The Fundamental Unit of Life - Cells

Who first observed cells?

Robert Hooke in 1665

What substance was Robert Hooke examining when he discovered cells?

Cork

What does the word 'cell' mean?

A Latin word for 'a little room'

What did Robert Hooke observe that living things appear to consist of?

Separate units

What is the skin peeled from an onion bulb called?

Epidermis

Why is the onion peel placed in water immediately after being peeled?

To prevent it from getting folded or dry

What solution is used to stain the onion peel?

Safranin solution

Why should care be taken while putting the cover slip on the slide?

To avoid air bubbles

What type of microscope is used to observe the onion peel?

Compound microscope

What are unicellular organisms?

Single-celled organisms

What are multicellular organisms?

Many cells group together to form various body parts

How do multi-cellular organisms come from a single cell?

Cells divide to produce cells of their own kind

Where do all cells come from?

Pre-existing cells

Name some cells from the human body.

Sperm, bone cell, smooth muscle cell, blood cells, ovum

What structures are visible under a microscope in onion bulbs of different sizes?

Similar small structures

What are cells considered to be of an organism?

Basic building units

In what year were cells first discovered by Robert Hooke?

1665

Who discovered free-living cells in pond water?

Leeuwenhoek

In what year did Leeuwenhoek discover free-living cells?

1674

Who discovered the nucleus in the cell?

Robert Brown

In what year did Robert Brown discover the nucleus?

1831

Who coined the term 'protoplasm' for the fluid substance of the cell?

Purkinje

In what year did Purkinje coin the term 'protoplasm'?

1839

Who presented the cell theory?

Schleiden and Schwann

In what years did Schleiden and Schwann present the cell theory?

1838 and 1839

Who expanded the cell theory to state that all cells arise from pre-existing cells?

Virchow

In what year did Virchow expand the cell theory?

1855

In what year was the electron microscope discovered?

1940

Give three examples of unicellular organisms.

Amoeba, Chlamydomonas, Paramoecium and bacteria

What characteristics of cells are related to the specific function they perform?

Shape and size

What is unique about the shape of Amoeba cells?

Changing shapes

What are the specific components within a cell known as?

Cell organelles

What three features are found in almost every cell?

Plasma membrane, nucleus, and cytoplasm

What is the outermost covering of the cell called?

Plasma membrane

What is the function of the plasma membrane?

Separates the contents of the cell from its external environment

What is the cell membrane also called?

Selectively permeable membrane

How do substances like carbon dioxide and oxygen move across the cell membrane?

Diffusion

How does diffusion happen?

From a region of high concentration to a region of low concentration

What is the movement of water molecules through a selectively permeable membrane called?

Osmosis

What is osmosis defined as?

Net diffusion of water across a selectively permeable membrane

What is a solution called if the medium surrounding the cell has a higher water concentration than the cell?

Hypotonic solution

What happens to a cell in a hypotonic solution?

The cell will gain water by osmosis and swell

What is a solution called if the medium has exactly the same water concentration as the cell?

Isotonic solution

What happens to a cell in an isotonic solution?

There will be no net movement of water across the cell membrane

What is a solution called if the medium has a lower concentration of water than the cell?

Hypertonic solution

What happens to a cell in a hypertonic solution?

The cell will lose water by osmosis and shrink

What organic molecules make up the plasma membrane?

Lipids and proteins

What is the process by which a cell engulfs food and other material from its external environment called?

Endocytosis

What type of cell has a cell wall?

Plant cells

What is the plant cell wall mainly composed of?

Cellulose

What is the shrinkage or contraction of the contents of a living plant cell away from the cell wall called?

Plasmolysis

What are the small green granules found in plant cells called?

Chloroplasts

What green substance do chloroplasts contain?

Chlorophyll

What darkly colored structure is found near the center of the cell?

Nucleus

What is the double-layered covering of the nucleus called?

Nuclear membrane

What does the nucleus contain when the cell is about to divide?

Chromosomes

What do chromosomes contain information for inheritance of characters in the form of?

DNA (Deoxyribo Nucleic Acid)

What are functional segments of DNA called?

Genes

What is DNA present as when the cell is not dividing?

Chromatin material

What is an undefined nuclear region containing only nucleic acids called?

Nucleoid

What are organisms called whose cells lack a nuclear membrane?

Prokaryotes

What are organisms called with cells having a nuclear membrane?

Eukaryotes

What is the fluid content inside the plasma membrane called?

Cytoplasm

What specialized structures does the cytoplasm contain?

Cell organelles

Why do viruses not show characteristics of life until they enter a living body?

Lack any membranes

Name some important cell organelles.

Endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, plastids

What is a large network of membrane-bound tubes and sheets in the cell called?

Endoplasmic reticulum (ER)

What are the two types of endoplasmic reticulum?

Rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER)

What particles are attached to the surface of the RER?

Ribosomes

What is the function of ribosomes?

Sites of protein manufacture

What does the SER help in?

Manufacture of fat molecules or lipids

What is the process of some proteins and lipids helping in building the cell membrane called?

Membrane biogenesis

What is one function of the ER?

Channels for the transport of materials

What crucial role does SER play in liver cells?

Detoxifying many poisons and drugs

What cellular component consists of a system of membrane-bound vesicles arranged approximately parallel to each other in stacks called cisterns?

Golgi apparatus

What are the functions of the Golgi apparatus?

Storage, modification and packaging of products in vesicles

What are membrane-bound sacs filled with digestive enzymes called?

Lysosomes

What is the function of lysosomes in the cell?

Waste disposal system of the cell

What do lysosomes contain that breaks down organic material?

Digestive enzymes

What are lysosomes also known as?

Suicide bags

What are known as the powerhouses of the cell?

Mitochondria

What form of energy is released by mitochondria?

ATP (Adenosine triphosphate)

What is ATP known as?

Energy currency of the cell

What do mitochondria have that allows them to make some of their own proteins?

Their own DNA and ribosomes

What is present only in plant cells?

Plastids

What are the two types of plastids?

Chromoplasts and leucoplasts

What are chromoplasts called that contain the pigment chlorophyll?

Chloroplasts

What are chloroplasts important for in plants?

Photosynthesis

What are primarily organelles in which materials such as starch, oils, and protein granules are stored?

Leucoplasts

What are storage sacs for solid or liquid contents called?

Vacuoles

What do vacuoles provide to plant cells?

Maintain turgidity and rigidity to the cell

What do vacuoles contain in single-celled organisms like Amoeba?

Food vacuole

What are the two main types of cell division?

Mitosis and meiosis

What process of cell division do most cells divide by for growth?

Mitosis

What does a mother cell divide into during mitosis?

Two identical daughter cells

What process do reproductive organs or tissues divide by to form gametes?

Meiosis

What does a cell divide into during meiosis?

Four new cells

What is the fundamental organizational unit of life?

Cell

What is the plasma membrane composed of?

Lipids and proteins

What is the function of the cell membrane?

Regulates the movement of materials