BIO-249 Lecture Exam 3: Cellular Transport & Molecular Genetics

• Identify the following fluid compartments inside and outside the cell:

  • Intracellular fluid

  • Extracellular fluid, which is made up of:

    • Interstitial fluid

    • Plasma

1. Intracellular Fluid

   • Fluid inside the cell

2. Extracellular Fluid: fluid outside the cell

   1. Interstitial Fluid: fluid BETWEEN the cells & outside the bloodstream

   2. Plasma: fluid in the bloodstream

      • Nutrients from the alimentary canal

      • O₂

      • Hormones & chemicals from cells

      • Waste materials

Organelle Functions

1. Nucleus

   • contains our genetic information (DNA) → blueprint for all proteins

   • Nucleolus: codes fro ribosomes

2. Smooth endoplasmic reticulum

   • Process lipids & detoxes hazardous chemicals

3. Rough endoplasmic reticulum

   • ribosomes sit on top to create proteins

4. Golgi apparatus

   • coordinates the movement of vesicles

5. Lysosomes

   • breakdown broken parts & pathogens

   • contains catalytic enzymes

6. Cytosol

   • Jelly substance that holds the organelles in place

7. Mitochondria

   • produces ATP (requires O₂)

8. Ribosomes

   • Produces proteins

9. Cytoskeleton

   • gives structural support/shape

   • Helps some cells move (immune cells & sperm)

   • protein filaments are woven together to make a scaffolding to the cell

Describe the four components of the cell membrane. Describe the function of each component.

1. Phospholipid Bilayer

   • bulk of the membrane

   • selective permeambility

2. Proteins

   • provides transport functionality & other special functions

   • Cell signaling

3. Carbohydrates

   • cell-to-cell recognition

   • determine

     1. cell identity

     2. cell type

     3. origin of cell

4. Cholerestrol

   • provides fluidity & stability to the cell membrane

   • increases resilience to cell recuptes due to extreme temperatures

• Why is the phospholipid molecule considered an amphipathic molecule?

• What part of the phospholipid is polar, and what part is nonpolar?

• Amphiphatic Molecule: contains hydrophilic & hydrophobic regions

  • Phosphate head: hydrophilic

  • Fatty acid tails: hydrophobic

• Naturally forming spherical membranes

  • polar phosphate heads will point externally (polar external environment)

  • Nonpolar tails will point inernally bc they’re hydrophobic

What molecular properties allow molecules to pass through the phospholipid bilayer of the cell membrane via simple diffusion, and why?

Properties

1. Small size

2. Nonpolar

3. Electroneutral

Phospholipid Bilayer is selectively permeable

• Proteins: too big

• Lipids: must be small

• Ions: charged

• Water: polar

• Carbohydrates: polar

• water & carbohydrates use other modes of transportation

• Describe how simple diffusion moves molecules in a sentence or two

• What three factors influence the speed (or the rate) of diffusion?

• Simple Diffusion

  • requires NO energy and moves down its concentration gradient

• Diffusion Rates

  1. Temperature

  2. Surface Area

     • maximize space to increase diffusion

  3. Concentration

• What is the definition of a concentration gradient for a chemical in space?

• What does moving molecules “down/along” or “up/against” their concentration gradient mean?

• Concentration Gradient

  • gradual change in the concentration of solutes in a solution

  • Moving DOWN/ALONG: going from high to low concentration

  • Moving UP/AGAINST: going from low to high concentration

• How is facilitated diffusion different from simple diffusion?

• How are they similar?

• Facilitated Diffusion: requires selective (allowing SOME chemicals) openings (proteins) in the barrier

  • Membrane proteins: channel & carrier

• Simple Diffusion: no membrane proteins involved

  • small, nonpolar, & electroneutral

• Neither uses ATP

• What is osmosis?

• Describe how water moves across a selectively permeable membrane during osmosis in 2-4 sentences.

• Why is the selectively permeable membrane important to osmosis?

• Osmosis: movement of H₂O based on the osmolyte concentration

• H₂O Movement

  • moves towards the HIGHER osmolyte concentration side (osmolytes are polar) until equilibrium is established

• Selective Permeability

  • allows CERTAIN molecules to pass through by diffusion

    • cell to control and maintain its internal composition

  • osmosis: water can always move across the selectively permeable barrier

• What is tonicity? Describe the effects on a cell (a red blood cell, for example) when placed in an isotonic, hypertonic, or hypotonic solution.

• Describe the initial solute concentrations inside and outside the cell and the resulting water movement in each case.

• What does it mean for a cell to crenate or lyse?

• Tonicity

  • ability of a surrounding solution to cause a cell to gain or lose water

  • Isotonic SOLUTION: NO net movement of water (equal osmolyte concentration)

  • Hypotonic SOLUTION: water moves INTO the cell (higher osmolyte conc inside the cell) → cell LYSES

  • Hypertonic SOLUTION: water moves OUT of the cell (higher osmolyte conc outside the cell) → cell CRENATES

• In a sentence or two, describe active membrane transport.

• In general, how is it different than passive membrane transport?

• Active Transport

  • ATP required

  • moves AGAINST the concentration gradient

• Passive Transport

  • NO ATP requirement and moves along its concentration gradient

• Describe the difference between primary active transport and secondary active transport. Note: Think carefully about the concentration gradients of the transported molecules.

• Primary Active Transport

  • ONLY 1 substance moving AGAINST its concentration gradient

• Secondary Active Transport

  • TWO substances involved

    1. Na⁺ ions move DOWN their concentration gradient using the cotransporter

       • utilizes facilitated diffusion

    2. Glucose moves AGAINST its concentration gradient

       • RELIES on the flow of the Na+ down their [ ] gradient

       • utilizes the potential energy of Na⁺ & secondary active transportation

  • does NOT use ATP directly to move glucose AGAINST its concentration gradient

  • RELIES on facilitated dussion to drive the transportation of other molecules

  • Cotransporter needs BOTH molecules to work

What is the other name for secondary active transport?

Cotransportation

Describe endocytosis and exocytosis in a couple of sentences each.

• Endocytosis: molecules are taken inside the cell, and vesicles are formed from the plasma membrane

• Exocytosis: molecules are secreted OUT of the cell

  • vesicles fuse with the plasma membrane

• NEED ATP, used in the digestive & circulatory systems

What is a gene, and in the simplest terms, how is it physically constructed?

• Gene: sequences of DNA that code for proteins

  • DNA is wrapped around a histone protein

  • Nucleosome: DNA & histone complex

  • Chromatin: pre-mitotic DNA and protein complex

Transcription Process

1. RNA polymerase unwinds the DNA double helix

2. RNA polymerase reads each base & creates an mRNA complementary strand

3. mRNA moves to the cytoplasm

Goal: creates mRNA (blueprint for proteins) in the nucleus

• What is the base-pairing rule? In other words, describe how specific nucleotides get matched up during transcription.

• Base Pairing Rule

  • A-T & C-G

  • Each connecting pair of nucleotides is called a base pair

Translation Process

1. mRNA is fed into the ribosome

2. tRNA connects the codon to the amino acid

   • binds to mRNA via a complementary codon

3. Peptide bonds are created to bind amino acids

Goal: using mRNA to form proteins in the cytoplasm

• What is the genetic code?

• What is a codon?

• What is the role of the START codon and the STOP codons in the translation process?

• Genetic Code: amino acid chart that uses mRNA codons to match with an amino acid (uses mRNA to form proteins)

  • translate information encoded within genetic material into proteins

• Codon: DNA/RNA sequence of 3 nucleotides

• START codon: initiate translation (start of the amino acid chain)

• STOP codon: tells tRNA to STOP translation, end of the amino acid chain → RELEASES the amino acid into the cytoplasm

• Describe what a single-nucleotide mutation (SNP) is.

• Given an SNP, you should be able to describe the changes in the mRNA and the potential changes in the protein.

• Single-nucleotide mutation: a single chain in the DNA/RNA sequence

• Mutation Effects

  • don’t really chaince the protein due to the amino acid redundancy

  • function MAY OR MAY NOT change (depends on location)

  • mutation COULD affect the active site OR an unimportant region