enzymes

• Enzymes


  Almost all enzymes are proteins that act as biological catalysts
• Enzymes


  • They speed up biological chemical reactions
  • They are highly specific to a type of reaction
  • They must maintain their specific shape in order to function, any alteration is detrimental
• Enzyme


  A catalyst that speeds up chemical reactions
• Functions of enzymes


  • Break down nutrients into useable molecules
  • Catalyze nearly all the chemical reactions taking place in the cells of the body
  • Create larger molecules from smaller ones
  • Coordinate biological reactions between different systems in an organism
• Enzymes


  • Not altered or consumed during reaction
  • Reusable
• Active site


  The small section of an enzyme dedicated to a specific reaction
• Enzyme action overview

  1. Enzyme reacts with desired substance (substrate)

  2. Substrate may need an environment different from the mostly neutral environment of the cell in order to react

  3. Active site can be more acidic or basic, or provide opportunities for different types of bonding to occur, depending on what type of side chains are present on the amino acids
• Active site


  The area on the enzyme where the substrate or substrates attach
• Enzyme molecules contain a special pocket or cleft called the active sites
• Lock and Key theory


  An enzyme is "structurally complementary to their substrates" and thus fit together perfectly like a lock and key
• Induced Fit theory


  The enzyme itself can change conformations to facilitate the transition state of the substrate, allowing the necessary functional groups at the active site to move closer to the substrate, enhancing the efficiency of the reaction
• Lock-and-Key model


  The active site has a rigid shape, only substrates with the matching shape can fit
• Induced Fit model


  The active site is flexible, not rigid, the shapes of the enzyme, active site, and substrate adjust to maximize the fit, which improves catalysis, there is a greater range of substrate specificity
• Enzyme Catalyzed Reactions

  1. Enzyme (E) and substrate (S) form enzyme-substrate complex (ES)

  2. Reaction occurs within ES complex to convert substrate to product (P)

  3. Products are released, allowing another substrate molecule to bind the enzyme, this cycle can be repeated millions of times per minute
• Enzyme-substrate complex


  Enzyme and substrate combine to form complex
• Enzyme-product complex


  1. An enzyme-product complex is formed

  2. The enzyme and product separate
• Environmental factors

  • Optimum temperature - the temp at which enzymatic reaction occur fastest
  • pH also affects the rate of enzyme-substrate complexes, most enzymes have an optimum pH of around 7 (neutral), some prefer acidic or basic conditions
• Enzyme naming

  The name of an enzyme in many cases end in -ase, e.g. sucrase catalyzes the hydrolysis of sucrose<|>The name describes the function of the enzyme, e.g. oxidases catalyze oxidation reactions<|>Sometimes common names are used, particularly for the digestion enzymes such as pepsin and trypsin<|>Some names describe both the substrate and the function, e.g. alcohol dehydrogenase oxides (ethanol)
• Cell Division


  1. Cells come from preexisting cells that have multiplied

  2. Described by Rudolf Virchow in 1858

  3. Stated "omnis cellula e cellula" (all cells come from cells)
• After around 40 or 50 divisions, cells lose too much DNA to keep dividing and have entered old age
• Cells with a damaged genome or major disorders will be aborted by cell death (apoptosis, autophagy and necrosis)
• Meiosis


  Sex cells divide to produce gametes (sperm or egg)<|>Gametes have half the number of chromosomes<|>Occurs only in gonads (testes or ovaries)<|>Male: spermatogenesis<|>Female: oogenesis<|>Similar to mitosis with some chromosomal differences
• Spermatogenesis


  1. 2n=46 human sex cell diploid (2n)

  2. n=23 n=23 meiosis I

  3. n=23 n=23 n=23 n=23 sperm haploid (n) meiosis II
• Homologous Chromosomes


  • Paternal
  • Maternal
  • Crossing Over - variation
  • Chiasmata: site of crossing over
• Sex Chromosomes

  XX chromosome - female<|>XY chromosome - male
• Meiosis I

  1. Prophase I

  2. Metaphase I - Tetrads align on the metaphase plate, Independent Assortment Occurs

  3. Anaphase I - Homologous chromosomes separate and move towards the poles, Sister chromatids remain attached at their centromeres

  4. Telophase I - Each pole has haploid set of chromosomes, Cytokinesis occurs and two haploid daughter cells are formed
• Meiosis II


  1. No interphase II (or very short - no more DNA replication)

  2. Prophase II - same as prophase in mitosis

  3. Metaphase II - same as metaphase in mitosis, metaphase plate

  4. Anaphase II - same as anaphase in mitosis, sister chromatids separate

  5. Telophase II - Same as telophase in mitosis, Nuclei form, Cytokinesis occurs, four haploid daughter cells produced, gametes = sperm or egg
• Plants turn solar energy into food which is nice of them because animals can't eat sunshine
• Sunshine plays a bigger role in our lives than you may think. All the food we eat and the fossil fuels we burn are products of photosynthesis
• When animals eat plants and other animals, that original solar energy is passed along the food chain
• Photosynthesis


  The process of changing light energy to chemical energy
• Photosynthesis


  • Energy stored as sugar
  • Occurs in plants and some algae
  • Plants need light energy, CO2, and H2O
  • Takes place in the chloroplasts, using chlorophyll, the green pigment in plants
• Photosynthesis reaction


  6 CO2 molecules + 12 H2O molecules + sunlight = C6H12O6 molecule + 6 H2O molecules + 6 O2 molecules
• Photosynthesis


  • Sunlight is converted into chemical energy
  • Water (H2O) is split into oxygen (O2)
  • Carbon dioxide (CO2) is fixed into sugars (C6H12O6)
• Organisms that carry out photosynthesis

  • Plants
  • Cyanobacteria
  • Certain bacteria
  • Most algae
  • Phytoplankton
• Photoautotrophs/Producers


  Organisms that make their own food and energy from the sun
• Consumers


  Herbivores and carnivores that depend on the products of photosynthesis
• Glucose


  A sugar molecule produced during photosynthesis when light energy is converted into chemical energy
• What plants do with glucose

  1. Glucose molecules can be broken apart for energy to power reactions

  2. Plants can also make glucose chains called polysaccharides
• Polysaccharides


  Long chains of glucose molecules, including cellulose and starch