Food and Digestion

Organisms need food for energy, growth, and repair of old and damaged tissues. Most animals eat plants or other animals, so their food is made up of large, complex molecules. These must be digested (broken down) to simpler, smaller molecules before they can be absorbed and carried to all parts of the body. Proteins are broken down into amino acids. Carbohydrates are broken down into simple sugars. Fats are broken down into fatty acids and glycerol.

1. Proteins are broken down into fatty acids and glycerol.

2. Fats are broken down into amino acids.

3. Carbohydrates are broken down into simple sugars.

8. Read the text and find English equivalents to the Russian sentences:

1. Митохондрии – это склады энергии клетки. Они выдают всю необходимую ей энергию.

2. При дыхании отбирается энергия, хранящаяся в пище.

3. Способ, с помощью которого организмы получают энергию для обеспечения жизненных процессов, называется дыханием.

4. Углекислый газ и вода являются продуктами отходов.

5. При этом процессе выделяется энергия в виде химического вещества, называемого АТФ.

Respiration

The way in which organisms obtain energy to power their life processes is called respiration, and this takes place in their cells. Respiration takes the energy stored in foods (such as glucose) and changes it into a form that can be used by the cell.

Mitochondria are the powerhouses of the cell; they release all the energy it needs. Glucose enters the mitochondria and combines with oxygen. This process gives off energy in the form of a chemical called ATP. Carbon dioxide and water are the waste products.

9. Read the text and find English equivalents to the Russian words:

Происходить, отходы, процесс избавления, скапливаться, выделять, распад, излишний, пища, испражнение.

Excretion

The chemical reactions that take place inside cells produce waste products. Getting rid of these is called excretion. Excretion is necessary because if the waste products were allowed to build up, they would poison and kill the organism. Plants and animals excrete carbon dioxide from respiration. Plants also excrete oxygen, a waste product of photosynthesis, during the day. Animals need to get rid of waste from the breakdown of excess proteins in their diet. Expelling waste matter after digestion is defecation, not excretion.

Read the text and answer the questions.

Growth

When an organism grows it adds more cells to itself and becomes more complex. Once an organism has grown, it cannot return to its original size. Growth occurs by a process called mitosis, during which the chromosomes in a cell double and divide, and then the cell splits into two. In this way each new cell ends up as an exact replica of the original cell.

1. What is “mitosis”?

2. What is growth?