Introduction to Cells Biology

Introduction to Cells

• Cells are the fundamental building blocks of the body.
• Similar cells group together to form tissues.
• Tissues group together to form organs.
• Organs group together to form organ systems.
• Organ systems work together to maintain an organism.

Two Main Classes of Cells

• Prokaryotic cells: Do not have a nucleus, organelles not enclosed by membranes.
• Eukaryotic cells: Well-defined nucleus, many organelles enclosed by membranes.

The Animal Cell

• Cells are the smallest functional unit within the body.
• Cells have diverse shapes and sizes depending on their function.
• Cells, tissues, organs, and systems collectively maintain homeostasis.
• Cells reproduce, communicate, and have a lifespan.

Plasma Membrane

• Located on the outside of the cell; phospholipid bilayer with proteins and sugars.
• Regulates what enters and leaves the cell and how the cell responds to signals (e.g., hormones, neurotransmitters).

Cytoplasm

• Fills the space between the nucleus and the cell membrane.
• Cytoplasm consists of the cytosol, organelles and other components essential for cell function.
• Cytosol is the liquid found in the inside of cells.

Nucleus

• Largest organelle in the cell.
• Contains genetic material (DNA) and controls cell activities (metabolic activities).
• When a cell is not dividing, the genetic material is in threads called chromatin.
• When dividing, the genetic material forms chromosomes.
• Contains RNA which is important in protein synthesis.

Deoxyribonucleic Acid (DNA)

• DNA carries genetic information to determine characteristics and the formation of proteins.
• The proteins, formed according to the DNA information, determine structure and function within the cell and the whole body.
• DNA is within chromosomes.

Protein Synthesis

• Protein synthesis involves transcription and translation, ultimately creating proteins for diverse roles.
• A video resource is available for further information on protein synthesis.

Mitochondria

• Mitochondria are responsible for aerobic respiration, producing energy in the form of ATP.
• They have a double membrane, with the inner membrane folded into cristae to increase surface area.
• Cells with high energy requirements will have more mitochondria.

Other Cytoplasmic Organelles

• Includes the endoplasmic reticulum (rough and smooth), ribosomes.
• Endoplasmic reticulum is a network of channels for synthesizing and transporting proteins and other cell components.
• Ribosomes are protein synthesis sites.

Golgi Complex

• Modifies, packages, and transports proteins synthesized in the endoplasmic reticulum.
• Essential for secretion of substances outside the cell.

Lysosomes

• Sac-like structures containing enzymes to break down wastes inside the cell.
• Breakdown products are recycled, or removed.

Cytoskeleton

• A network of protein fibres that determines cell shape, supports the cell, and allows movement and intracellular transport.
• The cytoskeleton comprises microfilaments, microtubules, and intermediate filaments.

The Cell Cycle

• The cell cycle ensures that cells divide and reproduce in a controlled manner.
• This process is carefully regulated for effective tissue maintenance.
• The cycle consists of periods of growth, DNA replication, and division.

Apoptosis

• Apoptosis is a normal programmed cell death process that eliminates damaged or no longer needed cells.
• It is different to necrosis, which is cell death due to a lack of oxygen (hypoxia).

Apoptosis vs Necrosis

• Necrosis involves leakage of cell components, and triggers inflammation.

• There are differences between apoptosis and necrosis, one being inflammation response.

Further Reading

• Recommended textbook for further study, including details of cell-related concepts.