Cell Theory

What is a cell?

A cell is the smallest unit of life that can function independently.

What happens when cells are combined?

They perform functions necessary for life.

Why is the small size of a cell ideal for biological processes?

Its small size allows faster transport of substances.

What are the major functions of the cell discussed in the module?

1. Regulation of the internal environment

2. Acquisition and utilization of energy

3. Responsiveness to the environment

4. Protection and support

What is homeostasis?

It is an organism's ability to keep a constant internal state.

Why is maintenance of internal conditions important?

Most cells of an organism require a specific set of conditions to function normally.

What is 37°C according to the module?

37 degrees Celsius is the peak or normal temperature of a human being.

What can a temperature greater than 37°C manifest as according to the module?

Soreness, headache, or weakness.

What is perspiration?

Perspiration serves as the cooling system to remove excess heat.

What does shivering do?

Shivering generates metabolic heat.

What do snoring and drooling during sleep indicate according to the module?

They indicate tiredness in a human.

What is chemical energy?

Chemical energy is stored in the bonds present in food molecules and is converted by cells into more usable forms.

What is the manifestation of gut heaviness called?

Bloating.

What can improper digestion be a sign of according to the module?

It can be a sign of no energy or stool scraps.

Why is energy needed by various cells?

Energy is needed by cells to perform their specific functions.

What do heart cells do?

Heart cells help pump blood.

What do intestinal cells do?

Intestinal cells help digest food.

What do skeletal cells do?

Skeletal cells help initiate motion.

What do nerve cells do?

Nerve cells help conduct information.

What must a cell do before deciding on the necessary response to an environmental change?

A cell must first be able to determine the changes that have taken place before deciding the necessary responses.

What is the ultimate purpose of a cell's response to environmental changes?

The response ultimately results in the maintenance of normal internal conditions.

What does tanned skin indicate according to the module?

Tanned skin means more pigment is released in that area to protect the underlying cells.

What does the pigment released in tanned skin protect against?

It especially protects against UV radiation, which can damage DNA.

What do immune cells do?

Immune cells provide protection against pathogens and other foreign bodies that may enter the general circulation.

What is the first line of defense?

The skin is the first line of defense.

What is spontaneous generation?

From prehistoric times to 1850, most people believed that under the right conditions, living things could spontaneously appear from non-living material.

What was the belief of spontaneous generation?

Living things could arise spontaneously from non-living material under the right conditions.

Who was Francesco Redi?

Francesco Redi (1626-1697) was a scientist who disproved the spontaneous generation theory through experiments involving meat and maggots.

How many containers did Francesco Redi use in his experiment?

He used three containers.

What happened in Redi's open container?

The open container yielded the formation of maggots in the meat.

What happened in Redi's cork-sealed container?

The cork-sealed container resulted in no formation of maggots in the meat.

What happened in Redi's gauze-covered container?

The gauze-covered container resulted in no formation of maggots in the meat.

What did Redi conclude from his experiment?

Living things can only appear when preexisting living cells, such as microorganisms, are present.

Why did many people reject Redi's claim that flies do not spontaneously generate?

One argument was that sealing the jar closed prevented magical essence from entering the rotting meat and bringing it to life.

What was another criticism against Redi's work?

"Scientists seek only to challenge belief systems and stir things up."

Who was Zacharias Janssens?

Zacharias Janssens (1585-1632) was credited in the module with inventing the first primitive microscope.

How did Zacharias Janssens' primitive microscope work?

It used multiple glass lenses placed at opposite ends of a sliding tube to magnify objects.

How much could Janssens' primitive microscope magnify objects?

It could magnify objects up to 9 times their normal size.

What was a problem with Janssens' primitive microscope?

The magnified specimens produced blurred images when viewed through the microscope.

When were cells unknown until?

Cells were unknown until the discovery of microscopes in the 1650s.

Who was Robert Hooke?

Robert Hooke (1635-1703) was a scientist who observed cork cells under a microscope.

What did Robert Hooke observe?

He observed cork cells under a microscope.

Why did Robert Hooke call the structures he observed "cells"?

The structures reminded him of the small rooms monks slept in.

Who was Anton van Leeuwenhoek?

Anton van Leeuwenhoek (1632-1723) was a scientist who observed microorganisms using his own practical microscope.

What did Leeuwenhoek study using his microscope?

He studied pondwater, sour milk, and semen.

What did Leeuwenhoek call moving organisms?

He called them "animalcules."

What effect did Leeuwenhoek's discoveries have on people?

His discoveries scared people and caused a sensation.

What belief about human sperm cells is shown in the module's image/text?

The historical belief shown was that human sperm cells contained tiny human beings.

What belief about pondwater animalcules is shown in the module?

The historical image/text refers to pondwater animalcules causing madness.

Who was Lazzaro Spallanzani?

Lazzaro Spallanzani (1729) believed that food spoilage came from the air and that the microbes causing spoilage could be killed by boiling.

What did Spallanzani believe caused food spoilage?

He believed that air was responsible for food spoilage and that microbes in the air caused it.

How could the microbes causing food spoilage be killed according to Spallanzani?

They could be killed by boiling.

Why did people reject Spallanzani's findings?

One argument was that sealing the flask shut blocked the entrance of a magical life force in the air from getting to the broth.

What was another reason people rejected Spallanzani's findings?

"Since few people had seen those microbes, few people believed him."

What happened in Trial 1 of Spallanzani's experiment?

Open Flask: He filled flasks with nutrient broth, boiled them, and left the containers open. After a few days, the broth was teeming with microorganisms.

What happened in Trial 2 of Spallanzani's experiment?

Sealed Flask: He filled flasks with broth, boiled them vigorously for a longer duration, and immediately sealed the glass necks shut.

What does "hermetically sealing" mean in Spallanzani's experiment?

It means the glass necks were immediately sealed shut, preventing outside material from entering.

What happened to the hermetically sealed flasks?

The flasks remained completely free of living organisms.

What was the key comparison in Spallanzani's two trials?

Open flask: boiled nutrient broth + exposure to the environment → microorganisms appeared.

Sealed flask: broth boiled vigorously for longer + hermetically sealed → remained free of living organisms.

Who was Louis Pasteur?

Louis Pasteur (1822) supported the idea that spontaneous generation was a myth.

What did Louis Pasteur invent?

He invented pasteurization.

How did Pasteur's experiment support the rejection of spontaneous generation?

He used a flask with boiled broth, exposed it to air minimally, and concluded that air did not spoil food; microorganisms caused the spoilage.

What is Louis Pasteur known as?

He is the father of modern microbiology.

What did Pasteur identify as the microbes that change grape juice into wine?

Yeasts.

What did Pasteur demonstrate about heat and food?

Heat can be used to sterilize foods and preserve them in sealed glass containers, and later cans.

Who was Matthias Schleiden?

Matthias Schleiden (1804-1881) proposed that all plants are composed of cells.

Who was Theodor Schwann?

Theodor Schwann (1810-1882) proposed that all animals are composed of cells.

Who was Robert Virchow?

Robert Virchow (1821-1902) proposed that all cells come from pre-existing cells.

What is Cell Theory?

Cell Theory is the foundational principle of biology, defining what a cell is.

What are the two frameworks of Cell Theory?

Classical Cell Theory (CCT)

Modern Cell Theory

What is the first principle of Classical Cell Theory?

Every living organism consists of one or more cells. An organism may be unicellular or multicellular based on its level of complexity.

What does unicellular mean according to Classical Cell Theory?

An organism that consists of one cell.

What does multicellular mean according to Classical Cell Theory?

An organism that consists of many cells.

What is the second principle of Classical Cell Theory?

The cell is the fundamental unit of life. It is the smallest structural and functional unit in all organisms.

What is the third principle of Classical Cell Theory?

Cells come from pre-existing cells.

What does "Omnis cellula e cellula" mean?

It expresses the idea that every cell comes from a pre-existing cell.

Who is credited in the module with the phrase "Omnis cellula e cellula"?

Francois Raspail, in 1830.

Why was Francois Raspail hindered from gaining recognition for Cell Theory?

He missed the significance of the cell nucleus and proposed an incorrect mechanism for cellular generation, theorizing that new cells formed from within old ones.

What is the fourth principle of Modern Cell Theory?

Energy flow occurs within cells. Biochemical processes and metabolism take place directly inside cells.

What does the module specifically state about digestion and cells?

Digestion starts from the cell.

What is the fifth principle of Modern Cell Theory?

Heredity is passed through cells. Genetic material (DNA) is passed from a cell during cellular division.

What is the sixth principle of Modern Cell Theory?

Basic chemical composition is the same. All cells within similar species share highly comparable chemical and structural composition.

What structures do all animal cells have according to the module?

All animal cells have a nucleus, ribosomes, and endoplasmic reticulum.

What structures do all plant cells have according to the module?

All plant cells have a cell wall and chloroplasts.