthesized discontinuously as a series of short fragments called Okazaki fragments.

Helicase

Unwinds the DNA helix.

Primase

Synthesizes short RNA primers.

DNA Polymerase III

Adds nucleotides to the growing DNA chain in the 5' to 3' direction.

DNA Polymerase I

Replaces RNA primers with DNA.

DNA Ligase

Joins Okazaki fragments by sealing nicks in the sugar-phosphate backbone.

Proofreading

DNA polymerase's ability to detect and correct mismatches during replication.

Mismatch repair

Process where enzymes detect and correct remaining mismatched bases after replication.

Telomeres

Non-coding repetitive sequences at the ends of chromosomes that prevent the loss of essential genes during DNA replication.

End-replication problem

The issue where the lagging strand in DNA replication cannot be fully replicated due to the removal of RNA primers, causing telomeres to shorten with each cell division.

Central Dogma of molecular biology

The concept explaining the flow of genetic information from DNA to RNA to Protein.

RNA Processing

Modifications to mRNA before translation, including 5' Cap Addition, 3' Poly-A Tail Addition, and RNA Splicing.

Post-Translational Modification

Chemical changes to proteins after synthesis, such as glycosylation and phosphorylation.

Mutations

Changes in the DNA sequence that can affect protein function, including point mutations and frameshift mutations.

Metabolism

The sum of all chemical reactions in an organism, categorized into catabolic and anabolic pathways.

Free energy change (ΔG)

The difference in free energy between reactants and products, determining if a reaction is spontaneous (exergonic) or requires energy input (endergonic).

ATP (Adenosine triphosphate)

The primary energy currency of the cell, consisting of three phosphate groups, a ribose sugar, and adenine.

Enzymes

Biological catalysts that speed up reactions by lowering the activation energy, with factors affecting their activity including temperature, pH, and regulation.

Energetic coupling

Using exergonic reactions to drive endergonic reactions, such as ATP hydrolysis to phosphorylate substrates.

ATP regeneration

The continuous production of ATP from ADP and phosphate through cellular processes like respiration or photosynthesis.

Cofactors

Inorganic ions that assist enzyme activity.

Coenzymes

Organic molecules, like vitamins, that participate in enzyme reactions by carrying chemical groups or electrons.

Michaelis-Menten kinetics

Describes how enzyme activity changes with substrate concentration, reaching Vmax when all active sites are occupied.