FACT: All living things are made of cell(s)
We know that all living things are made of cells because we can see the cells under a microscope. Before the microscope was invented people didn't know that there were cells or that there were microorganisms such has bacteria. Plant cells normally have strong walls and are more square/rectangular in shape. Animal cells don't have a cell wall and so they tend to be more round in shape but they can also come in all different shapes.
We know that all living things are made of cells because we can see the cells under a microscope. Before the microscope was invented people didn't know that there were cells or that there were microorganisms such has bacteria. Plant cells normally have strong walls and are more square/rectangular in shape. Animal cells don't have a cell wall and so they tend to be more round in shape but they can also come in all different shapes.
FACT: All cells are made of molecules
The main molecules in cells are proteins, carbohydrates, and fats. Fats make up cell membranes. Carbohydrates make up cell structures and can be broken down to release energy. Proteins are the doing molecules in cells. Proteins build other molecules, transport substances into and out of the cell, and communicate with other cells.
The main molecules in cells are proteins, carbohydrates, and fats. Fats make up cell membranes. Carbohydrates make up cell structures and can be broken down to release energy. Proteins are the doing molecules in cells. Proteins build other molecules, transport substances into and out of the cell, and communicate with other cells.
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FACT: All molecules are made of atoms
Organic molecules such as Fats, Proteins, and Carbohydrates all contain CARBON, OXYGEN, and HYDROGEN atoms. Proteins also contain atoms of nitrogen. These molecules can burn as they contain high energy C-C or C-H bonds.
Cells also contain molecules of minerals and water. These molecules have atoms of nitrogen, oxygen, hydrogen, and phosphorus. As these molecules do not contain high energy C-C or C-H bonds they cannot be used for energy by the cell. Images on the public domain.
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CellsA cell is the smallest unit of a living thing. A living thing, whether made of one cell (like bacteria) or many cells (like a human), is called an organism. Thus, cells are the basic building blocks of all organisms.
Several cells of one kind that interconnect with each other and perform a shared function form tissues, several tissues combine to form an organ (your stomach, heart, or brain), and several organs make up an organ system (such as the digestive system, circulatory system, or nervous system). Several systems that function together form an organism (like a human being). Here, we will examine the structure and function of cells. There are many types of cells, all grouped into one of two broad categories: prokaryotic and eukaryotic. For example, both animal and plant cells are classified as eukaryotic cells, whereas bacterial cells are classified as prokaryotic. Before discussing the criteria for determining whether a cell is prokaryotic or eukaryotic, let’s first examine how biologists study cells. |
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Image credit: modified from "Introduction: Figure 1" by OpenStax College, Biology, CC BY 3.0; a: modification of work by Ed Uthman, MD; b: modification of work by Umberto Salvagnin; c: modification of work by Anthony D'Onofrio, William H. Fowle, Eric J. Stewart, and Kim Lewis of the Lewis Lab at Northeastern University; scale-bar data from Matt Russell
All cells (Prokaryotes and Eukaryotes) share four common components:
- a cell membrane, an outer covering that separates the cell’s interior from its surrounding environment
- cytoplasm, consisting of a jelly-like cytosol within the cell in which other cellular components are found
- DNA, the genetic material of the cell
- Ribosomes, which synthesize proteins. However, prokaryotes differ from eukaryotic cells in several ways.
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Prokaryotes: Bacteria
Bacteria have a cell wall that is different than plants. Rather than being made of cellulose it is made of peptidoglycan. This allows the wall to be more flexible. In addition, bacteria are different than eukaryotes because their DNA is not enclosed in a membrane bound organelle. There is no nucleus. Bacteria have two types of DNA, chromosomal (a long circular structure) and plasmid (small circular structures that contain non-essential DNA). Bacteria also often have a flagellum, a long, whip-like structure that helps them move. |
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Eukaryotic Cells
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