- Define and explain Enzymes in Digestion in your own words
- Use key terms such as enzyme accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on Enzymes in Digestion: meet amylase, protease and lipase and see how enzymes speed up digestion.
Meet amylase, protease and lipase and see how enzymes speed up digestion.
Key ideas
Digestion and absorption
Food is broken down physically by chewing and chemically by enzymes as it travels through the gut. In the small intestine, finger-like villi provide a huge surface area for absorbing digested nutrients into the blood. Each villus has a rich blood supply to carry nutrients away quickly and a wall only one cell thick, so diffusion is rapid.
The hierarchy of organisation
Cells with a similar structure and function form a tissue, such as muscle tissue. Different tissues combine into an organ, such as the stomach, which contains muscle, glandular and epithelial tissue. Organs work together in organ systems, such as the digestive system. Plants are organised the same way: mesophyll tissue forms part of a leaf, which belongs to the shoot system.
Key term — enzyme: A biological catalyst, made of protein, that speeds up chemical reactions without being used up.
Name the three digestive enzymes and what each breaks down.
Amylase breaks down starch (carbohydrate); protease breaks down protein; lipase breaks down lipids (fats).
Answer: Amylase breaks down starch (carbohydrate); protease breaks down protein; lipase breaks down lipids (fats).
- Saying enzymes are used up or killed Enzymes are not used up in reactions, and they are not alive so they cannot be killed. High temperatures denature them by changing the shape of the active site.
- Thinking digestion finishes in the stomach The stomach churns food and starts protein digestion, but most chemical digestion and almost all absorption happen in the small intestine.
Practice
Cell → tissue → organ → organ system.
Any two of: large surface area; wall one cell thick for a short diffusion distance; rich blood supply to maintain a concentration gradient; many mitochondria for active transport.
The left ventricle pumps blood all around the body, which needs much higher pressure than pumping blood the short distance to the lungs, so its muscle wall is thicker.
Valves prevent the backflow of blood, keeping it moving in one direction through the heart and veins.
Quick check
Which of these best defines "enzyme"?
A student counts 21 pulse beats in 15 seconds after exercise. Calculate the heart rate.
- Enzymes in Digestion: meet amylase, protease and lipase and see how enzymes speed up digestion.
- Digestion and absorption: Food is broken down physically by chewing and chemically by enzymes as it travels through the gut.
- tissue: A group of similar cells working together to carry out a particular function, such as muscle tissue or xylem tissue.
- Watch out for: saying enzymes are used up or killed