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Chapter 4

Metabolic Processes

Metabolic Processes

General Information

  • Enzyme controlled
  • Metabolism - sum total of all reactions within the cell
  • Chain - products of one reaction will be the starting material for another reaction

Type of Metabolic Reactions

  • Anabolic - large molecules built from small molecules using dehydration
  • Example: sugar -->saccharide    mono sacharide --> polysacharide
  • Catabolic - break down of large molecules  to smaller ones
  • Uses hydrolosis which is adding H2O to break down carbs, proteins, and lipids
  • Controlled by enzymes

Control of Metabolic Reactions

  • Metabolic reactions require energy
  • Enzymes - globular protein that promote specific chemical reactions within a cell to occur by lowering the activation energy
  • Enzymes are not consumed, but repeatedly used
  • Uses specifity
  • Substrate - substrate undergoing chemical reaction
  • Enzyme must recognize specific substrate; depends on the shape of enzyme molecule
  • Active site - region of enzyme molecule that temporarily combines with substrate
  • Puts strain on particular chemical bond to make certain chemical reactions occur
  • Substrate & enzyme --> substrate/enzyme complex --> product (changed substrate and enzyme unchanged)

 

Click here to see an example of an enzyme & substrate!

Rate of Reactions

  • Depends on the quantity of enzymes/substrates
  • Diferent enzymes have varying rates of efficiency
  • Metabolic pathways - sequence of enzyme controlled reactions
  • There are hundreds of different kinds of enzymes in each cell

Names of Enzymes

  • Derived from substrate they reacti with + ase
  • Lipid + ase = lipase
  • Protein + ase = protease
  • Starch + ase = amylase (amylum)
  • Sucrose + ase = sucrase
  • Maltose + ase = maltase
  • Lactose + ase = lactase

Cofactor & Coenzymes

  • Cofactor - nonprotein component that helps activate enzymes by aiding active site attain its apporpriate shape and bind the enzyme to substrate
  • May be an ion (Cu, Fe, Zn, or small organic molecules such as vitamins and altered forms of vitamins
  • Vitamins - essential organic subsrates that human body cannot synthesize --> dietary
  • Factors that alter enzymes (denature) are heat, radiation, electricity, chemicals, pH
  • Most enzymes are inactive at 45 degrees C and denatured at 55 degrees C

Energy for Metabolic Reactions

  • Energy - capacity to change something or do work
  • Heat, light, sound, electrical, mechanical, chemical
  • Release of chemical energy
  • Chemical energy is found in bonds between atoms and are released when bonds are broken
  • Oxidation - release of energy by adding O2
  • Cellular respiration - process of releasing energy from food molecules and making it available to cells
  • Controlled by a sequence of chemical reactions (enzymes)
  • Some enzymes found in cytosol
  • Other enzymes found in mitochondria
  • Enzymes are physically positioned in exact sequence

Cellular Respiration

  • 3 distince reactions: Glycolosys, Citric Cycle, Electron Transport Chain
  • Glycolosys - breaking down gluclose to 6 carbon chain
  • Series of 10 enzymatic reactions
  • Occurs in cytosol
  • Anareobic phase
  • 3 main events follow:
  • (1) Phosphorilation of gluclose
  • (2) Gluclose split into 2 pyruvate
  • (3) 4 ATP synthesized, electron carrier molecules, NADH synthesized
  • Gluclose molecule yields gross 4 ATP, net 2 ATP
  • 2 NADH + H molecules ETC
  • 2 Pyruvic acid molecules
  • Citric - pyruvic acid goes through series of reactions
  • 8 NADH + H, 2 FADH2 and 2 ATP
  • Electron Transport Chain -occurs in mitochondria
  • Aerobic
  • Each NADH + H --> 3 ATP
  • Each FADH2 --> 2 ATP
  • 10 NADH + H --> 30 ATP
  • 2 FADH2 --> 4 ATP
  • Cellular Respiration Glycolosys -->2 ATP
  • Citric Acid Cycle --> 4 ATP
  • Electron Transport Chain --> 34 ATP
  • TOTAL 40 ATP

Carbohydrate Storage

  • Anabolic - converted into an amino acid
  • Excess gluclose -- glycogen & fat molecules
  • Gluclose goes through glycolsys and breaks down which makes NADH and 2 Pyruvic acid and continue to make energy
  • If intermediate enzyme were rate limiting then  an intermediate substance would accumulate
  • The product of the metabolic pathway inhibits the rate limiting regulating enzyme ( negative feedback response)
  • Accumulation of prodcut inhibits synthesis of the product
  • Decreased concentration of product stimulates synthesis
  • A single enzyme controls the rate of product

Nucleic Acid and protein Synthesis

  • Genetic code - communication between units of DNA information and particular amino acid
  • Gene - portion of a DNA molecule that contains the genetic information for making a particular protein
  • Genome - complete set of genetic instructionin a cell
  • Histone - proteins that DNA would around to form chromatin
  • Codon - each of the 20 Amino acids are represented in a triple code

Deoxyribose nucleic acid (DNA)

  • Nucleotides are the building blocks of nucleaic acids
  • Nucleotide constructed of 5-c sugar (ribose or deoxiribose) phosphate gropu and nitrogen bases (adenine, thymine, cytosine, gunaine)
  • Strands of DNA pair in anti parallel fashion
  • Complimentary base pairs A:T, G:C
  • Double helix - structural shape of DNA molecule

Ribonucleic Acid (RNA)

  • Single strand
  • Ribose used instead of Deoxyribose
  • Uracil (U) used instead of Thymine

Protein Synthesis

  • Transcription - the process of copying DNA information into the structure of mRNA molecule
  • RNA polymarese - binds to a promoter (codon coding for the beginning of a gene sequence)
  • DNA unwinds and pulls apart exposing a portion of the gene
  • Complimentary RNA nucleotides are strung together until it reaches a terminal signal at the end of a gene to form an mRNA molecule
  • DNA rewinds to assume its pervious shape and mRNA leaves the nucleus to associate with a ribosome for protein synthesis to occur
  • Translation - the series of codon we read from the mRNA strand by the ribosome in order to fit together their corresponding amino acid to synthesize protein
  • Transfer RNA - aligns amino acids in a way to allow them to bond
  • There is at least one tRNA molecule for each of the 20 amino acids
  • Amino acids are primed by ATP before bonding with tRNA
  • Anticodon - contains 3 nucleotides in a particular sequence unique to that type of RNA and complimentary to mRNA
  • Ribosomal RNA - the smaller subunit of the ribosome that reads the mRNA from the nucleus
  • Protein - larger subunit of the ribosome allowing for tRNA to bind its anticodon to the codon of the mRNA
  • Amino acids connected to the tRNA join to do the enzymatic activity of the ribosomal proteins and some RNA molecules (ribosomes) in the larger subunit of the ribosome
  • Chaperones - proteins that fold the newly formed polypeptide into its own unique shape and releases it as a seperate functional molecule
  • 3 ATP molecules are required for each amino acid to be linked together
  • Expression - protein produced determines the function a cell performs in the body (cellular differentation)
  • Ribonucleases - destroy the messengerRNA in the cytoplasm in order to control protein synthesis
  • Transcription factors - activate certain genes such as hormones and growth factors active transcription factors


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