What Are The Parts Of Cells And Their Functions – Take a look at your best friend, your dog – or even a snail using its muscular foot to move up a flower. Everyone looks quite different. And that’s because of the highly organized cells they’re made of. The human body has approximately 37 trillion cells.
This false color photo was taken through a microscope. It shows bacteria, an abundant type of single-celled organism on Earth. STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARYGetty Images Plus
- 1 What Are The Parts Of Cells And Their Functions
- 2 Cell Parts And Functions (understand) (practice)
What Are The Parts Of Cells And Their Functions
However, most living things are not multicellular. They consist of a single cell. Such single-celled organisms are generally so small that we would need a microscope to see them. Bacteria are among the simplest unicellular organisms. Protozoa, such as amoebae, are more complex types of single-celled life.
What Are Plant And Animal Cells?
A cell is the smallest unit of life. Inside each cell are a variety of structures called organelles. “Every cell has essential structures that are the same, like every house has a sink and a bed. But how big and complex they are, and how many of them there are, will vary from cell type to cell type,” says Katherine Thompson-Peer. She is a cell biologist at the University of California, Irvine.
If cells were homes, the simplest — prokaryotes (Pro-KAER-ee-oats) — would be one-room studio apartments. The kitchen, bedroom and living room would all share one space, Thompson-Peer explains. With few organelles, and all next to each other, all activities take place in the center of these cells.
Over time, some cells became more complex. Called eukaryotes (Yu-KAER-ee-oats), these now make up animals, plants, and fungi. Some unicellular organisms, such as yeasts, are also eukaryotes. These cells are all like single family homes – with walls and doors forming separate rooms. A membrane surrounds each organelle in these cells. These membranes “segregate different things that the cell does into different compartments,” explains Thompson-Peer.
The nucleus is the most important organelle in these cells. It contains the DNA of a eukaryotic cell. It is also what distinguishes these cells from prokaryotes. Even unicellular eukaryotes, such as amoeba, have a nucleus. But cellular complexity is most evident in multicellular organisms. If we follow the house analogy, a multicellular organism would be a high-rise building, says Thompson-Peer. It contains lots of home cells. “And they’re all a little different in terms of form. But they all work together to become a building.”
Cell Size And Shape
These amoebae have long, skinny “false feet” called pseudopodia that extend in front of them and drag them. micro_photo/iStock/Getty Images Plus
A cell membrane (also called plasma membrane). This thin, protective outer layer surrounds a cell, like the exterior walls of a house. It protects the structures inside and keeps the environment stable. This membrane is also somewhat permeable. This means it allows certain things to move in and out of a cell. Consider windows in a house with screens. These let air in but keep unwanted animals out. In a cell, this membrane allows nutrients and unwanted waste to leave.
Ribosomes. These are small factories that make proteins. Proteins are important for all functions in life. We need proteins to grow, to repair an injury, and to transport nutrients and oxygen in our bodies. To build proteins, a ribosome binds to a specific part of a cell’s genetic material called messenger RNA. This allows it to read the instructions that tell this factory which building blocks – called amino acids – to assemble to make a protein.
DNA. Every organism has a genetic code called DNA. It is short for deoxyribonucleic acid (Dee-OX-ee-ry-boh new-KLAY-ick). It’s like a huge instruction manual that tells the cells what to do, how and when. All that information is stored in nucleotides (NU-klee-uh-tides). These are chemical building blocks made of nitrogen, sugar and phosphate. When new cells develop, they make an exact copy of the old cells’ DNA so that the new ones know what tasks they are expected to perform.
Cell Parts And Functions (understand) (practice)
Every cell in an organism’s body has the same DNA. Yet these cells can look and function quite differently. And here’s why: Different cell types access and use different parts of the DNA instruction book. For example, an eye cell translates the parts of its DNA that tell it how to make eye-specific proteins. Similarly, a liver cell translates the sections of DNA that tell it how to make liver-specific proteins, Thompson-Peer explains.
You might think of DNA as a script for a play, she says. All actors in Shakespeare’s
Have the same script. Still, Romeo just reads his lines, Thompson-Peer says, before going off to do Romeo things. Juliet just reads her lines and then goes off to do things with Juliet.
Plant and animal cells have many of the same structures. But plants have some specialized structures for support and for making food. Trinset/istock/Getty Images Plus; edited by L. Steenblik Hwang
Solved Cells Must Import Substances To Serve Their Internal
A core. The nucleus is a protective membrane that surrounds a cell’s DNA. It keeps this genetic “instruction manual” safe from molecules that could damage it. The presence of a nucleus is what distinguishes a eukaryotic cell from a prokaryotic one.
Endoplasmic reticulum (En-doh-PLAZ-mik Reh-TIK-yoo-lum). This place, where a cell makes proteins and fats, has a long name. But you can call it “ER” for short. It is a flat sheet that folds tightly back and forth. Those called rough ERs make proteins. The ribosomes that attach to this ER give it that “rough” appearance. Smooth ER produces not only lipids (fatty compounds such as oils, waxes, hormones and most parts of the cell membrane) but also cholesterol (a waxy material in plants and animals). These proteins and other materials are packaged in small sacs that clip off the edge of the ER. These important products of cells are then transported to the Golgi (GOAL-jee) apparatus.
Golgi apparatus. This organelle modifies proteins and lipids in much the same way that car parts are added to the body of a car on a factory assembly line. For example, some proteins need carbohydrates attached to them. After these additions are made, the Golgi apparatus packages the modified proteins and lipids, then sends them in sacs called vesicles to where they will be needed in the body. It’s like a post office that receives lots of mail for different people. The Golgi apparatus sorts the cellular “mail” and delivers it to the correct body address.
Cytoskeleton. This network of small fibers and filaments gives structure to a cell. It is like the frame of a house. Different cells have different shapes and structures based on their function. For example, a muscle cell has a long, cylindrical structure so that it can contract.
Ever Wondered How Your Cells Work? They’re Like Tiny Factories.
Mitochondria. These power generators in the cell break down sugars to release their energy. Then the mitochondria (My-toh-KON-dree-uh) package that energy into a molecule called ATP. It is the form of energy that cells use to drive their activities.
Lysosomes. These organelles are the cell’s recycling centers. They break down and digest nutrients, waste or old parts of the cell that are no longer needed. If a cell is too damaged to repair, lysosomes help the cell destroy itself by breaking down and digesting any structural supports as well. That type of cell suicide is called apoptosis.
Vacuoles. In animal cells, several of these small sac-like structures act a bit like lysosomes, helping to recycle waste. In plant cells there is a large vacuole. It mainly stores water and keeps a cell hydrated, helping to give a plant its rigid structure.
Seen here under a microscope, chloroplasts are the structures in plant cells that make plants green. NNehring/E+/Getty Images Plus
Mitochondria: Form, Function, And Disease
Cell wall. This rigid layer covers the outside of a plant’s cell membrane. It is made of a network of proteins and sugars. It gives plants their rigid structure and provides some protection against pathogens and from stress, such as water loss.
Chloroplasts. These plant organelles use energy from the sun, along with water and carbon dioxide in the air, to make food for plants through the process called photosynthesis. Chloroplasts (KLOR-oh-plasters) have a green pigment inside them called chlorophyll. This pigment is what makes plants green. The interior of human cells is divided into the nucleus and the cytoplasm. The nucleus is a spherical or oval structure in the center of the cell. The cytoplasm is the region outside the nucleus that contains cell organelles and the cytosol, or cytoplasmic solution. Intracellular fluid is together the cytosol and the fluid inside the organelles and the cell nucleus.
Membranes are the gates of the cell. The cell membrane (or plasma membrane) is the selective barrier that surrounds the cell. It provides a barrier to the movement of molecules between the intra- and extracellular fluids because the cell membrane surrounds the cell, thereby separating the cellular contents from the surrounding environment.
The plasma membrane also serves to anchor adjacent cells together and to the extracellular matrix. Different signals and inputs can change the membrane’s sensitivity and permeability.
Table 2.1 Parts Of Cell, Their Main Characteristics And Chief Functions
Membranes are made of a double layer of lipids, mainly phospholipids, containing embedded proteins. The embedded proteins are important that facilitate moving molecules through the membrane. The membrane itself is organized into
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