The Fundamental Unit of Life - Cells (Flashcards)

A set of concise Q&A flashcards covering cell discovery, structure, organelles, membrane transport, plant vs. animal cells, and cell division from the notes.

Who first observed cells, and what term did he coin for them?

Robert Hooke observed cork in 1665 and coined the term 'cells' from the Latin 'a little room'.

What is a cell?

The basic structural and functional unit of life; living things are made up of cells; first evidence that living things occur as discrete units.

Which organisms are cited as unicellular in the notes?

Chlamydomonas, Paramoecium, and bacteria.

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

Schleiden and Schwann proposed that plants and animals are made of cells and that the cell is the basic unit of life; Virchow added that all cells arise from pre-existing cells.

What role did the electron microscope play in cell biology?

It allowed observation and understanding of the detailed structure of cells and their organelles.

What are cell organelles?

Membrane-bound structures within cells that perform specific functions, enabling division of labour inside the cell.

What are the three features seen in almost every cell?

Plasma membrane, nucleus, and cytoplasm.

What is the plasma membrane and why is it called selectively permeable?

The outer boundary of the cell that controls entry and exit of substances; it allows some movements and restricts others, and facilitates diffusion and osmosis.

What are diffusion and osmosis?

Diffusion is the spontaneous movement of substances from high to low concentration; osmosis is the diffusion of water across a selectively permeable membrane toward higher solute concentration.

Define hypotonic, isotonic, and hypertonic solutions.

Hypotonic: outside has higher water concentration; water enters the cell; it swells. Isotonic: equal water concentration; no net movement. Hypertonic: outside has lower water concentration; water leaves the cell; it shrinks.

What is endocytosis?

A process by which a cell engulfs external material; used by Amoeba to ingest food.

What is the cell wall and what is plasmolysis?

The cell wall is a rigid outer layer in plant cells made of cellulose; plasmolysis is the shrinkage of the cell contents away from the cell wall when the cell loses water.

How do prokaryotic cells differ from eukaryotic cells?

Prokaryotes lack a true nucleus and membrane-bound organelles; they have a nucleoid region and are generally smaller; eukaryotes have a defined nucleus and membrane-bound organelles.

What is cytoplasm?

The fluid inside the plasma membrane that contains organelles and is the site of many cellular activities.

What is the Endoplasmic Reticulum (ER) and its two types?

ER is a network of membrane-bound tubules; Rough ER has ribosomes and makes proteins; Smooth ER synthesizes lipids and aids membrane biogenesis; serves as a transport network.

What is the Golgi apparatus?

A stack of membrane-bound vesicles that modifies, stores, and packages substances manufactured in the cell and is involved in lysosome formation.

What are lysosomes?

Membrane-bound sacs containing digestive enzymes; digest foreign material and worn-out organelles; also called the 'suicide bags' of the cell.

What are mitochondria?

Powerhouses of the cell; double membrane with inner folds (cristae); generate ATP; contain their own DNA and ribosomes.

What are plastids and their types?

Plastids are plant cell organelles; types include chromoplasts (pigmented) and leucoplasts (starch/oil/protein storage); chloroplasts contain chlorophyll and are sites of photosynthesis; plastids have their own DNA and ribosomes.

What are chloroplasts and their significance?

Chloroplasts contain chlorophyll and are the site of photosynthesis; they have internal membrane systems and their own DNA and ribosomes.

What are vacuoles and their functions?

Storage sacs; plant cells have large central vacuoles that maintain turgidity and store substances; Amoeba has food vacuoles.

What are chromosomes and chromatin?

Chromatin is the thread-like form of DNA in non-dividing cells; chromosomes condense from chromatin during division and carry genetic information (genes).

What is the nucleus and its role in the cell?

A double-membrane bound organelle with pores that houses chromosomes; contains DNA and directs cellular activities and development; prokaryotes lack a true nucleus (nucleoid).

What are the two main types of cell division and their outcomes?

Mitosis: growth and repair; produces two identical daughter cells with the same chromosome number. Meiosis: formation of gametes; two consecutive divisions; four haploid daughter cells; chromosome number halved.

Where are proteins synthesized in the cell?

Ribosomes, especially on the rough endoplasmic reticulum (and some free-floating ribosomes) serve as the sites of protein synthesis.

What is the role of the central vacuole in plant cells?

Maintains turgidity and stores substances like amino acids, sugars, organic acids, and proteins; can occupy 50–90% of the cell volume in mature plant cells.