Protein Synthesis

• Proteins are the most varied molecules in living organisms, with the human body containing at least 10,000 different kinds of proteins
• Proteins in the body are large, complex molecules composed mainly of oxygen, hydrogen, carbon, and nitrogen
• Proteins act as enzymes or catalysts for chemical reactions in cells
• Proteins are made up of amino acids, which are the building blocks consisting of long chains of chemical units
• Our body can synthesize non-essential amino acids through metabolic processes from simple organic molecules, while essential amino acids must be obtained from dietary food intake
• The Central Dogma is a theory stating that genetic information flows only in one direction, from DNA to RNA to protein, or directly from RNA to protein
• DNA is double-stranded, forming a double helix, while RNA is usually single-stranded
• DNA contains deoxyribose sugar, while RNA contains ribose
• DNA uses the bases adenine, thymine, cytosine, and guanine, while RNA uses adenine, uracil, cytosine, and guanine
• There are three kinds of RNA involved in building proteins:

  1. Messenger RNA (mRNA): Travels from the nucleus to the ribosomes in the cytoplasm, where the information in the copy is used for protein production

  2. Ribosomal RNA (rRNA): RNA component of the ribosome, providing a mechanism for decoding mRNA into amino acids and interacting with tRNA

  3. Transfer RNA (tRNA): Adaptor molecule composed of RNA that brings amino acids from the cytoplasm to a ribosome
• Proteins are produced through the process of protein synthesis, which occurs in the ribosomes where cells generate new proteins
• Protein synthesis involves two major processes: transcription and translation
• Transcription involves DNA codes being transcribed into messenger RNA as units called codons, with each codon consisting of three nitrogenous bases coding for a particular amino acid
• In eukaryotic cells, transcription occurs in the nucleus, and after transcription, the resulting mRNA leaves the nucleus and enters the cytoplasm
• Translation takes place in the ribosome, where the code carried by mRNA is translated into a sequence of amino acids forming the protein molecule
• During translation, tRNA carries a special triplet of bases called an anticodon, which is complementary to a codon in the mRNA molecules
• Translation starts with a corresponding tRNA binding with the start codon, AUG, of an mRNA
• To determine which amino acid is encoded by a certain codon, one may use the genetic code table
• When the ribosome encounters a stop codon (UAA, UAG, or UGA), it detaches from the mRNA, marking the termination stage of translation
• The product of translation is a polypeptide chain that undergoes post-translational modification before becoming a functional protein
• The entire process of protein synthesis is described by the central dogma of molecular biology, which unifies the processes of replication, transcription, and translation
• Central Nervous System:

  • Receives and processes all information from all parts of the body
  • Controls the entire organ system of the body
• Brain is the "Control Center" of the nervous system
• Spinal Cord:

  • About 40-50cm long
  • Connects the brain and the body
  • Transmits impulses all over the body to and from the brain
  • Responsible for involuntary movements
• Peripheral Nervous System:

  • Carries impulses from the sensory nerves to the CNS and from the CNS to the motor nerves
• Autonomic PNS regulates all activities that are involuntary or done without conscious will
• Somatic PNS regulates the activities that are under conscious control
• Parasympathetic and Sympathetic are subdivisions of the Autonomic PNS:

  • Parasympathetic: "Rest and digest"
  • Sympathetic: "Fight or flight"
• Types of Neurons:

  • Sensory or Affective Neurons: carry impulses from the sense organs to the Spinal Cord and Brain
  • Interneurons or Associative Neurons: located in the CNS, analyze and interpret impulses
  • Motor or Effective Neurons: carry impulses from the Brain and Spinal Cord to the muscles
• Homeostasis involves Sensors, Communicating Systems, and a Control Center (Nervous System)
• Negative Feedback Mechanism helps maintain homeostasis
• Positive Feedback Mechanism is less common and amplifies a response
• Examples of mechanisms:

  • Eating sweets or foods with high sugar: Positive feedback
  • Lactation for female: Positive feedback
  • Contraction during childbirth: Positive feedback
  • When a person has fever: Negative feedback
  • Shivering: Negative feedback
  • When a person is hungry: Negative feedback
• Comparative Anatomy

  1. Homologous Structures

  2. Analogous Structures

  3. Vestigial Structures
• Analogous Structures


  Body parts of organisms that may perform the same function but of different origins
• Genetic information or Mutation


  Small mutations or changes in the DNA eventually lead to the evolution of new species
• Evolution


  The change in inherited traits over successive generations in a population of an organism
• Vestigial Structures


  Body parts that are useless or left over from a previous ancestor in which they were useful
• Fossil Records

  1. Imprints

  2. Compressions
• How are the ages of fossils determined?

  1. Relative dating

  2. Radiometric/Carbon dating