Name: lipids in cells: membranes, energy, and signals
Uploaded: 2023-04-30T11:41:03.000Z
Duration: 1 min 31 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Life Science

SC.912.L.18

SC.912.L.18.1

What are Lipids?

Lipids are a diverse group of organic compounds that comprise uncharged hydrocarbon chains, making them hydrophobic and insoluble in water.
Based on the number and type of hydrocarbons, lipids can be grouped into three major categories: triglycerides, phospholipids, and steroids.
Triglycerides, often called fats, are made up of glycerol and three fatty acid chains. Lipids are classified as saturated or unsaturated depending on the presence or absence of double bonds in the fatty acid chain.
Unlike triglycerides, phospholipids have only two fatty acid chains attached to a glycerol molecule. The third fatty acid chain is replaced by a charged phosphate group. The fatty acid chains in a phospholipid can also be saturated or unsaturated.
Phospholipids are amphipathic, meaning they contain both hydrophobic and hydrophilic groups.
Their hydrophilic phosphate heads face the water present outside and inside the cell, whereas the hydrophobic tails face each other to form a bilayer, the cell membrane.
The third type, steroids, such as cholesterol, have a unique structure with a carbon skeleton of four hydrocarbon rings and hence, chemically very different from triglycerides and phospholipids

what are lipids?

Lipids function as structural components of cellular membranes, in addition to acting as energy reservoirs and signaling molecules. They are thus crucial to all living organisms.&#160; The three biologically important classes of lipids are triglycerides, phospholipids, and steroids.
Non-Polar and Hydrophobic Characteristics of Lipids
Lipids are a structurally and functionally diverse group of hydrocarbons&#8212;compounds consisting of carbon and hydrogen atoms. The carbon-carbon and carbon-hydrogen bonds are nonpolar, which means that the electrons between the atoms are shared equally. These nonpolar bonds impart an overall nonpolar characteristic to lipids. Additionally, lipids are hydrophobic or &#8220;water-hating&#8221; in nature. This means they do not form hydrogen bonds with water molecules, rendering them nearly insoluble in water but soluble in organic solvents, such as chloroform or benzene.
Triglycerides &#8212; A Triester of Fatty Acids and Glycerol
The hydrocarbon backbone of triglycerides has a glycerol molecule with three hydroxyl (-OH) groups, each linked to a fatty acid chain. A fatty acid is a long hydrocarbon chain with a carboxyl group (&#8211;COOH) at one end. The carboxyl group of the fatty acid and the hydroxyl group of the glycerol form a stable bond with the release of a water molecule. The resulting molecule is called an ester (&#8211;COOR). Therefore, a triglyceride is a triester of glycerol and three fatty acids. The three constituent fatty acids can be identical or different and are usually 12&#8211;18 carbons long. They are either saturated or unsaturated depending on the presence or absence of double bonds in the hydrocarbon chains.
Phospholipids are an Integral Part of Cellular Membranes
Phospholipids are critical to the cell as they form the major constituents of cellular membranes. They are structurally similar to triglycerides but contain only two fatty acids&#8212;saturated or unsaturated&#8212;linked to a glycerol moeity. The third hydroxyl group of glycerol is linked to a negatively charged phosphate group.
Addition of another functional group, such as smaller polar molecules like choline or a serine residue, to the phosphate group results in diverse chemical properties of phospholipids.
Phospholipids are amphipathic molecules, meaning they have parts that are hydrophobic and others that are hydrophilic or &#8220;water-loving.&#8221; When phospholipids are added to water, they spontaneously form a bilayer, a thin film that is two phospholipid molecules thick. This self-organization takes place because the polar heads are attracted to water, while the hydrophobic fatty acids are buried in the center of the layer to evade contact with water. This phospholipid bilayer forms the cell membrane in all living organisms. It compartmentalizes the fluids in the interior and exterior of the cell. Embedded in the bilayer are proteins and steroids, another class of lipids. Additional phospholipid bilayers may further compartmentalize the interior of the eukaryotic cell, for instance, the lysosome and endoplasmic reticulum.
Steroids Consist of a Four Ring Structure
Steroids are another biologically important class of lipids composed of four carbon rings. They vary amongst each other based on the chemical groups attached to the carbon rings. Although steroids are structurally different from triglycerides and phospholipids, they are also hydrophobic and insoluble in water. They alter&#160;the fluidity of the cell membrane and also function as signaling molecules within the cell. Cholesterol is the most common steroid and is synthesized in the liver. It is present in the cell membrane and serves as the precursor of sex hormones in animals.

Lipids function as structural components of cellular membranes, in addition to acting as energy reservoirs and signaling molecules. They are thus crucial ...

Education

JoVE Core

Cell Biology

Unit 1

Biochemistry of the Cell

KEY TERMS AND CONCEPTS

lipids in cells: membranes, energy, and signals

Lipids are important cell molecules that act as membrane parts, energy stores, and signaling molecules. They are a diverse group of hydrocarbons, which are compounds made of carbon and hydrogen atoms. The carbon-carbon and carbon-hydrogen bonds are nonpolar, so lipids have an overall nonpolar character.

Lipids are also hydrophobic, or “water-hating.” They do not form hydrogen bonds with water, so they are nearly insoluble in water. They are, however, soluble in organic solvents such as chloroform or benzene.

Triglycerides are one major class of lipid. A triglyceride has a glycerol molecule with three hydroxyl (-OH) groups, and each one is linked to a fatty acid chain. A fatty acid is a long hydrocarbon chain with a carboxyl group (-COOH) at one end. The carboxyl group of the fatty acid and the hydroxyl group of glycerol form an ester bond as a water molecule is released. That is why a triglyceride is a triester of glycerol and three fatty acids. The fatty acids can be the same or different, and they are usually 12 to 18 carbons long. They may be saturated or unsaturated, depending on whether double bonds are present in the hydrocarbon chain.

Phospholipids are another major class and are critical because they make up the main part of cellular membranes. They are similar to triglycerides, but they have only two fatty acids attached to glycerol. The third hydroxyl group of glycerol is linked to a negatively charged phosphate group. A small polar group, such as choline or a serine residue, can also attach to the phosphate group and change the lipid’s chemical properties.

Phospholipids are amphipathic, which means they have both hydrophobic and hydrophilic parts. When placed in water, they spontaneously form a bilayer that is two phospholipid molecules thick. The polar heads face water, while the hydrophobic fatty acids stay hidden in the center. This bilayer forms the cell membrane in living organisms and separates the fluid inside the cell from the fluid outside. Proteins and steroids are embedded in the bilayer, and other phospholipid bilayers also help compartmentalize parts of eukaryotic cells, such as the lysosome and endoplasmic reticulum.

Steroids are the third biologically important class of lipids. They have a four-ring carbon structure and differ from one another by the chemical groups attached to those rings. Like other lipids, steroids are hydrophobic and insoluble in water. They help change membrane fluidity and also act as signaling molecules inside the cell. Cholesterol is the most common steroid. It is made in the liver, found in cell membranes, and serves as a precursor for sex hormones in animals.

Lipids in Cells: Membranes, Energy, and Signals

lipids-in-cells-membranes-energy-and-signals

the periodic table and organismal elements

the-periodic-table-and-organismal-elements

Elements in the Human Body and Periodic Table

Elements are the smallest units of matter that cannot be broken down further by chemical processes. Scientists know 118 elements, but not all of them occur naturally. Only a small number are essential for life, and living matter depends mostly on carbon, nitrogen, hydrogen, and oxygen. The periodic table organizes elements by their physical and chemical properties. Each square shows the element name, chemical symbol, atomic number, and atomic weight. The atomic number is the number of protons...

functional groups

Functional Groups in Organic Molecules

Functional groups are the part of an organic molecule that gives it specific chemical behavior. They help explain why compounds with similar carbon skeletons can react in different ways. In organic chemistry, these groups are often used to classify compounds. A functional group can change the properties of a molecule and affect how it behaves in a reaction. Knowing functional groups helps students recognize patterns in organic compounds. It also makes it easier to compare molecules that share...

types of chemical bonds

Chemical Bonds and How Atoms Join

Chemical bonds hold atoms together and help explain how different substances form. In chemistry, the main bond types are ionic bonds, covalent bonds, and metallic bonds. Ionic bonds form when electrons move from one atom to another. Covalent bonds form when atoms share electrons. Metallic bonds occur in metals, where electrons are held in a shared arrangement that gives metals their characteristic behavior. Understanding these bond types helps students compare how atoms connect in different...

noncovalent attractions in biomolecules

Biomolecule Interactions Without Covalent Bonds

Biomolecules often stay together through noncovalent attractions instead of covalent bonds. These weaker interactions help molecules recognize each other and form structures needed for life. The main noncovalent attractions are hydrogen bonds, electrostatic interactions, van der Waals forces, and hydrophobic interactions. Each one works in a different way, but all of them can influence how biomolecules fold, bind, and behave in cells. Hydrogen bonds form when a hydrogen atom is attracted to...

polymers

Polymer Chains and Their Properties

Polymers are large molecules made from repeating units called monomers. These long chains can form many common materials. Their structure helps explain why different polymers can behave in different ways. Polymers can be built in more than one way. Some form by addition polymerization, where monomers join together directly. Others form by condensation polymerization, which releases a small molecule as the chain grows. The type of polymer affects its properties and uses. Some polymers are...

Lipids are important cell molecules that act as membrane parts, energy stores, and signaling molecules. They are a diverse group of hydrocarbons, which are compounds made of carbon and hydrogen atoms. The carbon-carbon and carbon-hydrogen bonds are nonpolar, so lipids have an overall nonpolar character. Lipids are also hydrophobic, or “water-hating.” They do not form hydrogen bonds with water, so they are nearly insoluble in water. They are, however, soluble in organic solvents such as...

structure of lipids

How Lipid Molecules Are Built

Lipid molecules are built from hydrocarbon chains and a few key structural parts. Their shape helps explain why they behave differently from many other biological molecules. In high school biology, this structure is often linked to how lipids store energy and help form cell membranes. Some lipids are made from fatty acids joined to other small molecules. Triglycerides contain glycerol and three fatty acids, while phospholipids contain glycerol, two fatty acids, and a phosphate group. These...

chemistry of carbohydrates

Carbohydrate Structure and Bonding

Carbohydrates are built from sugar units and the bonds that link them. Their chemistry explains how simple sugars join to form larger molecules. It also helps show why carbohydrates have different structures and functions. The video focuses on the main sugar types found in carbohydrates. These include monosaccharides, disaccharides, and polysaccharides. Monosaccharides are single sugar units. Disaccharides contain two sugar units, while polysaccharides are long chains of many sugar units. The...

nucleic acids

DNA and RNA in Cells

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How Protein Shape Determines Function

Proteins are essential molecules in living things, and their shape affects how they work. Protein structure is described at several levels, including primary, secondary, tertiary, and quaternary structure. These levels help explain how a protein is built and how its final form supports its job. Primary structure is the sequence of amino acids in a protein. Secondary structure forms when parts of the chain fold into regular patterns. Tertiary structure is the overall three-dimensional shape of...

ph regulation in cells

Cell pH and Organelle Balance

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Cell chemistry explains the substances that make cells work. Water is the main component of cells, and it supports the chemical reactions that keep life going. Cells also contain organic molecules, which are carbon-based compounds, and inorganic ions, which are charged particles needed for cell function. Organic molecules in cells include carbohydrates, lipids, proteins, and nucleic acids. These molecules have different roles, but together they build cell structures, store energy, and carry...

key terms and concepts

Explore how lipids support cell membranes, store energy, and act as signals. Learn triglycerides, phospholipids, and steroids for high school biology.

Lipids in Cells: Membranes, Energy, and Signals | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

SC.912.L.18.3

Macromolecules

Biomolecules
Organisms contain a wide variety of organic molecules with numerous functions which depend on the chemical structures and properties of these ...

Polymers

Structure of Lipids

lipid-derived-compounds-in-the-human-body

Lipid-derived Compounds in the Human Body

Fats and lipids are crucial components in the human body. Some lipid-derived compounds, such as fat-soluble vitamins, eicosanoids, lipoproteins, and ...

Fats as Energy Storage Molecules

Amino acids

Amino acids are the monomers that comprise proteins. Each amino acid has the same fundamental structure, which consists of a central carbon atom, or the ...

Peptide Bonds

A peptide bond covalently attaches amino acids through a dehydration reaction. One amino acid&#x27;s carboxyl group and another amino acid&#x27;s amino ...

What are Proteins?

Protein and Protein Structures

Protein Organization

Globular Proteins

In organisms, proteins are the most abundant macromolecules. They act as the building blocks of life and play various crucial roles in the body. Proteins ...

Fibrous Proteins

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Protein Denaturation

The function of proteins depends on their native three-dimensional structure, which is dictated by the amino acid sequence of the specific protein. ...

Role of Proteins in the Human Body

Proteins are the building block of life. They are also&#160; the most abundant macromolecules with as many diverse roles in the body. They are part of ...

Mechanical Protein Function

Structural Protein Function

Introduction to Carbohydrates

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Chemistry of Carbohydrates

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Nucleic Acids and Nucleotides

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Nucleic Acid Structure

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The DNA Helix

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RNA Structure

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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 ...

Noncovalent Attractions in Biomolecules

Describe the basic molecular structures and primary functions of the four major categories of biological macromolecules.

Cellulose and Pectic Polysaccharides

&#160;Every plant cell has a cell wall that protects the cell, provides structural support, and gives the cell shape. Cellulose, the main structural ...

Membrane Carbohydrates

The plasma membrane is a dynamic barrier composed of lipids, proteins, and carbohydrates. It is the epicenter of many cellular processes required for cell ...

Describe the important structural characteristics of monosaccharides, disaccharides, and polysaccharides and explain the functions of carbohydrates in living things.

SC.912.L.18.2

Overview of Fatty Acid Metabolism

Lipids also are sources of energy that power cellular processes. Like carbohydrates, lipids are composed of carbon, hydrogen, and oxygen, but these atoms ...

What are Membranes?

A cell&#39;s plasma membrane demarcates the cell&#39;s borders and determines the nature of its interaction with the environment. Cells exclude certain ...

Membrane Fluidity

Membrane fluidity is explained by the fluid mosaic model of the cell membrane, which describes the plasma membrane structure as a mosaic of ...

Fluid Mosaic Model

Scientists identified the plasma membrane in the 1890s and its principal chemical components (lipids and proteins) by 1915. The model for plasma membrane ...

Membrane Lipids

Lipids are an essential component of all biological membranes. The average lipid content in mammalian membranes is 50%, though it can be as low as 20% in ...

Asymmetric Lipid Bilayer

Biological membranes show uneven distribution of different types of lipids in the inner and outer layers, resulting in transverse asymmetric membranes. ...

Lipids as Anchors

In the plasma membrane, the lipids forming the bilayer can also act as an anchor to tether proteins to the membrane. The three main types of lipid anchors ...

The Significance of Membrane Transport

The transport of solutes across the cell membrane is essential for metabolic processes, like maintaining cell size and volume, generating the action ...

Describe the structures of fatty acids, triglycerides, phospholipids, and steroids. Explain the functions of lipids in living organisms. Identify some reactions that fatty acids undergo. Relate the structure and function of cell membranes.

Ligand Binding Sites

Cofactors and Coenzymes

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Introduction to Enzymes

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Enzymes and Activation Energy

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Introduction to Enzyme Kinetics

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Turnover Number and Catalytic Efficiency

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Catalytically Perfect Enzymes

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Introduction to Mechanisms of Enzyme Catalysis

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Ligand Binding and Linkage

Cooperative Allosteric Transitions

Ribozymes

Enzyme Activity

Biological Catalysts

All living organisms continuously perform numerous biochemical reactions to sustain their presence. Most of these reactions require ...

Describe the structures of proteins and amino acids. Explain the functions of proteins in living organisms. Identify some reactions that amino acids undergo. Relate the structure and function of enzymes.

SC.912.L.18.4

Chemiosmosis

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Electron Transport Chain: Complex I and II

The mitochondrial electron transport chain (ETC) is the main energy generation system in the eukaryotic cells. However, mitochondria also produce ...

electron-transport-chain-complex-iii-and-iv

Electron Transport Chain: Complex III and IV

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The Electron Transport Chain

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the-supercomplexes-in-the-crista-membrane

The Supercomplexes in the Crista Membrane

The mitochondrial cristae membrane is the primary site for the oxidative phosphorylation (OXPHOS) process of energy conversion mediated through ...

ATP Synthase: Structure

ATP synthase or ATPase is among the most conserved proteins found in bacteria, mammals, and plants. This enzyme can catalyze a forward reaction in ...

ATP Synthase: Mechanism

In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear ...

The ADP/ATP Carrier Protein

ADP/ATP carrier or AAC protein is the most abundant carrier protein in the inner mitochondrial membrane. It transports large quantities of ADP and ATP, ...

ATP Yield

Cellular respiration produces 30 - 32 ATP per glucose molecule. Although most of the ATP results from oxidative phosphorylation and the electron transport ...

Discuss the use of chemiosmotic gradients for ATP production in chloroplasts and mitochondria.

SC.912.L.18.5

Fermentation

Most eukaryotic organisms require oxygen to survive and function adequately. Such organisms produce large amounts of energy during aerobic respiration by ...

biofuels-producing-ethanol-from-cellulosic-material

Biofuels: Producing Ethanol from Cellulosic Material

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
In this experiment, cellulosic material (such as corn stalks, leaves, ...

Discuss the role of anaerobic respiration in living things and in human society.

SC.912.L.18.6

Photosynthesis

Autotrophs

Almost all living organisms on Earth depend on photosynthesis, which is the process that converts sunlight energy into a simple sugar called ...

What is Photosynthesis?

All living organisms on Earth are directly or indirectly dependent on photosynthesis. It is the only biological process that can capture energy from ...

The Anatomy of Chloroplasts

Green algae and plants, including green stems and unripe fruit, harbor specialized organelles called chloroplasts to carry out photosynthesis. They ...

Photosystems

Photosystems are multiprotein complexes that form the functional units of photosynthesis in plants, algae, and cyanobacteria. They are found embedded in ...

The Photochemical Reaction Center

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The Antenna Complex

Plants and other photosynthetic organisms comprise pigments capable of absorption of direct sunlight. These pigments are present in the reaction center - ...

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The Z-Scheme of Electron Transport in Photosynthesis

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The Calvin Benson Cycle

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Identify the reactants, products, and basic functions of photosynthesis.

SC.912.L.18.7

Introduction to Cellular Respiration

Organisms harvest energy from food, but this energy cannot be directly used by cells. Cells convert the energy stored in nutrients into a more usable ...

What is Glycolysis?

Overview
Cells make energy by breaking down macromolecules. Cellular respiration is the biochemical process that converts &#34;food energy&#34; (from the ...

Identify the reactants, products, and basic functions of aerobic and anaerobic cellular respiration.

SC.912.L.18.8

A. All living things are composed of four basic categories of macromolecules and share the same basic needs for life.

B. Living organisms acquire the energy they need for life processes through various metabolic pathways (primarily photosynthesis and cellular respiration).

C. Chemical reactions in living things follow basic rules of chemistry and are usually regulated by enzymes.

D. The unique chemical properties of carbon and water make life on Earth possible.

Lipids in Cells: Membranes, Energy, and Signals

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