T2: Genes & Health

• What is the process by which gas exchange occurs in organisms?


  Diffusion
• What factors increase the rate of gas exchange by diffusion?

  • Increased surface area
  • Decreased diffusion distance
  • Steeper diffusion gradient
• What does Fick’s Law state about the rate of diffusion?

  The larger the surface area, difference in concentration, and shorter the diffusion distance, the quicker the rate.

  
• How are mammalian lungs adapted for rapid gas exchange?

  • Large surface area due to many alveoli
  • Good blood supply to maintain concentration gradient
  • Short diffusion distance as alveoli are one cell thick
• What is the main function of the cell membrane?

  Controlling the movement of substances in and out of the cell/organelle.
• What is the fluid mosaic model of the cell membrane?

  It describes the membrane's structure as a fluid combination of phospholipids and proteins.
• What are the types of movement through the cell membrane?

  • Diffusion
  • Facilitated diffusion
  • Osmosis
  • Active transport
  • Endocytosis/Exocytosis
• What is diffusion?

  The passive movement of small, non-polar, lipid-soluble molecules from high to low concentration.
• What factors increase the rate of gas exchange by diffusion?

  Increased surface area, decreased diffusion distance, and a steeper diffusion gradient.
• What is facilitated diffusion?

  A process that requires a channel protein to transport polar, charged, and water-soluble molecules across the membrane.
• What is osmosis?

  The movement of water molecules from an area of low solute concentration to an area of high solute concentration through a partially permeable membrane.
• What is active transport?

  A process that can transport all types of molecules through carrier proteins, requiring energy in the form of ATP.
• What are endocytosis and exocytosis?

  • Endocytosis: Transport of large particles into the cell via vesicles.
  • Exocytosis: Transport of large particles out of the cell via vesicles.
• What are the two types of nitrogenous bases in DNA?

  Purines and pyrimidines.
• What are the purine bases in DNA?

  Adenine and guanine.
• What are the pyrimidine bases in DNA?

  Cytosine and thymine.
• What is the sugar component of DNA?

  Deoxyribose.
• What type of bonds hold the structure of DNA together?

  Phosphodiester bonds between phosphate groups and carbon, and hydrogen bonds between bases.
• What is the structure of DNA?

  • Double-stranded
  • Alpha double helix
  • Sugar-phosphate backbone on each strand
• What are the bases in mRNA?

  Adenine, guanine, cytosine, and uracil.
• What is the sugar component of mRNA?

  Ribose.
• What is the structure of mRNA?

  Single-stranded and not usually folded, carrying codons that attach to tRNA via hydrogen bonds.
• What is the structure of tRNA?

  Single-stranded, folded into a specific pattern held together by hydrogen bonds, carrying anticodons complementary to mRNA codons.
• What are the two stages of protein synthesis?

  1. Transcription (occurs in the nucleus)
  2. Translation (occurs at the ribosomes)
• What happens during transcription?

  A molecule of mRNA is made in the nucleus using one DNA strand as a template.
• What is the role of RNA polymerase during transcription?

  It catalyzes the formation of mRNA by joining adjacent nucleotides with phosphodiester bonds.
• What occurs after mRNA is formed during transcription?

  mRNA moves out of the nucleus through a pore and attaches to a ribosome in the cytoplasm.
• What happens during translation?

  • mRNA attaches to a ribosome.
  • tRNA binds to specific amino acids based on its anticodon.
  • Amino acids are joined by peptide bonds to form a polypeptide chain until a stop codon is reached.
• What is a gene?

  A series of bases on a DNA molecule that codes for a series of amino acids in a polypeptide chain.
• What is the genetic code?

  The order of bases on DNA, consisting of triplets of bases that code for particular amino acids.
• What is the significance of triplets of bases in the genetic code?

  Each triplet of bases codes for a particular amino acid.
• What happens to amino acids after they are coded by a gene?

  The amino acids are joined together by peptide bonds to form a polypeptide chain.
• What is meant by non-coding sections of DNA?

  Parts of the genome that do not code for proteins.
• What happens to tRNA molecules after they detach from amino acids?

  They detach from the amino acids.
• What leads to the formation of a polypeptide chain?

  The process of tRNA molecules detaching from amino acids is repeated until a stop codon is reached on mRNA.
• What is a gene?

  A gene is a series of bases on a DNA molecule that codes for a series of amino acids in a polypeptide chain.
• What does the genetic code consist of?

  The genetic code consists of triplets of bases.
• What does each triplet of bases code for?

  Each triplet of bases codes for a particular amino acid.
• What are the two types of DNA regions mentioned?

  The two types are introns (non-coding) and exons (coding regions).
• What are the features of the genetic code?

  • Non-overlapping: Each triplet is read once and shares no bases.
  • Degenerate: More than one triplet can code for the same amino acid.
  • Triplet code: Each three bases code for one amino acid.
  • Contains start and stop codons for protein synthesis.