Biology: Cell Theory and Cytology

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Questions and Answers

What type of stain is hematoxylin and what color does it produce?

Basic stain, blue (correct)

Acidic stain, blue

Acidic stain, red

Basic stain, red

Which component of the cell does eosin primarily bind to?

Lipids

Polysaccharides

Nucleic acids

Basic components (correct)

In an electron microscope, what does an electron-dense structure appear as?

Grey to Black (correct)

Colorful

White

Transparent

What are the two main parts of a eukaryotic animal cell?

Cytoplasm and nucleus Signup and view all the answers

What type of cytoplasm can a cell have?

Both basophilic and acidophilic Signup and view all the answers

What is the primary focus of biology?

The structure and functions of living organisms Signup and view all the answers

Which of the following is NOT a branch of biology?

Quantum Physics Signup and view all the answers

What does cell theory state about cells?

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

Which of the following statements is true about prokaryotic cells?

They are structurally simpler than eukaryotic cells. Signup and view all the answers

What is the general structure of eukaryotic cells characterized by?

Presence of membrane-bound organelles Signup and view all the answers

In which year did Rudolf Virchow conclude that all cells come from pre-existing cells?

1855 Signup and view all the answers

What is a key distinction between prokaryotic and eukaryotic cells?

Prokaryotes do not have a nuclear envelope. Signup and view all the answers

Which organelle is typically found in eukaryotic cells but not in prokaryotic cells?

Mitochondria Signup and view all the answers

Which statement accurately describes membranous organelles?

They are surrounded by a lipid bilayer. Signup and view all the answers

What is a characteristic feature of the cell membrane as observed under electron microscopy (E.M.)?

It is recognized as a trilaminar membrane. Signup and view all the answers

Which component of the cell membrane is hydrophobic?

Fatty acid tails of phospholipids Signup and view all the answers

What is the primary role of the glycocalyx on the cell membrane?

To protect the cell and facilitate cell recognition. Signup and view all the answers

Which structure is NOT classified as a non-membranous organelle?

Mitochondria Signup and view all the answers

How is the structure of the cell membrane described in terms of its thickness?

It is too thin to be clearly seen with light microscopy. Signup and view all the answers

What type of proteins are found within the cell membrane that span across its structure?

Integral proteins Signup and view all the answers

In which layer are the polar heads of phospholipids located?

On both the outer and inner surfaces. Signup and view all the answers

What distinguishes integral proteins from peripheral proteins in the cell membrane?

Integral proteins span the entire membrane or are partially embedded. Signup and view all the answers

Which of the following accurately describes the role of cholesterol in the cell membrane?

It restricts the movement of fatty acid tails. Signup and view all the answers

What is the primary function of the glycocalyx?

To aid in cell recognition and intercellular adhesion. Signup and view all the answers

Which of the following is NOT a function of the integral membrane proteins?

Binding to the external surface of the membrane. Signup and view all the answers

What characterizes the fatty acid tails of the phospholipid bilayer?

They are hydrophobic and directed inward. Signup and view all the answers

What is the primary characteristic of passive transport?

Moves molecules down the concentration gradient Signup and view all the answers

What types of molecules primarily compose the cell membrane?

Lipids and proteins. Signup and view all the answers

Which of the following is a type of active transport?

Sodium-potassium pump Signup and view all the answers

In which type of transport do molecules move against their concentration gradient?

Active transport. Signup and view all the answers

What occurs during phagocytosis?

Engulfing of solid particles using pseudopodia Signup and view all the answers

Which of the following correctly describes the relationship between glycoproteins and glycolipids?

Glycoproteins are linked to proteins, while glycolipids are linked to lipids. Signup and view all the answers

What distinguishes receptor-mediated endocytosis from other forms of endocytosis?

It involves specific binding of ligands to receptors Signup and view all the answers

Which statement accurately describes pinocytosis?

It primarily involves the uptake of fluid materials. Signup and view all the answers

What happens to clathrin after a coated vesicle is formed in receptor-mediated endocytosis?

Clathrin is recycled back to the cell membrane. Signup and view all the answers

Which process requires energy to move molecules across the cell membrane?

Pinocytosis Signup and view all the answers

What is the role of pseudopodia in phagocytosis?

To create a cytoplasmic vesicle for solid material uptake Signup and view all the answers

Study Notes

Biology

Biology is the study of life.
It explores living organisms (plants, animals, and humans).
It encompasses their structure, functions, and interactions with their environment.
Several branches of biology exist, including cell biology, histology, genetics, physiology, and embryology.

Cytology & Cell Biology

A field of biology focusing on the study of cells.
It investigates cell structure, physiological properties, interactions with the environment, division, function, and death.
This research occurs at both microscopic and molecular levels.

Cell Theory

States that all living organisms are made up of cells.
Cells are the fundamental structural and functional units of life.
New cells arise from pre-existing cells.
Matthias Schleiden concluded plants are made of cells (1838).
Theodore Schwann concluded animals are made of cells (1839).
Rudolf Virchow concluded all cells come from pre-existing cells (1855).

Cellular Organization

Classified into two main categories: prokaryotes (before nucleus) and eukaryotes (true nucleus).
Prokaryotes are simple cells, lacking a nuclear envelope and membranous organelles.
Eukaryotes are more complex, possessing a nuclear envelope and compartments known as cell organelles (mitochondria, Golgi apparatus, lysosomes).

Cell Membrane Function

Maintains the structural integrity of the cell.
Controls the movement of substances into and out of the cell.
Creates a transport system (selective permeability).

General Structure of Eukaryotic Animal Cells

Composed of two main parts: the cytoplasm and the nucleus.
Cytoplasm consists of organelles, inclusions, and cytosol.
Organelles are living structures essential for cell life.
Inclusions are non-living structures not essential for cell life.
Cytosol is a viscous fluid containing enzymes, ions, O2, CO2, and metabolites.

Membranous Cell Organelles

They have a membrane.
Examples include:
- Cell membrane (plasma membrane or plasmalemma).
- Mitochondria.
- Endoplasmic reticulum.
- Golgi apparatus.
- Lysosomes.
- Peroxisomes.

Non-membranous Cell Organelles

They lack a membrane.
Examples include:
- Ribosomes.
- Microtubules.
- Microfilaments.
- Intermediate filaments.
- Centrioles.
- Cilia.
- Flagella.

The Cell membrane (Plasma membrane or Plasmalemma)

It envelops the cell.
By light microscopy (LM), it's difficult to see, as it's only 7.5-10 nm thick.
By electron microscopy (EM), it appears as a trilaminar membrane (trilamellar or unit membrane) composed of two electron-dense layers separated by an electron-lucent intermediate layer.
The outer surface of the cell membrane is covered by the cell coat (glycocalyx) with a fuzzy appearance under EM.

Molecular Structure of the Cell Membrane

Comprised of lipids, proteins, and carbohydrates:
- Lipids: Phospholipids arranged in a bilayer with a phosphate head (hydrophilic) and a fatty acid tail (hydrophobic). Cholesterol molecules are embedded within the hydrophobic tails, regulating membrane fluidity.
- Proteins: Integral proteins spanning the membrane and peripheral proteins bound to the cytoplasmic side.
- Carbohydrates: Sugar chains linked to proteins (glycoproteins) and lipids (glycolipids), found on the external surface and forming the cell coat (glycocalyx).

Glycocalyx

Comprised of glycoproteins and glycolipids.
Fuzzy appearance under EM.
Functions:
- Cell recognition.
- Intercellular adhesions.
- Contains digestive enzymes in some cases.

Transport Across the Cell Membrane

Divided into three main types:
- Passive Transport: Movement of molecules down the concentration gradient, without needing energy.
  - Simple Diffusion: e.g., Movement of O2 and CO2.
  - Facilitated Diffusion: e.g., Transport of glucose through transporter (carrier) proteins.
- Active Transport: Movement of molecules against the concentration gradient, requiring energy. e.g., Sodium-potassium pump.
- Vesicular Transport: Transport of large molecules via vesicle formation.
  - Endocytosis: Uptake of materials across the cell membrane into the cytoplasm.
    - Phagocytosis (cell eating): Uptake of solid materials, forming phagocytic vesicles (phagosomes).
    - Pinocytosis (cell drinking): Uptake of fluid materials, forming pinocytotic vesicles.
  - Exocytosis: Release of materials from the cell.
  - Transcytosis: Movement of materials across a cell through endocytosis and exocytosis.

Receptor-Mediated Endocytosis

Involves integral membrane proteins called receptors that bind specific molecules called ligands.
Binding of the ligand to its receptor triggers their accumulation in a cell membrane region called a coated pit.
Coated pits are lined with a specific protein, clathrin, on the cytoplasmic surface.
The coated pit invaginates and pinches off, forming a coated vesicle carrying the ligand and its receptor into the cell.
Clathrin molecules detach from the coated vesicles and recycle back to the cell membrane for the formation of new coated pits.

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Description

Explore the essential concepts of biology, focusing on cell theory and the study of cells in cytology. This quiz covers the foundational principles of cellular organization, their structure, function, and the key scientists who contributed to our understanding of cells. Test your knowledge on how cells are fundamental to all living organisms!