Name: lipids, fats, and cell membranes
Uploaded: 2020-09-24T15:06:53.000Z
Duration: 3 min 38 s
Channel: JoVE

K12 Standards

Next Generation Science Standards

High School

Life Science

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

HS-LS1-6

Structure of Lipids

الليبيدات مجموعة من الجزيئات الكارهة للماء ومنها الدهون الثلاثية،المُستخدمة لتخزين الطاقة،والدهون الفوسفورية،وهي مكوّنات أساسية لبنية أغشية الخلايا. تتكون الدهون الثلاثية ومعظم الدهون الفوسفورية من غليسرول وسلاسل من الأحماض الدهنية. تحتوي الأحماض الدهنية على مجموعات ميثيل على أحد طرفي السلسلة ومجموعات كربوكسيل على الطرف المقابل.يُسمى الكربون المتصل بمجموعة الكربوكسيل كربون ألفا،ويُعرف الكربون المتصل بمجموعة ميثيل بكربون أوميغا. تتفاوت الأحماض الدهنية من حيث طول سلسلة الهيدروكربون،ومن حيث وجود روابط ثنائية فيها. الأحماض التي فيها روابط ثنائية هي أحماض دهنية غير مشبعة،وتلك التي فيها روابط أحادية هي أحماض دهنية مشبعة،لأنها تشبع بأكبر عدد ممكن من ذرات الهيدروجين.غالبًا ما تشترك الأحماض الدهنية في الأسماء،ولكن يمكن تسميتها بصورة منتظمة وفقًا لعدد ذرات الكربون،وكذلك عدد وموضع الروابط الثنائية في السلسلة الكربونية. توجد عدة طرق للترقيم. النظام الذي يعتمد الكربوكسيل،يعدّموضع جميع الروابط الثنائية من الكربون الكربوكسيلي،والذي يأخذ الرقم 1.أما النظام الذي يعتمد أوميغا،فيعدّموضع الرابطة الثنائية الأقرب إلى كربون أوميغا،بحيث يأخذ كربون أوميغا الرقم 1. على سبيل المثال،حمض اللينولينيك،وهو حمض دهني من فئة أوميغا-3،يحتوي على 18 ذرة كربون وروابط ثنائية عند موضعي 9 و 12 و 15،إذا بدأنا العد من جهة الكربوكسيل. هذا سيُسمى 18:3 دلتا 9،12،15 وفقًا للنظام الذي يعتمد الكربوكسيل ويُسمى 18:3 أوميغا 3،وفقًا للنظام الذي يعتمد أوميغا.يمكن أن توجد الأحماض الدهنية في تشكيلين:المقرون والمفروق. في التشكيل المقرون،تكون ذرتي الهيدروجين على الكربون المشارك في الرابطة الثنائية في الطرف ذاته من الرابطة،بينما في التشكيل المفروق،تكون ذرات الهيدروجين على الطرفين المتقابلين. من حيث البنية،الأحماض الدهنية المقرونة تشكّل سلاسل منحنية،بينما تشكّل الأحماض الدهنية المفروقة سلاسل مستقيمة.تبيّن أن تناول الدهون المفروق هو المسؤول عن العديد من أمراض القلب والأوعية الدموية،بينما يُعرف تناول الأحماض الدهنية المقرونة،مثل أوميغا-3 وأوميغا-6 على أنه مفيد للصحة. تُستخدم الدهون الثلاثية،أو المعروفة عمومًا بالدهون،و تستخدم بصورة أساسية في تخزين الطاقة. تتكون من ثلاثة أحماض دهنية متصلة بالجليسرول عبر روابط إسترات بين الأطراف الهيدروكسيلية للجليسرول والأطراف الكربوكسيلية للأحماض الدهنية،متسببة بتشكيل جزيء غير قطبي.إذا كانت الأحماض الدهنية الثلاثة من نوع واحد،تُعرف بالدهون الثلاثية البسيطة. أما إذا اختلفت الأحماض الدهنية الثلاثة،فتُعرف بالدهون الثلاثية المختلطة. نوع آخر من الليبيدات،وهو الليبيدات الفوسفورية،يُشكّل سمة بنيوية مهمة للأغشية البيولوجية.تحتوي على رؤوس محبة للماء تتكون من مجموعات فوسفات معدّلة مع مجموعات كحول محبة للماء،وذيول أحماض دهنية كارهة للماء. يمكن أن يتفاوت تركيب هذه الرؤوس والذيول،فينتج عن ذلك أنواع مختلفة من ليبيدات الأغشية. ليبيدات الجلسيروفوسفوليبيد،هي نوع شائع من الليبيدات الفوسفورية،يتكون من حمضين دهنيين ومجموعة ذات قطبية عالية مرتبطة بكل ذرة كربون من ذرات الجليسرول،بواسطة إسترات أو روابط فوسفات ثنائي الإستر،على التوالي.

هيكلية الدهون

تشتمل الدهون على مجموعة متنوعة من المركبات ذات الطبيعة غير القطبية إلى حد كبير. هذا لأنها هيدروكربونات تتضمن في الغالب روابط كربون-كربون غير قطبية أو روابط كربون-هيدروجين. الجزيئات غير القطبية كارهة للماء (“كره للماء”) ، أو غير قابلة للذوبان في الماء. تؤدي الدهون وظائف مختلفة في الخلية. تخزن الخلايا الطاقة للاستخدام طويل الأمد في شكل دهون. توفر الدهون أيضاً عزلاً عن البيئة للنباتات والحيوانات. على سبيل المثال، تساعد في الحفاظ على الطيور المائية والثدييات جافة عند تكوين طبقة واقية فوق الفراء أو الريش بسبب طبيعتها المقاومة للماء. الدهون هي أيضاً اللبنات الأساسية للعديد من الهرمونات وهي مكون مهم لجميع أغشية الخلايا. تشمل الدهون الشحوم والزيوت والشموع والفوسفوليبيد والستيروئيدات. التركيب العام للدهون يتكون جزيء الدهون من مكونين رئيسيين—الجلسرين والأحماض الدهنية. الجلسرين مركب عضوي (كحول) يحتوي على ثلاث كربون وخمسة هيدروجين وثلاث مجموعات هيدروكسيل (OH). الأحماض الدهنية لها سلسلة طويلة من الهيدروكربونات التي ترتبط بها مجموعة الكربوكسيل، ومن هنا جاء اسم “الحمض الدهني.” قد يتراوح عدد الكربون في الأحماض الدهنية من 4 إلى 36. والأكثر شيوعاً هي تلك التي تحتوي على 12–18 ذرة كربون. في جزيء الدهون، ترتبط الأحماض الدهنية بكل جزيء من جزيئات’ الجلسرين الثلاثة مع رابطة استر من خلال ذرة أكسجين. يؤدي ضم ثلاثة أحماض دهنية إلى العمود الفقري للجليسرول في تفاعل التجفاف إلى تكوين ثلاثي الجلسرين. قد تكون الأحماض الدهنية الثلاثة في ثلاثي الجلسرين متشابهة أو غير متشابهة. الفوسفوليبيد هو نوع شائع آخر من الدهون. إنه جزيء أمفيباثي، مما يعني أنه يحتوي على جزء كاره للماء وجزء محب للماء. سلاسل الأحماض الدهنية كارهة للماء ولا يمكنها التفاعل مع الماء؛ في حين أن المجموعة المحتوية على الفوسفات هي محبة ماء وتتفاعل مع الماء. تواجه مجموعات الرأس المحبة للماء من الفوسفوليبيد المحلول المائي. يتم عزل ذيول الكارهة للماء في منتصف الطبقة الثنائية. الأحماض الدهنية قد تكون الأحماض الدهنية مشبعة أو غير مشبعة. في سلسلة الأحماض الدهنية، إذا كان هناك روابط أحادية فقط بين الكربون المتجاور في سلسلة الهيدروكربون، فإن الحمض الدهني يكون مشبعاً. حمض الستيريك (حمض الشمع) مثال على الأحماض الدهنية المشبعة. عندما تحتوي سلسلة الهيدروكربون على رابطة مزدوجة، يكون الحمض الدهني غير مشبع. حمض الأوليك (حمض الزيت) مثال على الأحماض الدهنية غير المشبعة. معظم الدهون غير المشبعة سائلة في درجة حرارة الغرفة وتسمى بالزيوت. إذا كان هناك رابطة مزدوجة واحدة في الجزيء، فهي دهون أحادية غير مشبعة (مثل زيت الزيتون)، وإذا كان هناك أكثر من رابطة مزدوجة واحدة، فهي دهون متعددة غير مشبعة (مثل زيت الكانولا). تتراكم الأحماض الدهنية الطويلة المستقيمة ذات الروابط الأحادية بإحكام وتكون صلبة في درجة حرارة الغرفة. تعتبر الدهون الحيوانية التي تحتوي على حامض دهني وحمض البالميتيك (حمض النخيل) (شائعة في اللحوم) والدهون مع حمض البوتيريك (حمض الزبدة) (شائع في الزبدة) أمثلة على الدهون المشبعة. يمكن أيضاً تصنيف الأحماض الدهنية إلى سيس و ترانس. روابط سيس و ترانس تشير إلى تكوين جزيء حول الرابطة المزدوجة. إذا كانت الهيدروجين موجودة في نفس المستوى، فهي عبارة عن دهون سيس. إذا كانت ذرات الهيدروجين على مستويين مختلفين، فهي دهون ترانس. تتسبب الرابطة المزدوجة سيس في حدوث انحناء أو “تعقّد” يمنع الأحماض الدهنية من التعبئة بإحكام، مما يحفظها سائلة في درجة حرارة الغرفة. زيت الزيتون وزيت الذرة وزيت الكانولا وزيت كبد الحوت أمثلة على الدهون غير المشبعة. تساعد الدهون غير المشبعة على خفض مستويات الكوليسترول في الدم. بينما تساهم الدهون المشبعة في تكوين طبقة الصفيحات في الشرايين. الدهون المتحولة تعمل صناعة الأغذية على هدرجة الزيوت صناعياً لجعلها شبه صلبة وذات قوام مرغوب فيه للعديد من المنتجات الغذائية المصنعة. خلال هذه العملية، يتم إنشاء روابط مزدوجة لـ سيس– قد يتحول التشكل في سلسلة الهيدروكربون إلى روابط مزدوجة في تشكل ترانس–. المارجارين وبعض أنواع زبدة الفول السوداني والسمن أمثلة على دهون ترانس المهدرجة صناعياً. أظهرت الدراسات الحديثة أن الزيادة في دهون المتحولة ترانس في النظام الغذائي للإنسان قد تؤدي إلى مستويات أعلى من البروتينات الدهنية منخفضة الكثافة (LDL)، أو الكولسترول “السيئ”، والذي بدوره قد يؤدي إلى ترسب اللويحات في الشرايين، مما يؤدي إلى الإصابة بأمراض القلب. 
 أحماض أوميغا الدهنية الأحماض الدهنية الأساسية هي تلك التي يحتاجها جسم الإنسان ولكنه لا يصنعها. وبالتالي ، يجب استكمالها من خلال تناولها عن طريق النظام الغذائي. تندرج أحماض أوميغا-3 الدهنية ضمن هذه الفئة وهي واحدة من اثنين فقط معروفتان للبشر (الآخر هو أحماض أوميغا-6 الدهنية). هذه أحماض دهنية متعددة غير مشبعة وهي أوميغا-3 لأن الرابطة المزدوجة تربط الكربون الثالث من سلسلة’ الهيدروكربونات بالكربون المجاور لها. حمض ألفا لينولينيك هو مثال على أحماض أوميغا-3 الدهنية. يحتوي على ثلاث روابط سيس المزدوجة، ونتيجة لذلك، لها شكل منحني. يعتبر السلمون والسلمون المرقط والتونة مصادر جيدة لأحماض أوميغا-3 الدهنية. تشير الأبحاث إلى أن أحماض أوميغا-3 الدهنية تقلل من خطر الموت المفاجئ من النوبات القلبية، وتقلل من الدهون الثلاثية في الدم، وتقلل من ضغط الدم، وتمنع تجلط الدم عن طريق تثبيط تخثر الدم. كما أنها تقلل الالتهاب وقد تساعد في تقليل خطر الإصابة ببعض أنواع السرطان لدى الحيوانات. هذا النص مقتبس من <a href="https://openstax.org/books/biology-2e/pages/3-3-lipids">Openstax, Biology 2e, Chapter 3.3: Lipids</a>.

تشمل الدهون مجموعة متنوعة من المركبات غير القطبية إلى حد كبير في الطبيعة. هذا لأنها هيدروكربونات تشمل في الغالب غير قطبية ...

Education

JoVE Core

Chemistry

الكيمياء

واحد

Biochemistry

الكيمياء الحيوية

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

lipids, fats, and cell membranes

Lipids are nonpolar molecules that do not mix well with water. They are hydrophobic, which means “water fearing,” because they contain mostly nonpolar carbon-carbon and carbon-hydrogen bonds. In cells, lipids store long-term energy as fats, help insulate plants and animals, and form protective water-repellent layers on feathers and fur. They are also part of cell membranes and serve as building blocks for many hormones. Common lipids include fats, oils, waxes, phospholipids, and steroids.

A fat molecule is built from glycerol and fatty acids. Glycerol is an alcohol with three carbons, five hydrogens, and three hydroxyl groups. Fatty acids have a long hydrocarbon chain with a carboxyl group attached. Their chains can range from 4 to 36 carbons, but 12 to 18 carbons is most common. In a fat, three fatty acids join to one glycerol backbone through ester bonds in a dehydration reaction. This forms a triacylglycerol. The three fatty acids may be the same or different.

Phospholipids are another major lipid type. They are amphipathic, which means they have both a hydrophobic part and a hydrophilic part. The fatty acid tails repel water, while the phosphate-containing head attracts water. In water, the heads face outward toward the solution and the tails gather in the middle of the bilayer.

Fatty acids can be saturated or unsaturated. Saturated fatty acids have only single bonds between carbon atoms. Stearic acid is one example. Unsaturated fatty acids contain one or more double bonds. Oleic acid is an example, and most unsaturated fats are liquid at room temperature and are called oils. Monounsaturated fats, such as olive oil, have one double bond. Polyunsaturated fats, such as canola oil, have more than one. Straight saturated fatty acids pack tightly, so they are usually solid at room temperature. Animal fats with stearic acid and palmitic acid, as well as butter with butyric acid, are examples.

Unsaturated fatty acids can also be cis or trans. These terms describe the arrangement around a double bond. In cis fats, the hydrogens are on the same plane. In trans fats, they are on different planes. The cis double bond creates a kink that prevents tight packing, which helps keep the fat liquid. Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats. Unsaturated fats tend to lower blood cholesterol levels, while saturated fats can contribute to plaque formation in arteries.

Trans fats are often made by hydrogenating oils to make them more semi-solid for processed foods. During this process, some cis double bonds can change to trans double bonds. Margarine, some peanut butter, and shortening are examples of artificially hydrogenated trans fats. Studies show that more trans fats in the diet can raise low-density lipoproteins, or LDL, the “bad” cholesterol. This can increase plaque buildup in arteries and raise the risk of heart disease.

Omega-3 fatty acids are essential fatty acids, which means the body needs them but does not make them. They must come from the diet. Omega-3s are one of only two known essential fatty acid groups for humans, along with omega-6 fatty acids. They are polyunsaturated, and the name omega-3 means the third carbon from the end is part of a double bond. Alpha-linolenic acid is an example. It has three cis double bonds and a curved shape. Salmon, trout, and tuna are good sources. Research suggests omega-3 fatty acids can reduce the risk of sudden death from heart attacks, lower blood triglycerides, decrease blood pressure, prevent blood clotting, and reduce inflammation. They may also help lower the risk of some cancers in animals.

Lipids, Fats, and Cell Membranes

functional groups

Functional Groups in Organic Chemistry

Functional groups in organic chemistry are groups of atoms that give molecules specific properties. When these groups attach to a carbon skeleton, they can change how the molecule behaves. Some functional groups make a molecule hydrophilic, or water-attracting. Others make it hydrophobic, or water-repelling. Functional groups are a key part of organic chemistry and are also found in major biological molecules. They appear in carbohydrates, proteins, lipids, and nucleic acids. Each functional...

structure of lipids

Lipids are nonpolar molecules that do not mix well with water. They are hydrophobic, which means “water fearing,” because they contain mostly nonpolar carbon-carbon and carbon-hydrogen bonds. In cells, lipids store long-term energy as fats, help insulate plants and animals, and form protective water-repellent layers on feathers and fur. They are also part of cell membranes and serve as building blocks for many hormones. Common lipids include fats, oils, waxes, phospholipids, and steroids. A...

chemistry of the cell

Cell Chemistry: Water and Macromolecules

Cell chemistry includes water, organic molecules, and inorganic ions. These materials shape how cells store energy, build structures, and carry out life processes. Most cellular chemistry and metabolism happen in the watery cytoplasm. Water is a key part of the cell because it has special properties tied to its polarity. In a water molecule, hydrogen and oxygen form polar covalent bonds, so the molecule has no net charge but does have a slightly positive end and a slightly negative end. Oxygen...

dna base pairing

Chargaff’s Rules and DNA Pairing

Chargaff’s rules and DNA base pairing explain how DNA strands match up. In double-stranded DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). Chargaff also found that A equals T, G equals C, and the total amount of purines (A and G) equals the total amount of pyrimidines (C and T). Watson and Crick later showed why these matches matter. A forms two hydrogen bonds with T, while G forms three hydrogen bonds with C. These pairings keep the DNA double helix a...

chemistry of carbohydrates

Carbohydrates as Energy and Storage Molecules

Carbohydrates are important energy sources in human and animal diets. Grains, fruits, and vegetables are natural sources of carbohydrates. They help provide energy to the body, especially through glucose, a simple sugar found in starch and many staple foods. Carbohydrates are identified by the stoichiometric formula (CH2O)n, where n is the number of carbons in the molecule. This means the ratio of carbon to hydrogen to oxygen is usually 1:2:1. The name carbohydrate comes from this pattern,...

protein and protein structure

How Protein Shape Controls Function

Proteins are a major class of organic molecules in living systems, and their shape helps determine what they do. They can act as structural, regulatory, contractile, or protective molecules. They also take part in transport, storage, membranes, toxins, and enzymes. All proteins are polymers of amino acids arranged in a linear sequence. A protein’s function depends on its three-dimensional form. For example, an enzyme works when its active site can bind a specific substrate. If local changes or...

amino acids

Amino Acids and Protein Building

Amino acids are the building blocks of proteins. Each amino acid has the same basic structure. A central carbon atom, called the alpha carbon, is bonded to an amino group, a carboxyl group, and a hydrogen atom. Each amino acid also has an R group, or side chain, attached to the central carbon. The R group is different for every amino acid. It helps determine whether an amino acid is acidic, basic, polar, or nonpolar. Scientists call these molecules amino acids because they contain both amino...

peptide bonds

Peptide Bond Formation and Shape

Peptide bonds join amino acids into peptides and polypeptides. They form when the carboxyl group of one amino acid reacts with the amino group of another. This dehydration reaction releases a water molecule and creates a covalent link. As more amino acids are added, the chain becomes a polypeptide. Each polypeptide has a free amino group at one end. This end is the N-terminal, or amino-terminal. The other end has a free carboxyl group. This end is the C-terminal, or carboxyl-terminal. The...

nucleic acids

DNA and RNA: Genetic Instructions

DNA and RNA are the nucleic acids that store genetic information and help direct cell activity. These macromolecules carry the cell’s genetic blueprint and the instructions it uses to function. DNA is the genetic material in all living organisms, from single-celled bacteria to multicellular mammals. In eukaryotic cells, DNA is found in the nucleus and also in organelles such as chloroplasts and mitochondria. In prokaryotes, DNA is not enclosed in a membrane. The full genetic content of a cell...

dna replication

DNA Copying: Leading and Lagging Strands

DNA replication copies genetic material before a cell divides. Each original DNA strand serves as a template for a new complementary strand. The result is semiconservative replication, which means each new DNA molecule contains one old strand and one new strand. The two daughter cells then receive DNA with the same sequence. Replication starts when helicase separates the two strands of the double helix. This creates a Y-shaped replication fork. Primase then adds short RNA primers that give DNA...

from dna to protein

The Genetic Code and Codons

The genetic code and codons explain how cells turn DNA information into proteins. Genes first direct the sequence of mRNA, and mRNA then directs the sequence of amino acids that make up proteins. Specific proteins and RNAs carry out this decoding. Cells copy DNA into mRNA so the original DNA stays protected while the cell uses the message for protein synthesis. Copying DNA to RNA is relatively simple. One nucleotide is added to the mRNA strand for every nucleotide read on the DNA strand.

polymers

Polymer Chains and How They Form

Polymers are long chains of molecules made from repeating units called monomers. The word polymer comes from the Greek words "poly," meaning many, and "mer," meaning parts. Polymers can be found in nature, such as DNA and proteins, or made synthetically, such as plastics. A polymer’s shape helps define its properties. Some polymers form linear chains, while others are branched or arranged in complex networks. Functional groups on a polymer also affect how it behaves. The repeating units in a...

key terms and concepts

Explore how lipids store energy, build cell membranes, and differ as saturated, unsaturated, trans, and omega-3 fats in high school biology.

Lipids, Fats, and Cell Membranes | JoVE K12

chemistry

JoVE Core Chemistry brings general chemistry concepts to life using concise and easy-to-understand animated video lessons. Plus, in the scientist-in-action videos, we demonstrate classical and original research experiments performed in today's laboratories worldwide.

new-york-state-science-learning-standards

New York State Science Learning Standards

matter-and-energy-in-organisms-and-ecosystems

Matter and Energy in Organisms and Ecosystems

HS-LS1-6.

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

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Cell Structure

Background
Cells represent the most basic biological units of all organisms, whether it be simple, single-celled organisms like bacteria, or large, ...

Visualizing Onion and Cheek Cells
ExpandImmediately before the experiment, wash and peel onion bulbs for the class.
Remove the entire brown outer skin and ...

Visualizing Onion and Human Cells
ExpandIn this experiment you will prepare different types of cells from a plant and animal, onion and human ...

What are Cells?

Cell Diversity

The concept of a cell started with microscopic observations of dead cork tissue by Robert Hooke in 1665. Hooke coined the term &#34;cell&#34; based on the ...

Cytoplasm

The cytoplasm consists of organelles and a framework of protein scaffolds called the cytoskeleton suspended in an aqueous solution, the cytosol. The ...

The Nucleus

The nucleus is a membrane-bound organelle that acts as a control center in a eukaryotic cell. It contains chromosomal DNA, which controls gene expression ...

The Central Dogma

The DNA Helix

Nucleic Acids

DNA as a Genetic Template

Structure of a Gene

A gene is the fundamental unit of heredity. Every individual has two copies of each gene, one inherited from each parent. Although most people contain the ...

Chromosome Structure

Base-pairing and DNA Repair

What is Gene Expression?

A gene is a stretch of DNA that serves as the blueprint for functional RNAs and proteins. Since DNA is comprised&#160; of nucleotides and proteins are ...

RNA Structure

The basic structure of RNA consists of a string of ribonucleotides attached by phosphodiester bonds. Although most RNA is single-stranded, it can form ...

Protein Families

Types of RNA

Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs perform diverse ...

Conservation of Protein Domains

Transcription

Transcription is the synthesis of RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene sequence. ...

Globular and Fibrous Proteins

Translation

Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes ...

Intrinsically Disordered Proteins

Ribosomes

Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that ...

Protein Complex Assembly

Protein and Protein Structures

Conjugated Proteins

Proteins: From Genes to Degradation

Amyloid Fibrils

What are Proteins?

Proteins are polymers of amino acids linked together by peptide bonds. Proteins and polypeptides are interchangeably used to refer to long chains of amino ...

Ligand Binding Sites

Protein Organization

Proteins are polymers of amino acid residues. They are versatile and responsible for different cellular functions, including DNA replication, molecular ...

Protein-Protein Interfaces

Protein Folding

Proteins are chains of amino acids linked together by peptide bonds. Upon synthesis, a protein folds into a three-dimensional conformation, critical to ...

Conserved Binding Sites

Cofactors and Coenzymes

Enzymes are proteins made of amino acids. The functional group of each constituent amino acid catalyzes a wide variety of chemical reactions via ionic ...

Cooperative Allosteric Transitions

Protein Kinases and Phosphatases

GTPases and their Regulation

Covalently Linked Protein Regulators

protein-complexes-with-interchangeable-parts

Protein Complexes with Interchangeable Parts

Mechanical Protein Function

Structural Protein Function

Protein Networks

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells. [Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.]

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Levels of Organization

Biological organization is the classification of biological structures, ranging from atoms at the bottom of the hierarchy to the Earth&#x27;s biosphere. ...

Animal and Plant Cell Structure

Animal and plant cells not only differ in their structure, function, and mode of nutrition but also in how they reproduce, specialize, and organize into ...

structural-organization-of-the-human-body-an-overview

Structural Organization of the Human Body: An Overview

It is convenient to consider the body&#39;s structures in terms of fundamental levels of organization that increase in complexity: subatomic particles, ...

Overview of Human Digestion

The human body contains a monogastric digestive system. In a monogastric digestive system, the stomach only contains one chamber in which it digests food. ...

Anatomy of the Intestines

Although digestion of proteins, carbohydrates, and lipids may begin in the stomach, it is completed in the intestine. The absorption of nutrients, water, ...

Accessory Organs

Accessory organs are those that participate in the digestion of food but do not come into direct contact with it like the mouth, stomach, or intestine do. ...

Lipid Digestion

Lipids are large molecules that are generally not water-soluble. Since most of the digestive enzymes in the human body are water-based, there are specific ...

Protein Digestion

Protein digestion begins in the stomach, where the highly acidic environment can easily disrupt protein structure by exposing the peptide bonds of ...

Carbohydrate Digestion

Carbohydrate digestion and metabolism break down simple and complex carbohydrates from food into saccharides (i.e., sugars) for the body to use as energy. ...

What is a Nervous System?

Overview

The nervous system is the collection of specialized cells responsible for maintaining an organism&rsquo;s internal environment and coordinating ...

The Parasympathetic Nervous System

Overview

The parasympathetic nervous system is one of the two major divisions of the autonomic nervous system. This parasympathetic system is responsible ...

The Sympathetic Nervous System

Overview

The sympathetic nervous system&mdash;one of the two major divisions of the autonomic nervous system&mdash;is activated in times of stress. It ...

Oogenesis

In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from ...

What is a Sensory System?

Sensory systems detect stimuli&mdash;such as light and sound waves&mdash;and transduce them into neural signals that can be interpreted by the nervous ...

Fertilization

During fertilization, an egg and sperm cell fuse to create a new diploid structure. In humans, the process occurs once the egg has been released from the ...

What is the Skeletal System?

Overview

The adult human skeleton comprises 206 bones that are connected through cartilage, tendons, and ligaments. The skeleton provides a rigid ...

an-introduction-to-the-zebrafish-danio-rerio

An Introduction to the Zebrafish: Danio rerio

Zebrafish (Danio rerio) are small freshwater fish that are used as model organisms for biomedical research. The many strengths of these fish include their ...

Physiology of the Circulatory System

Homeostasis
Conditions in the external environment of an organism can change rapidly and drastically. To survive, organisms must maintain a fairly ...

Anatomy of the Circulatory System

The human circulatory system consists of blood, blood vessels that carry blood away from the heart, around the body, and back to the heart, and the heart ...

Measuring Blood Pressure
ExpandTo prepare for the blood pressure exercise, simply place the appropriate number of alcohol swabs, sphygmomanometers, and ...

Anatomy of the Heart

The human heart is made up of three layers of tissue that are surrounded by the pericardium, a membrane that protects and confines the heart. The ...

Measuring Circulatory System Function in Humans
ExpandBefore starting the experiment go to the front of the room and collect an alcohol swab, a ...

Blood Flow

Blood is pumped by the heart into the aorta, the largest artery in the body, and then into increasingly smaller arteries, arterioles, and capillaries. The ...

What Are Osmoregulation and Excretion?

Organisms must keep bodily fluids at a constant temperature and pH while maintaining specific solute concentrations in order to support life functions. ...

Blood Withdrawal I

Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN
Blood collection is a common requirement for ...

Kidney Structure

The kidneys are two large bean-shaped organs located in the upper abdomen. They filter the blood several times a day to remove toxins and rebalance water ...

Blood Withdrawal II

Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN
The collection of blood from mice and rats for ...

What is the Immune System?

Overview

The immune system comprises diverse biological structures and processes that protect the body from disease. These processes can be classified ...

Bone Remodeling

Bone remodeling is a continuous and balanced process of bone resorption by osteoclasts and bone formation by osteoblasts. In adults, it helps maintain ...

Spermatogenesis

Spermatogenesis is the process by which haploid sperm cells are produced in the male testes. It starts with stem cells located close to the outer rim of ...

Bone Structure

Within the skeletal system, the structure of a bone, or osseous tissue, can be exemplified in a long bone, like the femur, where there are two types of ...

Breathing

The process of breathing, inhaling and exhaling, involves the coordinated movement of the chest wall, the lungs, and the muscles that move them. Two ...

Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. [Clarification Statement: Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, and organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.] [Assessment Boundary: Assessment does not include interactions and functions at the molecular or chemical reaction level.]

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What is Homeostasis?

Maintaining homeostasis requires that the body continuously maintain its internal conditions. Each physiological condition has a particular set point, ...

Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. [Clarification Statement: Examples of investigations could include heart rate response to exercise, stomate response to moisture and temperature, and root development in response to water levels.] [Assessment Boundary: Assessment does not include the cellular processes involved in the feedback mechanism.]

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Lipids, Fats, and Cell Membranes

Description

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