Lecture%2C+16+presentation+02-14-25%2C+1+slide%3Apage

Learning Outcomes for Lecture 02/12/25

• G-Protein-Coupled Receptors (GPCRs)

  • Interact with G-proteins, functioning as cellular switches.

  • Exhibit a one-to-one relationship: One ligand activates one receptor resulting in one response.

• Tyrosine Kinase Receptors

  • Often dimerize (pair up) after ligand binding.

  • Phosphorylate each other on tyrosines, allowing them to trigger multiple responses from a single ligand.

  • Critical for growth factor signaling and have implications in cancer biology.

• Ligand-Gated Ion Channel Receptors

  • Open and close in response to ligand binding.

  • Regulate ion flow into and out of the cell, crucial for neuronal communication.

• Intracellular Receptors

  • Bind ligands in the cytosol and move to the nucleus.

  • Activate gene expression, important in hormone signaling.

Exercise on Properties of Amino Acids

• Evaluate the properties of amino acids (aas) surrounding phosphorylated tyrosine (Y):

  • Amino acid sequence: AVGYTCKPKRDYEPA

  • Properties:

    • Non-polar: A, V, G, P, A

    • Polar: T, C

    • Charged: K, R, D, E

Outline for Lecture on 02-14-25: Living vs Non-Living

1. Key Distinctions Between Living and Non-Living

2. Cell Division Cycle Studies

   1. Prokaryotic and Unicellular Eukaryotic Cell Division

   2. Multicellular Eukaryotes

      • Key roles for cell division

      • Phases of the Cell Division Cycle:

        • Interphase (G1, S, G2)

        • Mitosis (Prophase, Prometaphase, Metaphase, Anaphase, Telophase)

        • Cytokinesis

Characteristics: Living vs Non-Living

• Non-Living:

  • Reproduce: No

• Living:

  • Reproduce: Yes

Bacterial Cell Division: Binary Fission

• Origin of Replication:

  • Bacterial chromosomes with a single circular DNA molecule (E. coli), 500 times larger than the bacterium when extended.

  • Plasma membrane and cell wall structure associated with fission.

Unicellular Organisms: Eukaryotes

• Example: Euglena

  • Reproduces via longitudinal cell division (1 cell divides into 2 identical cells). Each resulting cell is a complete organism.

Key Roles of Cell Division

• Embryonic Development and Growth

• In Adults:

  • Normal controlled cell division for reproduction, replacement of aged cells, and wound healing.

  • Abnormal uncontrolled cell division leading to tumor growth and cancer.

  • Keloid development as an example of abnormal cell behavior.

Importance of Understanding Cell Division

• Ability to stimulate cell division in immune responses.

• Preventing undesirable cell division in cancer and genetic defects.

Eukaryotic Multicellular Cell Division

• Cell division is more complex than in unicellular organisms.

• Involves processes like mitosis or meiosis.

• During mitosis, results in two daughter cells identical to each parent cell.

Important Information on Human Cells

• A typical human cell contains 2 meters of DNA, significantly larger than the cell diameter.

• Human genome: ~40,000 genes in 3.5 x 10^9 base pairs across multiple DNA molecules (chromosomes).

Important Definitions

• Genome: Total genetic material in an organism (e.g., human genome).

• Haploid: Cells with one set of chromosomes (1n).

• Diploid: Cells with two sets of chromosomes (2n).

• Polyploid: Cells with more than 2 sets (e.g., tetraploid, hexaploid, octoploid).

Role of Cell Division in Embryonic Development

• Humans start as one fertilized egg which divides and specializes into various cell types.

• Differentiation: The process where cells specialize during development.

Detailed Definitions of Chromosome Content

• Somatic Cells: Body cells containing two sets of chromosomes (2n), totaling 46 in humans.

• Gametes: Sperm and egg cells, each containing one set of chromosomes (1n), totaling 23.

Chromosome Movement in Mitosis

• Mechanisms of movement during anaphase:

  • "Pac-Man" Mechanism: Chromosomes move on microtubules.

  • "Reeling In" Mechanism: Chromosomes are drawn towards the poles.

Cytokinesis Process

• Animals: Cleavage furrow formation using microfilaments.

• Plants: Cell plate formation through vesicles carrying cell wall material. ‘

Phases of the Cell Division Cycle in Somatic Cells

1. Events during Mitosis.

2. Critical events in cell division.

3. Precise events during cell division.

4. Mechanisms of chromosome movement.

Reading Assignment

• Read Chapter 13 minus sections on "Behavior of chromosome sets in the Human Life Cycle" and "The variety of sexual life cycles."

G-Protein-Coupled Receptors (GPCRs):

• Interact with G-proteins and function as cellular switches.

• Have a one-to-one relationship: One ligand activates one receptor, resulting in one response.

Tyrosine Kinase Receptors:

• Dimerize after ligand binding and phosphorylate each other on tyrosines.

• Trigger multiple responses from a single ligand and are critical for growth factor signaling.

Ligand-Gated Ion Channel Receptors:

• Open and close in response to ligand binding and regulate ion flow, crucial for neuronal communication.

Intracellular Receptors:

• Bind ligands in the cytosol and move to the nucleus to activate gene expression, important in hormone signaling.