2.1 Introduction to Cells

Introduction to Cells

Cell theory, structure, types

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Introduction

In this task, you are to be assessed on your understanding so far of the topics that you were assigned to read about. Namely, the cell theory, its kinds, and its parts.

Cell Theory

The original cell theory states that the cell is the basic structural and functional unit of living organisms and all cells come from other cells. The scientists Matthias Schleiden and Theodore Schwann are credited with establishing the cell theory in 1839.

Watch the youtube video to learn more: https://www.youtube.com/watch?v=4OpBylwH9DU&t=3s

Cell Theory

Multiple Choice

Which of the following is not true about the cell theory?

• All living things are made up of cells. Viruses are not made of cells, hence they are technically 'not alive'.

• Cells cannot come from other things, they only come from other pre-existing cells.

• The characteristics of life such as metabolism, reproduction, and adaptation are all related to the cellular activities, hence cell is the basic unit of life.

• Organisms are only allowed to survive, grow, develop, and reproduce when they are composed of eukaryotic cells.

Surface area and volume ratio

As a cell grows bigger, its internal volume enlarges and the cell membrane expands. Unfortunately, the volume increases more rapidly than does the surface area, and so the relative amount of surface area available to pass materials to a unit volume of the cell steadily decreases.

What's wrong with too large cells?

If the cell grows too large, the plasma membrane will not have sufficient surface area to support the rate of diffusion required for the increased volume. In other words, as a cell grows, it becomes less efficient. There is also DNA overload which means that the larger the cell grows, the greater the demands are placed on the cell's DNA. At some point there is not sufficient DNA for the cell's proper functioning.

Multiple Choice

What is the ideal size of cells considering their surface area and ratio?

• small volume, small surface area

• small volume, large surface area

• large volume, small surface area

• large volume, large surface area

Multiple Select

Which of the following is the benefit of having large surface area but low volume? Select all possible answers.

• cells can divide faster

• cells can transport materials in and out quicker

• cells can reach maturity faster

• cells will make the organisms maintain homeostasis less

History of Cell Study

If you've watched the youtube video, you would probably be familiar with some personalities who contributed a lot to the study of cells.

Multiple Choice

Who discovered the animalcules from dental scrapings using a small primitive microscope?

• Robert Hooke

• Theodore Schwann

• Matthias Schleiden

• Anton Von Leeuwenhoek

Multiple Choice

Who first coined the term "cells"?

• Robert Hooke

• Theodore Schwann

• Matthias Schleiden

• Anton Von Leeuwenhoek

Multiple Choice

What were "cells" compared with?

• animals

• little rooms

• plants

• stars

Multiple Choice

What are cell parts called?

• systemelles

• organelles

• tissuelles

• celluelles

Organization of Life

As life and its metabolic activities can be studied at various levels, we should remember that life processes does not only exist on the organism level. Being alive is not just having the ability to breathe or move, it is also seen from the millions of activities that happen between organ systems, between organs, between tissues, and within cells.

Organization of Life

That being said, the traits of a living organism, its ability to copy and pass on its genes, to maintain homeostasis, and to metabolise chemical products all occur in the cellular level. For that reason, cell is the basic functional and structural unit of life.

Organization of the Body​

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Cells are the basic unit of structure and function of life.

Group of cells working together are called tissues.

Group of tissues that collectively functions together are called organs.

Organisms like us are made of different organ systems that allow us to survive. ​

Prokaryotes and Eukaryotes

Structurally speaking, there are two big groups of cells, those with naked DNA, and those whose DNA are wrapped by a membrane. They differ in so many ways including size and complexity.

​Prokaryotes and Eukaryotes

Prokaryotes are simple, small, and includes the bacteria. On the other hand, eukaryotes are bigger, more complex, and has membrane-bound organelles. They include yeast, algae, fungus, plant and animal cells.

​Prokaryotes and Eukaryotes

The DNA ​of cells contain all the information it needs to function and mature into specific kinds of cells. DNA in prokaryotes are just suspended in its cytoplasm. In eukaryotes, DNA is enclosed within the nucleus, which is the brain of the cell. They also have membrane-bound structures or organelles.

Prokaryotes

• pro - before

• karyo - nucleus

• prokaryotes are cells that came before there were nucleus

• they are very small, about 1/10 of the size of most eukaryotes

• they do not have membrane bound organelles

• examples include, bacteria (such as ecoli, salmonella, Clostridium tetani)

Eukaryotes

• Eu - "true"

• karyo - nucleus

• Eukaryotes are cells that do have nuclear membrane to cover its DNA

• they are bigger and more complex with some specialized organelles and internal structures

• examples include protists, fungi, animals, and plants

Multiple Choice

Which of the following is a collection of cells that works together to perform a function?

• Cells

• Tissues

• Organelles

• Organs

Multiple Choice

In cells, these molecules contain the instructions to tell itself what type of cell it needs to be.

• DNA / Genes
• Cytoplasm
• Cell Membrane
• Mitochrondria

Multiple Choice

Which type of cell has complex structures and has membrane-bound organelles?

• Prokaryotic Cells

• Bacteria Cells

• Eukaryotic Cells

• E-coli bacterium

Multiple Choice

Prokaryotic cells do not have

• DNA

• Cell membrane

• Cytoplasm

• Nucleus

Multiple Choice

Which of these organisms are not eukaryotes?

• Yeast

• Algae

• Fungi

• Bacteria

Multiple Choice

What are the two types of cells?

• Prokaryotic & Eukaryotic

• Bacteria & Eukaryotic

• Eukaryotic

• Animal & Plant

Specialized Cells

Cells within an organism obviously need to be specialized at what they do. Some cells have longer body shape, some cells are more flat, and some others come in the form of cylinders. The way they appear, their shape, their structure and their particular parts is related to their function. Example, a cell that needs to produce more heat and energy must have more mitochondria inside it. A cell in that is meant to receive, pass on, or transport substances must have more protein gates on its membranes.

Specialized Cells Examples

Nerve Cells - long, thin, and interconnected cells; these cells function to send signals to the different parts of the body to perceive or to react to the surroundings.

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Fat Cells - round, thick, and high fat amount cells; these cells function to preserve energy, produce heat, and to protect body from cold.

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White blood cells - ​round, has many 'protein sensors'; they determine dangers in the body and respond quickly to avoid infection.

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​Red blood cells - flat, thin in the middle, thick on the perimeter; these cells have a good amount of space with small volume to efficiently absorb and transfer oxygen to different parts of the body.

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Multiple Choice

This cell sends signals throughout the body. 

• Nerve Cell
• Red Blood Cell
• White Blood Cell
• Xylem

Multiple Choice

This cell collects and delivers oxygen around the body

• Nerve Cell
• Red Blood Cell
• White Blood Cell
• Xylem

Multiple Choice

This cell stores fat and serves as an energy and heat source for the bdoy

• White Blood Cell

• Bone Cell

• Red Blood Cell

• Fat cells

Multiple Choice

The role of these specialized cells is to help fight off infection and foreign bodies.

• Palisade Cells
• Nerve Cells
• White Blood Cells
• Red Blood Cells