Cell Structure and Function: Prokaryotes, Eukaryotes, and Membrane Dynamics

What is the smallest living subunit of an organism?

A cell

What are the two main domains of prokaryotes?

Archaea and Bacteria

What distinguishes prokaryotes from eukaryotes regarding nuclei?

Prokaryotes do not have a true membrane-bound nucleus, while eukaryotes do.

What structure in prokaryotes helps with mobility?

Flagella

What is the typical shape of prokaryotic chromosomes?

Circular

What type of DNA do eukaryotes possess?

Linear DNA

What is a key feature of eukaryotic cells that allows compartmentalization?

Membrane-bound organelles

What is the function of the endoplasmic reticulum?

It synthesizes lipids, detoxifies drugs, and stores calcium ions.

What is the role of the Golgi apparatus in a cell?

It modifies, sorts, and ships proteins and lipids.

What process describes the engulfing of large particles by a cell?

Phagocytosis

What is the function of lysosomes?

They contain enzymes that break down macromolecules.

What is the difference between exocytosis and endocytosis?

Exocytosis is the process of secreting large molecules, while endocytosis is the process of taking in large molecules.

What is selective permeability in the context of cell membranes?

It refers to the ability of the membrane to differentiate between different molecules.

What is the significance of compartmentalization in eukaryotic cells?

It allows for greater functional efficiency by creating different physical environments for various tasks.

What is the function of transport vesicles?

They carry polypeptides and transport unfinished molecules to different environments.

What is the role of the nucleolus within the nucleus?

It synthesizes RNA for ribosomes.

What is the difference in cell size between prokaryotes and eukaryotes?

Prokaryotes are typically smaller than eukaryotes.

What is the process of autophagy?

It is the breakdown of unused products by lysosomes.

What is the main function of the central vacuole in plant cells?

It stores water and other substances.

What is the difference between catabolic and anabolic reactions?

Catabolic reactions break down large macromolecules and release energy, while anabolic reactions use energy to create larger biomolecules.

What is the unique characteristic of the prokaryote Thiomargarita magnifica?

It challenges the boundary between prokaryotes and eukaryotes.

How do vesicles move within the cell?

Motor proteins help drag vesicles along the cytoskeleton.

What is the role of motor proteins in relation to the cytoskeleton?

Motor proteins interact with elements of the cytoskeleton and require ATP to function, effectively 'walking' along microtubules.

What is the primary function of mitochondria?

Mitochondria are the site of cellular respiration in eukaryotic cells.

Describe the structure of mitochondria.

Mitochondria have a smooth outer membrane and highly folded inner membranes called cristae, with a matrix that contains circular chromosomes and specialized ribosomes.

What is the primary function of chloroplasts?

Chloroplasts are the site of photosynthesis in plant cells.

Describe the structure of chloroplasts.

Chloroplasts have a triple membrane structure with smooth outer and inner membranes and a convoluted innermost membrane called thylakoids, which contain chlorophyll.

What is the endosymbiotic theory?

The endosymbiotic theory suggests that modern eukaryotes evolved from ancestral cells that engulfed prokaryotic organisms, leading to a mutualistic relationship.

What evidence supports the endosymbiotic theory?

Mitochondria and chloroplasts reproduce like prokaryotes, have similar DNA and ribosomes, and possess two membranes with characteristics of both prokaryotes and eukaryotes.

What are phospholipids and their role in cell membranes?

Phospholipids are amphipathic molecules with hydrophilic and hydrophobic regions, forming the dynamic structure of cell membranes.

What does the fluid mosaic model describe?

The fluid mosaic model depicts the cell membrane as a mosaic of proteins floating in a fluid bilayer of phospholipids, where proteins are not randomly distributed.

How does temperature affect membrane fluidity?

As temperatures cool, membranes transition from a liquid to a solid state; membranes rich in unsaturated fatty acids remain more fluid than those rich in saturated fats.

What is the role of cholesterol in membrane fluidity?

Cholesterol maintains membrane fluidity at low temperatures by preventing phospholipid packing and restrains movement at higher temperatures.

What are the two types of membrane proteins?

Peripheral proteins are bound to the membrane surface, while integral proteins penetrate the hydrophobic core, with transmembrane proteins spanning the entire membrane.

What are the functions of cell-surface proteins?

Cell-surface proteins are involved in transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton.

How do transport proteins facilitate movement across membranes?

Transport proteins, including channel and carrier proteins, assist hydrophilic and large substances in crossing the membrane, often down their concentration gradients.

What is osmosis?

Osmosis is the diffusion of free water molecules across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Define tonicity in relation to cells.

A solution is isotonic if its solute concentration is the same as that inside the cell, hypertonic if it is less, and hypotonic if it is greater.

What is the function of aquaporins?

Aquaporins are channel proteins that facilitate the rapid passage of water molecules across the cell membrane.

What is facilitated diffusion?

Facilitated diffusion is the process by which transport proteins speed up the passive movement of molecules across the plasma membrane.

What is active transport?

Active transport requires energy (ATP) to move substances against their concentration gradient, allowing cells to maintain different solute concentrations than their environment.

How do ion channels function?

Ion channels are gated channels that open or close in response to stimuli, allowing specific ions to flow across the membrane.

What is the role of carrier proteins?

Carrier proteins undergo shape changes to transport solutes across the membrane, typically down their concentration gradient without using energy.

What is the significance of cell-cell recognition?

Cell-cell recognition is facilitated by glycoproteins and glycolipids, which help cells identify and interact with each other.

What is selective permeability in membranes?

Selective permeability refers to the plasma membrane's ability to control the exchange of materials, allowing some substances to cross more easily than others.

What happens to membranes as temperatures change?

Membranes can switch from a liquid to solid state as temperatures decrease, affecting their fluidity and functionality.