Biology is designed for multi-semester biology courses for science majors. It is grounded on an evolutionary basis and includes exciting features that highlight careers in the biological sciences and everyday applications of the concepts at hand. To meet the needs of today’s instructors and students, some content has been strategically condensed while maintaining the overall scope and coverage of traditional texts for this course. Instructors can customize the book, adapting it to the approach that works best in their classroom. Biology also includes an innovative art program that incorporates critical thinking and clicker questions to help students understand—and apply—key concepts.

By the end of this section, you will be able to:Explain the processes of digestion and absorptionCompare and contrast different types of digestive systemsExplain the specialized functions of the organs involved in processing food in the bodyDescribe the ways in which organs work together to digest food and absorb nutrients

Chemical reactions play an important role in our digestive system. This activity will allow you to observe one of those reactions, known as a decomposition reaction.  Decomposition is a reaction that breaks down a complex substance into simpler substances. You will be using the enzyme amylase to break down a starch into a simple sugar. This lab will simulate what is happening in your mouth when your saliva (which contains the enzyme amylase) begins to break down the complex carbohydrate starch.

The digestive system is amazing: it takes the foods we eat and breaks them into smaller components that our body can use for energy, cell repair and growth. This lesson introduces students to the main parts of the digestive system and how they interact. In addition, students learn about some of the challenges astronauts face when trying to eat in outer space.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Liver ischemia and reperfusion injury (IRI) is a major cause of liver transplant failure. Such injuries involve many inflammatory processes and activate liver macrophages. Activation of the Notch1 protein and the Notch pathway modulate inflammatory responses, but the exact molecular mechanisms at play are not yet understood. To narrow this gap, a recent study investigated macrophage Notch1 in a mouse model of liver IRI. Liver ischemia and reperfusion activated the Notch1 protein in liver macrophages, and knocking out the Notch1 gene from macrophage precursors worsened the damage and increased inflammation. Macrophage Notch1 deficiency also inhibited the expression of β-catenin. This led to a TAK1-mediated inflammatory response and RIK3-mediated hepatocyte necroptosis, a type of inflammatory cell rupture. Restoring Notch1 to macrophages using lentivirus alleviated the liver damage in this knockout model and reduced some of the inflammatory response..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

The most recent knowledge of the anatomy, physiology, biochemistry, biophysics, and bioengineering of the gastrointestinal tract and the associated pancreatic, liver and biliary tract systems is presented and discussed. Gross and microscopic pathology and the clinical aspects of important gastroenterological diseases are then presented, with emphasis on integrating the molecular, cellular and pathophysiological aspects of the disease processes to their related symptoms and signs.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Salmon are famous for their swims upriver to spawn. Many people focus on this amazing feat of stamina, but even more remarkable is their ability to switch from living in freshwater to seawater, and back again. Most fish make their homes in just one type of water. So how do salmon do it? A team of biologists at Skidmore College, the U.S. Geological Survey, and the University of Gothenburg recently uncovered changes in the expression of certain genes that explain in part how Atlantic salmon make the transition. Atlantic salmon are born in freshwater, and between the ages of one and four migrate downstream to the sea. Before starting this migration, the fish undergo a months-long process preparing them for life in seawater. This is called smoltification. During this time, fish develop gill cells called ionocytes that contain specialized proteins that pump out excess salt..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Cirrhosis is a chronic disease involving permanent scarring of the liver And it's currently the 11th leading cause of death worldwide In its most advanced form, the disease impairs kidney function, causing what’s known as hepatorenal syndrome While inflammation is believed to play a role in cirrhosis No studies have examined the link between inflammation and hepatorenal syndrome until now Researchers from Spain tracked inflammation responses in 161 patients hospitalized for advanced cirrhosis Patients who developed hepatorenal syndrome showed a much stronger inflammatory response than those without the disease The relatively small patient sample means that these results should be interpreted with caution But the findings could still provide meaningful clues for treating patients with cirrhosis Helping doctors identify potential targets for slowing disease progression Solé et al..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"The intestinal tract is home to a variety of microbes that live in a delicate balance with their host. Although this symbiosis is well-studied for bacteria, gut fungi (mycobiota) are often neglected due to their lower abundance in the gut microbiome. While fungi are traditionally investigated using culture-dependent methods, next-generation sequencing has allowed for more in-depth understanding. Fungi may colonize the gut as soon as birth, and the gut mycobiota can be affected by many factors throughout life, such as the environment, diet and nutrition, and the seasons. Gut fungi regulate many physiological functions in their hosts, including metabolism, control of aging, and disease progression. Immune homeostasis, in particular, is linked to gut mycobiota, and fungi can affect both innate and adaptive immune responses in the gut. Gut mycobiota have also been linked with intestinal diseases, and imbalanced fungal community composition can alter intestinal homeostasis..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Autoimmune hepatitis (AIH) is a chronic immune-mediated liver disease that’s often treated with the steroid prednisone. Gut microbiome disruption and immune follicular T helper (Tfh) cells play important roles in AIH pathogenesis and progression but how microbes and Tfh cells interact in the context of AIH and prednisone treatment remains unclear. A recent study investigated the effects of both probiotic and prednisone treatment on Tfh cells and AIH indicators. In both human patients and mice, the probiotic Lactobacillus significantly increased the abundance of beneficial gut bacteria and in humans, Lactobacillus enhanced prednisone’s ameliorative effects on clinical AIH indices, such as the serum levels of liver damage–related enzymes. In mice with experimental AIH (EAH), Lactobacillus and prednisone both exerted similar effects, decreasing intestine and liver injury and Lactobacillus again improved prednisone efficacy, reducing the circulating levels of liver damage markers..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

The liver (hepar) is an extremely important organ in the body of mammals and vertebrates as it provides functions essential for life. It is the largest internal organ and has numerous functions including production of bile and protein, fat and carbohydrate metabolism. During foetal development, the liver has an important haemopoetic function, producing red and white blood cells from tissue between the hepatic cells and vessel walls.

Students learn the function of the liver and how biomedical engineers can use liver regeneration to help people. Students test the effects of toxic chemicals on a beef liver by adding hydrogen peroxide to various liver and salt solutions. They observe, record and graph their results.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Cancer involves the reprogramming of the body’s cells to allow them to grow, divide, and travel throughout the body. One of the processes involved – metabolic reprogramming – allows cells to use new energy sources for fuel, switching from oxidative phosphorylation to glycolysis. and enabling tumor cells to grow uncontrolled. A recent study evaluated the involvement of the tumor suppressor gene PTEN in metabolic reprogramming. Researchers compared cancerous and noncancerous liver tissue from 128 patients with hepatocellular carcinoma. They found that in cancerous liver tissue, PTEN had a reciprocal relationship with another protein, PI3K. PTEN was downregulated in HCC tissues, and its loss predicted a poor prognosis. Overexpressing PTEN blocked the switch to glycolysis, while elevated PI3K expression was observed in HCC tissues and was inhibited by PTEN overexpression..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"In the US and east Asia, non-alcoholic fatty liver disease (NAFLD) affects at least a quarter of the population. This disease is the manifestation of metabolic syndrome in the liver and can progress to non-alcoholic steatohepatitis (NASH). The gut microbiome is likely a contributing factor in NAFLD development and progression. Recently, researchers sought to identify the mechanisms that link the two together. They used a high-fat/fructose/cholesterol diet (HFC) to induce NALFD-like symptoms in mice and found that adding the prebiotic inulin to their diet ameliorated these symptoms. Inulin-fed mice had global changes to their microbiome, particularly elevated levels of the bacterial groups Bacteroides and Blautia. Inulin supplementation also increased their gut concentrations of short-chain fatty acids, like acetate. Further experiments found that species from Bacteroides and Blautia had a synergistic effect on acetate production..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Alzheimer’s disease is the sixth leading cause of death and one of the most prevalent forms of dementia, affecting over 50 million people worldwide. Unfortunately, the molecular signaling pathways underlying neurodegeneration in Alzheimer’s disease are not clearly understood. A recent study identified a link between two physiological phenomena that are affected in Alzheimer's disease: disrupted calcium signaling, which is associated with memory loss and cognitive dysfunction; and increased iron accumulation, which results in neurotoxicity in the brain. Using genetically modified human cell lines and mice, the researchers studied the mechanistic connections between calcium signaling and iron transport. They found that calcium (Ca²⁺) signaling through CAMKK2 and CAMK4 proteins had direct effects on transferrin protein-mediated iron transport..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related death worldwide. Despite advancements in HCC diagnosis and treatment, current staging systems lack specificity and can’t easily predict patient survival. Researchers now report a new prognostic and diagnostic approach based on tracking genes that control iron metabolism in the body. Iron is critical for normal cell metabolism, growth, and proliferation. That goes extra for tumor cells, which have an increased demand for iron. But too much iron can lead to cell death—a process known as “ferroptosis”—which some researchers are harnessing to eliminate harmful cancer cells. In the current study, researchers used high-throughput sequencing to identify genes associated with iron metabolism and ferroptosis in patients with HCC. Based on four genes, patients could be divided into a low-risk group and a high-risk group with poorer overall survival and HCC samples could be distinguished from normal samples..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"The gut microbiota influences many physiological processes in mammals, and disruption of this diverse bacterial community can impair liver function, leading to disease. However, the molecular mechanisms of gut microbiota–intestine–liver communication are unclear. By analyzing public hepatic transcriptomics datasets, researchers recently identified pregnane X receptor (PXR) as a regulator of many differentially expressed genes in microbe-free vs. normal mice. The PXR target genes were largely associated with xenobiotic metabolism. Additional experiments in mice revealed that PXR deletion induced sex-specific changes in gut microbiota composition and hepatic gene expression. Microbiota depletion with antibiotics also induced PXR-dependent alterations in hepatic gene expression that differed between male and female mice. Further studies in male mice confirmed that elimination of the microbiota altered hepatic lipid and xenobiotic metabolism, and this effect was dependent on the presence of PXR..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.