Vacuoles

Vacuoles are surrounded by membranes. They are sort of like a storage bubble in the cytoplasm. Vacuoles in animal cells are considerably smaller than those in plant cells. In animal cells vacuoles may store food that needs to be digested. Food cannot pass through membranes until it is broken into smaller particles. The lysosome can fuse with the vacuole membrane and squirt digestive enzymes into the food vacuole to break down what is in there. Your white blood cells do this when they eat invading bacteria. Vacuoles can also store the undigestible wastes until they can fuse with the cell membrane and squirt the wastes outside.

Vacuoles in animal cells can form when the cell membrane surrounds a material and pinches off to bring the substance inside the cell. This process is called endocytosis.

The cell sap vacuole in plants is much larger than animals. In addition to storing important substances, it also helps support the plant. The pressure of water filling the cell sap vacuole pushes out against the cell wall. This gives the wall enough strength to hold up fairly large gree (non-woody) plants. We all know the first indication that we are not giving our house plants enough water. They start to droop or wilt. Now you know why, so keep that cell sap vacuole filled with water.

The Cell Wall

Since plants don't have bones, they need a little something extra to support them. The cell wall is made of a tough fiber called cellulose which does this job. When you combine the stiff cell wall with the outward pressure of a full cell sap vacuole, you get enough strength to hold up large plants. Tree cell walls contain other tough materials such as lignin, which make them even stronger.

Some Interesting Facts about Cellulose

Cell walls are made of cellulose fiber. We have many uses for cellulose. Wood and cork are the dead cellulose cell walls of trees. Paper is wood broken down into individual cellulose fibers. Cotton is cellulose fibers. It is fortunate that most organisms do not have the digestive enzymes needed to digest cellulose fiber. Even organisms that we think of as living off of cellulose, like cows deer, or termites can't digest cellulose. They have living inside of them, tiny microorganisms that do all the cellulose digesting. Because we can't digest cellulose cell walls, it is an important part of our diet called fiber or roughage. By the way, we too, have microorganisms in our large intestine that do eventually break down some of the fiber, releasing some B vitamins in the process. Unfortunately, another product of the breakdown is methane gas.

Structure of a chloroplast

Chloroplasts are the food producers of the cell. They are only found in plant cells. Every green plant you see is working to convert the energy of the sun into sugars. That process happens in the chloroplast. Mitochondria work in the opposite way and break down the sugars and nutrients that the cell receives. Plants are the basis of all life on Earth. They create sugars, and the byproduct of that process is the oxygen that we breathe.

MAKING FOOD

Super basic process of photosynthesis The purpose of the chloroplast is to make sugars and starches. They use a process called photosynthesis to get the job done. Photosynthesis is the process of a plant taking energy from the Sun and creating sugars. When the energy from the Sun hits a chloroplast, chlorophyll uses that energy to combine carbon dioxide and water. The result gives the molecules sugar and oxygen. Plants and animals then use the glucose for food and energy. Animals use the oxygen to breathe.