The Fundamental Unit of Life - Cell Biology

A set of Q&A flashcards covering core concepts from cell discovery, structure, theory, differences between plant and animal cells, and basic cell sizes based on the lecture notes.

Why is the cell considered the fundamental unit of life?

Because all living organisms are made of one or more cells; cells are the basic units that carry out life processes, and organisms arise from cell division with cells containing organelles that enable life functions.

Define cell biology.

The branch of biology that studies the structure, function, growth, and life processes of cells.

How was the word 'cell' derived?

From the Latin 'cellula' meaning 'a little room'; Robert Hooke named them after observing cork's box-like compartments.

What were the contributions of Robert Hooke and Robert Brown to cell science?

Hooke (1665) discovered cells in cork; Brown (1831) discovered the nucleus within cells.

Do all organisms have cells of the same size? Provide examples.

No. Sizes vary: ostrich egg cell is very large; nerve cells can be very long; typical bacteria are 1–2 μm, PPLO ~0.1 μm, mycoplasmas ~0.3 μm, human RBCs ~7 μm in diameter.

What features are seen in onion peel cells versus human cheek cells?

Onion cells show cell wall, nucleus, cytoplasm, and a vacuole; human cheek cells show cell membrane and nucleus (no rigid cell wall).

List three key differences between plant and animal cells.

Plant cells have a cell wall, chloroplasts, and a large central vacuole; animal cells lack cell walls and chloroplasts and have smaller vacuoles; nucleus location differs (plant nucleus often pushed to the side due to the large vacuole).

What did the invention of the compound and electron microscopes reveal?

They revealed detailed structural features of the cell and its organelles.

Who discovered cells and how?

Robert Hooke discovered cells in 1665 by examining cork slices with a microscope; Leeuwenhoek observed free-living cells in pond water in 1674 with improved lenses.

Who coined the term 'protoplasm' and when?

Purkinje in 1839.

What does the cell theory state and who contributed to it?

Schleiden and Schwann (1838–1839) proposed that all plants and animals are composed of cells and that the cell is the basic unit of life; Virchow (1855) stated that cells arise from pre-existing cells.

What is a cell?

The basic structural and functional unit of life; the smallest unit capable of carrying out life processes.

What are cell organelles?

Specialized components within a cell that perform dedicated functions enabling the cell to live and function.

What is the typical size of a eukaryotic cell?

About 10–20 micrometers (μm).

What are the typical sizes of bacteria, PPLO, viruses, and red blood cells?

Typical bacteria: 1–2 μm; PPLO ~0.1 μm; viruses ~0.02–0.2 μm; human RBCs ~7 μm in diameter.

What is the smallest cell type mentioned and its approximate size?

Mycoplasmas, about 0.3 μm in size.

What is the largest isolated single cell mentioned?

The ostrich egg.

What is the longest cell type mentioned?

Nerve cell.

What is the difference between onion and cheek cells in terms of cell walls?

Onion cells have a cell wall; human cheek cells have only a cell membrane (no rigid cell wall).

What is the meaning of the term 'Protoplasm'?

The fluid substance of the cell.

What is the significance of the nucleus in plant vs animal cells as per the notes?

Animal cell nuclei are generally central; plant cell nuclei are often pushed to the side by the large central vacuole.

How do multicellular organisms arise according to the notes?

All cells divide to produce cells of their own kind; all cells come from pre-existing cells.

What is the role of cell organelles in a cell?

Organelles perform specific functions; together they enable the cell to live and carry out its functions.

What is the hierarchical organization inside a cell from atoms upward?

Atoms form molecules, which form cell organelles and structures within the cell.