Cell: The Fundamental Unit of Life

Fill-in-the-blank flashcards covering key definitions, scientists, organelles, processes, and comparisons from the lecture notes on cells.

According to Cell Theory, all living cells arise from _ cells by division.

pre-existing

Cell Theory declares the cell is the basic unit of _ and function in all living organisms.

structure

In 1665, _ first discovered the cell.

Robert Hooke

In 1674, _ observed living cells using a microscope.

Anton van Leeuwenhoek

In 1833, _ discovered the nucleus.

Robert Brown

In 1835, Felix Dujardin discovered the _ content of the cell.

fluid

In 1838, _ Schleiden proposed that all plants are made up of cells.

Matthias

In 1839, J. E. Purkinje named the fluid content of the cell _.

protoplasm

In 1839, Theodor _ proposed that all animals are made up of cells.

Schwann

In 1845, Carl Heinrich _ proposed that the cell is the basic unit of life.

Braun

In 1855, Rudolf Virchow proposed that all cells arise from _ cells.

pre-existing

An organism made of only one cell is called a _ organism.

unicellular

Euglena, Paramecium, and Yeast are examples of _ organisms.

unicellular

An organism made of more than one cell is called a _ organism.

multicellular

The smallest known cell is _, measuring about 0.1 µm.

Mycoplasma

The largest known cell is the _ egg, measuring about 18 cm.

ostrich

The smallest human cell is the _ cell (≈ 5 µm).

sperm

The largest human cell is the _ cell (≈ 120 µm).

ovum

The longest human cell is the _ cell, reaching up to 1 m.

nerve

Variation in cell shape depends mainly upon the cell’s _.

function

Human red blood cells are circular and _ to pass easily through capillaries.

biconcave

Nerve cells are _ to conduct impulses from one point to another.

branched

White blood cells can _ their shape to engulf microorganisms.

change

A compound microscope can magnify up to about _ times.

2000

An electron microscope can magnify up to about _ times.

500000

The process by which a cell obtains food molecules is called _.

nutrition

Breaking down food into smaller soluble units suitable for cell use is _.

digestion

The process by which cells absorb water and minerals is called _.

absorption

The cellular process of building complex chemicals from simple ones is _.

biosynthesis

Elimination of unwanted by-products from the cell is called _.

excretion

Expulsion of useful substances synthesized by the cell is _.

secretion

Cellular locomotion by cilia or _ is termed movement.

flagella

A cell’s ability to respond to external factors is called _.

irritability

Breaking down food molecules to obtain chemical energy is _.

respiration

Copying DNA and increasing cell number via division is _.

reproduction

Almost every cell contains plasma membrane, nucleus, and _.

cytoplasm

The plasma membrane consists of two layers of _ molecules with proteins floating in them.

lipid

The cell wall of plants is primarily made of cellulose, hemicellulose, and _.

pectin

A nucleus is absent in mature red blood cells and _ tube cells.

sieve

Chromatin fibres are composed of DNA and the protein _.

histone

Stretches of DNA on chromosomes that carry heredity are called _.

genes

Endoplasmic reticulum studded with ribosomes is called ER.

rough

Rough ER mainly synthesizes _ proteins and membrane proteins.

secretory

Smooth ER detoxifies drugs and poisons especially in _ cells.

liver

Smooth ER stores calcium ions particularly in _ cells.

muscle

Stacks of flattened sacs in the Golgi body are called _.

cisternae

The Golgi body face situated near the cell membrane is the _ face.

trans

Lysosomes are filled with _ enzymes.

hydrolytic

Self-digestion of an entire cell by its own lysosomes is called _.

autolysis

Large, permanent, sap-filled sacs in plant cells are called _.

vacuoles

Folded inner membrane projections of mitochondria are called _.

cristae

Mitochondria synthesize the energy-rich compound _.

ATP

Plastids that carry out photosynthesis are called _.

chloroplasts

The orange pigment giving colour to carrots is _.

carotene

Colourless plastids storing starch in potato tubers are called _.

amyloplasts

Stacks of membrane-bound discs in chloroplast grana are _.

thylakoids

Each centrosome contains two perpendicular structures known as _.

centrioles

Hollow tubes of the cytoskeleton made of tubulin are called _.

microtubules

_ are present in animal cells but absent in most plant cells.

Centrioles

_ (such as chloroplasts) are present in plant cells but absent in animal cells.

Plastids

Vacuoles in animal cells are generally _ and temporary.

small

Plastids are double-membrane organelles in plants responsible for making and storing _.

food

The cell wall prevents drying out or _ of plant cells.

desiccation

The semi-permeable plasma membrane helps maintain cellular _.

homeostasis

The unit commonly used to measure cell size is the _.

micrometer

1 µm is equal to 1/1000 of a _.

millimeter