Cells and Cell Theory

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Questions and Answers

What is a key characteristic that distinguishes prokaryotic cells from eukaryotic cells?

Prokaryotic cells are more complex than eukaryotic cells.

Prokaryotic cells contain a cytoskeleton.

Prokaryotic cells have a membrane-bound nucleus.

Prokaryotic cells lack a membrane-bound nucleus. (correct)

Which of the following statements best represents the principles of Cell Theory?

Only multicellular organisms consist of cells.

Cells do not replicate and remain unchanged.

All living organisms are composed of cells. (correct)

Cells can arise from spontaneous generation.

Which of the following components is NOT typically found in both prokaryotic and eukaryotic cells?

Nucleus (correct)

Plasma membrane

Ribosomes

Cytoplasm

What does the fluid-mosaic model describe?

The dynamic and flexible nature of the plasma membrane. Signup and view all the answers

Which region of the cell is primarily responsible for genetic material storage?

Nucleus Signup and view all the answers

What is the main function of mitochondria in the cell?

To carry out oxidative metabolism and produce ATP Signup and view all the answers

What are the three different types of cytoskeletal components?

Microfilaments, intermediate filaments, and microtubules Signup and view all the answers

What structure directs the formation of the mitotic spindle during cell division?

Centrosome Signup and view all the answers

Which type of cytoskeletal component is primarily responsible for cellular contraction?

Microfilaments Signup and view all the answers

What is a key characteristic of centrioles?

They are composed of nine triplet microtubules organized in a cylinder Signup and view all the answers

What is the main function of microvilli in epithelial cells?

To increase surface area for absorption Signup and view all the answers

Which type of membrane junction serves to create seals between adjacent cells?

Tight junctions Signup and view all the answers

Which organelle is responsible for the synthesis of proteins that are secreted from the cell?

Rough endoplasmic reticulum Signup and view all the answers

What is the main role of lysosomes within a cell?

Digestion of macromolecules Signup and view all the answers

What distinctive appearance does the rough endoplasmic reticulum (RER) have?

Ribosome-studded Signup and view all the answers

Which function is primarily associated with the smooth endoplasmic reticulum (SER)?

Detoxification of foreign substances Signup and view all the answers

What characterizes the Golgi apparatus in a cell?

Flattened stacks of interconnected membranes Signup and view all the answers

What component is not a part of the endomembrane system?

Mitochondria Signup and view all the answers

What happens during the interphase before Meiosis I?

DNA is replicated. Signup and view all the answers

What is a key event that occurs during prophase I of meiosis?

Tetrad formation and crossing over Signup and view all the answers

What is independent assortment in meiosis?

The random orientation of chromosome pairs during metaphase I. Signup and view all the answers

Which statement is true regarding the outcome of meiosis II?

It proceeds without interphase. Signup and view all the answers

What is one source of genetic variability during meiosis?

Crossing over during prophase I. Signup and view all the answers

What is the primary role of the nucleus in a cell?

To control cell processes Signup and view all the answers

Which structure within the nucleus is responsible for ribosome production?

Nucleolus Signup and view all the answers

Which of the following accurately describes passive transport?

Includes processes such as diffusion and osmosis Signup and view all the answers

How does the nuclear membrane facilitate communication between the nucleus and the cytoplasm?

Via nuclear pores Signup and view all the answers

What is the primary purpose of chromatin in the nucleus?

To condense into chromosomes during cell division Signup and view all the answers

What is a characteristic of osmosis?

It specifically refers to the movement of water molecules Signup and view all the answers

What defines the concept of selective permeability in cell membranes?

Only specific substances are allowed to pass while others are excluded Signup and view all the answers

What best describes the primary function of cilia?

Move materials across the cell surface Signup and view all the answers

Study Notes

Cells: Definition and Functions

Cells are the basic unit of life, discovered in 1665 by Robert Hooke.
Cell Theory established by Schleiden and Schwann states that all organisms are made of cells, cells are the smallest living units, and new cells arise from existing ones.
Cellular functions encompass membrane transport, cell division, and the cell cycle.

Prokaryotic vs Eukaryotic Cells

Prokaryotic cells are simpler, lack a membrane-bound nucleus, and contain genetic material in a nucleoid.
- Two types: Archaea and Bacteria.
Eukaryotic cells are more complex, featuring a membrane-bound nucleus, organelles, and a cytoskeleton for structural support.

Anatomy of the Cell

Cells consist of three main regions:
- Plasma membrane
- Cytoplasm
- Nucleus

Plasma Membrane

Described by the fluid-mosaic model, allowing selective permeability.
Specializations include microvilli (increase surface area) and membrane junctions (tight junctions, desmosomes, hemidesmosomes, gap junctions).

Cytoplasm Components

Comprises the material inside the plasma membrane and outside the nucleus.
Contains cytosol (fluid medium), organelles (cellular machinery), and inclusions (non-functional units).

Cytoplasmic Organelles

Ribosomes: Sites of protein synthesis, found free in cytoplasm or on rough endoplasmic reticulum (RER).
Endomembrane system: Network for cellular function (includes RER, Golgi apparatus, vesicles).
- RER: Studded with ribosomes, synthesizes proteins for secretion.
- Smooth Endoplasmic Reticulum (SER): Lipid synthesis, calcium storage, and detoxification.

Golgi Apparatus and Lysosomes

Golgi apparatus: Modifies, packages, and transports proteins and cell wall components.
- Has two faces: cis (forming) and trans (maturing).
Lysosomes: Digestive vesicles containing enzymes for breaking down macromolecules and clearing debris.

Mitochondria and Cytoskeleton

Mitochondria: Powerhouses of the cell that utilize oxygen to convert nutrients into ATP.
Cytoskeleton: Protein network providing structural support and facilitating movement within the cell.
- Composed of microfilaments (actin for contraction), intermediate filaments (mechanical support), and microtubules (transport and organization).

Nuclear Structure

Nucleus: Control center contains DNA organized in three regions: nuclear membrane, nucleolus, and chromatin.
Nuclear membrane: Double phospholipid barrier with pores for material exchange.
Nucleoli: Sites of ribosome production.

Cellular Projections

Not present in all cells; include cilia for moving materials and flagella for cell propulsion.

Membrane Transport Mechanisms

Movement of substances across the plasma membrane is via passive (no energy required) and active (energy required) transport.
Passive transport includes diffusion, osmosis, and filtration.
Active transport includes endocytosis and exocytosis, requiring energy expenditure.

Meiosis Overview

Meiosis includes two main stages: Meiosis I and Meiosis II; both begin with DNA replication during interphase.
Meiosis I features synapsis and crossing over for genetic diversity, independent assortment ensures random distribution of chromosomes.
Resulting cells are haploid; completion of meiosis in females occurs upon fertilization.

Mitosis vs. Meiosis

Mitosis results in two identical diploid cells; Meiosis results in four genetically diverse haploid cells.
Genetic variability arises from random fertilization, crossing over, and independent assortment.

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Description

This quiz explores the fundamental concepts of cells, their organization, and various cellular functions such as membrane transport and cell division. Additionally, it examines the impact of cancer on individuals and society. Gain a deeper understanding of the historical context of cell discovery and the contributions of key scientists.