Cytology and Cell Theory Quiz

Study Notes

Cells are the smallest independent living entities capable of independent life (e.g., flagellates, amebas)
All living things are made of cells
Cells originate from pre-existing cells

Metabolism and Energy Generation: Cells undergo essential chemical processes to sustain life
Reproduction by Cell Division:
- Mitosis: Asexual reproduction where cells divide to form new cells
- Meiosis: Occurs in testes and ovaries as part of sexual reproduction
Sensitivity and Response to Stimulation: Cells react to stimuli within their environment

The human body is made up of approximately 75 trillion cells
The body contains around 200 different cell types.
Cell sizes vary within the body, ranging from 5 μm (e.g., small lymphocytes) to 150 μm (e.g., the female ovum)
Cell number is influenced by body size
Cell size is influenced by the cell's function

The shapes of human cells vary greatly (shape is influenced by function):
- Ova are round
- Neurons have processes
- Muscle cells have fibrils
- White blood cells (WBCs) exhibit changeable shapes
Animal cells are mostly round and irregular in shape
Plant cells have fixed, rectangular shapes due to their cell walls

Eukaryotic Cells:
- Have a defined nucleus enclosed by a nuclear membrane
- Contain membrane-bound organelles (e.g., Golgi apparatus, mitochondria, endoplasmic reticulum)
- Include human, animal, and plant cells
Prokaryotic Cells:
- Lack a defined nucleus (no nuclear membrane)
- Possess a nucleoid (region of DNA concentration)
- Lack membrane-bound organelles (e.g., endoplasmic reticulum, Golgi apparatus)
- Include bacteria (bacterium)

Plant Cells contain
- Cell wall: Provides structural support
- Chloroplasts: Sites of photosynthesis
- Plastids: Involved in storage and pigment production
- Large central vacuole: Stores water and other substances
Animal cells do not have these structures.

Forms the outer boundary of all cells
Consists of a lipid bilayer
Composed of:
- Lipids: About 35% (phospholipids and cholesterol)
- Proteins: About 60%
- Carbohydrates: About 5%

Phospholipids:
- Hydrophilic heads face outwards
- Hydrophobic fatty acid tails are in the middle
Proteins:
- Intrinsic proteins (integral) or transmembrane proteins: Embedded within the cell membrane
- Extrinsic proteins (peripheral): Located on the outer and inner surfaces, often involved in transport and as receptors
Carbohydrates: Form a glycocalyx coat on the outer surface of the cell membrane

Microvilli: Finger-like projections that increase surface area for absorption, found in the intestines
Cilia: Motile processes extending from the free surface of cells, found in the respiratory system and oviduct
Stereocilia: Non-true cilia, but long microvilli, found in the epididymis, involved in absorption
Flagella: Cilia-like structures, found in the tail of mature sperm, facilitating sperm movement

Transfer of Nutrients and Metabolites:
- Active Transport: Requires energy to move substances across the membrane against their concentration gradient
- Passive Transport: Does not require energy, movement is driven by concentration gradients
  - Osmosis: Movement of water across a selectively permeable membrane
    - Hypertonic: Higher solute concentration outside the cell, causing water to leave the cell
    - Isotonic: Equal solute concentration inside and outside the cell, water movement is balanced
    - Hypotonic: Lower solute concentration outside the cell, water enters the cell
- Phagocytosis: Intake of solid material by the cell
- Pinocytosis: Intake of liquid material by the cell
- Exocytosis: Discharge of materials outside the cell
- Endocytosis: Intake of materials inside the cell
Cell Signaling and Communication: The cell membrane plays a crucial role in receiving signals from the environment and initiating intracellular responses.
Structural Support: Provides a barrier that helps maintain the cell's shape and integrity.