Cell Theory and Types of Organisms

Questions and Answers

What is the primary function of the cell membrane?

Forms the boundary of the cell and regulates substance entry (correct)

Provides mechanical support to the cell

Synthesizes proteins

Stores genetic material

Which organelle is involved in energy production?

Ribosomes

Mitochondria (correct)

Golgi Complex

Lysosomes

What distinguishes plant cells from animal cells in terms of structure?

Presence of lysosomes

Presence of cell wall (correct)

Absence of cell wall

Presence of centrosome

What best describes unicellular organisms?

Organisms consisting of a single cell Signup and view all the answers

Which of the following is NOT a function of the cell wall?

Regulates substance entry Signup and view all the answers

Which component of the nucleus contains RNA for ribosome formation?

Nucleolus Signup and view all the answers

What percentage of the cytoplasm is composed of water?

90% Signup and view all the answers

Which of the following statements is true regarding chromosomes?

Chromosomes condense during cell division. Signup and view all the answers

What do chromatin fibers consist of?

Deoxyribonucleic acid (DNA) and proteins Signup and view all the answers

Which structure serves as the control center of the cell?

Nucleus Signup and view all the answers

Which of the following cell types is specifically mentioned as being spindle-shaped?

Muscle cells Signup and view all the answers

What shape are mesophyll cells in leaves?

Long and rectangular Signup and view all the answers

Which of the following best describes the size of blood cells compared to nerve cells?

Blood cells are smaller than nerve cells. Signup and view all the answers

Which type of cell has projections called pseudopodia?

White blood cells Signup and view all the answers

What is the shape of guard cells of stomata in leaves?

Kidney-shaped or bean-shaped Signup and view all the answers

What term did Robert Hooke use to describe the small boxes he observed in cork?

Cellulae Signup and view all the answers

What invention is directly linked to the discovery of the cell?

Microscope Signup and view all the answers

What was one of the primary functions of cells according to the information provided?

Reproduction Signup and view all the answers

What did Hooke discover about the cork cells he observed?

They were empty spaces surrounded by walls. Signup and view all the answers

What type of microscope was crucial for discovering the detailed structure of the cell?

Electron microscope Signup and view all the answers

What is the primary characteristic that differentiates unicellular organisms from multicellular organisms?

The number of cells they contain Signup and view all the answers

What term describes a group of similar cells working together to carry out a specific function?

Tissue Signup and view all the answers

Which of the following organisms is classified as unicellular?

Chlamydomonas Signup and view all the answers

What aspect of cells does Cell Theory emphasize?

Cells are structural and functional units of living organisms Signup and view all the answers

What is the correct order of organization in multicellular organisms, starting from cells?

Cells → Tissues → Organs → Organ systems → Organism Signup and view all the answers

Which of the following is NOT a characteristic of multicellular organisms?

They can reproduce solely through cell division Signup and view all the answers

What is a common shape for cells devoted to transport functions?

Tubular Signup and view all the answers

Why do cells in multicellular organisms become specialized?

To improve efficiency in performing specific functions Signup and view all the answers

Which structure is present in plant cells but absent in animal cells?

Plastids Signup and view all the answers

What is the primary purpose of cell division in living organisms?

To repair old and worn-out cells Signup and view all the answers

Which of the following is a distinguishing feature of animal cells compared to plant cells?

Presence of lysosomes Signup and view all the answers

How are cells typically studied under a microscope?

By staining them with dye Signup and view all the answers

What feature of vacuoles differentiates plant cells from animal cells?

Plant cells have one or two large vacuoles Signup and view all the answers

What is the primary function of the cell wall?

Provides rigidity and shape to plant cells Signup and view all the answers

Which of the following statements accurately describes ribosomes?

They are involved in protein synthesis. Signup and view all the answers

What is a unique characteristic of mitochondria?

They are the sites of respiration and energy release. Signup and view all the answers

Which organelle is responsible for the transport of substances within the cell?

Endoplasmic reticulum (ER) Signup and view all the answers

What does the large central vacuole in plant cells primarily store?

Water and organic compounds Signup and view all the answers

Which structure is only found in animal cells?

Centrosome Signup and view all the answers

Which of the following is involved in the secretion and storage of substances?

Golgi complex Signup and view all the answers

What function do lysosomes perform in animal cells?

Digestion of foreign bodies Signup and view all the answers

What is the main function of the nucleus in a cell?

To control all activities of the cell Signup and view all the answers

Which type of plastid is responsible for photosynthesis?

Chloroplasts Signup and view all the answers

What distinguishes plant cells from animal cells?

Only plant cells have cell walls Signup and view all the answers

What is the primary role of vacuoles in plant cells?

To store food, water, and pigments Signup and view all the answers

Which of the following is NOT a type of plastid?

Riboplasts Signup and view all the answers

What is true about red blood cells (RBCs) in humans?

They are enucleate (without a nucleus) Signup and view all the answers

What is the function of chloroplasts in plant cells?

To perform photosynthesis Signup and view all the answers

How does the structure of vacuoles differ between mature and young plant cells?

Mature cells typically have one large vacuole Signup and view all the answers

Study Notes

Cell Theory

Proposed by Schleiden and Schwann, stating that all living organisms are made of cells.
Key points of cell theory:
- Cells are the basic structural and functional units of life.
- New cells arise from the division of existing cells.

Types of Organisms

Unicellular organisms consist of a single cell; examples include:
- Plants: Bacteria, Chlamydomonas, Yeast.
- Animals: Amoeba, Paramecium.
Multicellular organisms comprise multiple cells; examples include:
- Plants: Peepal, Neem, Rose.
- Animals: Earthworm, Fish, Frog, Humans.

Cell Specialization

In multicellular organisms, cells become specialized to perform specific functions, forming:
- Tissues: Groups of similar cells performing a specific function.
- Organs: Combinations of different tissues.
- Organ Systems: Groups of organs working together.
- Complete Organism: Entire living entity.

Cell Shapes

Cells exhibit various shapes influenced by their functions, such as:
- Rounded, spherical, oval, elongated, tubular, cylindrical, cuboidal, discoidal, irregular.

Composition of Cells

Cytoplasm: Jelly-like substance within the membrane, containing up to 90% water; site for many cellular processes.
Nucleus: Control center, discovered by Robert Brown, consisting of:
- Nuclear Envelope: Double membrane with pores.
- Nucleoplasm: Fluid within the nucleus.
- Nucleolus: Site for ribonucleic acid (RNA) production.
- Chromatin: DNA-protein complex, visible as chromosomes during division.

Protoplasm

Living matter of the cell, composed of cytoplasm and nucleus.

Chromosomes

Humans possess 46 chromosomes (23 pairs); visible only during cell division.
Different species have varying chromosome counts.

Cell Structure

Basic parts of a typical cell include:
- Cell membrane: Selectively permeable boundary.
- Cytoplasm: Contains organelles.
- Nucleus: Central control center.

Plant vs. Animal Cells

Plant cells have a cell wall and plastids; animal cells have centrioles and lysosomes.
Differences include:
- Cell wall: Present in plant cells, absent in animal cells.
- Vacuoles: One or two large in plants versus small or few in animals.

Cell Division Importance

Cell division is crucial for organism growth, tissue repair, and rejuvenating worn-out cells.

Microscopy and Staining

Cells are studied using microscopes; staining enhances visibility of various parts.

Key Cell Organelles and Functions

Mitochondria: Energy production site.
Endoplasmic Reticulum: Transport and support network.
Golgi Complex: Storage and secretion.
Lysosomes: Breakdown of waste and foreign material.
Ribosomes: Protein synthesis.
Plastids: Specialized for photosynthesis and pigment storage in plants.
Vacuoles: Storage structures, more prominent in plant cells.

Vacuoles

Plant cells typically contain a single large vacuole for turgor pressure, filled with cell sap.
Animal cells may have small or temporary vacuoles.

Conclusion on Cells

Cells are the fundamental units of life, performing vital functions essential for survival and reproduction.

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Description

Explore the fundamental concepts of cell theory, including the structure and function of cells. Learn about unicellular and multicellular organisms, cell specialization, and the various shapes cells can take based on their roles in living organisms.