Biology Quiz: Cells and Organisms

Cells and Organisms

• Amoebas reproduce asexually, primarily through cell division.
• Multicellular organisms consist of multiple cells, similar to how Legos form complex structures like castles.
• An individual is composed of approximately 40 trillion cells.

Microscopy

• Microscopy enhances human ability to observe small objects.
• Light microscopes can magnify up to 1600 times and resolve structures that are 200 nanometers apart.
• Transmission Electron Microscopes (TEM) can magnify up to 50 million times, resolving objects less than 1 angstrom apart.
• Scanning Electron Microscopes (SEM) detail textures on a metal-coated specimen but with less magnification than TEM.

Cell Components

• All cells (bacteria, archaea, eukarya) possess six essential components including DNA, RNA, ribosomes, proteins, cell membrane, and cytoplasm.
• DNA carries genetic information; RNA transports it to ribosomes for protein synthesis.
• Cell membranes act as barriers between internal and external environments, also known as plasma membranes.

Bacteria

• Bacteria are the most diverse and abundant organisms on Earth, possessing a cell wall to maintain shape and prevent bursting due to water intake.
• The nucleoid region contains a single circular DNA strand, essential for the cell's daily operations.
• Some bacteria have flagella for movement, while others lack them.

Archaea

• Archaea resemble bacteria but can survive in more extreme environments (extremophiles).
• Encountered in extreme heat, cold, salinity, and acidity, both bacteria and archaea can thrive in conditions unsuitable for many life forms.
• Discoveries of extremophiles contribute to hypotheses about extraterrestrial life.

Eukarya

• The domain Eukarya consists of unicellular organisms (like certain protists) and multicellular organisms (plants, fungi, animals).
• Eukaryotic cells are more complex and contain membrane-bound organelles, including a well-defined nucleus.

Membrane Structure

• Cell and organelle membranes consist of a phospholipid bilayer, featuring hydrophilic heads and hydrophobic tails.
• The Fluid Mosaic Model describes the dynamic nature of cell membranes, with components able to move fluidly.

Membrane Proteins

• Membrane proteins are crucial for transport, facilitating the entry and exit of substances in and out of the cell.

Lysosomes

• Lysosomes are organelles filled with digestive enzymes for breaking down food, capturing bacteria, and recycling cellular debris.
• Produced in the Rough Endoplasmic Reticulum, they maintain a lower pH (4.8) to optimize enzyme function.

Vacuoles

• Plant cells often contain a large central vacuole for digestion and storage of substances, contributing to cell growth.
• Contractile vacuoles in some protists regulate water levels by expelling excess water.

Peroxisomes

• Peroxisomes are present in all eukaryotic cells, containing enzymes that break down toxic substances.
• They originate from the endoplasmic reticulum and help neutralize harmful byproducts like hydrogen peroxide, particularly in liver and kidney cells.