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Anti-Cancer Genes Article (from Newsela)

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Anti-Cancer Genes Article (from Newsela)

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Seeing Through Cell Membranes Article (from PBS)

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Seeing Through Cell Membranes Article (from PBS)

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AI Lets Scientists See Through Cell Membranes

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Current techniques for visualizing cells are limited, costly, and damaging to the very cells being studied. A new model hopes to change that.

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Cells and the Functions of Their Parts Article and Diagram (from National Geographic)

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Cells and the Functions of Their Parts Article and Diagram (from National Geographic)

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Image

Illustration of a plant cell with the organelles and components labeled.

Illustration by SPL/Science Source

This lists the logos of programs or partners of NG Education which have provided or contributed the content on this page. Leveled by

Thursday, May 23, 2019

As is often repeated, cells are the basic building blocks of all life. They are responsible for generating the energy that sustains life, eliminating waste, and replicating to replace damaged tissues. From single-celled organisms to humans, complex function is possible because of cells and the flexible functions of their parts.

Bacteria: Basic but Capable

Some organisms consist of a single cell, with only the most basic components. They contain genetic material ( DNA), ribosomes, cytoplasm, and a cell membrane. Bacteria, for example, mainly consist of these most basic parts of a cell, and sometimes also a cell wall. Yet bacteria are capable of causing human illnesses, from mild food poisoning to deadly tuberculosis. Conversely, they are also capable of promoting human health; for example, bacteria living in the human gut aid in digestion and nutrient absorption, among other things.

Due to the dynamic capabilities of their limited cell parts, bacteria are also able to form biofilms. A biofilm is a layer of microbes held together by a protective film of secreted, or released, molecules. The secretory capabilities and properties of the bacterial cell membrane, including cell surface structures, such as proteins and flagella, contribute to bacteria's ability to form biofilms. Some biofilms are harmful and may grow on medical equipment and cause infection. They also form on industrial materials, such as oil and gas pipelines. Biofilm-associated corrosion of these materials accounts for 20 percent of total corrosion damages, costing billions of U.S. dollars to prevent and fix. This type of corrosion may even result in environmental damages from pipeline leaks.

Genetic material has the ability to exist in mobile segments. This allows bacteria to exchange portions of DNA through a process called horizontal gene transfer. Unlike vertical gene transfer, which occurs when parents pass on DNA to their offspring, horizontal gene transfer involves genetic material moving from one living organism to another, regardless of relatedness. This capability allows the rapid spread of antibiotic resistance in bacteria. Horizontal gene transfer is more common in prokaryotic organisms, such as bacteria, because they lack a nuclear membrane that protects an organism's genetic material from foreign DNA.

Yeast and Slime Molds

More complex single-celled organisms, such as yeast, are eukaryotic. Unlike prokaryotic cells, eukaryotic cells contain a nucleus as well as other organelles. Organelles are like the cell's organs, in that they are cell parts that perform specific sets of tasks. The organelles in yeast allow it to perform processes like fermentation, which humans have harnessed for our use and enjoyment in making bread, wine, beer, and even biofuel. Fermentation is possible because of certain enzymes within yeast that allow it to convert sugars into alcohol. Enzymes are proteins, and, like all proteins, they are produced by ribosomes within a cell.

Other single-celled organisms, such as cellular slime molds, a type of amoeba, can aggregate to form a multicellular structure. These social amoebas will function as individual organisms when soil nutrients are present. In times of low nutrients, however, they band together to migrate in a slug-like form to search for food. The cellular communication between amoebas during aggregation involves many cell parts, including the cytoskeleton and the nuclear membrane. In this case, the nuclear membrane controls the entry of key molecules from the cytoplasm into the nucleus. In here, these molecules regulate gene transcription, or copying-the first stage of gene expression.

Ultimately, the aggregate amoeba typically differentiates into stalk cells and spore cells. A large vacuole-that is, an empty space-forms within stalk cells as they undergo cell death and form a column. This process lifts up the spore cells and then scatters them to a new location. Many cell parts play a role in this complex behavior of social amoebas, including functions of the mitochondria. These are critical to cell movement, differentiation and patterning of cells within the multicellular slug.

Complex Organisms: Specialized Cells

In true multicellular organisms, a variety of organelles allow equally incredible feats. Chloroplasts in plant cells allow the organism to capture the sun's energy and produce food. In a growing animal, the cytoskeleton sorts critical parts and molecules within the cell. In doing this, it defines the ends of the cells to enable specific functions as an embryo progresses to a developed organism.

Following development, specialized cells within multicellular organisms perform specific functions in support of the body. Meanwhile, diverse organelles contribute to the ability of cells to accomplish vital tasks. For example, mature red blood cells in mammals lack a nucleus. They want to clear out as much cellular space as possible for a protein called hemoglobin, which allows the cell to carry oxygen from the lungs to the rest of the body. White blood cells are part of the body's immune system. They use lysosomes to engulf and destroy bacteria, preventing infection.

In another example, neurons in the human brain allow problem solving, memory, and emotion. A neuron's cell parts are critical to these functions. Neurons secrete neurotransmitters in response to environmental signals, and this secretion is regulated by organelles called Golgi bodies. These organelles are capable of making special vesicles, or sacs, to transport neurotransmitters outside the neuron, where they aid in cell communication to help regulate things like mood. A long axon fiber extends from the cell and releases these critical signaling chemicals. Then, a neighboring cell's many fingerlike dendrites receive the signals. Internal and external cell structures work together to execute cell-level functions.

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Tyson Brown, National Geographic Society

Author

National Geographic Society

Production Managers

Gina Borgia, National Geographic Society
Jeanna Sullivan, National Geographic Society

Program Specialists

Sarah Appleton, National Geographic Society
Margot Willis, National Geographic Society

Last Updated

May 23, 2019

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Director

Tyson Brown, National Geographic Society

Author

National Geographic Society

Production Managers

Gina Borgia, National Geographic Society
Jeanna Sullivan, National Geographic Society

Program Specialists

Sarah Appleton, National Geographic Society
Margot Willis, National Geographic Society

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Cells and the Versatile Functions of Their Parts

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Image Illustration of a plant cell with the organelles and components labeled. Illustration by SPL/Science Source This lists the logos of programs or partners of NG Education which have provided or contributed the content on this page. Leveled by Thursday, May 23, 2019 As is often repeated, cells are the basic building blocks of all life.

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Introduction to the cell | Cells | High school biology | Khan Academy

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Mitosis Slideshow from the Biomedical Beat Blog (National Institute of General Medical Sciences)

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Mitosis Slideshow from the Biomedical Beat Blog (National Institute of General Medical Sciences)

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The intricate process of mitosis-a cell splitting into two identical daughter cells-plays a pivotal role in sustaining life. Many scientists study this process to understand what's needed for it to progress normally and why it sometimes goes awry, such as in cancer. During their research, the scientists often create eye-catching images and videos, and we showcase some of those visuals here.

Check out our post Make Like a Cell and Split: Comparing Mitosis and Meiosis for more info on mitosis, and visit our  image and video gallery for more examples of mitosis, as well as other scientific photos, illustrations, and videos.

Yeast cells undergo mitosis to multiply. Nuclear envelopes are shown in green, and spindle pole bodies, which help pull apart chromosomes, are shown in magenta.
Credit: Alaina Willet, Kathy Gould's lab, Vanderbilt University.

Microtubules (red) direct chromosomes (blue) to align during mitosis. The scientists who took this image were investigating how the protein Plk1 (green) regulates chromosome alignment in human cells.
Credit: Robert Lera and Mark Burkard, University of Wisconsin-Madison.

Spindle pole bodies (glowing dots) move toward the ends of yeast cells to separate chromosomes during mitosis. Contractile rings (glowing bands) form in cells' middles and constrict to help them split.
Credit: Alaina Willet, Kathy Gould's lab, Vanderbilt University.

This snapshot shows abnormal mitosis in African clawed frog cells. The chromosomes (pink) are being pulled in four directions instead of the usual two by the green fibers.
Credit: Tamara Potapova and Gary Gorbsky, Oklahoma Medical Research Foundation.

This time-lapse video shows two cells over 2 hours. The one on the top right goes through mitosis. The one on the bottom left goes through programmed cell death, also known as apoptosis.
Credit: Dylan T. Burnette, Vanderbilt University School of Medicine.

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The intricate process of mitosis-a cell splitting into two identical daughter cells-plays a pivotal role in sustaining life. Many scientists study this process to understand what's needed for it to progress normally and why it sometimes goes awry, such as in cancer.

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Studying Cells Article (from the National Institute of General Medical Sciences)

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Studying Cells Article (from the National Institute of General Medical Sciences)

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National Institute of General Medical Sciences (NIGMS)

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What are cells?

Cells provide structure and function for all living things, from microorganisms to humans. Scientists consider them the smallest form of life. Cells house the biological machinery that makes the proteins, chemicals, and signals responsible for everything that happens inside our bodies.

What do cells look like?

Cells come in different shapes—round, flat, long, star-like, cubed, and even shapeless. Most cells are colorless and see-through. The size of a cell also varies. Some of the smallest are one-celled bacteria, which are too small to see with the naked eye, at 1-millionth of a meter (micrometer) across. Plants have some of the largest cells, 10–100 micrometers across. The human cell with the biggest diameter is the egg. It is about the same diameter as a hair strand (80 micrometers).

How many different types of human cells are there?

The trillions of cells that make up a human are organized into about 200 major types. All of a person’s cells contain the same set of genes (see more on genes). However, each cell type “switches on” a different pattern of genes, and this determines which proteins the cell produces. The unique set of proteins in different cell types allows them to perform specialized tasks. For instance, red blood cells carry oxygen throughout the body. White blood cells kill germ invaders. Intestinal cells release molecules that help digest food. Nerve cells send chemical and electrical messages that produce thoughts and movement. And heart cells contract in unison to pump blood.

Fibroblast cells with nuclei (blue, circular, center), energy factories (green, surrounding the nucleus), and the actin cytoskeleton (red, outermost). Credit: Dylan Burnette and Jennifer Lippincott-Schwartz, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health.

Researchers used fluorescent tags to illuminate the intricate network of microtubule (yellow, center filaments) and actin filament (purple, outermost) fibers that build a cell's structure. Credit: Torsten Wittmann, Scripps Research Institute.

What are eukaryotic and prokaryotic cells, and how are they different?

When putting cells into categories, scientists can tell eukaryotic cells apart from prokaryotic cells because they look different. Eukaryotic cells make up animals, plants, fungi, and some single-celled organisms. And they have a number of structures inside them, called organelles. The most prominent organelle is the nucleus, which contains the cell’s genetic material, or DNA (see more on DNA). Prokaryotic cells don’t have a nucleus or other organelles. They are single-celled microorganisms that tend to be smaller than eukaryotic cells. There are two types of prokaryotic cells—bacteria and archaea.

What are some of the major organelles in a human cell?

In addition to the nucleus, the most prominent organelles include the following:

Mitochondria, the cell’s power plants, convert energy from food into the body’s main energy source, adenosine triphosphate (ATP).

Ribosomes are molecular factories that make proteins.

The endoplasmic reticulum (ER), a network of interconnected sacs, processes newly made secreted and membrane proteins and produces fatty substances called lipids.

The Golgi complex receives proteins and lipids from the ER, packages them, and sends them to their final destinations inside the cell, within the cell membrane, or outside the cell.

Lysosomes, the cell’s garbage dumps, break down waste materials and dispose of them or recycle them.

How do cells move?

Many types of cells can move. Single-celled organisms move to find food. And even cells inside multicellular organisms may need to get around. For example, immune system cells must move toward invaders. And sperm needs to “swim” to fertilize eggs.

Cells move in several ways. Some simply float through water or other liquids. Some push themselves along using long, thin proteins, called flagella, and cilia that stick outside the cell membrane and wave around. Some “crawl” along, using what’s called amoeboid movements, in which cytoplasm-filled protrusions scoot the cell forward.

Within cells, nutrients and organelles move around to carry out various cellular functions. This kind of internal movement is called cyclosis, or cytoplasmic streaming. The internal structure of cells, which is called the cytoplasm, creates a directional flow that pushes the contents of the cells around.

Scientists study cell movement to better understand how cells work, including how cancer cells move from one tissue to another and how white blood cells move to heal wounds and attack invaders.

Thin, hair-like biological structures called cilia are tiny but mighty. Working together, cilia play essential roles in human health, such as sweeping debris from the lungs. Credit: Zvonimir Dogic, Brandeis University.

This is a pig cell in the process of dividing. The image shows the chromosomes (purple, shorter, center) and the cell skeleton (green, fibrous, outer). Credit: Nasser Rusan, National Heart, Lung, and Blood Institute, National Institutes of Health.

How do scientists study cells?

Cell biologists rely on an array of tools to peer into the body and examine cells. Imaging techniques magnify organelles and track cells as they divide, grow, interact, and carry out other vital tasks. Biochemical or genetic tests allow researchers to study how cells respond to environmental stressors, such as rising temperatures or toxins. These tests can also label specific proteins using fluorescent tags and other chemicals that allow scientists to visualize proteins at work inside cells. Sophisticated computational tools then integrate and analyze all the data.

How do our bodies make more cells?

One cell divides into two in a process called mitosis. Mitosis produces two genetically identical “daughter” cells from a single parent cell. Another type of cell division, meiosis, creates four daughter cells that are genetically distinct from one another and from the original parent cell. Only a few special cells can perform meiosis: those that will become eggs in females and sperm in males.

How and why do cells die?

Cells come equipped with what they need to self-destruct. This is called programmed cell death, or apoptosis. And it serves a healthy and protective role in our bodies. For example, it helps shape our fingers and toes before birth, and it kills off diseased cells during our lives. Another kind of cell death, called necrosis, is unplanned and not protective. Necrosis can happen after a sudden traumatic injury, infection, or exposure to a toxic chemical.

What are stem cells?

Stem cells can renew themselves millions of times. Other cells in the body, such as muscle and nerve cells, cannot do this. Embryonic stem cells are undifferentiated, meaning they can turn into any type of cell in the body. Tissue-specific stem cells (sometimes called adult or somatic stem cells) arise later in development. They also can replenish cells. The primary role of tissue-specific stem cells is to maintain and repair the tissue in which they’re found.

How do problems in cells lead to disease?

Changes to the genes inside a cell, called mutations, can alter the cell’s ability to divide, make proteins, remove waste, or perform other tasks. These genetic mutations can lead to birth defects, cancer, and other diseases. Cells that are damaged through physical trauma or infection can, in extreme cases, contribute to harmful inflammation and organ malfunction.

How does studying cells aid our understanding of human health and disease?

Learning about how cells work—and what happens when they don’t work properly—teaches us about the biological processes that keep us healthy. It also uncovers new ways to treat disease. Cellular research has already led to cancer treatments, antibiotics, medicine that lowers cholesterol, and improved methods for delivering drugs. However, much more remains to be discovered. For example, understanding how stem cells and certain other cells regenerate could offer insight on how to repair damaged or lost tissue.

This image shows the uncontrolled growth of cells in the second most common form of skin cancer, squamous cell carcinoma. Credit: Markus Schober and Elaine Fuchs, The Rockefeller University, New York, N.Y.

Learn More

NIGMS is a part of the National Institutes of Health that supports basic research to increase our understanding of biological processes and lay the foundation for advances in disease diagnosis, treatment, and prevention. For more information on the Institute’s research and training programs, visit https://www.nigms.nih.gov.

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National Institute of General Medical Sciences (NIGMS)

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The National Institute of General Medical Sciences (NIGMS) supports basic research that increases understanding of biological processes and lays the foundation for advances in disease diagnosis, treatment, and prevention.​

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Natural and Human Impacts on Wildlife Article (from Nature Works)

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Natural and Human Impacts on Wildlife Article (from Nature Works)

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Natural and Human Impacts on Wildlife - NatureWorks

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Humans are now responsible for causing changes in the environment that hurt animals and plant species. We take up more space on Earth for our homes and cities. We pollute habitats. We illegally hunt and kill animals. We bring exotic species into habitats. All of these activities take resources and h…

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Human Impact on Marine Environments Article (from Science Learning Hub)

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Human Impact on Marine Environments Article (from Science Learning Hub)

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Throughout human existence we have relied on the oceans - for food, as a waste dump, for recreation, for economic opportunities and so on. However, it's not only our activities in the marine environment that affect life in the sea - it's also the things we do on land.

With more than half the world's population now living within 100 kilometres of the coast, it's not surprising that our activities are taking their toll. Human impacts have increased along with our rapid population growth, substantial developments in technology and significant changes in land use. Over-fishing, pollution and introduced species are affecting life in the sea - and New Zealand is no exception!

Fisheries

Humans living near the coast have probably always used the ocean as a source of food. However, with advances in fishing equipment, larger ships and new tracking technologies, many fish stocks around the world have reduced significantly. Fish stocks on continental shelf areas are now widely considered to be fully or over exploited. Aside from reducing fish stocks, unsustainable fishing practices can have other negative impacts on the marine environment. For example, some fishing techniques such as dredging and trawling can cause widespread damage to marine habitats and organisms living on the sea floor. These techniques also often capture non-target species (known as bycatch) that are then discarded.

In New Zealand, fisheries are managed by a quota system that sets catch limits for commercially important species and aims at sustainable management of our fish stocks. The Royal Forest and Bird Protection Society (NZ) publishes the Best Fish Guide to try and encourage us to make more sustainable choices when purchasing seafood. The list evaluates fish stocks and bycatch levels and the fishing methods used.

Pollution

Our oceans have long been used as an intentional dumping ground for all sorts of waste including sewage, industrial run-off and chemicals. In more recent times, policy changes in many countries have reflected the view that the ocean does not have an infinite capacity to absorb our waste. However, marine pollution remains a major problem and threatens life in the sea at all levels.

Some marine pollution may be accidental, for example, oil spills caused by tanker accidents. Some may be indirect, when pollutants from our communities flow out to sea via stormwater drains and rivers. Some effects may not be immediately obvious, for example, bioaccumulation - the process where levels of toxic chemicals in organisms increase as they eat each other at each successive trophic level in the food web.

All marine pollution has the potential to seriously damage marine habitats and life in the sea. Scientists are concerned that marine pollution places extra stress on organisms that are already threatened or endangered.

Eutrophication

Eutrophication is the result of a particular type of marine pollution. It is caused by the release of excess nutrients into coastal areas via streams and rivers. These nutrients come from fertilisers used in intensive farming practices on land. Additional nutrients in the sea can lead to excessive phytoplankton growth that results in 'blooms'. When these large numbers of organisms die, the sharp increase in decomposition of the dead organisms by oxygen-using bacteria depletes oxygen levels. In some cases, this can result in the death by oxygen starvation of large numbers of other organisms such as fish.

Introduced species

Since the arrival of humans in New Zealand, introduced species in our terrestrial ecosystems have contributed to a significant loss of biodiversity. Introduced species also present a threat to our marine environment. It is not always easy to monitor or prevent the introduction of unwanted marine organisms, and visiting ships may introduce them accidentally on their hulls, in ballast water or on equipment.

Not all introduced species will spread or even survive, but once established, they may be difficult or impossible to remove. For example, the Japanese seaweed, wakame Undaria pinnatifida, which probably arrived in 1987, is now widespread. Scientists are still monitoring its impact on our native marine organisms.

In New Zealand, the Ministry of Primary Industries is responsible for providing border inspectors who manage risks from people, planes, vessels (like ships) and goods coming into the country. They also coordinate responses when new, harmful pests and diseases are detected in our country.

Nature of science

Ocean acidification

There is evidence to suggest that human activities have caused the amount of carbon dioxide in our atmosphere to rise dramatically. This impacts on the marine environment as the world's oceans currently absorb as much as one-third of all CO ₂ emissions in our atmosphere. This absorption of CO ₂ causes the pH to decrease, resulting in the seawater becoming more acidic.

Scientists have long understood that an increase in carbon dioxide in the atmosphere will result in higher levels of dissolved CO ₂ in seawater. However, a relatively recent discovery is that even small changes in water pH can have big impacts on marine biology. Ocean acidification is a worldwide issue, but as CO ₂ is more soluble in colder water, it is of particular concern in New Zealand's temperate oceans.

It is difficult to predict the overall impact on the marine ecosystem but many scientists fear that ocean acidification has the potential to decrease marine biodiversity on a very large scale.

New Zealanders are aware that old ways of managing our seas are in need of a rethink. The Sustainable Seas National Science Challenge is tasked with helping New Zealand enhance the value of our marine resources while ensuring they are safeguarded for future generations.

Related content

Useful links

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Throughout human existence we have relied on the oceans - for food, as a waste dump, for recreation, for economic opportunities and so on. However, it's not only our activities in the marine environment that affect life in the sea - it's also the things we do on land.

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Human impacts on ecosystems | Interactions in ecosystems | High school biology | Khan Academy

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Human Activities Affecting Ecosystems Article (from Science News for Students)

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Human Activities Affecting Ecosystems Article (from Science News for Students)

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Only 3 percent of Earth’s land is unchanged by people

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A sweeping survey of land-based ecosystems finds that very few still support all the animals they used to. Reintroducing lost species could help.

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