Week 2 Flashcards
Classes of biomolecules
Proteins: Provide structural support and act as catalysts (enzymes) for chemical reactions.
Nucleic Acids: Encode and transmit genetic information
Carbohydrates: Serve as energy sources and structural components (e.g., cell walls in plants, algae).
Lipids: Form cell membranes, store energy, and function as signaling molecules.
DNA
Genetic material that specifies protein amino acid sequences.
RNA
Key roles in protein synthesis and gene expression regulation
Polymers
Large molecules made of repeating units (monomers) connected by covalent bonds
Monomers of each polymer
Proteins—> amino acids
Nucleic acids—> nucleotides
Carbohydrates—> simple sugars/monosaccharides
Lipids—> not defined by specific monomers, but all hydrophobic
Functional groups
Atom groups with specific chemical properties influencing molecule behavior
Protein structure and function
Amino Acids: Composed of a central carbon bonded to:
◦ An amino group (-NH₂).
◦ A carboxyl group (-COOH).
◦ A hydrogen atom.
◦ An R group (side chain, determines properties).
Peptide Bonds:
◦ Covalent bonds linking amino acids, formed via dehydration reactions (water molecule released).
Protein Function: Determined by sequence of amino acids and resulting 3D structure.
Components of nucleic acids
Nucleotide Structure:
- 5-carbon sugar (ribose or deoxyribose)
- nitrogenous base (A, T, C, G in DNA; A, U, C, G in RNA).
- One or more phosphate groups.
Bases:
- Pyrimidines: Single ring (C, T, U). Purines: Double ring (A, G).
Phosphodiester Bonds link nucleotides in strand, releasing water during bond formation.
DNA Double Helix:
◦ Complementary base pairing (A-T, G-C).
◦ Sugar-phosphate backbone on the outside; bases on the inside.
Carbohydrates structure and function
Simple Sugars (Monosaccharides):
◦ Basic formula: CxH2xOx (eg Glucose, fructose)
Complex Carbohydrates: Formed by glycosidic bonds (dehydration reaction).
◦Types:
Disaccharides (e.g., sucrose). Polysaccharides (Energy storage: Starch (plants), glycogen (animals). Structural: Cellulose (plant cell walls))
Lipids: characteristics and types
defined by their hydrophobic properties, not specific structure.
Types:
Triacylglycerols: Glycerol backbone w/ 3 fatty acids (energy storage).
(eg Saturated fats: No double bonds; straight chains. Unsaturated fats: One or more double bonds; kinked chains)
◦ Phospholipids: Major cell membrane component.
◦ Signaling Molecules: Include steroid hormones.
Van der Waals Forces: Weak interactions between hydrocarbon chains stabilize lipid structures.
Dehydration reactions
Combine monomers into polymers by releasing water
Hydrolysis
Breaks polymers into monomers by adding water
Cell theory
- 19th century, scientists like Matthias Schleiden, Theodor Schwann, and Rudolf Virchow.
1) All organisms are made up of cells: Organisms can be unicellular ( e.g., bacteria) or multicellular (cells perform different functions: e.g., skin cells for protection, muscle cells for movement, nerve cells for communication).
2) cell is the fundamental unit of life: Cells are the simplest unit that can carry out all life processes: metabolism, reproduction, response to stimuli, and adaptation to the environment. Anything smaller (e.g., molecules, atoms) is not considered alive because it does not exhibit all characteristics of life.
3) Cells come from preexisting cells:Cells reproduce through cell division (mitosis or meiosis). This leads to the creation of daughter cells from a parent cell, maintaining the continuity of life.
Structure and function of cells
structure of a cell is intimately linked to its function, with each cell’s shape and components designed to carry out specific tasks.
Prokaryotic cells
◦ No nucleus, Genetic material is located in nucleoid region.
◦ Small size: Typically 1-2 micrometers in diameter.
◦ Cell wall in many prokaryotes, provides structure/protection.
◦ Circular DNA: typically in a single circular chromosome.
◦ Flagella: Some prokaryotes have flagella, which help in movement.
Eg Bacteria and Archaea.
Structure:No membrane-bound organelles.Simpler internal organization compared to eukaryotic cells.
Functionality:High SA to V ratio (smaller size) efficient for nutrient absorption.
Eukaryotic cells
Nucleus present: Contains cell’s DNA in linear chromosomes.
Larger size: typically much larger than prokaryotic cells.
Membrane-bound organelles
Organelles:
Nucleus: Controls cellular activities, regulating gene expression.
Mitochondria: Powerhouse of the cell; produces energy (ATP).
Endoplasmic Reticulum (ER): Rough (w/ ribosomes)—> proteins; smooth—> lipids.
Golgi Apparatus: Modifies, sorts, packages proteins for secretion
Lysosomes: Break down waste materials.
◦ Compartmentalization: The presence of membrane-bound organelles allows for specialized environments within the cell, more complex cellular processes and better regulation of metabolic functions.
Transcription and translation in prokaryotes vs eukaryotes
Prokaryotes: Transcription and translation occur simultaneously in the cytoplasm because there is no nucleus separating the two processes.
Eukaryotes: Transcription occurs in the nucleus, and translation occurs in the cytoplasm. This separation allows for more regulation of gene expression in eukaryotes.
.
Phospholipid membrane
Lipids (main component), Proteins (embedded in or associated with the membrane), Carbohydrates (attached to lipids or proteins)
Phospholipids are the most important component of cell membranes. Have a glycerol backbone, a phosphate group, and two fatty acid tails.
◦ The phosphate head is hydrophilic, the fatty acid tails are hydrophobic
◦ Amphipathic molecules: Phospholipids have both hydrophilic and hydrophobic parts.
Membrane fluidity
Membranes are dynamic and “fluid,” meaning that lipids and proteins can move laterally within the membrane.
Factors Affecting Fluidity:
◦ Length of Fatty Acid Tails: Longer tails result in less fluidity due to stronger van der Waals interactions between tails.
◦ Saturation of Fatty Acids: Saturated fatty acids (no double bonds) make the membrane more rigid. Unsaturated fatty acids (with double bonds) introduce kinks, preventing tight packing and increasing fluidity.
◦ Cholesterol: affects membrane fluidity depending on temperature: high temps, cholesterol decreases fluidity by stabilizing the membrane. low temps, cholesterol increases fluidity by preventing tight packing of phospholipids.
Types of membrane proteins
Integral Membrane Proteins: permanently attached to membrane, may span entire lipid bilayer (transmembrane) or be associated with only one side of the membrane.
Peripheral Membrane Proteins: Temporarily attached to the membrane, either to the lipid bilayer or to integral proteins, through weak noncovalent interactions.
• Functions of Membrane Proteins:
Transporters: Move ions/molecules across membrane.
Receptors: Receive signals from environment/ binding
Enzymes: Catalyze biochemical reactions at the membrane.
Anchors: Attach to other proteins, maintaining cell structure.
Fluid mosaic model
Proposed by: S. Jonathan Singer and Garth Nicolson (1972)
Key Concepts:
Fluid: Membranes are not rigid structures. Lipids and proteins move laterally within the bilayer.
Mosaic: The membrane is a mix of different types of molecules, including lipids, proteins, and carbohydrates.
Spontaneous formation of membranes
Liposomes and Early Life: ability of phospholipids to spontaneously form liposomes in water is important for understanding how first cell membranes might have formed. Liposomes could encapsulate essential molecules like nucleic acids, which might have been crucial for the origin of life.
◦ process likely occurred in early environments (e.g., tidal flats), where liposomes could form, break, and reform, allowing for the gradual development of more complex membranes.
Self-Healing: if a tear occurs, phospholipids spontaneously rearrange to seal the membrane, preventing the hydrophobic tails from being exposed to water.
Endomembrane system
group of organelles that communicate and interact via vesicles. It includes structures like the nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, and the cell membrane.
Compartments: Divides the cell into distinct spaces where specific functions can occur.
Vesicle Transport: Organelles communicate by transporting proteins, lipids, and other molecules in vesicles.
Exocytosis & Endocytosis: Vesicles can fuse with the cell membrane to expel contents (exocytosis) or bring in substances from the exterior (endocytosis).
Nucleus
Nucleus The nucleus is the central organelle housing cell’s genome (DNA), essential for controlling cell activities like growth, metabolism, and protein synthesis.
Nuclear Envelope: Double lipid bilayer membrane w/ nuclear pores (Large protein complexes that allow passage of molecules (e.g., mRNA, proteins) between the nucleus and cytoplasm)
DNA Storage: Holds the cell’s genetic material.
RNA Synthesis: mRNA is transcribed from DNA, moves through nuclear pores to ribosomes for translation.
