Name: carbon backbones in biomolecules
Uploaded: 2019-03-11T09:20:59.000Z
Duration: 1 min 12 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

Carbon Skeletons

有机化合物
 
 含有碳原子的结构主链
 
 称为碳骨架
 
 碳元素最多可形成四个键
 
 有助于其灵活性
 
 例如甲烷 仅含有一个碳原子
 
 和四个单键 是最简单的碳氢化合物
 
 随着碳原子增多
 
 链延长形成新分子
 
 每增加一个碳原子 骨架就可以形成
 
 分支侧链 比如异己烷
 
 或者保持笔直不分支 比如己烷
 
 此外 这些结构中可能在不同位置
 
 含有双键 形成己烯
 
 甚至形成环形
 
 比如环己烯

碳骨架

所有有机化合物的骨架都是碳骨架。每个碳原子可以形成四个键，随着碳骨架长度的增加，结构变化的可能性就会出现，比如环结构、双键和分支侧链。

<h4>碳是有机分子的基础</h4>
 
地球上的生命是以碳为基础的，因为构成生物体的所有大分子都依赖于碳原子。每个有机分子的核心是一个碳骨架，其它原子与之结合。其它原子的多样性赋予每个分子独特的性质。碳可以形成四个键，很少成为离子，使其成为分子中非常灵活的成分。这些特性使碳成为地球上所有生命的重要组成部分，不仅在这个星球上，而且在整个宇宙中都发现了丰富的碳。
 
碳-碳键构成碳骨架的基础。氢原子容易与碳原子结合。只含有氢和碳的分子叫做碳氢化合物。碳氢化合物通常形成长链或在不同的点上有突出的分支。改变键的数量会改变分子的性质：例如，具有一个或多个双键的长烃尾的脂肪酸的行为与没有双键的脂肪酸不同。
 
 <h4>同分异构体是排列相同数量原子的不同方式</h4>
 
化学式相同但结构不同的分子称为同分异构体。同分异构体的一个例子可以在两个共享化学式C6H14的不同分子中看到。正己烷有一条直的碳原子链，而异己烷在第二个碳原子上有一个支点。其它异构体在碳-碳双键的两侧可能有不同的化学基团排列，从而产生两种可能的结构。其它的可能仍然是彼此的镜像，也称为对映体。就像左手和右手的手指和大拇指一样，对映体的部分都是一样的，但叠加时它们不会排成一行。
 
 <h4>碳架上的官能团</h4>
 
生物分子的独特性质是由与碳骨架结合的官能团，如氨基（NH2）或（CH3）赋予的。官能团可以由碳以外的原子组成，改变分子的结构和化学性质。官能团之间的相互作用对于生物系统中几乎所有的事情都是至关重要的，对官能团性质的了解影响到许多领域的研究，例如合成药物的设计。

地球上的生命以碳为基础，因为构成生物体的所有大分子都含有碳原子。所有有机化合物都具有碳骨架。

Education

教育

JoVE Core

Biology

生物学

Fundamentals

基础知识

Chemistry of Life

生命化学

KEY TERMS AND CONCEPTS

关键术语与概念

carbon backbones in biomolecules

Carbon backbones give biological molecules their structure and flexibility. Living things are built from macromolecules that contain carbon atoms, and organic compounds are defined by a carbon backbone. Carbon is tetravalent, so each carbon atom can bond with four other atoms. Its valence electrons are stable, so carbon rarely becomes an ion.

As carbon chains get longer, they can form ring structures, double bonds, and branching side chains. Carbon-carbon bonds create the carbon skeleton. Hydrogen atoms bond readily to carbon, and molecules made only of hydrogen and carbon are called hydrocarbons. These hydrocarbons often form long chains or have branches at different points.

Changing the number of bonds changes a molecule’s properties. A fatty acid with a long hydrocarbon tail and one or more double bonds behaves differently from a fatty acid with no double bonds. The same chemical formula can also produce different structures. Molecules with the same formula but different arrangements are called isomers, and an example is C6H14, where hexane is a straight chain and isohexane has a branch on the second carbon atom.

Some isomers are mirror images of each other. These are called enantiomers. Carbon skeletons also gain unique properties from functional groups attached to them. Examples include amino groups (–NH2) and methyl groups (–CH3), which can change a molecule’s structure and chemical behavior. These effects matter in areas such as synthetic drug design.

Carbon Backbones in Biomolecules

the periodic table and organismal elements

the-periodic-table-and-organismal-elements

Periodic Table Basics for Living Things

The periodic table helps explain which elements living things need and how those elements are related. Elements are the smallest units of matter that cannot be broken down further by chemical processes. There are 118 known elements, but not all occur naturally, and even fewer are essential for life. Living matter is made mostly of carbon, nitrogen, hydrogen, and oxygen. Together, these elements make up most of the human body and are also found in all life on Earth. Smaller amounts of calcium,...

atomic structure

Atoms and Their Subatomic Particles

Atoms are the smallest units of elements, and they make up all matter. Each atom contains three subatomic particles: protons, neutrons, and electrons. These particles give an atom its mass and its charge. The idea that matter is made of tiny particles goes back to Democritus, a Greek philosopher around 450 B.C. He used the word atomos, which means “indivisible.” The idea was not accepted at the time, but it returned many centuries later. In the 19th century, John Dalton proposed an atomic...

isotopes

Atomic Mass and Isotope Basics

Atomic mass and isotopes are linked by the number of protons and neutrons in an atom. The number of protons sets an element’s atomic number, or Z. For example, every atom with eight protons is oxygen. Atoms of the same element can still differ because they can have different numbers of neutrons. The mass number, or A, is the total of protons and neutrons. Atoms with the same atomic number but different mass numbers are called isotopes. Elements can have several isotopes. Carbon-12, carbon-13,...

electron behavior

Electron Shells and Valence Electrons

Electrons are negatively charged subatomic particles that occupy regions around the positively charged nucleus of an atom. Their location is linked to energy levels called shells. They are also grouped into sub-shells and orbitals within each shell. An electron’s shell shows its general energy level. Electrons closer to the nucleus have less energy, while electrons farther away have more energy. The sub-shell gives a more exact location and energy level. An orbital is the shape of the region...

electron orbital model

Electron Orbitals and Energy Levels

Electron orbitals show where electrons are most likely to be found around the atomic nucleus. They also help explain energy levels, orbital shapes, and three-dimensional orientation. In an atom, electron location is described first by a shell, or principal energy level. It is then described by a subshell within that shell and by the individual orbitals inside each subshell. The first shell is closest to the nucleus. It has only one subshell and one spherical orbital, called the 1s orbital.

covalent bonds

Electronegativity and Covalent Bond Polarity

Covalent bonds form when two atoms share electrons to fill their valence shells. The way those shared electrons are pulled depends on electronegativity, which is an atom’s ability to attract electrons in a bond. When atoms have similar electronegativities, they form nonpolar covalent bonds. When their electronegativities differ, the bond is polar because the electrons are shared unevenly. The number of covalent bonds an atom can make depends on its valence electrons. Oxygen has six valence...

ionic bonds

Ionic Compounds and Electrolytes

Ionic compounds form when atoms gain or lose electrons to reach a more stable electron configuration. The charged particles that result are called ions. Ionic bonds are electrostatic attractions between oppositely charged ions. The most reactive elements include those with one valence electron, such as potassium, and those that need one more valence electron, such as chlorine. Ions that lose electrons become positive cations. Ions that gain electrons become negative anions. Cations and anions...

hydrogen bonds

Hydrogen Bonds in Water

Hydrogen bonds in water are weak attractions between atoms that are already part of other chemical bonds. One atom is electronegative, such as oxygen, and carries a partial negative charge. The other is a hydrogen atom that is bonded to another electronegative atom and has a partial positive charge. These attractions form because hydrogen has very weak electronegativity when it binds with a strongly electronegative atom like oxygen or nitrogen. The electrons in that bond are shared unequally.

van der waals interactions

Intermolecular Forces in Polar Solutions

Intermolecular forces are the attractions and repulsions that act between atoms and molecules. These electrostatic forces come from particles with permanent, partial, or temporary charges. For neutral atoms and molecules, the main types are ion-dipole, dipole-dipole, and dispersion forces, which are together called van der Waals forces. Polar molecules have a partial positive end and a partial negative end. That separation of charge creates a dipole. In water, oxygen is more electronegative...

elements and compounds

Elements, Compounds, and Bonding

Elements and compounds are the two main kinds of pure substances. A pure substance contains only one kind of matter. An element contains only one type of atom. A compound contains two or more types of atoms joined by a chemical bond. Elements can be atomic or molecular, depending on their basic units. They are unique forms of matter with specific chemical and physical properties. Ordinary chemical reactions cannot break an element into a smaller substance. There are 118 elements, but only 98...

molecular shapes

Electron Geometry and Lone Pairs

Electron geometry and lone pairs help explain why molecules take specific shapes. The arrangement of electron groups around a central atom controls the molecular geometry. Valence electrons form bonding pairs, which sit mainly between bonded atoms, or lone pairs, which belong to one atom only. Electron pairs in the valence shell spread out to reduce repulsion. They do this by maximizing the distance between one another. A diatomic molecule has two regions of electron density, and these are...

pH Scale in Everyday Solutions

pH measures how acidic or basic a water-based solution is. It depends on the concentration of hydronium ions, H3O+, in the solution. In one liter of pure water at neutral pH, there are 1×10−7 moles of hydronium ions. Because hydronium ion levels can vary over a very wide range, measuring pH directly in moles is not practical. The pH scale converts hydronium ion concentration into a negative logarithm. Pure water has a pH of 7 and is neutral. Most solutions fall between 0 and 14, but some, such...

chemical reactions

Atoms, Bonds, and Chemical Reactions

Chemical reactions rearrange atoms to form new substances. In a reaction, the starting materials are called reactants, and the new substances are called products. The atoms stay the same type and number, but their bonds change, so the substances become different compounds. During a chemical reaction, bonds between atoms break and form again. This means the shared electrons are rearranged. Some reactions happen on their own, while others need an energy source such as heat or light. In biology,...

redox reactions

Electron Transfer in Redox

Redox reactions are chemical reactions that involve electron transfer between atoms or molecules. When one particle gains electrons, another must lose them at the same time. That is why oxidation and reduction always happen together. The two roles in a redox reaction are linked. The atom that is oxidized acts as the reducing agent, or reductant. The atom that is reduced acts as the oxidizing agent, or oxidant. A simple way to remember the ideas is OIL-RIG, which means oxidation is losing...

cohesion

Water Molecules and Surface Tension

Water molecules stick to each other through cohesion. Water is neutral overall, but it is a polar molecule. The oxygen atom in one water molecule has a partial negative charge, and it can bind with a hydrogen atom that has a partial positive charge in another water molecule. This forms a hydrogen bond. Each water molecule can form up to four hydrogen bonds with other water molecules, and these bonds give water its cohesive nature. Cohesion helps water form droplets on a surface. Water does not...

adhesion

Water Climbing by Adhesion

Water can climb or stick to surfaces because of adhesion, which is the attraction between different kinds of molecules. In water, this is easy to see on polar surfaces such as glass or cellulose in plants. The positive hydrogen side of water is more attracted to the negative oxygen in silica than to nearby water molecules. This attraction helps explain capillary action. If a narrow glass tube is placed in a beaker of water, water molecules attach to the tube’s surface and the water level rises.

states of water

Water Phase Changes and Ice Density

Water changes between solid, liquid, and gas states as temperature and molecular motion change. In this lesson, the focus is on how water freezes, melts, vaporizes, and returns to liquid or solid form. The balance between intermolecular forces, which pull molecules together, and kinetic energy, which pushes them apart, controls each state. Water freezes when intermolecular forces become stronger than kinetic energy. Unlike most substances, ice is less dense than liquid water. This happens...

specific heat

How Specific Heat Affects Temperature

Specific heat capacity describes how much energy a substance needs to rise by 1 degree Celsius for each gram. It is often written with calories, grams, and degrees Celsius, but it can also be shown in joules, kilograms, and Kelvin. For water, 1 gram needs 1 calorie to increase by 1°C, which is also written as 1 cal/g-°C or 4186 J/kg/K. Water has a high specific heat capacity, so it takes in a large amount of heat before its temperature changes much. It also gives off a lot of heat when it...

vaporization

Vaporization, Boiling, and Evaporation

Vaporization changes a liquid into vapor when temperature adds enough kinetic energy to overcome intermolecular forces. It is a surface phenomenon, which means it starts at the liquid’s surface. The energy needed to vaporize a set amount of liquid at a given pressure and constant temperature is called the heat of vaporization. Water shows this process clearly. When liquid water is vaporized, it becomes steam. One way this happens is boiling, which occurs when vapor bubbles form beneath the...

solvents

Water as a Biological Solvent

Water acts as a biological solvent in many living systems. A solvent is a substance, usually a liquid, that dissolves another substance called a solute. When a solvent and a solute mix, they form a solution, which is a uniform mixture of both parts. Water is called a universal biological solvent because its polar structure helps it dissolve many other polar compounds. Polarity means that one side of the molecule has a slight positive charge and the other side has a slight negative charge.

carbon skeletons

Carbon backbones give biological molecules their structure and flexibility. Living things are built from macromolecules that contain carbon atoms, and organic compounds are defined by a carbon backbone. Carbon is tetravalent, so each carbon atom can bond with four other atoms. Its valence electrons are stable, so carbon rarely becomes an ion. As carbon chains get longer, they can form ring structures, double bonds, and branching side chains. Carbon-carbon bonds create the carbon skeleton.

key terms and concepts

Learn how carbon chains build organic molecules, how isomers differ in structure, and how functional groups like amino and methyl groups change properties.

Carbon Backbones in Biomolecules | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

biology

JoVE Core系列通过300多节动画视频课简明易懂地讲解生物学中的关键概念，以及150余段视频展示科学家在现代实验室开展实际研究实验，让生物学变得平易近人。

Florida Department of Education

Physical Science

SC.912.P.8

SC.912.P.8.12

myJoVE Corporation

Characteristics of Life

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protein-complexes-with-interchangeable-parts

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HS-LS1-1

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HS-LS1-2

Carbon Backbones in Biomolecules

Description

Transcript

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