MCAT Biology CH 1: Cell Theory, Eukaryotic & Prokaryotic Cells, Viruses (UNIT 1)

What is cell theory?

A set of principles that define what a cell is and how it relates to life.

What types of cells make up eukaryotic organisms?

Plants, animals, fungi, and protists.

What are membrane-bound organelles?

Structures within eukaryotic cells that compartmentalize specific functions.

What is the function of the cytoskeleton in eukaryotic cells?

Helps maintain cell shape and organize contents.

What are prokaryotic cells?

Simpler cells, such as bacteria, that lack a nucleus.

What is binary fission?

The process by which prokaryotic cells grow and reproduce.

What are viruses?

Infectious agents that are not considered living cells but can infect prokaryotic and eukaryotic cells.

Who was the first to observe a living cell under a microscope?

Anton van Leeuwenhoek in 1674.

What did Robert Hooke discover in 1665?

He observed cork and coined the term 'cells' for the structures he saw.

What are the three original tenets of cell theory?

1. All living things are composed of cells. 2. The cell is the basic functional unit of life. 3. All cells arise from preexisting cells.

What is the fourth tenet added to cell theory?

Cells carry genetic information in the form of DNA, passed from parent to daughter cells.

What distinguishes eukaryotic cells from prokaryotic cells?

Eukaryotic cells have a true nucleus and membrane-bound organelles.

What is the function of the nucleus?

Acts as the control center of the cell, storing genetic information and directing RNA and protein synthesis.

What are mitochondria responsible for?

Generating energy in the form of ATP through the Krebs cycle and electron transport chain.

What role do lysosomes play in the cell?

Contain hydrolytic enzymes that break down waste and damaged organelles.

What is the difference between rough ER and smooth ER?

Rough ER is covered in ribosomes and assists in protein synthesis; smooth ER is involved in lipid synthesis and detoxification.

What does the Golgi apparatus do?

Modifies, packages, and sorts proteins and lipids for delivery.

What are peroxisomes?

Organelles that carry out oxidative reactions, including fatty acid breakdown and detoxification.

What is the nuclear envelope?

A double membrane structure that encloses the nucleus and separates it from the cytoplasm.

What are nuclear pores?

Structures embedded in the nuclear envelope that regulate the passage of materials in and out of the nucleus.

What is apoptosis?

Programmed cell death where cells intentionally break down their own components.

What is the cytosol?

A semi-fluid substance that facilitates the movement of molecules within the cell.

What is the significance of the microscope in cell biology?

It allowed for the observation of cells, leading to the development of cell theory.

What is genetic recombination in prokaryotes?

A process that increases genetic diversity among prokaryotic cells.

What is the role of the endoplasmic reticulum?

Involved in protein and lipid synthesis, with rough ER focusing on proteins and smooth ER on lipids.

What is a key characteristic of prokaryotic organisms?

They are always single-celled.

How do eukaryotic cells form tissues?

By coming together with specialized roles.

What must exit the nucleus through nuclear pores?

Messenger RNA (mRNA).

What is the role of histones in the nucleus?

Histones wrap around DNA, forming a complex called chromatin.

What are the two forms of chromatin?

Euchromatin (loosely packed and transcriptionally active) and heterochromatin (densely packed and less active).

What structures are formed when chromatin condenses during cell division?

Chromosomes.

What is the nucleolus responsible for?

Producing ribosomal RNA (rRNA) and assembling it with ribosomal proteins to form ribosome subunits.

What is the nucleoplasm?

A viscous, gel-like substance that supports nuclear structures and allows diffusion of molecules.

What is the primary function of mitochondria?

ATP production, serving as the powerhouses of the cell.

What are the two membranes of mitochondria called?

Outer membrane and inner membrane.

What is the intermembrane space in mitochondria?

The space between the outer and inner membranes where small molecules and ions can pass freely.

What are cristae in mitochondria?

Infoldings of the inner membrane that increase surface area for energy-producing reactions.

What is found in the mitochondrial matrix?

Enzymes of the citric acid cycle, mitochondrial DNA, and mitochondrial ribosomes.

What is unique about mitochondrial DNA?

It is circular and allows mitochondria to replicate independently of the nucleus.

How is mitochondrial DNA inherited?

Exclusively through the maternal line.

What theory explains the origin of mitochondria?

The endosymbiotic theory, which suggests they originated from an ancestral eukaryotic cell engulfing an aerobic prokaryote.

What is the function of the endoplasmic reticulum (ER)?

Synthesis, folding, modification, and transport of cellular materials.

What are the two types of endoplasmic reticulum?

Rough ER and smooth ER.

What distinguishes rough ER from smooth ER?

Rough ER has ribosomes on its surface, while smooth ER does not.

What is the main role of rough ER?

Protein synthesis for proteins destined to leave the cell or be embedded in membranes.

What does smooth ER synthesize?

Lipids, including phospholipids and steroids.

What role does smooth ER play in liver cells?

Detoxifying drugs and poisons.

What is the Golgi apparatus?

A critical component of the cell's transport and modification system.

What are the structural components of the Golgi apparatus?

A series of flattened, membrane-bound sacs called cisternae.

What is glycosylation?

The addition of carbohydrate groups to proteins during modification in the Golgi apparatus.

What happens to proteins after they are modified in the Golgi?

They are repackaged into new vesicles and directed to specific destinations within the cell.

What is the cis face of the Golgi apparatus?

The side that receives incoming vesicles.

What is the trans face of the Golgi apparatus?

The side where modified products are sent out.

What process allows a protein to be released into the extracellular space?

Exocytosis

What two organelles work together to synthesize, modify, sort, and deliver biomolecules?

Endoplasmic Reticulum (ER) and Golgi Apparatus

What is the main function of the cytoskeleton?

To provide shape and structural support to the cell.

What are the three main types of protein-based filaments in the cytoskeleton?

Microfilaments, microtubules, and intermediate filaments.

What protein makes up microfilaments?

Actin

How do microfilaments contribute to muscle contraction?

They interact with myosin and use ATP to generate force.

What is the role of microtubules in the cell?

They act as internal highways for transporting materials and form motile structures like cilia and flagella.

What is the structure of microtubules?

Hollow tubes made from polymerized tubulin.

What arrangement of microtubules is found in cilia and flagella?

9+2 arrangement (nine pairs in a ring with two in the center).

What is the function of the mitotic spindle during cell division?

To separate chromosomes.

What are centrioles made of?

Nine triplets of microtubules arranged in a ring.

What is the primary function of intermediate filaments?

To provide mechanical strength and help maintain cell shape.

How do intermediate filaments vary among cell types?

Their composition varies, making them useful as molecular markers for different tissue types.

What are the four major types of tissue in the human body?

Epithelial tissue, connective tissue, muscle tissue, and nervous tissue.

What is the main role of epithelial tissue?

To cover the body and line internal cavities.

What is the basement membrane?

A thin supporting layer that provides structural support to epithelial cells.

How can epithelial tissue be classified?

Based on the number of layers (simple or stratified) and the shape of the cells (cuboidal, columnar, or squamous).

What is the functional part of an organ called?

Parenchyma

What is the primary role of connective tissue?

To provide support and structure to organs.

What is the extracellular matrix?

A network of fibers and ground substance produced by connective tissue cells.

What proteins are commonly found in the extracellular matrix?

Collagen and elastin.

What distinguishes prokaryotic cells from eukaryotic cells?

Prokaryotic cells lack a nucleus and membrane-bound organelles.

What are the three domains of life?

Bacteria, Archaea, and Eukarya.

How do bacteria and archaea differ from each other?

They share structural similarities but differ in important biochemical and genetic ways.

What type of reproduction do prokaryotic cells typically undergo?

Binary fission.

What is cytokinesis?

The final step of cell division where the cell is pinched into two daughter cells.

What role do motor proteins like kinesin and dynein play in the cell?

They transport materials along microtubules.

What is the significance of tissue formation in multicellular organisms?

It allows for division of labor and specialization among cells.

Where do Archaea typically live?

In extreme environments such as hot springs, salt lakes, and deep-sea vents.

What unique features do Archaea have?

Unique cell membrane composition and gene expression machinery that resemble eukaryotes.

How do bacteria differ from Archaea in terms of habitat?

Bacteria are more widespread and include many harmless or beneficial species.

What is the human microbiome primarily composed of?

Bacterial species.

What are the three major shapes of bacteria?

Cocci (spherical), Bacilli (rod-shaped), and Spirilli (spiral-shaped).

What are obligate aerobes?

Bacteria that require oxygen for survival.

What are obligate anaerobes?

Bacteria that cannot survive in the presence of oxygen.

What is a facultative anaerobe?

Bacteria that can survive in both oxygen-rich and oxygen-poor environments.

What are aerotolerant anaerobes?

Organisms that do not use oxygen for metabolism but can survive in its presence.

What is a key difference between prokaryotic and eukaryotic cells?

Prokaryotes do not have a membrane-bound nucleus or organelles.

What is the function of the bacterial cell wall?

Provides structural support and helps maintain cell shape.

What is peptidoglycan?

A polymer that makes up the bacterial cell wall.

What distinguishes Gram-positive bacteria from Gram-negative bacteria?

Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thinner layer and an outer membrane.

What is lipopolysaccharide (LPS)?

A large molecule in the outer membrane of Gram-negative bacteria that contributes to membrane integrity and triggers immune responses.

What are flagella used for in bacteria?

Movement and chemotaxis, allowing bacteria to sense and respond to environmental chemicals.

What are the three major parts of a bacterial flagellum?

Filament, hook, and basal body.

What is the nucleoid in prokaryotes?

The region where the genetic material (DNA) is located, not enclosed in a nuclear membrane.

What are plasmids?

Small, circular pieces of DNA that replicate independently and often carry genes for survival advantages.

What is the structure of prokaryotic ribosomes?

They consist of two subunits (30S and 50S), forming a 70S ribosome.