It's metabolism and the process of glycolysis that takes that energy out of the sugar related molecules.

TOPIC 4. BIOCHEMISTRY

Overview

Biochemistry is one of the important fields of chemistry. Biochemists have to understand both the living world and the chemical world to be the best at their jobs. The key thing to remember is that biochemistry is the chemistry of the living world. Plants, animals, single-celled organisms... They all use the same basic chemical compounds to live their lives. Biochemistry is not about the cells or the organisms. It's about the smallest parts of those organisms, the molecules. It's also about the cycles that happen to create those compounds.

Those cycles that repeat over and over are the things that allow living creatures to survive on Earth. It could be the constant process of photosynthesis in plants that creates sugars or the building of complex proteins in the cells of your body. Every cycle has a place and they are just one building block that helps organisms live. In each of those cycles, molecules are needed and changed. It's one big network of activity where each piece relies on all of the others.

Start with the Basics

While we have been talking about all of these cycles, we think it's important that you understand the different types of molecules you will find in biochemistry. You should be thanking us. We aren't going to go into the citric acid cycle and its ten steps. We won't even look at the eleven steps involved in the breakdown of glucose (glycolysis). At your level of understanding, it's enough to understand the difference between a steroid, an amino acid, and a carbohydrate. There will be plenty of time for you to memorize the pathways and the movement of molecules during each step of a cycle.

METABOLISM

Metabolism is such a big word to explain a simple idea. We all need energy to survive. Plants, animals, or bacteria, we all need energy. Energy doesn't just float around in a form we can use to survive. We need to eat (mainly sugars) and digest food. That process of chemical digestion and its related reactions is called metabolism. Metabolism is the total of all of the chemical reactions an organism needs to survive.
Sounds a lot like biology. Why's it here in biochemistry? Two main chemical processes make our world go round. There are two simple chemical reactions. The first is called glycolysis. That's the breakdown of sugars. The second process is called photosynthesis. That is the reaction that builds sugars. You need to remember that the overall metabolism of an organism includes thousands of chemical reactions. Glycolysis and photosynthesis are the cornerstones to life.

BUILDING UP

First, you need to build up the molecules that store energy. We'll start with photosynthesis. It's no use explaining the breakdown of sugars without telling you how they were made.

LIGHT (Energy) + CO₂ + H₂O --> C₆H₁₂O₆ + O₂

This is the reaction that only plants can do (and some algae/bacteria). They take sunlight and combine carbon dioxide (CO₂) and water (H₂O). They create Glucose (C₆H₁₂O₆) and oxygen gas (O₂). Remember, plants put the energy in glucose.

BREAKING DOWN

It's metabolism and the process of glycolysis that takes that energy out of the sugar related molecules.

C₆H₁₂O₆ + O₂--> Usable Energy (ATP) + CO₂ + H₂O

Cells then use that extra energy to power the functions of the cell. The energy isn't still floating around; it's stored in an excitable compound called adenosine triphosphate (ATP). ATP is the power molecule used all over organisms and their cells to power the secondary reactions that keep us alive.

CYCLES

CYCLES AROUND YOU

There are many types of cycles in living organisms and across the Earth. One of these is labeled the Carbon Cycle. It's a large cycle that involves the movement of carbon through living and non-living organisms. Plants are a good starting point when looking at the carbon cycle on Earth. Plants have a process called photosynthesis that enables them to take carbon dioxide out of the atmosphere and combine it with water. Using the energy of the Sun, plants make sugars and oxygen molecules. All of the non-photosynthetic creatures on the planet use the oxygen. Every creature on the planet uses the sugars and starches created by plants.

Another part of the carbon cycle happens when organisms (plant and animal) break sugars down into energy, water, and carbon dioxide. Animals are the non-photosynthetic creatures of the planet. They are not able to create their own food. Instead, they eat plants or other animals. A process of metabolism breaks down the sugars and starches they eat. The results are energy for the creature, water, and carbon dioxide molecules. The carbon dioxide then returns to the atmosphere where the plants use it again.

SMALL CYCLES

There are also smaller cycles that happen in individual cells. The Kreb's cycle is a term used to describe the citric acid cycle that occurs in the mitochondria during glycolysis. This smaller cycle takes a molecule called pyruvic acid and pulls energy out of it. Carbon dioxide (CO₂) is also released during the process.

LIPIDS

Lipids are another type of organic molecule (contains carbon). When you think of fats, you should know that they are lipids. Lipids are also used to make steroids and waxes. So if you pick out some ear wax and smell it, that's a lipid, too!

Date: 2016-01-03; view: 159