Evolutionary Origin of Cells and Their General Features

Flashcards covering the foundational concepts of cell biology, including cell theory, distinctions between prokaryotes and eukaryotes, organelle functions, and cytoskeleton composition.

What is the Cell Theory developed in the 1830s?

The theory states that: 1. Cells are the basic/smallest unit of life. 2. All living things consist of cells. 3. All cells come from other cells.

What four basic features are shared by all cells?

Plasma membrane, cytosol/cytoplasm, chromosomes (carry genes), and ribosomes (make proteins).

According to the transcript, what are the typical diameters of prokaryotic and eukaryotic cells?

Typical bacteria are $1-5\,\text{mm}$ in diameter, while eukaryotic cells are typically $10-100\,\text{mm}$ in diameter.

In a prokaryotic cell, where is the DNA located?

The DNA is located in an unbound region called the nucleoid.

What is the function of the prokaryotic glycocalyx?

It is an outer gelatinous covering that traps water and can form a capsule for protection.

What specific roles do pili and flagella play in prokaryotes?

Pili allow bacteria to attach to surfaces and to each other, while flagella allow certain bacteria to swim.

How do surface area and volume change relative to each other as a cell size increases?

As the surface area increases by a factor of $n^2$, the volume increases by a factor of $n^3$, meaning small cells have a greater surface area relative to volume.

What are the three main types of fibers in the cytoskeleton?

Microtubules (thickest), Microfilaments or actin filaments (thinnest), and Intermediate filaments (middle range).

What are the structural characteristics and diameter of microtubules?

They are hollow tubes with a $25\,\text{nm}$ diameter (with a $15\text{-nm}$ lumen) made of tubulin dimers containing $\alpha\text{-tubulin}$ and $\beta\text{-tubulin}$.

Describe the structure of centrioles within a centrosome.

A centrosome has a pair of centrioles, each featuring nine triplets of microtubules arranged in a ring.

What are microfilaments made of and what is their diameter?

They consist of two intertwined strands of actin and have a diameter of $7\,\text{nm}$.

Which proteins typically make up intermediate filaments and what is their size?

They are fibrous proteins (such as keratins) coiled into cables with a diameter of $8-12\,\text{nm}$.

What is the function of the nucleolus?

The nucleolus is the site within the nucleus where ribosomes are made.

Which components make up the endomembrane system?

Nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles (in plants), and plasma membrane.

What are the functional differences between Smooth ER and Rough ER?

Smooth ER lacks ribosomes and handles lipid synthesis, carbohydrate metabolism, and detoxification; Rough ER has ribosomes, aids in protein synthesis, and acts as a membrane factory.

What is the function of the Golgi apparatus?

It consists of stacks of flattened membranous sacs that modify, concentrate, package, and sort proteins and phospholipids for release in vesicles.

What the primary function of a lysosome?

It is a membranous sac of hydrolytic enzymes that breaks down ingested substances, cell macromolecules, and damaged organelles for recycling.

How do peroxisomes handle hydrogen peroxide ($H_2O_2$)?

Peroxisomes contain enzymes that transfer hydrogen atoms to oxygen to produce $H_2O_2$ as a by-product, which is then converted into water by another enzyme.

What is the Serial Endosymbiosis Theory?

The theory that prokaryotic cells engulfed bacteria (like ancestors of mitochondria and chloroplasts) which were not digested, resulting in double-membrane organelles with their own DNA and replication.

What are the three specialized structures found in plant cells?

Chloroplast (photosynthesis), Central Vacuole (storage and water balance), and Cell Wall (support).