Cellular Biology: Prokaryotic and Eukaryotic Cells

Cellular Biology

Synthesis of Cell Theory

• Each living organism is made up of one or more cells (structural unit).
• The smallest living organisms are single cells, and cells are structural units of multicellular organisms.
• All cells come from preexisting cells (the source drive).

Forms of bacteria:

• Bacilli
• Coccobacilli
• Vibrio
• Spirochetes / Spirilla

Prokaryotic and Eukaryotic Cells

Prokaryotic Cells: Are those that have no internal membranes or an organized nucleus (bacteria).

Eukaryotic Cells: They have internal membranes and an organized nucleus.

Difference Between Animal and Plant Cells

Plasma membrane: Structure that separates the intracellular from the extracellular environment. It has a semipermeable molecular composition that regulates what enters and exits the cell through a transport mechanism.

Passive Transport

Diffusion: Passage of molecules (no energy cost) from a higher concentration to a lower concentration.

Osmosis: Water flow from a medium of higher concentration to a lower concentration.

Active Transport

(With expenditure of energy) - Membrane transporters (e.g., Na-K pump). Passage of molecules against the concentration gradient.

• Endocytosis
  • Pinocytosis (liquid intake)
  • Phagocytosis (solid intake)
• Exocytosis (substances exit across membrane vesicles)

Cellular Organelles

• Endoplasmic Reticulum: Network of canals that manufacture lipids (smooth ER) and proteins (rough ER, with ribosomes) that are carried throughout the cell.
• Golgi Apparatus: A network of channels and vesicles that carry substances outside the cell. It packages molecules produced in the reticulum. It manufactures lysosomes, peroxisomes, and glyoxysomes (in plant cells), which are vesicles with enzymes to digest or degrade molecules, and performs cellular digestion.
• Vacuoles: Vesicles that store substances or waste.
• Lysosomes: Vesicles that perform cellular digestion.
• Ribosomes: Responsible for the manufacture of proteins.
• Centrioles: Involved in mitosis.
• Cellular Nutrition: Includes processes for the cell to obtain energy for all its activities.

Autotrophs have chloroplasts for photosynthesis.

Cell Metabolism

• Dynamic reactions that occur in the cell in order to obtain energy from molecules to grow and renew.
• Cellular Respiration: Main metabolic pathway by which the cell obtains energy as ATP (adenosine triphosphate). It takes place in the mitochondria.

Cell Movement

Cells receive environmental stimuli and respond to them. The most common response to these stimuli is movement, which can be of two types:

• Amoeboid: By formation of pseudopodia, which are expansions of the plasma membrane produced by the movement of the cytoplasm.
• Vibrating: Movement of cilia or flagella of the cell.