Eukaryotic Cell and Structure Quiz

Eukaryotic Cell

• A eukaryotic cell is the functional and structural unit of a living organism, considered the building blocks of life.
• Cell biology, or cytology, is the study of cells.
• Prokaryotic cells are found in bacteria; they are small and do not have a membrane-bound nucleus.
• Eukaryotic cells are large and possess a distinct nucleus surrounded by a nuclear membrane. Examples include animal and plant cells.
• The human body contains approximately 100 trillion cells.
• Different cell types exist, including epithelial cells (from epithelium tissue), fibroblast cells (connective tissue), osteocytes (bone cells), chondrocytes (cartilage cells), muscle cells/myocytes, nerve cells/neurons, and blood cells (red and white blood cells).

Cell Structure

• The cell has a covering called the plasma membrane (or cell membrane).
• Inside the cell, the interior contains cytoplasm and a nucleus.
• Eukaryotic cells contain various organelles, such as the nucleus, ribosomes, cell membrane, mitochondria, rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi bodies, centrioles, and the nuclear membrane with nuclear pores.

Plasma Membrane

• Also known as the cell membrane or plasmalemma.
• The outer boundary of the cell.
• Separates the cell's interior from the extracellular environment.
• Composed of phospholipids, proteins, carbohydrates, and cholesterol.
• Functions as a selective barrier, controlling the passage of substances into and out of the cell.
• Facilitates the transport of specific molecules.

Membrane Types

• Impermeable membrane: Substances cannot cross.
• Freely permeable membrane: Substances can cross with ease.
• Selectively permeable membrane: Allows certain substances to cross.
• Extensions of the cell membrane, such as microvilli, cilia, and flagella, are structures found on some types of cells for enhanced absorption or movement.

Cytoplasm

• The region between the plasma membrane and the nuclear envelope.
• Clear, gel-like substance.
• Primarily composed of water.
• Contains various molecules (proteins, carbohydrates, lipids, enzymes, sodium, potassium, phosphates, magnesium, and bicarbonate).
• Houses major cellular organelles (mitochondria, Golgi apparatus, endoplasmic reticulum, ribosomes, lysosomes, centrioles, and microtubules).
• Plays a role in transporting materials within the cell and digesting cellular waste.

Mitochondria

• Rod-shaped organelles considered the power generators of cells.
• Synthesize high-energy molecules like adenosine triphosphate (ATP).
• Convert oxygen and nutrients into ATP.
• Number depends on the cell's metabolic demands.
• Contain an outer and inner membrane; the inner membrane has folds called cristae.
• The matrix is the space enclosed by the inner membrane, where many steps of cellular respiration occur due to the enzyme concentration.

Endoplasmic Reticulum

• A network of tubules within the cell.
• Involved in synthesizing proteins, carbohydrates, and lipids.
• Facilitates storage and transport of these molecules.
• Two types:
  • Rough endoplasmic reticulum (RER): Studded with ribosomes, responsible for protein synthesis.
  • Smooth endoplasmic reticulum (SER): Lacks ribosomes, involved in carbohydrate and lipid metabolism.

Golgi Apparatus (Golgi Complex)

• Stack of flattened membrane discs called cisternae (varying in number from 3 to 10).
• Typically located near the nucleus.
• Acts as a distribution and packaging center for cellular products.
• Modifies proteins and lipids, prepares them for export or transport to other parts of the cell.

Ribosomes

• Granule-shaped structures.
• Contain RNA.
• Responsible for protein synthesis using instructions from DNA.
• Two types:
  • Fixed ribosomes: Attached to the endoplasmic reticulum.
  • Free ribosomes: Scattered in the cytoplasm.

Lysosomes

• Roughly spherical bodies enclosed by a single membrane.
• Contain hydrolytic enzymes (e.g., acid phosphatase).
• Involved in intracellular digestion (breaking down materials).
• Digest cellular waste products, fats, carbohydrates, proteins, and other macromolecules.
• Commonly found in cells involved in defense and waste removal, like white blood cells (macrophages).

Centrioles

• Cylinder-shaped organelles found in animal cells.
• Made up of microtubules.
• Play a crucial role in cell division.

Microtubules

• Tubular structures made up of proteins.
• Provide structural support and stability to cells.
• Essential for cell division processes.

Nucleus

• The administrative center of the cell.
• Contains the cell's hereditary material (DNA).
• Coordinates cell activities, such as growth, metabolism, protein synthesis, and reproduction.
• Typically a single nucleus per cell.
• Enclosed by a double-layered nuclear envelope with pores facilitating molecular transportation between the nucleus and cytoplasm.
• Contains nucleoplasm (semifluid matrix), nucleolus, and chromatin.

Nucleolus

• A membrane-less organelle within the nucleus.
• Involved in ribosome production.
• Visible as a dark spot under a microscope.

Chromatin

• Thread-like structures composing chromosomes.
• Made of DNA and proteins.
• Humans typically have 46 chromosomes in most cells (23 pairs) and 23 in reproductive cells.
• Chromosomes consist of two thread-like components called chromatids joined by a centromere, a part near the center.