Cell parts and functions · EduSite Academy

▶ Cell parts and their functions

Within cells, special structures are responsible for particular functions. For example, mitochondria help release energy that the cell can use for other tasks, and the nucleus contains the genetic information. The cell membrane forms the boundary that controls what enters and leaves the cell. In plant cells, chloroplasts enable photosynthesis and the cell wall provides structure.

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▶ Comparing animal and plant cells

Plant cells have a cell wall in addition to a cell membrane, whereas animal cells have only a cell membrane. Plants use cell walls to provide structure to the plant. Plant cells contain organelles called chloroplasts, while animal cells do not. Chloroplasts allow plants to make the food they need to live using photosynthesis.

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📄 Learn and try: Cell parts and functions

##Cells are the smallest unit of life

All living things—including plants, animals, and even you!—are made of tiny units called cells. Cells are the smallest unit that can carry out all of the functions of life. These functions include:

taking up nutrients and water,
getting rid of waste,
providing energy, and
interacting with the environment.

To carry out their functions, cells rely on many specialized parts. Each of these parts has its own role in helping the cell work properly.

##Cell diagrams represent real cells

Cells are too small to be seen with the naked eye. So, we use microscopes to see and study real cells. These powerful tools magnify objects, allowing them to be seen up close. Microscopes can also capture zoomed-in photographs, which are called micrographs.

Even with these tools, some parts of a cell can still be hard to see clearly. This is why we often use diagrams to represent cells.

Cell diagrams are models that show the parts that make up a cell. Cell diagrams are useful because they show details that are hard to see, even under a microscope. Cell diagrams often make cell parts look a little bit different than they do in real cells. This makes the cell parts easier to understand, and it can highlight their functions.

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Now, let's take a closer look at the parts that make up animal and plant cells, and how each one helps the cell do its job.

##The cell membrane and cytoplasm provide structure for the cell

Every cell is surrounded by a cell membrane—a structure that provides a barrier between the inside and outside of the cell. The cell membrane plays a role in helping the cell communicate and interact with other cells. It also controls what moves into and out of the cell. It allows needed materials, such as oxygen and nutrients, to enter the cell, and helps remove waste.

Inside the cell membrane is the cytoplasm. The cytoplasm is a jelly-like fluid that fills the cell and contains all of the cell’s internal parts. The cytoplasm helps keep the cell's parts in place, and provides the environment they need to carry out their functions. Many important chemical reactions happen in the cytoplasm, and materials move through it to get from one part of the cell to another.

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##Mitochondria produce energy for the cell

An important cell part found in the cytoplasm is the mitochondrion (plural: mitochondria). These cell parts are examples of organelles—specialized structures inside the cell that carry out specific tasks.

Mitochondria are often called the "powerhouses" of the cell because they produce the energy the cell needs to function. Mitochondria take in nutrients, such as sugars, and break them down in a way that releases energy.

This energy is then used to power everything the cell does—including building new parts, sending signals, and moving materials around. Some cells, such as muscle cells, need more energy than others, so they contain more mitochondria.

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##The nucleus and ribosomes provide instructions for the cell

Another important organelle is the nucleus, which acts as the cell's control center. The nucleus contains the cell's DNA molecules. These molecules hold the instructions that tell the cell how to grow and function. By storing and controlling the cell's DNA, the nucleus helps the cell carry out the right functions at the right time.

Working closely with the nucleus are small structures called ribosomes. Ribosomes use the instructions from the cell's DNA to build specific molecules, usually proteins. Proteins carry out many functions in the cell. For example, they help the cell grow, communicate, and carry out chemical reactions.

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##Cell walls and chloroplasts provide structure and food for plant cells

Plant and animal cells share many of the same parts. However, plant cells have a few important structures that animal cells do not. One of these is the cell wall. The cell wall is a strong outer layer that surrounds the plant cell membrane. It helps the cell keep a rigid shape and protects it from damage. The cell wall is what makes plant stems firm and helps plants stand upright.

Another structure unique to plant cells is the chloroplast. Chloroplasts allow plants to make their own food through a process called photosynthesis. During this process, chloroplasts capture energy from sunlight. They then use this energy to turn carbon dioxide and water into sugars and release oxygen. Plants can use the sugars for energy and growth. Chloroplasts are what give plants their green color.

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##Vacuoles provide storage and support for the cell

Vacuoles are a cell's storage structures. They are found in both plant and animal cells, but they have slightly different functions in each. In animal cells, vacuoles are usually small and there may be several of them. They help the cell by storing water, nutrients, and waste. They also isolate materials that could harm the cell.

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In plant cells, vacuoles are much larger and more important to the cell's structure. Most plant cells have one large central vacuole that stores water, nutrients, and waste. As it fills with water, this vacuole helps the plant cell keep its shape by pressing against the cell wall, similar to how air helps a balloon stay firm.

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###Check for understanding

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##Key points

Cells are the smallest unit that can carry out all of the functions of life. To carry out these functions, cells rely on a variety of specialized parts.
A micrograph is a photograph of real cells taken with the help of a microscope. A cell diagram is a model that represents a real cell and shows parts that are hard to see.
The cell membrane is the barrier that surrounds the cell and controls what enters and leaves. The cytoplasm is the jelly-like fluid that fills the cell and contains all of the cell's internal parts. Together, the cell membrane and cytoplasm give structure to the cell.
Mitochondria are organelles that break down nutrients to produce energy for the cell. The cell uses this energy to carry out all of its functions.
The nucleus stores the cell's DNA molecules. These molecules hold instructions that the ribosomes use to build proteins.
Plant cells have two parts that animal cells do not have: the cell wall and chloroplasts. The cell wall is a strong outer layer that provides support and protection. Chloroplasts capture sunlight to make food for the plant through photosynthesis.
Vacuoles are storage structures in cells, holding water, nutrients, and waste. In plant cells, a large central vacuole also helps maintain the cell’s shape.

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