Biology Chapter 5
STRUCTURE
(Cellulose, Chitin, Peptidoglycan) β-1,4-glycosidic linkage
3 things carbohydrates do
1. provide fibrous STRUCTURE materials 2. indicate cell IDENTITY 3. STORE chemical energy
photosynthesis
A complex set of reactions that can summarized as the following chemical reaction: CO₂ + H₂O + sunlight → (CH₂O)₄ + O₂ It is how plants make carbohydrates (such as starch) to store for later use.
What is the structure of Starch?
A polysaccharide consisting of 2 types of alpha-glucose monomers joined by glycosidic linkages. One is amylose, unbranched molecule containing only alpha-1,4 glycosidic linkages. The other is amylopectin, branch of monomers that binds to the 6th carbon in every 30th amylose monomer.
What is the structure of cellulose?
A polysaccharide consisting of beta-glucose monomers joined by beta-1,4 glycosidic linkages. Each glucose molecule is flipped in relation to the ones beside it. There are hydrogen bonds between parallel strands.
glycogen
A polysaccharide that is used for energy storage in animal cells (such as in liver and muscles). α-1,4-glycosidic linkage
starch
A polysaccharide that is used for energy storage in plant cells (such as in potatoes). α-1,4-glycosidic linkage
peptidoglycan
A polysaccharide that is used for structural support in bacterial cell walls (think of it holding the bacteria cell together). β-1,4-glycosidic linkage
cellulose
A polysaccharide that is used for structural support in cell walls of plants and many algae (the material that makes up wood & strings in celery). β-1,4-glycosidic linkage
chitin
A polysaccharide that is used for structural support in the cell walls of fungi and external skeletons of insects and crustaceans (think cockroaches and lobster). β-1,4-glycosidic linkage
glycoprotein
A protein that is covalently bonded to a carbohydrate (usually oligosaccharides). They are key molecules in cell-cell recognition/signaling. IDENTITY
Monosaccharide
A simple sugar. A aldehyde sugar is made if the carbonyl group is at one end of the molecule (aldose). A ketone sugar is made if the carbonyl group is in the midsection of the molecule (ketose).
How are monosaccharides named and distinguished?
According to the number of carbons (pentose = 5 carbons, triose = 3) and depending on whether the carbonyl group is at the end of the chain (aldose) or in the middle (ketose). Monosaccharides are further distinguished by the location of their functional groups. The same type of carbohydrate can also be distinguished by the orientation of its functional groups (eg alpha glucose and beta glucose).
What explains why carbohydrates store only about half the amount of energy as is stored in lipids?
Although many bonds that exist in carbohydrates are C-H and C-C bonds, which have similar electronegativities, carbohydrates also consists of O-H bonds, which are polar and holds less energy. In contrast, almost all bonds in lipids are nonpolar.
Why do carbohydrates have much higher free energy than carbon dioxide or water?
Because carbohydrates are far more ordered (less entropy) and because their bonds are far less polar.
How does electronegativity affect the amount of potential energy stored in a chemical bond?
Bonds between atoms of widely-differing electronegativities will store less energy because the electrons will be held tightly towards one molecule. However, if the electronegativities of the two atoms in the bond are close to the same, the electrons will be at almost the furthest point away from any nucleus. Thus, the electrons and bond will store a lot of potential energy.
what is the large number of bonds carbs contain that give it high free energy?
C-H
What are some roles that carbohydrates can play?
Carbohydrates can function as structural molecules, serve as markers for cell identity, store energy
Why is the carbohydrate name misleading?
Carbohydrates do not consist of carbon bonded to water (They instead consist of many C-H bonds as well as Hydroxyl and Carbonyl functional groups).
What supports the evidence that polysaccharides played little to no role in the evolution of life?
Cells and lab experiments have not suggested any possible mechanism for monosaccharide polymerization in the early stages of earth's history. No reactions catalyzed by polysaccharides have been discovered (or likely will be- polysaccharides lack the structural and chemical complexity necessary for a good catalyst). Finally, the monosaccharides cannot provide the information required for themselves to be copied or store any information in cells.
What is the function of cellulose?
Cellulose is the major component of the cell wall in plants.
What is the function of chitin?
Chitin stiffens the cell walls of fungi
Starch
Consists entirely of alpha-glucose molecules that are joined by glycosidic linkages (alpha-linkages 1,4) . Performs storage role in plants such as in potatoes.
Glycosidic Linkage
Covalent bond that forms between two monosaccharides when a condensation reaction takes place. They form alpha-linkages which are easy for enzymes to break, and beta-linkages which are difficult for enzymes to break.
What structures do carbohydrates exist in?
Either chain (rare) or ring (common) structures.
amylase
Enzyems involved in breaking alpha-glycosidic linkages in starch.
phosphorylase
Enzyme involved in catalyzing the hydrolysis of alpha-glycosidic linkages in glycogen.
Amylases
Enzymes that break the alpha-glycosidic linkages in starch.
How is the chemical energy stored in glucose converted to usable energy for cells?
Exergonic reactions lead to the breakdown of glucose and the capture of released energy through synthesis of a molecule called adenosine triphosphate. ATP then drives endergonic reactions such as moving muscles, repairing cell components.
What are some problems regarding the origin of carbohydrates?
Firstly, no one can explain why ribose came to predominate the prebiotic soup. Second, it seems unlikely that monosaccharides were able to polymerize during chemical evolution.
Pentose
Five-carbon sugars (example: ribose)
What occurs in the formation a glycosidic linkage?
Formation of glycosidic linkage is a condensation reaction that occurs when a hydroxyl group from two monosaccharides reacts.
α-glycosidic linkage
Found in energy storage: starch & glycogen
β-glycosidic linkage
Found in structural support: cellulose, chitin, and peptidoglycan
What is the structure of glycogen?
Glycogen is a polymer of alpha glucose consisting of many alpha-1,4 glycosidic linkages. In contains a branching-off strand at approximately every 10th monomer.
What is the function of glycogen?
Glycogen is the polysaccharide that animals use to store monosaccharides.
How do carbohydrates function as identity-displaying molecules?
Glycoproteins (a carbohydrate covalently bonded to a membrane protein) project outside the cell membrane and serve to identify the cell's identity to other cells. Each cell type has different combinations of glycoproteins which make each one unique.
What do investigators suspect about the origin of carbons?
Investigators suspect that sugars are synthesizes on dust particules and debris in outer earth and could have rained down to earth while the planet was forming.
What is the significance of the flipping, alternating structure of cellulose?
It allows cellulose to be a linear molecule (unlike glygogen and starch, which are helices) and for the hydrogen bonds to form between strands.
What is the structure of chitin?
It has a similar structure to cellulose, but the sugar glucose is replace with one called N-acetylglucosamine.
What is an important difference between Glycosidic Linkages and Peptide and Phosphodiester bonds?
Peptide and Phosphodiester bonds always form at the same spot at their monomers. However, because glycosidic linkages occur at hydroxyl groups and because hydroxyl groups are numerous and in various places, the location and geometry of glycosidic linkages can vary widely.
What is the structure of peptidoglycan?
Peptidoglycan consists of two types of monosaccharides (N-acetyl glucosamine and N-acetyl muramic acid) that alternate with each other and are linked by beta-1,4-glycosidic linkages. In addition, one of the monosaccharides has a chain of amino acids that allows side-by-side chains to peptide bond.
What is the function of peptidoglycan?
Peptidoglycan stiffens the cell walls of bacteria
Glycogen
Performs energy storage role in animals such as in muscles and the liver. Joined by alpha-linkages 1,4. Highly branched helices.
polysaccharides
Polymers that form when monosaccharides are linked together after a condensation (or dehydration) reaction occurs during glycosidic linkage.
Polysaccharides (complex carbohydrates).
Polymers that form when monosaccharides are linked together. The simplest ones are disaccharides (formed of 2 sugars) and oligosaccharides (formed of a few sugars).
Polysaccharides
Polymers that result when monosaccharides are linked together through condensation. Also known as complex carbohydrates.
disaccharides
Polysaccharide consisting of two monosaccharides.
Dissaccharides
Polysaccharide made by two monosaccharides.
branched and unbranched helixes
Polysaccharides α-1,4-glycosidic linkages that form this type of 3D structure (starch & glycogen)
parallel stands joined by hydrogen bonds
Polysaccharides β-1,4-glycosidic linkages taht form this type of 3D structure (cellulose, chitin, peptidoglycan).
Glycoprotein
Protein that is covalently bonded to a carbohydrate- usually an oligosaccharide.
Hexose
Six-carbon sugars (example: glucose that moves around in our bloodstreams)
What is the function of starch?
Starch is the polysaccharide in which most plants store monosaccharides.
How do structural polysaccharides differ from polysaccharides designed to simply store monosaccharides?
Storage polysaccharides typically are long chains of monosaccharides which have simple alpha linkages as the only way of keeping them connected. They are usually shaped in helices. In contrast, structural polysaccharides are usually long and straight, and often have groups projecting from the side that can further reinforce the chain.
Why are structural polymers composed of monosaccharides so effective?
Structural polysaccharides form long straight strands that can bond with adjacent strands. Accordingly, they are very good at resisting breaking with mechanical force. They also resist chemical force exceedingly well, as few animals have digestive enzymes capable of hydrolyzing the Beta-1,4-glycosidic linkages that connect the monosaccharides.
Carbohydrate
Sugar that encompasses the monomer monosaccharides, small polymers called oligosaccharides, and large polymers called polysaccharides. They are molecules formed from a carbonyl (C=O) group, several hyrdroxyl (-OH) groups, and several carbon-hydrogen bonds. They serve as raw materials for synthesizing other molecules, provide fibrous structural material, indicate cell identity, and store chemical energy.
aldose
The carbonyl group is found at the END of a carbon chain.
ketose
The carbonyl group is found in the MIDDLE of a carbon chain.
Why are carbohydrates named thus?
The chemical formula for many carbohydrates is (CH2O)n (where n= a natural number), so the name implies that carbohydrates are molecules in which carbon is surrounded by water- although it is an inaccurate description of the molecule.
adenosine triphosphate (ATP)
The energy that is released when sugars are processed...summarized as the following chemical reaction: CH₂O + O₂ + ADP + P₁ → CO₂ + H₂O + ATP
Glycosidic Linkage
The linkage resulted from condensation reaction that holds monosaccharides together when they form polysaccharides.
phosphorylase
The most important ENZYME involved in catalyzing the hydrolysis of α-glycosidic linkages in GLYCOGEN.
amylases
The most important ENZYME involved in catalyzing the hydrolysis of α-glycosidic linkages in STARCH.
Phosphorylase
The most important enzyme involved in catalyzing the hydrolysis of alpha-glycosidic linkages in glycogen.
Photosynthesis
The process that converts kinetic energy from sunlight into chemical energy stored in the bonds of carbohydrates.
Sugars and other carbohydrates
These are highly variable in structure. They have a carbonyl group and several to many hydroxyl groups.
carbohydrate
These are made up of monomers called monosaccharides ("one sugar"), oligosaccharides ("few sugars"), and polysaccharides ("many sugars").
Why are sugars fundamental to life?
They provide chemical energy in cells and furnish some molecule building blocks for synthesizing larger, more complex molecules.
Trioses
Three-carbon sugars
Peptidoglycan
Used for structural support in bacterial cell walls. Joined by beta-linkages 1,4. Parallel strands joined by peptide bonds.
Cellulose
Used for structural support in cell walls of plants and many algae. Joined by beta-linkages 1,4. Parallel strands joined by hydrogen bonds.
Chitin
Used for structural support in the cell wall of fungi and the external skeleton of insects and crustaceans. Joined by beta-linkages 1,4. Parallel strands joined by hydrogen bonds.
glycosidic linkage
_____________ is when simple sugars polymerize and a condensation reaction occurs between two hydroxyl groups, resulting in this kind of covalent bond.
glycosidic linkage
a covalent bond that results after a condensation reaction between two hydroxyl groups (OH) location and geometry of these bonds vary widely
Polysaccharides
also known as complex carbs, polymers of monosaccharide monomers
The alpha-glycosidic linkages in starch are hydrolyzed by? what do they play a key role in?
amylase enzymes--play key role in carb digestions
what cells mostly contain phosphorylase?
animal cells, in order to break down glycogen to provide glucose
glycogen
animal storage
peptidoglycan
bacterial cell walls
Why do carbs have more free energy than CO2?
bc C-C bonds and C-H bonds the electrons are held less tightly and shared more equally, than between C-O
simplest polysaccharide
disaccharide (2 monosaccharide monomers)
What do carbs participate in when cells need energy?
exergonic reactions that synthesize ATP, the free energy in ATP is used to drive the exergonic reactions and perform cell work
pentose
five carbon sugar (ex: ribose, deoxyribose)
chitin
fungi cell walls, animal exoskeletons, some algae
How do monosaccharide monomers vary?
location of carbonyl group (aldose is at end, ketose in middle) number or carbons present (tri,pent, hex), spatial arrangement, linear vs ringed
formation of carbs
monosaccarides polymerize to form polymers called polysaccharides, joined by glycosidic linkages
The hydrolysis of alpha-glycosidic linkages in glycogen is catalyzed by the enzyme
phosphorylase
cellulose
plant cell walls
Starch
plant storage polysaccharide
Why don't polysaccharides play a role in the origin of life?
polymerization requires special enzymes, they do not catalyze any known reactions, monomers cannot provide info to copy themselves
The enzymes amylase and phosphorylase catalyze the hydrolysis of α-glycosidic linkages in glycogen and starch, the released glucose subunits can then be used in
production of ATP
glycoproteins
proteins joined to carbohydrates by covalent bonds, they display information key in cell-to-cell recognition and cell-cell signaling
monosaccharide
simple sugar
hexose
six carbon sugar (ex: glucose)
Carbohydrate function
store and provide chemical energy for cells
carbs perform a wide variety of functions ex:
structure, basis for other molecules, cell identity, storing chemical energy
triose
three carbon sugar
