Organisation

• A tissue is a group of cells with a similar structure and function.
• An organ is a group of tissues working together for a specific function.
• The stomach contains muscle tissue and also glandular tissue which releases enzymes.
• Organs are grouped into organ systems which work together to form organisms.
• Food contains three main nutrients: carbohydrates such as starch, protein, and lipids, also known as fats.
• Large food molecules are broken down into small molecules by enzymes during digestion.
• The human digestive system consists of the mouth, esophagus, stomach, small intestine, and large intestine.
• In the mouth, food is chewed and enzymes in the saliva begin to digest a starch into smaller sugar molecules.
• The food then passes down the esophagus into the stomach where enzymes begin the digestion of proteins and the stomach also contains hydrochloric acid which helps the enzymes to digest proteins.
• The food spends several hours in the stomach, churning action of the stomach muscles turns the food into a fluid increasing the surface area for enzymes to digest the fluid.
• The fluid passes into the small intestine where chemicals are released into the small intestine from the liver and pancreas.
• The pancreas releases enzymes which continue the digestion of starch and protein and start the digestion of lipids.
• The liver releases bile which helps to speed up the digestion of lipids and also neutralizes the acid released from the stomach.
• The fluid makes its way through the large intestine where water is absorbed into the bloodstream and finally the feces is released from the body.
• In the digestive system, large food molecules are digested into smaller molecules and then the products of digestion are absorbed into the bloodstream.
• The products of digestion are then used by the body to build new carbohydrates, lipids, and proteins.
• Some of the glucose produced is used in respiration.
• Enzymes catalyze chemical reactions, speeding them up.
• Enzymes are large protein molecules with a groove on their surface called the active site.
• The substrate is the molecule that the enzyme breaks down.
• Proteins are broken down by enzymes called proteases, which are found in the stomach, pancreatic fluid, and small intestine.
• Starch, an example of a carbohydrate, is broken down by enzymes called carbohydrates, specifically amylase, which are found in the saliva and pancreatic fluid.
• Lipids, which consist of a molecule of glycerol attached to three molecules of fatty acids, are digested by the enzyme lipase, which is found in the pancreatic fluid and small intestine.
• Bile, which is not an enzyme, is produced in the liver and stored in the gallbladder to speed up the digestion of lipids.
• Enzymes speed up chemical reactions and have a groove on their surface called the active site where the substrate molecule fits perfectly.
• The enzyme breaks down the substrate into products.
• Enzymes are specific because the substrate must fit perfectly into the active site, a theory known as the lock and key theory.
• The rate of an enzyme catalyzed reaction increases as the temperature increases.
• At a certain temperature, the enzyme is working at its fastest possible rate, known as the optimum temperature.
• Most human enzymes have an optimum temperature of 37 degrees Celsius, which is human body temperature.
• As the temperature increases past the optimum, the activity of the enzyme rapidly decreases to zero, because at high temperatures the enzyme molecule vibrates and the shape of the active site changes, causing the substrate to no longer fit perfectly into the active site.
• The active site is denatured when the conditions are too acidic or too alkaline, causing the enzyme to no longer catalyze the reaction.
• Each enzyme has a specific optimum pH, for example, this enzyme works best at an acidic pH, while another enzyme works best at an alkaline pH.
• Enzymes speed up chemical reactions and have a groove on their surface called the active site where the substrate molecule fits perfectly.
• The enzyme breaks down the substrate into products.
• Enzymes are specific because the substrate must fit perfectly into the active site, a theory known as the lock and key theory.
• The rate of an enzyme catalyzed reaction increases as the temperature increases.
• At a certain temperature, the enzyme is working at its fastest possible rate, known as the optimum temperature.
• Most human enzymes have an optimum temperature of 37 degrees Celsius, which is human body temperature.
• As the temperature increases past the optimum, the activity of the enzyme rapidly decreases to zero, because at high temperatures the enzyme molecule vibrates and the shape of the active site changes, causing the substrate to no longer fit perfectly into the active site.