Last week we introduced cells as the basic unit of structure and function in living organisms. But in order to function, a cell needs energy.

Many living organisms—including humans—ingest food as a means to create energy. The organism’s digestive system breaks down the food’s biological macromolecules such as carbohydrates into sugars. When those sugar molecules are broken down, energy is produced. We measure this energy in units of adenosine triphosphate (ATP). ATP is used by cells as a source of energy.

Other organisms, such as plants, can produce energy without ingesting food. Plants produce energy from light through a process known as photosynthesis. As a human, your food comes from either plants or animals that eat plants. This means that the energy in your body depends, on some level, on plant photosynthesis. Without plant photosynthesis, we wouldn’t be able to get the energy we need from our food.

This week, we will look at ways cells create energy, the ways they acquire what they need to create energy, and how they transfer energy throughout an organism’s body.

The living cells of every organism constantly use energy. Cells import molecules, metabolize or otherwise modify them, then transport them around the cell, potentially even distributing products back out of the cell to the entire organism.

Metabolism is the sum of all chemical reactions that occur in a living organism. A key feature of metabolism is that chemical reactions often make the materials needed for other chemical reactions. Metabolism both builds bigger molecules from smaller ones and dismantles molecules to release atoms and energy.

Photosynthesis is one of the most important sets of chemical reactions in all of nature for more than just the energy it produces. In addition to being the pathway through which energy and carbon (in the form of glucose) enter the web of life, it also releases oxygen into the environment. Life as we know it would not exist without photosynthesis. This is quite an important role in nature!

You will participate in a class discussion related to topics in biology.

You will also complete a laboratory experiment on parts of the cell, including cell membranes.

And you will demonstrate your knowledge of course concepts with a quiz.

Next week we will study the life cycle of single cells and cell reproduction. Combined, these processes allow for existing cells to make new cells. The ability of living organisms to produce new cells is important for three of the major characteristics of life: growth, healing, and reproduction.       

Week 3 Outcomes

By the end of this week, you should be able to

• describe the scientific concepts relating to energy;
• explain the relationship between enzymes and energy in the context of metabolism;
• describe the role of metabolic pathways in living organisms;
• explain the processes and outcomes of cellular respiration and fermentation;
• explain the process of photosynthesis including the light dependent and light independent (Calvin cycle) reactions;
• compare/contrast cellular organelles;
• add specified amounts of stock solution from the lab kit to obtain specific solution concentrations;
• use dialysis bags to test osmosis for various concentrations; and
• apply concepts and/or argue a position related to a scientific topic.