Animal and Plant Cell Structure and Function

A Cell’s Structure and Function

Cells come in many different shapes and sizes. However, all cells, both eukaryote and prokaryote, have certain things in common. For example, all cells have cytoplasm and a cell membrane. The cell membrane is a protective membrane that surrounds a cell and selects what molecules can enter and exit the cell.

Ribosomes are structures in both prokaryotes and eukaryotes that build proteins according to the cell’s DNA. Genetic instructions from the DNA travel through the nuclear membrane to reach the ribosomes. Ribosomes then use the information in DNA to build proteins. Each cell builds proteins for its own uses, including for growth and repair. Ribosomes are the smallest and most common organelles in a cell. In eukaryotes, ribosomes either float freely throughout the cytoplasm or are attached to an organelle called the endoplasmic reticulum (pronounced en-doh-PlAZ-mik-ri-TIK-yuh-luhm).

The endoplasmic reticulum (ER) is a network of membranes where many proteins are built because many ribosomes attach themselves to it. The part of the ER that has ribosomes attached to it is called rough endoplasmic reticulum. Smooth endoplasmic reticulum has no ribosomes attached to it. Because of its role in making proteins, the ER is located near the cell nucleus.

The Golgi (pronounced GOHL-jee) complex is a series of membranes that adjusts the shape of proteins and transports them to their place in the cell. The Golgi complex transports proteins by wrapping them in vesicles—small sacs that bud off from a membrane.

Plant vs. Animal Cells

Animal cells and plant cells share most of the same organelles because they are both eukaryotes, but there are some differences. The following are organelles that differ between a plant cell and an animal cell:

Vacuole

Vacuoles are sac-like organelles that store water for the cell. Vacuoles in animal cells are small and float freely in the cytoplasm. Plants cells contain a larger central vacuole. Up to ninety percent of a plant cell may be taken up by the central vacuole. This vacuole fills with water and waste from the cell. A plant wilts if its cells lose water in their central vacuoles.

Chloroplasts

Chloroplasts are only found in plant cells. Chloroplasts contain a green pigment called chlorophyll. This pigment gives plant cells their green color. It also absorbs sunlight, which begins a process of turning carbon dioxide and water into a kind of sugar called glucose, which plants use for energy, growth, and development. Animals do not have chloroplasts and so they must eat other organisms for energy and nutrients.

Cell Wall

A cell wall is a stiff, shell-like wall that surrounds the cell membrane of plant cells and helps plants stand up. Plant cell walls are made of cellulose, which is a type of sugar molecule. Animals often have skeletons (or exoskeletons in the case of insects) to help support them. Because animal cells are not confined by a rigid cell wall, they have developed more kinds of cells, especially those that enable movement.

Centrosome

Centrosomes are only found in animal cells. They are sets of tubular organelles that help the cell divide.