Living Organisms: Unicellular vs Multicellular

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Questions and Answers

What is regarded as the most basic unit of life?

Cell (correct)

Tissue

Organism

Organ

Which of the following is an exception to the cell theory?

Bacteria (correct)

Red blood cells

Fungi

Nerve cells

What do all living cells have in common?

They possess a cell membrane. (correct)

They can conduct photosynthesis.

They are large enough to be seen without a microscope.

They contain a well-defined nucleus.

How do viruses differ from living cells according to the cell theory?

They lack protoplasm. Signup and view all the answers

Which cellular structure is found in the vast majority of living cells?

Nucleus Signup and view all the answers

What is the primary function of the nuclear lamina?

Providing support and structure to the nucleus Signup and view all the answers

What is a defining characteristic of coenocytic hyphae?

They are multinucleate. Signup and view all the answers

What is contained within the granular regions of the nucleolus?

Mature ribosomal precursor particles Signup and view all the answers

What is the typical size range for most cells?

5 - 15 micrometers Signup and view all the answers

Which of the following statements about chromatin and chromosomes is correct?

Chromatin is less condensed than chromosomes. Signup and view all the answers

Why is the cell principle considered better than cell theory?

It includes all modern findings about cells. Signup and view all the answers

How does the nucleus regulate molecular flow?

Via nuclear pores Signup and view all the answers

What is the constricted region of linear chromosomes known as?

Centromere Signup and view all the answers

What is one of the primary functions of cytoplasm?

To provide protection and support to the cell Signup and view all the answers

Which of the following describes lipid droplets?

Fatty acid storage found in both plant and animal cells Signup and view all the answers

What is the primary role of telomeres?

Stabilizing the ends of chromosomes Signup and view all the answers

How many chromosomes do humans have in their diploid cells?

46 Signup and view all the answers

What is a characteristic of cytoplasmic streaming?

It involves the movement of the cytoplasm within the cell membrane. Signup and view all the answers

What primarily fills the nucleoplasm?

Dissolved salts, enzymes, and organic molecules Signup and view all the answers

Which structure is NOT found in the nucleus?

Microtubules Signup and view all the answers

What comprises the structure of ribosomes?

Ribonucleoproteins Signup and view all the answers

At which location does DNA replication start on a chromosome?

Origin of replication Signup and view all the answers

Which of the following statements about chromosome number is correct?

Chromosome number varies by species without significance. Signup and view all the answers

Which component of ribosomes is typically larger?

Large subunit Signup and view all the answers

What is a key characteristic of multicellular organisms that distinguishes them from unicellular organisms?

Have specialized cells for different functions Signup and view all the answers

Which of the following statements correctly describes unicellular organisms?

They may exist as bacteria, protozoa, algae, or fungi. Signup and view all the answers

What main factor limits the size of unicellular organisms?

Surface area to volume ratio Signup and view all the answers

Which feature primarily differentiates the lifespan of unicellular organisms from multicellular organisms?

Load of work on each cell type Signup and view all the answers

Which organisms are classified as eukaryotic?

Yeasts and protozoans Signup and view all the answers

What is the primary role of specialized cells in multicellular organisms?

To allow for complex organism structures Signup and view all the answers

What type of organisms primarily exhibit a low level of operational efficiency?

Unicellular organisms Signup and view all the answers

Which statement accurately reflects the injury response of multicellular organisms?

Injuries can lead to the death of the whole organism. Signup and view all the answers

What aspect of the cell theory was formulated by Matthias Schleiden and Theodor Schwann?

Cells are the basic unit of life. Signup and view all the answers

Which organism is an example of a unicellular plant?

Chlorella Signup and view all the answers

What type of ribosomes are primarily found in eukaryotic cells' cytosol?

80S ribosomes Signup and view all the answers

Which statement about ribosomes is accurate?

Ribosomes play a protective role during protein synthesis. Signup and view all the answers

What is the primary function of the Rough Endoplasmic Reticulum (RER)?

Protein synthesis and transport Signup and view all the answers

Which form of protein translocation involves moving proteins through nuclear pores?

Gated Transport Signup and view all the answers

What describes organellar ribosomes?

Smaller and found in mitochondria and chloroplasts Signup and view all the answers

What process is primarily managed by the Endoplasmic Reticulum?

Creation, packaging, and secretion of cellular products Signup and view all the answers

Which characteristic distinguishes Smooth Endoplasmic Reticulum (SER) from Rough Endoplasmic Reticulum (RER)?

Absence of ribosomes on the surface Signup and view all the answers

Which of the following is NOT true about ribosome biogenesis in eukaryotes?

Ribosomes are formed through self-replication. Signup and view all the answers

Study Notes

Unicellular Organisms

Single-celled organisms and the most primitive form of life, possibly dating back 3.8 billion years.
Main groups include bacteria, archaea, protozoa, algae, and fungi.
Categorized as prokaryotic (no nucleus) and eukaryotic (with nucleus) based on cellular organization.
Mostly microscopically small, classified as microorganisms.
Examples include:
- Bacteria: Escherichia coli, Mycobacteria
- Protozoans: Amoeba, Paramecium
- Algae: Chlorella, Chlamydomonas, Diatoms
- Fungi: Yeast

Multicellular Organisms

Composed of many specialized cells for various functions, increasing complexity.
Many bacteria species, such as Myxobacteria, can form multicellular structures.
Most eukaryotic organisms are multicellular with developed body structures and specific organs.
Examples of unicellular plants include Chlamydomonas and Chlorella; Acetabularia is a large unicellular green algae.

Differences Between Unicellular and Multicellular Organisms

Body Structure: Unicellular has one cell; multicellular consists of numerous cells.
Division of Labour: Unicellular may operate at cellular level, multicellular at organ/system levels.
Operational Efficiency: Higher in multicellular organisms.
Cell Specialization: Unicellular carries out all life processes; multicellular cells have specific functions.
Cell Exposure: Unicellular cells are completely exposed; multicellular only outer cells face the environment.
Injury or Death: Unicellular can survive some cell damage; multicellular can be affected by damage.
Cell Size and Lifespan: Unicellular sized by surface area limits; multicellular can grow larger but often have shorter lifespans due to specialization.
Regeneration: Regenerative capacity decreases with specialization in multicellular organisms.

Common Functions of Unicellular and Multicellular Organisms

All organisms must uptake nutrients, excrete waste, respond to stimuli, and reproduce.

What is a Cell?

Basic functional unit of all living organisms.
Discovered by Robert Hooke in 1665.
Self-replicating and responds to environmental changes.
Known as the building block of life with cell biology as its study.

Cell Theory

Formulated by Matthias Schleiden, Theodor Schwann, and Rudolf Virchow.
Key principles:
- All living organisms consist of cells.
- The cell is the fundamental unit of life.
Highlights the structural and functional unity across diverse life forms.

Exceptions to Cell Theory

Viruses lack protoplasm, made of proteins and nucleic acids.
Bacteria lack organized nuclei and associated structures; chromosomes are in direct contact with cytoplasm.
Coenocytic fungi and some protists can be multinucleate.

Cellular Hierarchy

Organism (e.g., Humans)
Organ system (e.g., Respiratory system)
Organ (e.g., Lung)
Tissue (e.g., Epithelial tissue)
Cell (e.g., Monocyte)

Diversity in Cell Size and Shape

Most cells are microscopic, with significant variation.
Typical cell sizes range from 5-15 micrometers; nerve cells can be up to 1-2 meters.
Notable sizes: ostrich egg (175 mm), human cells (3-4 microns to 90-100 cm).

Chromatin and Chromosomes

Chromatin: DNA and protein structure found in the nucleus of eukaryotic cells.
Chromosomes: Highly condensed DNA converting chromatin into a compact form during cell division.

Functions of the Nucleus

Governs cell function, regulates molecular flow, and facilitates DNA replication and ribosome production.

Cytoplasm

Space between the cell membrane and nucleus where metabolism occurs.
Functions include support, protection, storage, and transport.

Ribosomes

Composed of RNA and proteins, crucial for protein synthesis.
Types include:
- Cytosolic Ribosomes: Found in eukaryotic cell cytosol.
- Organellar Ribosomes: Smaller, located in mitochondria and chloroplasts.

Endoplasmic Reticulum (ER)

Large organelle contiguous with the nuclear membrane.
Types include:
- Rough ER: Studded with ribosomes, involved in protein synthesis.
- Smooth ER: Lacks ribosomes, site of lipid synthesis and detoxification.
The ER processes instructions from the nucleus and is essential for product creation and secretion.

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Description

This quiz explores the fascinating world of unicellular and multicellular organisms. Learn about the various types of unicellular organisms, including bacteria, archaea, protozoa, algae, and fungi, and understand their significance in the biological hierarchy. Dive into the differences between prokaryotic and eukaryotic organisms.