Biomolecules

• Biochemistry


  Scientific discipline that seeks to explain life at the molecular level
• Molecules studied in biochemistry

  • Nucleic acids
  • Carbohydrates
  • Proteins
  • Lipids
• Biochemistry


  • Involves the study of the physical structure and chemical reactivity of biomolecules
  • Is a chemical science and a study in thermodynamics
• Cells


  Building blocks of all organisms
• In single-celled organisms, the cell is everything - no hierarchy of organization
• Cell Theory


  • Cells are basic units of life
  • All living organisms are made up of cells
  • All cells come from preexisting cells
• 4 Common Components in Cells

  • Enclosing plasma membrane which separates the cell's interior from the environment
  • Cytoplasm made of cytosol, in which other components of the cell are found
  • DNA - genetic material of the cell
  • Ribosomes - synthesize proteins

  
• Prokaryotes


  • Are smaller than eukaryotes because of efficiency: Their surface area to volume ratio is more favorable for moving material in and out of the cell; smaller size = bigger SA:V
  • They lack modifications found in eukaryotes that aid internal transport
• Prokaryotes are unicellular; may stick together to form associations & biofilms
• Prokaryotes are <1 mm in diameter
• Prokaryotes


  • Have a nucleoid (chromosome is single, circular, & double-stranded DNA)
  • Have plasmids
  • Reproduces asexually through binary fission
  • Genetic recombination occurs through horizontal gene transfer
  • Flagella are simpler in nature
  • Metabolic processes include oxygenic & anoxygenic photosynthesis
  • Most are chemolithotrophic (can use energy stored in bonds of inorganic molecules)
  • Cell wall contains peptidoglycan
• Prokaryotes (organisms in domains Archaea and Bacteria) are believed to be much like the first cells
• Organelles unique to animal cells

  • Centrosome - consists of 2 centrioles that helps organize microtubules
  • Lysosome - breaks down large biomolecules & old organelles

  
• Organelles unique to plant cells

  • Cell wall (cellulose) - rigid body
  • Chloroplast - photosynthesis
  • Plastids - stores substances
  • Central vacuole - maintains pressure against cell wall
  • Plasmodesmata - connects the cytoplasm to cytoplasms of adjacent cells

  
• Types of Junctions


  • Tight junction - watertight seals that prevents materials from leaking between cells; found in epithelial cells
  • Gap junction - protein-lined pore that allows water and small molecules to pass through adjacent cells
  • Desmosomes - "welds" adjacent cells together, often found in cells of organs and tissues that stretch (skin, lungs, cardiac muscle)
• Properties of Life


  • Order - organisms are highly organized, coordinated structures that consist of one or more cells
  • Sensitivity or Response to Stimuli - organisms respond to diverse stimuli. Positive response is when an organism moves toward a stimulus. Negative response is when an organism moves away from the stimulus
  • Reproduction - Unicellular organisms reproduce through binary fission. Multicellular organisms often produce specialized reproductive cells–gametes and oocyte and sperm cells. After fertilization (fusion of an oocyte and a sperm cell), a new individual develops. Associated with heredity
  • Adaptation - consequence of evolution by natural selection; enhances the reproductive potential of the individuals exhibiting it. including their ability to survive to reproduce; not constant and can be positive and negative
  • Regulation/Homeostasis - "steady state"; refers to the relatively stable internal environment required to maintain life
  • Energy Processing - all organisms use a source of energy for their metabolic activities
  • Evolution - diversity of life on Earth is a result of mutations, or random changes in hereditary material over time; an organism that evolves characteristics fit for the environment will have greater reproductive success
• Levels of Organization of Living Things

  • Atom
  • Molecule
  • Macromolecules
  • Organelles
  • Cells
  • Tissues
  • Organs
  • Organ System
  • Organism
  • Population
  • Community
  • Ecosystem
  • Biosphere
• Evolution is the source of diversity
• Phylogenetic Tree


  Shows the evolutionary relationships among biological species based on similarities and differences in genetic or physical traits or both

  
• Carl Woese


  • Microbiologist that constructed a phylogenetic tree using data obtained from sequenced ribosomal RNA genes
  • Bacteria, Archaea: prokaryotic cells with microbes that lack membrane-enclosed nuclei and organelles
  • Archaea: extremophiles
  • Eukarya: includes unicellular organisms (protists), together with three remaining kingdoms (fungi, plants, and animals)

  
• Branches of Biological Study

  • Molecular biology and biochemistry
  • Forensic science
  • Neurobiology
  • Paleontology
  • Zoology and botany
• Cell Types


  • Epithelial cells - protect the body's surface and cover the organs and body cavities within
  • Bone cells - support and protect the body
  • Immune system cells - fight invading bacteria
  • Blood and blood cells - carry nutrients and oxygen throughout the body while removing carbon dioxide
• Cell Membrane


  • Extremely pliable structure composed of a phospholipid bilayer
  • Cholesterol contributes to the fluidity of the membrane, with various proteins embedded within the membrane

  
• Hydrophilic phosphate head


  Phosphate + glycerol; negatively-charged; attracted to water in the intracellular fluid
• Hydrophobic lipid tail


  Saturated and unsaturated fatty acids; uncharged; meet at INNER region of the membrane
• Phospholipids


  Amphipathic; contains BOTH a hydrophilic and hydrophobic region
• Intracellular fluid (ICF)


  Fluid interior of the cell

  
• Extracellular fluid (ECF)


  Fluid environment outside the enclosure of the cell membrane
• Interstitial fluid (IF)


  Extracellular fluid not contained within blood vessels
• Membrane Proteins


  • Integral protein - embedded in the membrane
  • Peripheral protein - typically found on the inner and outer surface of the lipid bilayer but can also be attached to the internal or external surface of an integral protein

  
• Integral Membrane Proteins


  • Channel protein - selectively allows particular materials, such as certain ions, to pass into or out of the cell
  • Cell recognition proteins - mark a cell's identity so that it can be recognized by other cells
  • Receptor - selectively bind a specific molecule outside the cell that induces a chemical reaction within the cell
  • Ligand - specific molecule that binds to and activates a receptor
  • Glycoprotein - a protein that has carbohydrate molecules attached, which extend into the extracellular matrix; attached tags aid in cell recognition

  
• Glycocalyx


  Fuzzy-appearing coating around the cell formed from glycoproteins and other carbohydrates attached to the cell membrane

  
• Functions of Cell Membrane

  • Allow cell to bind to another cell
  • Contain receptors for hormones
  • Have enzymes to break down nutrients
  • Product of a person's genetic makeup
  • Give each of the individuals' trillions of cells the "identity" of belonging in the person's body
• Transport across the Cell Membrane

  • Regulation of the concentration of substances inside the cell; includes ions and waste products
  • Makes use of the membrane's selective permeability

  
• Passive Transport


  • Diffusion - movement of particles from an area of higher concentration to an area of lower concentration
  • Facilitated diffusion - used for large, charged, polar substances; passive so does not require ATP
  • Osmosis - diffusion of water through a semipermeable membrane; occurs when there is an imbalance of solutes outside vs. inside the cell
  • Hypertonic - solute is highly concentrated outside the cell, water will come out from the cell into the solution resulting in crenation; in plant cells: plasmolyzed
  • Hypotonic - solution outside the cell has solute in lower concentration, water from the solution will go inside the cell resulting in lysis; in plant cells: turgid
  • Isotonic - solute inside and outside the cell is equal; achieved through homeostasis; in plant cells: flaccid
• Active Transport


  • Requires ATP, often with the help of carrier proteins, usually against its concentration gradient
  • Sodium-potassium pump (Na+/K+ ATPase) - abundant in nerve cells (neurons), maintaining electrochemical gradients across cell membranes
  • Electrical gradient - difference in electrical charge across a space
  • Secondary active transport - active transport that powers the transport of another substance
  • Symporters - move two substances in the same direction
  • Antiporters - move two substances in opposite directions
• Forms of Active Transport without Membrane Carriers

  • Endocytosis - bringing into the cell; invagination and becomes an intracellular vesicle; often brings materials into the cell that must be broken down or digested
• ATPase


  Abundant in nerve cells (neurons), maintaining electrochemical gradients across cell membranes
• Electrical gradient


  Difference in electrical charge across a space
• Secondary active transport


  Active transport that powers the transport of another substance