IBDP Biology - Carbs, Lipids, Proteins, Enzymes

What is the molecular structure of carbohydrates?

Monosaccharides form ring structures (typically 5 or 6 carbon atoms in a ring). Disaccharides are formed by two monosaccharides joined together by a glycosidic bond. Polysaccharides are long chains of monosaccharides linked together.

What is the molecular structure of lipids?

Has long chains of hydrocarbons (glycerol) with a carboxyl group at one end called fatty acids.

What is the molecular structure of carbohydrates?

Monosaccharides form ring structures (typically 5 or 6 carbon atoms in a ring). Disaccharides are formed by two monosaccharides joined together by a glycosidic bond. Polysaccharides are long chains of monosaccharides linked together.

What is the molecular structure of lipids?

Has long chains of hydrocarbons (glycerol) with a carboxyl group at one end called fatty acids.

What is the molecular structure of proteins?

monomers of proteins are amino acids, which have a central carbon bonded to an amine group, a carboxyl group, and an R-group; built from a combination of 20 amino acids

What is the molecular structure of nucleic acids?

Nitrogenous bases, pentose sugar molecule, and phosphate group.

Elements in Carbohydrates

C, H, O

Elements in Proteins

C, H, O, N, and sometimes S

Elements in Lipids

C, H, O (P + N for phospholipids)

Elements in Nucleic Acids

C, H, O, N, P

Anabolism

synthesis of complex molecules from simpler molecules.

Catabolism

breakdown of complex molecules into simpler molecules.

What bonds are formed with carbohydrates?

Glycosidic Bond

What bonds are formed with proteins?

Peptide Bond

What bonds are formed between lipids?

Ester Bond

State & Explain Examples of Monosaccharides

i. Glucose: primary source of energy for all cells

ii. Fructose: sugar found in fruit

iii. Deoxyribose: pentose sugar found in DNA

iv. Ribose: five-carbon sugar found in RNA

State & Explain Examples of Disaccharides

i. Sucrose: common table sugar (glucose + fructose)

ii. Lactose: sugar found in milk (glucose + galactose)

State & Explain Examples of Polysaccharides

i. Starch: storage form of glucose in plants

ii. Glycogen: storage form of glucose in animals

iii. Cellulose: structural polysaccharide in plant cell wells

Cellulose

typically about 1500 units of glucose, 1-4 bonds between alternately orientated glucose molecules, straight chain, unbranched chain, used for very high tensile strength.

Function: forms cell walls of plants and prevents plant cells from bursting in high pressure.

Starch

there are two types of starch: amylose and amylopectin. overall starch is insoluble, does not affect the osmotic balance of cells, molecules vary in size, easy to add/remove glucose units.

Function: Useful for glucose (energy) storage in seeds, and storage organs such as potato cells. Temporary store in leaf cells when glucose is being made faster by photosynthesis than exported.

Amylose

300-300,000 glucose units, chain is unbranched and forms helix, carbon atom 1 links to carbon atom 4 on next a-glucose; all glucose can be orientated the same way. Bent and unbranched chain.

Amylopectin

2000-200,000 glucose units; hydrophilic and too large to be soluble in H20, has globular shape. Has a bent and branched chain.

Glycogen

500,000 units, branches many times, repeating glucose subunits, has bent and branched chain. Does not affect osmotic balance of cells and is easy to add/remove glucose molecules.

Function: useful in cells for glucose. Used for energy storage and stored in the liver and some muscles.

Lipids are more efficient at energy storage than carbohydrates because...

Lipids are normally used for long-term energy storage whereas carbohydrates are used for short-term energy storage. The amount of energy released, also, in cell respiration per gram of lipids, is double that for carbohydrates. Lipids add 1/6 as much to body mass as carbohydrates.

Saturated Fats (Fatty Acid)

no double bonds between carbon atoms, typically solid at room temperature, unhealthy (high levels of cholesterol) found in butter, cheese, red meat, and tropical oils.

Monounsaturated Fats (Fatty Acid)

one double bond present between carbon atoms, typically liquid at room temperature, heart-healthy, found in plant-based oils

Polyunsaturated Fats (Fatty Acid)

more than one double bond in the carbon chain, typically liquid at room temperature, essential for body functions, found in vegetable oils and seeds/nuts

Cis- Isomers of Unsaturated Fatty Acids

i. Very common in nature

ii. Hydrogen atoms are on the same of the two carbon atoms

iii. Double bond causes a bend in the fatty acid chain

iv. Only loose packed

v. Triglycerides formed from cis-isomers have melting points (liquid at room temperature)

Trans- Isomers of Unsaturated Fatty Acids

i. Rare in nature (usually artificially produced to product solid fats like margarine from vegetable oils

ii. Hydrogen atoms are NOT on the same side of the two carbon atoms

iii. Double bond causes NO bend in the fatty acid chain.

iv. Triglycerides formed from trans-isomers have melting points (solid at room temperature)

How many amino acids are synthesized by ribosomes? How many amino acids do we know exist?

There are 20 standard amino acids that are synthesized by ribosomes, however there are 22 amino acids we know of which include (selenocysteine and pyrrolysine).

Generalized Structure of Amino Acid

The generalized structure of an amino acids has an amine group (NH2), an alpha carbon, an R-group, and a carboxylic acid group.

How are amino acids polymerized?

They are polymerized to form proteins through a process called dehydration synthesis (condensation reaction). This happens through the formation of peptide bonds between the carboxyl group of one amino acid and the amine group of another amino acid.

Give 3 reasons that explain why there can be a huge range of possible polypeptides.

1. There are 20 standard amino acids each with unique chemical properties due to their distinctive R groups.

2. Polypeptides can vary in length, so they can be from a few amino acids to several thousands.

3. Amino acids in a polypeptide chain can also be in a different order, meaning a small change in the sequence can lead to a completely different protein with unique properties.

What are the four levels of protein structure?

1. Primary

2. Secondary

3. Tertiary

4. Quaternary

Explain how the various protein levels are acheived.

1. Primary (polypeptide) - order/sequence of the amino acids of which the protein is composed of. Formed by covalent peptide bonds between adjacent amino acids. Controls all the other levels of structure.

2. Secondary - amin acid chain folds or turn on themselves. Held together by H bonds (between R groups). H bonds provide a level of stability. Fibrous.

3. Tertiary - polypeptide folds and coils to form a complex 3D structure; caused by R-group interactions: H bonds, ionic bonds, and hydrophobic/hydrophilic interactions. Globular.

4. Quaternary - the interactions between multiple polypeptides; some interact with prosthetic groups (non-protein compounds that attach to proteins to assist them in various ways). Fibrous and Globular.

Description of Fibrous Proteins & Examples

r-groups are hydrophobic which makes them insoluble, long and narrow, structural (strength support), insoluble (generally), amino acid sequence is repetitive, less sensitive to changes in pH, heat, etc.

Examples of fibrous proteins are collagen (structural proteins in connective tissues), elastin (provides elasticity in tissues), keratin (found in hair, nails, and skin).

Description of Globular Proteins & Examples

r-groups are hydrophilic which makes them soluble, compact, spherical, helps with functional roles (catalysis, regulation, transport, immune response), amino acid chain is irregular, and is more sensitive to pH, heat, etc.

Examples of these proteins include hemoglobin (transport protein), enzymes (catalysts), and insulin (regulates glucose levels).

Conjugated Proteins & Examples

proteins that consist of a protein component and a non-protein group called a prosthetic group. Prosthetic group can be a metal ion, lipid, carbohydrate, or nucleic acid. The prosthetic group plays a role in the protein's function, such as catalysis, transport, or structural stability.

Examples include hemoglobin (transports oxygen in blood), glycoproteins (cell signaling and immune response), and lipoproteins (transporting fats in the blood).

Non-Conjugated Proteins & Examples

composed of amino acids and do not have any non-protein components or prosthetic groups. These proteins are used in forming structural components or enzymes.

Examples include albumin (mains osmotic pressure and transport), globulins (immune responses), keratin (found in hair, nails, and skin).

Effects of Enzymes on Metabolic Reactions

1. Enzymes accelerate metabolic reactions without being consumed in the process; they bind to the substrate at their active sites, form an enzyme-substrate complex. This interaction helps transforms substrates into products more efficiently.

2. Enzymes also lower the activation energy (the energy needed to start a reaction). The reactants need energy to convert into products, so enzymes provide an alternative reaction pathway with a lower activation energy, allowing the reaction to proceed more easily and at a faster rate.

Factors the Affect Enzyme Rate of Reaction

1. Substrate Concentration

2. Enzyme Concentration

3. Temperature

4. pH levels

How does temperature affect the enzyme's rate of reaction?

low temperatures have insufficient thermal energy necessary for activation of reaction to occur (not enough energy to begin reaction). Higher temperatures decrease enzyme stability because the increase in thermal energy disrupts the hydrogen bonds holding enzymes together. As a result, the enzyme (the active site) will denature (loose its shape) and a reaction can does not occur.

How does pH affect the enzyme's rate of reaction?

changes in the charge of the enzyme and the subsequent solubility of the protein and perhaps alter the shape. A change in shape and/or charge of active site will affect the substrate's ability to bind to it. No reaction will occur.

How does substrate concentration affect the enzyme's rate of reaction?

increased substrate concentration will increase the rate of reaction. At an optimum concentration of substrate molecules, all active sites are full and working at maximum efficiency. Any increase above optimum concentration will have no added effect because there aren't any extra empty active sites available to bind to.

Competitive Inhibition on the Effect on Rate of Enzymatic Reaction

inhibitor resembles the substrate and competes with the substrate for binding to the active site of the enzyme. The inhibitor binds to the active site, preventing the substrate from binding. If the substrate concentration is high enough, it can out outcompete the inhibitor restoring enzyme activity. Since they are competing, more substrate is required to meet the enzyme's maximum activity. Reversible.

Non-Competitive Inhibition on the Effect on Rate of Enzymatic Reaction

inhibitor binds to an allosteric site (site other than active site) on the enzyme. This bind induces a conformational change in the enzyme that either reduce the enzyme's ability to bind or decreases the enzyme's catalytic efficiency. The inhibitor can bind whether or not the substrate is bound, reduce the enzyme's overall catalytic function. Maximum rate of reaction is reduced because even in high substrate concentrations, some of the enzyme molecules are still inhibited and cannot catalyze the reaction. Irreversible.