1. The living cell
Contents
1.1 How do you recognize a living organism?
Pebble plants (also known as living stones) are plants that can be found in the dry areas of Southern Africa. As their name suggests, they resemble small stones found in the surrounding environment. Despite their appearance, pebble plants are living organisms, whereas the stones that surround them are lifeless.
Pebble plants are real, living plants.
Think about the different things that separate these plants from their non-living environment. Why are stones not considered living organisms? You can respond by commenting.
1.2 The basic requirements of life
What is required for life to be possible? The birth and existence of life requires:
- water in liquid form
- elements that render life possible, such as carbon, hydrogen, nitrogen, oxygen and phosphorous
- a source of energy, such as the Sun.
There can be no life without energy. Energy is used to construct complex chemical compounds, to move, and to make different things happen. All life on planet Earth receives most of its energy from the Sun.
Plants need water and sunlight, among other things. Animals require water as well as energy produced by plants.
Plants, algae and some bacteria are capable of photosynthesis. This means that they can make use of light energy from the Sun to produce chemical energy and store this energy in chemical compounds. All other organisms are dependent on the chemical energy produced by plants.
The solar energy bound by green plants and other producers moves through the food chain and is used by consumers, such as herbivores and predators.
All life on planet Earth is organic. This means that it is based on different carbon compounds. Carbon is an element that can form a variety of molecular structures, such as chains and wheels.
The molecules that are significant for living organisms, such as carbohydrates, fats, and proteins, are comprised of carbon chains that have joined together with elements such as hydrogen, nitrogen and oxygen. To thrive, life also requires other elements, such as phosphorous, potassium, calcium, magnesium and iron.
Solar energy is bound into chemical energy by plants. This chemical energy is used by herbivores and other consumers.
1.3 The cell
All living organisms are comprised of one or multiple cells. The cell contains a lot of water. Therefore, water is essential for all living cells.
Animal cells contain the following parts:- The cell is defined by the cell membrane. It regulates the movement of substances to and from the cell.
- The cell is filled with cytoplasm, where various important reactions take place.
- The nucleus comprises the "brains" of the cell. The nucleus contains the cell's genome in DNA form.
- The Golgi apparatus is involved in the production of materials.
- The mitochondrion is where the cell produces energy. Muscle cells, for example, contain a number of mitochondria.
- Unlike plant cells, animal cells do not contain a cell wall nor a vacuole.
Animal cell.
The different parts of the plant cell have different functions:
- The nucleus comprises the "brains" of the cell. It contains the cell's genome in DNA form.
- The cell membrane regulates what substances can move to and from the cell.
- The cytoplasm is where various important reactions take place.
- The cell wall of a plant cell provides protection and support.
- The vacuole of the plant cell is used to store water.
- The chloroplasts of the plant cell are where photosynthesis takes place.
- Like the animal cell, the plant cell also has mitochondria,.
Both plant and animal cells can join together to form larger structures. These structures are known as cell tissue. For example, the human muscle cells form muscular tissue, whereas the superficial cells of a plant's leaves form superficial tissue.
Plant cell.
Learn the parts of the cell
Animal cell.
Plant cell.
