Cell Theory Postulates

Questions and Answers

What is considered the basic unit of life according to cell theory?

Atoms

Organelles

Tissues

Cells (correct)

Which of the following statements is consistent with the cell theory?

Viruses are considered living organisms in the context of cell theory.

Cells can spontaneously generate from non-cellular materials.

Disease can occur in cells that are identical.

All living things consist of one or more cells. (correct)

What component is not found in prokaryotic cells?

Cell wall

Ribosomes

Plasma membrane

Nucleus (correct)

Which scientist first observed living cells?

Anton van Leeuwenhoek Signup and view all the answers

What structure provides protection and maintains the shape in prokaryotic cells?

Cell wall Signup and view all the answers

What did Robert Hooke observe in cork that led him to coin the term 'cell'?

The honeycomb-like structure in dead tissue Signup and view all the answers

What is the primary function of a capsule in prokaryotic cells?

To protect against host immune responses Signup and view all the answers

Which of the following is NOT a characteristic of prokaryotic cells?

Presence of a nucleus Signup and view all the answers

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

It modifies, sorts, and packages molecules. Signup and view all the answers

Which component of a plant cell wall is primarily composed of carbohydrates?

Cellulose Signup and view all the answers

What role do lysosomes play in cellular function?

They contain enzymes for breaking down waste. Signup and view all the answers

What function do peroxisomes serve within a cell?

They detoxify harmful substances and break down fatty acids. Signup and view all the answers

How does the plasma membrane function as a selective barrier?

It selectively regulates what enters and exits the cell. Signup and view all the answers

Which of the following accurately describes the cytoplasm?

It is a jelly-like substance where chemical reactions occur. Signup and view all the answers

What is the primary role of secretory vesicles?

To transport cargo to the membrane for release. Signup and view all the answers

Which structures appear during cell division and assist in pulling apart chromosome pairs?

Centrioles Signup and view all the answers

What is the primary function of nuclear pores?

To regulate the flow of materials in and out of the nucleus Signup and view all the answers

Which statement accurately describes the mitochondria?

It has an inner membrane with folds known as cristae Signup and view all the answers

What is the role of the rough endoplasmic reticulum (ER)?

Protein synthesis and modification Signup and view all the answers

Chloroplasts are essential for which biological process?

Photosynthesis Signup and view all the answers

What characterizes the smooth endoplasmic reticulum?

It is involved in lipid synthesis Signup and view all the answers

Which of the following statements is true about chromatin?

It consists of DNA spread out in non-dividing cells Signup and view all the answers

What is the main function of ribosomes?

Synthesizing proteins Signup and view all the answers

What is the primary function of the cytoskeleton?

To maintain cell shape and provide mechanical support Signup and view all the answers

What is the primary function of plasmids in bacteria?

Provide antibiotic resistance. Signup and view all the answers

Which of the following characteristics distinguishes gram-positive bacteria from gram-negative bacteria?

Structure of the cell wall. Signup and view all the answers

What is the appearance of gram-positive bacteria after staining?

Purple/blue. Signup and view all the answers

What is contained within the cytoplasm of a bacterial cell?

Water, enzymes, and nutrients. Signup and view all the answers

Which component is responsible for maintaining the shape of eukaryotic cells?

Cytoskeleton. Signup and view all the answers

What type of DNA structure does plasmid consist of?

Circular double-stranded DNA. Signup and view all the answers

What is the main function of ribosomes in cells?

Synthesize proteins. Signup and view all the answers

Which structure is NOT a characteristic of eukaryotic cells?

Absence of a nucleus. Signup and view all the answers

What is the term used for the type of cell that has a true nucleus and membrane-bound organelles?

Eukaryotic cell Signup and view all the answers

Which term describes the type of cell division that occurs in sex cells?

Meiosis Signup and view all the answers

What differentiates the Rough ER from the Smooth ER?

Rough ER contains ribosomes. Signup and view all the answers

How many parts is Interphase divided into?

3 Signup and view all the answers

What role does Maturation-Promoting Factor play in the cell cycle?

It marks the start of Mitosis. Signup and view all the answers

Which cell part is present in plant cells but not in animal cells?

Cell Wall Signup and view all the answers

What is the primary function of the Smooth ER?

Lipid synthesis Signup and view all the answers

Which of the following is NOT a function of the Rough ER?

Detoxification Signup and view all the answers

Study Notes

Postulates of Cell Theory

Cells are the basic unit of life and the building blocks of all living organisms.
All living organisms are composed of cells, and diseased cells originate from healthy ones.
All cells arise from pre-existing cells through division.

Timeline of Cell Theory

1665: Robert Hooke observes cells in a cork slice and names them “cells” based on a honeycomb-like structure.
1670: Anton van Leeuwenhoek observes living cells in pond water using a microscope.

Prokaryotic Cells

Lack a nucleus and membrane-bound organelles, simpler in structure.
Have components including:
- Capsule: Gelatinous outer covering for protection and adherence to surfaces.
- Cell Wall: Provides protection and maintains cell shape, composed of peptidoglycan.
- Plasmid: Circular DNA molecule that can provide antibiotic resistance.
- Cytoplasm: Jelly-like substance containing water, enzymes, and organelles for metabolic processes.
- Ribosomes: Sites for protein synthesis, composed of RNA and proteins.

Gram Staining

A technique that differentiates bacteria:
- Gram-positive: Retains purple dye due to thick peptidoglycan layer.
- Gram-negative: Appears red/pink after staining due to a thinner peptidoglycan layer surrounded by an outer membrane.

Eukaryotic Cells

More complex; contain a nucleus and membrane-bound organelles.
Components include:
- Nucleus: Houses genetic material and regulates cell activities.
- Mitochondria: Generates ATP through cellular respiration; has inner folds called cristae.
- Chloroplasts: Contain chlorophyll for photosynthesis in plants.
- Endoplasmic Reticulum (ER):
  - Rough ER: Studded with ribosomes; involved in protein synthesis.
  - Smooth ER: Lacks ribosomes; synthesizes lipids and detoxifies toxins.
- Golgi Apparatus: Modifies, sorts, and packages molecules for transport.

Plant vs. Animal Cells

Plant Cells: Have a cell wall made of cellulose, large central vacuoles for storage and maintenance of turgor pressure.
Animal Cells: No cell wall; contain centrioles that assist during cell division.
Both contain lysosomes for digestion and peroxisomes for fatty acid breakdown.

Cell Division and Cycle

Mitosis: Process of cell division creating identical daughter cells.
Meiosis: Involves two rounds of division producing unique sex cells.
Cytokinesis: Final stage of cell division, splitting the cell into two.
Interphase consists of three stages: G1, S (DNA synthesis), and G2 phase.

Key Cell Cycle Regulators

Maturation-Promoting Factor (MPF): Activates cyclin-dependent kinases (CDKs) to initiate mitosis.
MPF provides checkpoints by either promoting or stopping the cell cycle based on conditions such as DNA integrity.

Summary

Understanding cell structures and functions is foundational in biology as it delves into the mechanics of life at the microscopic level.
Familiarity with differences between prokaryotic and eukaryotic cells enhances comprehension of diverse life forms and their complexities.

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Description

Explore the fundamental postulates of Cell Theory, which highlight the significance of cells as the basic unit of life and their role in all living organisms. This quiz covers key principles that underpin this foundational concept in biology.