Introduction to Cell Biology

Posted on Aug 24, 2024 in Biology

The Cell Theory

  1. All living things are composed of one or more cells.
  2. Cells are the basic unit of structure and function in an organism.
  3. Cells come only from the reproduction of existing cells.

Prokaryote

No Nucleus / Very small / Limited organization / No membrane-bound organelles (only DNA and ribosomes) example: Bacteria

Eukaryote

Nucleus / Small (larger than Prokaryotes) / Organization / Membrane-bound organelles / Example: Plants and animals

Scientists and Their Contributions

  • Anton van Leeuwenhoek: Invented the Microscope
  • Robert Hooke: Discovered cells using cork
  • Matthias Schleiden: All plants are composed of cells
  • Theodor Schwann: All animals are composed of cells
  • Robert Brown: Discovered the nucleus
  • Rudolf Virchow: Organized information into the cell theory

Cell Organelles

Nucleus

Control center of a cell / Protected by the nuclear membrane / Houses the nucleolus and genetic material

Nuclear Membrane

Located outside the nucleus / Protects the nucleus

Nucleolus

Center of the nucleus / Produces ribosomes

Chromatin

Genetic material consisting of DNA and proteins / Prior to cell division – Chromatin / During cell division – Chromosomes

Mitochondria

Powerhouse of the cell / ATP – energy

Golgi Apparatus

Packages and sorts proteins / The shipping and handling of the cell

Endoplasmic Reticulum

Surface for all chemical activity / Connects cell membrane to nuclear membrane

  • Rough ER: Studded with ribosomes / Helps with proteins
  • Smooth ER: No ribosomes / Helps with lipids

Ribosomes

Produced by the nucleolus / Produce proteins / Found on Rough ER or free-floating in the cytoplasm

Lysosomes

Contains the digestive enzymes of the cell / Suicide sacs

Vacuoles

More prominent in plant cells than animal cells / Used for storage of minerals, water, and food

Plastids

Used for the storage of pigment (example: Chloroplast in plant cells)

Plant Cell

Cell wall, plastids, vacuoles

Animal Cell

Centrioles (animal cell division)

Plasma Membrane

“Fluid Mosaic” model contains phospholipids, proteins, and carbohydrates, is the gatekeeper of the cell, consists of a Phospholipid bilayer: Hydrophilic (head) and Hydrophobic (tail)

Passive Transport

Is a movement of biochemical and other atomic or molecular substances across cell membranes without the need for energy input.

  • Diffusion: The movement of molecules through a semi-permeable membrane from HIGH concentration to LOW concentration.
  • Osmosis: The diffusion of water.
  • Facilitated Diffusion: Use of carrier proteins to get molecules across the membrane (without expending energy).

Active Transport

Is the movement of molecules across a cell membrane in the direction against some gradient or other obstructing factor.

  • Exocytosis: The process of removing something from the cell.
  • Endocytosis: The process of bringing something into the cell; uses lysosomes to break the membrane.
  • Pinocytosis: Cell drinking.
  • Phagocytosis: Cell eating.

Cell Cycle

Interphase

  • G1 phase: Cell growth, increase in size, synthesize new proteins and organelles.
  • S phase: DNA replication.
  • G2 phase: Final preparation for division.

Prophase

First and longest phase of mitosis, chromosomes become visible, nuclear membrane and nucleolus disappear, centrioles move, spindle fibers form.

Metaphase

Chromosomes line up in the center (equator) / Spindle fibers lengthen.

Anaphase

Centromere splits, sister chromatids separate and become individual chromosomes, spindle fibers shorten, chromosomes move toward the poles.

Telophase

Chromosomes become a dense tangle of genetic material, the nuclear envelope and nucleolus reform, spindles break, centrioles pair.

Cytokinesis

The division of cytoplasm, often occurs simultaneously with telophase.

Homologous

Refers to chromosomes / Each chromosome pair = male + female (one from each parent)

Diploid

(2n) Two sets of chromosomes / Example: Body cells

Haploid

(n) Single set of chromosomes / Example: Gametes (sex cells)

Meiosis

A process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.

Meiosis 1

  • Interphase 1: DNA Replication occurs forming duplicate chromosomes.
  • Prophase 1: Each chromosome pairs with its corresponding homologous chromosome to form a TETRAD / Crossing over can occur (Exchange of information between homologous chromosomes during prophase 1).
  • Metaphase 1: Spindle fibers attach to the chromosomes (line up).
  • Anaphase 1: Spindle fibers pull homologous chromosomes toward opposite ends of the cell.
  • Telophase 1 & Cytokinesis: Nuclear membranes form, the cell separates into two cells (Both Haploid).

Meiosis 2

  • Prophase 2: Meiosis 1 results in 2 haploid daughter cells, DNA replication does not occur during meiosis 2.
  • Metaphase 2: Chromosomes line up.
  • Anaphase 2: Sister chromatids separate and move toward opposite ends of the cell.
  • Telophase 2 & Cytokinesis: Meiosis 2 results in 4 haploid daughter cells.

Mitosis vs. Meiosis

  • Mitosis: Growth, maintenance, and repair / Example: Body cells / Produces 2 diploid cells (genetically identical) / 1 division.
  • Meiosis: Reproduction / Example: Sex cells (gametes) / Produces 4 haploid cells (not genetically identical) / 2 divisions with crossover.

Cancer

Is an uncontrolled growth and spread of abnormal cells. A tumor is a mass of cells that grows more rapidly than surrounding tissue.

  • Malignant: Very dangerous and harmful.
  • Benign: Harmless, non-cancerous.

Metastasis is the process where cancer spreads from one area of the body to a different one.

Types of Cancer

  • Carcinoma: The most common site for cancer, found in tissues that cover the body surfaces and linings of most body cavities and form solid tumors. Example: Breast, lung, skin, and mouth.
  • Sarcoma: Less common but usually more dangerous, they form solid tumors, they occur in the middle layers of tissues. Example: Bone, muscles, and connective tissues.
  • Lymphoma: Develops in the lymphatic system, forms solid tumors. Example: Hodgkin’s disease.
  • Leukemia: Cancer of the blood-forming parts of the body, characterized by an abnormal increase in the number of white blood cells.

Cancer Detection

  • MRI: Devices that use magnetic fields, radio waves, and computers to generate an image of internal tissue of the body without radiation.
  • CAT scan: Machine uses radiation to view internal organs not normally visible on x-rays.

Cancer Treatment

  • Surgery: Remove tumor and surrounding tissue.
  • Radiotherapy: Uses radiation to kill cancerous cells, can also destroy healthy cells.
  • Chemotherapy: Uses drugs to kill cancerous cells, treats cancer that has spread throughout the body.