Cell Structure, Function, and Type

A Peek Inside the Animal Cell

Animal cells are eukaryotic cells. Cheek, nerve, and muscle cells are all examples of animal cells. Because there are many different types, each animal cell has a specialized function. But all animal cells have the same parts, or organelles. Use this image as a guide while going through following list, which describes the organelles found in a eukaryotic (or animal) cell.

• Cell membrane: A double layer that separates the inside of the cell from the outside environment. It is semi-permeable, meaning it only allows certain molecules to enter the cell.
• Nucleus: A membrane-bound organelle that contains the genetic material, such as DNA, for a cell. Inside the nucleus is the nucleolus that plays a role in assembling subunits required to make ribosomes.
• Mitochondria: The cell’s powerhouses that provide energy to the cell for it to function. Much of the energy in the form of ATP is produced here.
• Ribosomes: The cell’s protein factories that can be found floating in the cytoplasm or attached to the endoplasmic reticulum.
• Vacuoles: Small sacs in a cell that store water and food for survival. This organelle also stores waste material that is mostly in the form of water.
• Endoplasmic reticulum: A network of membranes that functions as a cell’s transportation system, shuttling proteins and other materials around the cell. The smooth endoplasmic reticulum lacks ribosomes, and the rough endoplasmic reticulum has ribosomes.
• Lysosomes: Sac-like structures that contain digestive enzymes that are used to break down food and old organelles.
• Golgi apparatus: A stack of flattened pouches that plays a role in processing proteins received from the endoplasmic reticulum. It modifies proteins from the endoplasmic reticulum and then packages them into a vesicle that can be sent to other places in the cell.

Keep In Mind

Some of the organelles in animal cells are also present in plant cells. In addition, all organelles are found in the cytoplasm of the cell. The only exception is the nucleus, which it is separated from the cytoplasm because it has its own membrane.

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Plant Cells

Recall that plant cells are also eukaryotic cells. Structurally, these cells are similar to animal cells because some of the parts in a plant cell are also found in an animal cell. However, there are some notable differences. The following image shows the structure of a plant cell.

First, only plant cells have a cell wall. The purpose of this structure is to provide protection and support to plant cells. The cell wall also enforces the overall structural integrity of the plant cell, and it is found outside the cell membrane. The next organelle is a chloroplast. It is found in the cytoplasm of only plant cells. Chloroplasts are photosynthetic compounds used to make food for plant cells by harnessing energy from the sun. These organelles play a role in photosynthesis.

Chloroplasts and mitochondria are both designed to collect, process, and store energy for the cell. Thus, organisms are divided into autotrophs or heterotrophs based on how they obtain energy.

Autotrophs are organisms that make energy-rich biomolecules from raw material in nature. They do this by using basic energy sources such the sun. This explains why most autotrophs rely on photosynthesis to transform sunlight into usable food that can produce energy necessary for life. Plants and certain species of bacteria are autotrophs.

Animals are heterotrophs because they are unable to make their own food. Heterotrophs have to consume and metabolize their food sources to absorb the stored energy. Examples of heterotrophs include all animals and fungi, as well as certain species of bacteria.

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Did You Know?

More than 99% of all energy for life on Earth is provided through the process of photosynthesis.

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Let’s Review

• This lesson focused on the cell theory, different cell types, and the various cell parts found in plant and animal cells.
• The cell theory is an in-depth explanation, supported with scientific data, to prove a cell is a living thing and has unique characteristics.
• Cells are the basic building blocks of life. Coming in various sizes and shapes, cells have specialized functions.
• Two broad types of cells are prokaryotic and eukaryotic cells.
• Prokaryotes are single-celled organisms that lack a nucleus, while eukaryotes are multicellular organisms that contain a nucleus and other organelles.
• Organelles are specialized structures with a specific cellular function.
• Both animal and plant cells have similar organelles such as ribosomes, mitochondria, and an endoplasmic reticulum.
• Cell walls and chloroplasts are only found in plant cells. Cell walls provide protection and support to plant cells, giving them rigidity in their shape. Chloroplasts harness energy from the sun for plants through the process of photosynthesis.
• Living things can be classified as autotrophs or heterotrophs based on how they obtain energy. Plants are autotrophs which rely on photosynthesis to produce energy while heterotrophs such as animals must consume and metabolize food into energy.

In the next TEAS science lesson you’ll learn about cellular reproduction.

Cell Structure, Function, and Type Flashcards