This lesson introduces the basics of biology, including the process researchers use to study science. It also examines the classes of biomolecules and how substances are broken down for energy.
*There is no review video for this section. Each topic discussed will be further expanded upon in upcoming lessons with review videos that cover the material within this section.
The study or science of living things is called biology. Some characteristics, or traits, are common to all living things. These enable researchers to differentiate living things from nonliving things. Traits include reproduction, growth and development, homeostasis, and energy processing. Homeostasis is the body’s ability to maintain a constant internal environment despite changes that occur in the external environment. With so many living things in the world, researchers developed a taxonomy system, which is used for classification, description, and naming. As shown below, there are seven classification levels in the classical Linnaean system.
Specificity increases as the levels move from kingdom to species. For example, in the image the genus level contains two types of bears, but the species level shows one type. Additionally, organisms in each level are found in the level above it. For example, organisms in the order level are part of the class level. This classification system is based on physical similarities across living things. It does not account for molecular or genetic similarities.
Did You Know?
Carl Linnaeus only used physical similarities across organisms when he created the Linnaean system because technology was not advanced enough to observe similarities at the molecular level.
A researcher classifies a newly discovered organism in the class taxonomy level. What other taxonomic level is this new organism classified in?
To develop the taxonomic system, researchers had to ask questions. Researchers use seven steps to answer science questions or solve problems. Recall that these make up the scientific method, described below:
Sometimes, just a few steps of the scientific method are necessary to research a question. At other times, several steps may be repeated as needed. The goal of this method is to find a reliable answer to the scientific question.
Test Tip
Using the first letter in each of the steps, you can create a mnemonic device to remember the steps. For example: “People Really Have Elephants On Compact Cars.” Try creating your own mnemonic device!
Over the course of many years during which scientists are able to collect sufficient and reliable data, the scientific method can be used to create a law or theory. A law is a rule that describes patterns observed in nature. A scientific theory explains the how and why of things that happens in nature through observations and experiments. Scientists widely accept both laws and theories, but they can be modified over time.
In a study, a researcher describes what happens to a plant following exposure to a dry and hot environment. What step of the scientific method does this most likely describe?
From oceans and streams to a bottle, water is fundamental for life. Without water, life would not exist. Because of water’s unique properties, it plays a specific role in living things. The molecular structure of water consists of an oxygen atom bonded to two hydrogen atoms. The structure of water explains some of its properties. For example, water is polar. The oxygen atom is slightly negatively charged, while both hydrogen atoms are slightly positively charged.
As shown in the image, a single water molecule forms hydrogen bonds with nearby water molecules. This type of bonding creates a weak attraction between the water molecules. Hydrogen bonding contributes to water’s high boiling point. Water is necessary for biochemical processes like photosynthesis and cellular respiration. It is also a universal solvent, which means water dissolves many different substances.
Keep In Mind
It takes a lot of heat to create hot water. This is because of water’s high specific heat capacity, which is the amount of heat required to raise the temperature of 1 kilogram of water by 1 degree Celsius. This property of water also makes it ideal for living things.
Only two water molecules are needed to show bonding. Remove the partial negative/positive signs and put a − sign next to the oxygen atom and a + sign next to each hydrogen (H) atom. Remove the solid lines between the H and O but keep the dashed line connecting one water molecule to the next.
Phospholipids, a class of lipids, are a structure with a phosphate “head” and a fatty acid “tail”. The phosphate head is a molecule structure consisting of a phosphate atom and four oxygen atoms, making the head carry a polar charge to be soluble in water; hydrophilic. This is opposite the two fatty acid chains in the tail, which are nonpolar and water insoluble, or hydrophobic. This structure is important in creating the permeable, or semi-permeable membranes of cells, which help the flow of specific ions through designated channels of a cell.
Biomolecules, or biological molecules, are found in living things. These organic molecules vary in structure and size and perform different functions. Researchers group the wide variety of molecules found in living things into four major classes for organizational purposes: proteins, carbohydrates, lipids, and nucleic acids. Each class of biomolecules has unique monomers and polymers. Monomers are molecules that covalently bond to form larger molecules or polymers.
The following table lists characteristics of each class of biomolecule.
Bio molecule | Monomers | Function | Example |
---|---|---|---|
Protein | Amino acid | A substance that provides the overall basic structure and function for a cell | Enzymes |
Carbohydrate | Monosaccharides | A form of storage for energy | Glucose Cellulose Starch Disaccharides |
Lipid | Glycerol and fatty acids | A type of fat that provides a long-term storage for energy | Fats Steroids Oils Hormones |
Nucleic Acid | Nucleotides | A substance that aids in protein synthesis and transmission of genetic information | DNA RNA |
During protein synthesis in a cell, the primary structure of the protein consists of a linear chain of monomers. Which of the following is another way to describe this structure?
Just like water, energy is essential to life. Food and sunlight are major energy sources. Metabolism is the process of converting food into usable energy. This refers to all biochemical processes or reactions that take place in a living thing to keep it alive.
A metabolic pathway is a series of several chemical reactions that take place cyclically to either build or break down molecules. An anabolic pathway involves the synthesis of new molecules. These pathways require an input of energy. Catabolic pathways involve the breakdown of molecules. Energy is released from a catabolic pathway.
Living things use several metabolic pathways. The most well-studied pathways include glycolysis, the citric acid cycle, and the electron transport chain. These metabolic pathways either release or add energy during a reaction. They also provide a continual flow of energy to living things.
Connections
Energy flows through living things. Energy from the sun is converted to chemical energy via photosynthesis. When living things feed on plants, they obtain this energy for survival.
The following image provides an overview of cellular respiration. Glycolysis, the citric acid cycle, the electron transport chain, and oxidative phosphorylation collectively make up this process. Cellular respiration takes place in a cell and is used to convert energy from nutrients into ATP.
Be Careful
Some of these metabolic pathways produce energy in different parts of the cell. Glycolysis takes place in the cytoplasm of the cell. But the citric acid cycle and oxidative phosphorylation occur in the mitochondria.
Why are metabolic pathways cyclic?
Order the levels of biological organization in the proper order of the hierarchy, beginning with the largest, or most broad.
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Place the steps of the scientific method in the correct order.
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