2: The Cell as the Basic Unit of Life Flashcards
What are the main inorganic chemical constituents of organisms?
Water and inorganic ions (mainly nitrate, magnesium, calcium, and iron).
What are the important functions of water?
- As a reactant: water takes part in some chemical reactions.
- As a medium for chemical reactions: It is also a good solvent that dissolves many substances. It provides an aqueous medium for chemical reactions to take place.
- As a medium of transport: substances dissolve in water and are carried around the body.
- As a cooling agent: water removes heat when it evaporates from the body of an organism, acting as a cooling agent.
- Provides support: water gives shape and provides support to organisms. It also provides buoyancy for aquatic plants and animals.
Which substances in humans are dissolved and transported in water?
Nutrients, waste, and gases dissolve in blood and are carried around the body. Meanwhile, blood contains about 90% water.
How do humans and plants cool down respectively?
Humans produce more sweat when the body temperature is high. Sweat mainly consists of water; its evaporation helps cool down the body.
Plants lose water in the form of water vapour to the atmosphere through transpiration. This helps take away heat away from the plants, preventing them from overheating.
How does water provide support to soft-bodied animals and plants respectively?
Some soft-bodied animals, like earthworms and jellyfish, have a fluid-filled cavity in their bodies. The hydrostatic pressure built up inside the body cavity gives support to the animals.
When plant cells are full of water, they become turgid and press against each other. This gives support to young seedlings so that the seedlings can stand upright.
What are the main functions of nitrate?
It is a source of nitrogen in plants for the synthesis of proteins. Animals obtain nitrogen through feeding on plants and other animals.
What are the main functions of magnesium?
It is a component of chlorophyll in plants. It also activates some enzymes that are needed for regulating some metabolic reactions.
What are the main functions of calcium?
It is the main component of bones and teeth. It is required in some processes like muscle contraction, blood clotting and sending messages in the nervous system. It also helps strengthen the cell wall in plants.
What are the main functions of iron?
It is a component of haemoglobin, which is an oxygen-carrying component in red blood cells. It also activates some enzymes.
What are the main organic chemical constituents of organisms?
Carbohydrates, lipids, proteins, and nucleic acids. They are often called biomolecules, and all contain carbon atoms.
What are the main functions of carbohydrates?
Carbohydrates contain carbon, hydrogen, and oxygen atoms. Glucose, starch, and cellulose are three common types of carbohydrates.
Glucose is directly broken down in respiration to release energy for body activities.
Starch acts as an energy reserve in plants. It is broken down to glucose to release energy when needed.
Cellulose is the main component of plant cell walls.
What are the main functions of lipids?
Lipids also contain carbon, hydrogen, and oxygen atoms, but they have a much greater hydrogen-to-oxygen ratio than carbohydrates. Triglycerides and phospholipids are two common types of lipids.
Triglycerides act as an energy reserve in our body. They also help reduce heat loss from the body by acting as a heat-insulating layer under the skin and protect the internal organs by cushioning them as a shock absorber.
Phospholipids are the main component of cell membranes.
What are the main functions of proteins?
Proteins contain carbon, hydrogen, oxygen, and nitrogen atoms, while some also contain sulphur atoms. Proteins make up many body tissues like hair, muscles, and skin.
Enzymes are proteins that can speed up (catalyse) reactions in our body.
Antibodies are proteins that are important in defending our body against diseases.
What are the main functions of nucleic acids?
Nucleic acids contain carbon, hydrogen, oxygen, nitrogen, and phosphorus atoms. There are two types of nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
DNA carries genetic information that controls activities of the cells and determines the features organisms.
RNA is involved in the synthesis of proteins.
What is the discovery of cells?
In 1665, an English scientist Robert Hooke designed a microscope and used it to examine a thin slice of cork. He observed that cork seemed to be made up of many small irregular boxes. He called these boxes “cells”.
What is the Cell Theory?
The Cell Theory was proposed by Theodor Schwann. It (with modifications by other scientists) states that:
1. all organisms are made up of one or more cells
2. the cell is the basic unit of life, it is the smallest. until that shows all the characteristics of life
3. all cells come from pre-existing cells.
What are electron microscopes and two common types of electron microscopes?
Electron microscopes were invented in the 1930s. They use electron beams instead of light to form an image. They can produce images with higher magnifications and resolution, thus allowing scientists to study cells in greater detail. Two common types of electron microscopes are transmission electron microscopes and scanning electron microscopes.
What are the functions of transmission electron microscopes?
In a transmission electron microscope, electron beams pass through the specimen to form an image. They can be used to study the internal structures of a specimen. They produce two-dimensional, black-and-white images magnified up to 1.5 million times.
