Cell: The Unit of Life Practice Flashcards

A comprehensive set of practice questions and answers covering the fundamental concepts of cell biology, including prokaryotic and eukaryotic structures, cell theory, and organelle functions based on lecture notes.

What makes an organism classified as 'living' or 'animate'?

The presence of a cell.

What is the status of any structure that is less than a complete cell?

It does not have independent existence.

What is the basic structural and functional unit of life?

The cell.

Which organism is a known exception to the cellular unit of life because it lacks independent existence?

A virus.

What are the two primary components of a virus?

A protein coat and genetic material ($DNA$ or $RNA$).

Why is a virus described as a 'connecting link'?

It is the link between living and non-living things.

Who first observed dead plant cells in cork in $1665$?

Robert Hooke.

What specific part of the cell did Robert Hooke actually observe under his microscope?

The cell wall.

Who was the first scientist to observe a living cell under a microscope?

Anton Von Leeuwenhoek.

List four types of living cells observed by Anton Von Leeuwenhoek.

Bacteria, Protozoans, Spermatozoa, and $RBCs$.

Who discovered and first observed the nucleus?

Robert Brown.

In what year did Matthias Schleiden study that plants are composed of cells and tissues?

$1838$ (Page 2 notes indicate $1833$ for initial study).

What was the nationality and profession of Matthias Schleiden?

German botanist.

What was the nationality and profession of Theodore Schwann?

German zoologist.

What did Theodore Schwann discover regarding the outer layer of animal cells?

It has a thin outer layer nowadays called the plasma membrane.

What unique character of plant cells did Theodore Schwann identify?

The cell wall.

Who formulated the initial Cell Theory?

Matthias Schleiden and Theodore Schwann.

What is the primary hypothesis of the Cell Theory?

All living organisms are composed of cells or products of cells.

What are examples of 'products of cells' according to the transcript?

Secretions and hormones.

What was the major drawback of the original Cell Theory formulated by Schleiden and Schwann?

It did not explain how new cells are formed.

Who modified the Cell Theory in $1855$?

Rudolf Virchow.

What does the phrase 'Omnis-cellula-E-cellula' mean?

New cells arise from pre-existing cells.

How do new cells arise according to Rudolf Virchow's modification?

Through cell division.

Which mature human cell is an exception to the cell theory because it lacks a nucleus?

Mature $RBCs$.

Which mature plant cell is an exception to the cell theory because it lacks a nucleus?

Mature Sieve tubes.

What is an example of a multi-nucleated cell mentioned in the notes?

Rhizopus.

What determines the shape of a cell?

The function it performs.

What is the shape of columnar epithelial cells?

Long and narrow.

What is the specific shape of human Red Blood Cells ($RBCs$)?

Round and biconcave.

What is the characteristic shape of White Blood Cells ($WBCs$)?

Amoeboid.

How are nerve cells described in terms of their shape?

Long and branched.

What is the shape of tracheids in plants?

Elongated.

What is the shape of mesophyll cells in plants?

Round and oval.

What is the smallest living cell, and what is its typical length?

$PPLO$ (Mycoplasma) at $0.1 \text{ to } 0.3 \text{ }\nu\text{m}$.

What is the typical size range of bacteria?

$3 \text{ to } 5 \text{ }\nu\text{m}$.

What is the diameter of an $RBC$?

$7 \text{ }\nu\text{m}$.

What is the typical size range of a eukaryotic cell?

$10 \text{ to } 20 \text{ }\nu\text{m}$.

What is the largest known living cell?

The egg of an ostrich.

What is the longest living cell in the human body?

The Nerve Cell (Neuron).

What is the size range of viruses?

$0.02 \text{ to } 0.2 \text{ }\nu\text{m}$.

What is the main arena of cellular activities where chemical reactions occur?

The Cytoplasm.

What is the cell wall of fungi composed of?

Chitin.

What is the cell wall of bacteria composed of?

Peptidoglycan.

Is the cell wall present in animal cells?

No, it is absent.

What are the two main components of the plasma membrane?

Lipids and proteins.

Which organelle is known as the 'brain of the cell' and contains genetic material?

The Nucleus.

What are non-membrane bound organelles found in both prokaryotic and eukaryotic cells?

Ribosomes.

Name a non-membrane bound organelle found only in animal cells that helps in cell division.

The Centrosome.

What are the three double-membrane bound organelles?

Mitochondria, Plastids, and Nucleus.

Describe the nucleus in a prokaryotic cell.

It lacks a well-defined nucleus; genetic material is naked and directly in the cytoplasm.

What is the circular, genomic $DNA$ region in a prokaryote called?

The Nucleoid.

What proteins are absent in prokaryotic $DNA$ but present in eukaryotic cells for packaging?

Histone proteins.

What type of proteins help in $DNA$ packaging in prokaryotes?

Polyamines.

What is the size of ribosomes in the cytoplasm of prokaryotes?

$70S$.

What is the size of ribosomes in the cytoplasm of eukaryotes?

$80S$.

Where can you find $70S$ ribosomes within a eukaryotic cell?

In the Chloroplasts and Mitochondria.

Which group of organisms is used to exemplify prokaryotic cells?

Bacteria (including Blue-green algae/Cyanobacteria) and Mycoplasma.

What are rod-shaped bacteria called?

Bacillus.

What are spherical bacteria called?

Coccus.

What are comma-shaped bacteria called?

Vibrio.

What are spiral-shaped bacteria called?

Spirillum.

What is a plasmid?

Extra-chromosomal, circular, and self-replicating $DNA$.

What unique phenotypic character do plasmids often provide to bacteria?

Antibiotic resistance.

What are the three layers of the bacterial cell envelope?

Glycocalyx, Cell wall, and Plasma membrane.

What are the two forms of glycocalyx in bacteria?

Slime layer (loose) and Capsule (thick and rigid).

What are the two nitrogenous sugars that compose peptidoglycan?

$NAM$ ($N$-acetyl muramic acid) and $N$-acetyl glucosamine ($NAG$).

Who developed the staining technique used to classify bacteria as positive or negative?

Christian Gram.

What is the color of Gram-positive bacteria after staining?

Blue, purple, or violet.

What is the color of Gram-negative bacteria after staining with Safranine?

Pink.

What are mesosomes and what is their primary function?

Invaginations of the plasma membrane used for respiration and $DNA$ replication.

What are chromatophores?

Invaginations of the plasma membrane containing photosynthetic pigments in some bacteria.

What are the three parts of the bacterial flagellum?

Filament, Hook, and Basal Body.

What protein thread composes the bacterial flagellum?

Flagellin.

What is the structural arrangement of microtubules in eukaryotic flagella?

$9+2$ arrangement.

What are pili and what is their function in bacteria?

Elongated tubular structures used for conjugation (reproduction).

What are fimbriae and what is their function?

Bristle-like structures that help in attachment to surfaces or host tissues.

What is a polysome?

A chain of multiple ribosomes attached to a single M-$RNA$.

What is the function of ribosomes in all cells?

Protein synthesis (Translation).

What are the reserved materials stored in prokaryotic cells called?

Inclusion bodies.

Name three types of inclusion granules found in bacteria.

Cyanophycean granules, Phosphate granules, and Glycogen granules.

What is the function of gas vacuoles in Cyanobacteria?

They provide buoyancy.

Which model describes the structure of the plasma membrane, and who proposed it?

Fluid Mosaic Model, proposed by Singer and Nicolson.

In what year was the Fluid Mosaic Model proposed?

$1972$.

What is the 'mosaic' in the Fluid Mosaic Model?

The mixture of proteins floating in the sea of phospholipids.

What is the approximate composition of a human erythrocyte ($RBC$) membrane?

$52 \text{ percent}$ protein and $40 \text{ percent}$ lipids.

What part of the phospholipid is hydrophobic and composed of saturated hydrocarbons?

The Tail.

What acts as a stabilizing agent in the eukaryotic plasma membrane?

Cholesterol.

What is passive transport across the cell membrane?

Movement of molecules along the concentration gradient without the use of $ATP$.

What is facilitated diffusion?

Transport of polar molecules across the membrane with the help of carrier or channel proteins.

What is osmosis?

The diffusion of water across a selectively permeable membrane.

What is active transport?

Movement of molecules against the concentration gradient ($uphill$) using $ATP$, such as the $Na \text{ slash } K \text{ pump}$.

What are the two types of endocytosis?

Phagocytosis (cell eating) and Pinocytosis (cell drinking).

What is the 'endomembrane system'?

A system of organelles including the ER, Golgi, lysosomes, and vacuoles that are structurally and functionally connected.

What are the two types of endoplasmic reticulum (ER)?

Rough $ER$ ($RER$) and Smooth $ER$ ($SER$).

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

Protein synthesis.

What is the primary function of the Smooth Endoplasmic Reticulum ($SER$)?

Lipid and steroidal hormone synthesis.

Who discovered the Golgi apparatus in $1898$?

Camillo Golgi.

What are the two faces of the Golgi apparatus?

The Cis-face (convex/forming) and the Trans-face (concave/maturing).

What is the primary function of the Golgi body?

Modification, packaging, and delivery of proteins and lipids.

What organelle is formed by the Golgi apparatus and contains hydrolytic enzymes?

The Lysosome.