Cell Biology- Biological Macromolecules

Question 1

Biological macromolecules are

Answer 1

large molecules essential for life.

include carbohydrates, lipids, nucleic acids, and proteins.

Question 2

Macromolecules

Answer 2

are large molecules, or polymers, made up of the polymerisation of smaller monomer subunits. An example of this can be seen in heamoglobin, a large and complex molecule.

Question 3

polymer

Answer 3

A large molecule, or polymer, composed of the polymerisation of smaller monomer subunits.

Question 4

monomers

Answer 4

building blocks

Question 5

dehydration synthesis

Answer 5

Most macromolecules are made from single subunits, or building blocks, calledmonomers. The monomers combine with each other using covalent bonds to form larger molecules known aspolymers. In doing so, monomers release water molecules as byproducts. This type of reaction isdehydration synthesis, which means “to put together while losing water.”

In a dehydration synthesis reaction the hydrogen of one monomer combines with the hydroxyl group of another monomer, releasing a water molecule. At the same time, the monomers share electrons and form covalent bonds. As additional monomers join, this chain of repeating monomers forms a polymer. Different monomer types can combine in many configurations, giving rise to a diverse group of macromolecules. Even one kind of monomer can combine in a variety of ways to form several different polymers. For example, glucose monomers are the constituents of starch, glycogen, and cellulose.

Question 6

hydrolysis reactions

Answer 6

Polymers break down into monomers during hydrolysis. A chemical reaction occurs when inserting a water molecule across the bond. Breaking a covalent bond with this water molecule in the compound achieves this . During these reactions, the polymer breaks into two components: one part gains a hydrogen atom (H+) and the other gains a hydroxyl molecule (OH–) from a split water molecule.

Question 7

Catalysts in Dehydration andhydrolysis reactions

Answer 7

dehydration reactions involve the formation of new bonds, requiring energy, while hydrolysis reactions break bonds and release energy. These reactions are similar for most macromolecules, but each monomer and polymer reaction is specific for its class. For example, catalytic enzymes in the digestive system hydrolyze or break down the food we ingest into smaller molecules. This allows cells in our body to easily absorb nutrients in the intestine. A specific enzyme breaks down each macromolecule. For instance, amylase, sucrase, lactase, or maltase break down carbohydrates. Enzymes called proteases, such as pepsin and peptidase, and hydrochloric acid break down proteins. Lipases break down lipids. These broken down macromolecules provide energy for cellular activities.

Question 8

Types of simple carbohydrate

Answer 8

Monosaccharides

Disaccharides

Question 9

Types of complex carbohydrates

Answer 9

Oligosaccharides

Polysaccharides

Question 10

Monosaccharides

Answer 10

Glucoses
Fructose
Galactose

Monosaccharides are the simplest form of carbohydrate, often seen in our most common dietary sugars. Most monosaccharides have a sweet taste, but this is not an exclusive property of these groups.

Glucose, galactose, and fructose are isomeric monosaccharides (hexoses), meaning they have the same chemical formula but have slightly different structures. Glucose and galactose are aldoses, and fructose is a ketose.

Monosaccharides can exist as a linear chain or as ring-shaped molecules. In aqueous solutions they are usually in ring forms (Figure 3.6). Glucose in a ring form can have two different hydroxyl group arrangements (OH) around the anomeric carbon (carbon 1 that becomes asymmetric in the ring formation process). If the hydroxyl group is below carbon number 1 in the sugar, it is in the alpha (α) position, and if it is above the plane, it is in the beta (β) position.

During cellular respiration, energy releases from glucose, and that energy helps make adenosine triphosphate (ATP). Plants synthesize glucose using carbon dioxide and water, and glucose in turn provides energy requirements for the plant. Humans and other animals that feed on plants often store excess glucose as catabolized (cell breakdown of larger molecules) starch.

Galactose (part of lactose, or milk sugar) and fructose (found in sucrose, in fruit) are other common monosaccharides. Although glucose, galactose, and fructose all have the same chemical formula (C6H12O6), they differ structurally and chemically (and are isomers) because of the different arrangement of functional groups around the asymmetric carbon. All these monosaccharides have more than one asymmetric carbon

Question 11

Disaccharides

Answer 11

Sucrose
Lactose
Maltose
Disaccharides (di- = “two”) form when two monosaccharides undergo a dehydration reaction (or a condensation reaction or dehydration synthesis). During this process, one monosaccharide’s hydroxyl group combines with another monosaccharide’s hydrogen, releasing a water molecule and forming a covalent bond. A covalent bond forms between a carbohydrate molecule and another molecule (in this case, between two monosaccharides). Scientists call this a glycosidic bond (Figure 3.7). Glycosidic bonds (or glycosidic linkages) can be an alpha or beta type. An alpha bond is formed when the OH group on the carbon-1 of the first glucose is below the ring plane, and a beta bond is formed when the OH group on the carbon-1 is above the ring plane.

common disaccharides include lactose, maltose, and sucrose (Figure 3.8). Lactose is a disaccharide consisting of the monomers glucose and galactose. It is naturally in milk. Maltose, or malt sugar, is a disaccharide formed by a dehydration reaction between two glucose molecules. The most common disaccharide is sucrose, or table sugar, which is comprised of glucose and fructose monomers.

Question 12

Oligosaccharides

Answer 12

Raffinose

Stachyose

Question 13

Polysaccharide

Answer 13

Starch
Glycogen
Cellulose

Question 14

Cellulose

Answer 14

Source: plant
Subunit: B-glucose
Bonds: 1-4
Branches: no
Shape: straight

Question 15

Amylose

Answer 15

Source: plant
Subunit: A-glucose
Bonds: 1-4
Branches: no
Shape: looped

Question 16

Amylopectin

Answer 16

Source: plant
Subunit: a-glucose
Bonds: 1-4 and 1-6
Branches: yes (~per 20 subunits)
Shape: branched

Question 17

Glycogen

Answer 17

Source: Animal
Subunit: a-glucose
Bonds: 1-4 and 1-6
Branches: yes (~per 10 subunits)
Shape: branched (more so than amylopectin)

Question 18

Lipids

Answer 18

Lipids are molecules that contain hydrocarbons and make up the building blocks of the structure and function of living cells

Examples of lipids include:
Fats, oils and waxes
Certain vitamins (such as A, D, E and K)
Hormones
Cell membranes

Question 19

Saturated fats

Answer 19

Chain of carbon atoms saturated with hydrogen
Solid at room temp
High melting point

have straight carbon chains because they only contain single carbon-carbon bonds. Saturated fats pack together closely and are solid at room temperature. Saturated fats are typically found in animal products. Butter is a good example.

Question 20

Monounsaturated fats

Answer 20

Chain of carbon atoms with one double bond
Liquid at room temp
Lower melting point

Question 21

Polyunsaturated

Answer 21

Chain of carbon atoms with multiple double bonds
Liquid at room temp
Lowest melting point

Question 22

Trans fats

Answer 22

Partially hydrogenated (adding hydrogen causes trans fats to form)
Liquid oils industrially converted into solids
High melting point

Question 23

Unsaturated fats

Answer 23

have a kink in their chain caused by a double bond or even a triple bond between carbons. Because of these kinks, unsaturated fats can’t pack together very closely, making them liquid at room temperature. They are typically found in plant products. Vegetable oil is a good example

Question 24

Triglycerides

Answer 24

Lipids that store energy are called triglycerides. These molecules have three long chains of fatty acids attached to a glycerol backbone. In many organisms, extra carbohydrates are often stored as triglycerides in fat tissue.

Question 25

Phospholipids

Answer 25

Phospholipidsare major plasma membrane constituents that comprise cells’ outermost layer. Like fats, they are comprised of fatty acid chains attached to a glycerol or sphingosine backbone. However, instead of three fatty acids attached as in triglycerides, there are two fatty acids forming diacylglycerol, and a modified phosphate group occupies the glycerol backbone’s third carbon (Figure 3.19). A phosphate group alone attached to a diacylglycerol does not qualify as a phospholipid. It is phosphatidate (diacylglycerol 3-phosphate), the precursor of phospholipids. An alcohol modifies the phosphate group. Phosphatidylcholine and phosphatidylserine are two important phospholipids that are in plasma membranes.

The head is the hydrophilic part, and the tail contains the hydrophobic fatty acids. In a membrane, a bilayer of phospholipids forms the structure’s matrix, phospholipids’ fatty acid tails face inside, away from water; whereas, the phosphate group faces the outside, aqueous side (Figure 3.20).
Phospholipids are responsible for the plasma membrane’s dynamic nature. If a drop of phospholipids is placed in water, it spontaneously forms a structure that scientists call a micelle, where the hydrophilic phosphate heads face the outside and the fatty acids face the structure’s interior.

Question 26

Liposome

Answer 26

A spherical vesicle having at least one lipid bilayer. The liposome can be used as a vehicle for administration of nutrients and pharmaceutical drugs.

Question 27

Micelle

Answer 27

Spherical conformation of a single lipid layer

Question 28

Bilayer Sheet

Answer 28

Linear conformation of a lipid bilayer.

Question 29

Steroids

Answer 29

A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration.

Steroids have two principal biological functions:
as important components of cell membranes which alter membrane fluidity.
as signalling molecules.

Hundreds of steroids are found in plants, animals and fungi.

Unlike the phospholipids and fats that we discussed earlier,steroidshave a fused ring structure. Although they do not resemble the other lipids, scientists group them with them because they are also hydrophobic and insoluble in water. All steroids have four linked carbon rings and several of them, like cholesterol, have a short tail. Many steroids also have the –OH functional group, which puts them in the alcohol classification (sterols).

Cholesterol is the most common steroid. The liver synthesizes cholesterol and is the precursor to many steroid hormones such as testosterone and estradiol, which gonads and endocrine glands secrete. It is also the precursor to Vitamin D. Cholesterol is also the precursor of bile salts, which help emulsifying fats and their subsequent absorption by cells. Although lay people often speak negatively about cholesterol, it is necessary for the body’s proper functioning. Sterols (cholesterol in animal cells, phytosterol in plants) are components of the plasma membrane of cells and are found within the phospholipid bilayer.

Question 30

Proteins

Answer 30

Proteins are polymers formed from monomers called amino acids joined together by peptide bonds.

A chain of amino acids can also be called a polypeptide.

Question 31

Amino acids

Answer 31

are the monomers that comprise proteins. Each amino acid has the same fundamental structure, which consists of a central carbon atom, or the alpha (α) carbon, bonded to an amino group (NH2), a carboxyl group (COOH), and to a hydrogen atom. Every amino acid also has another atom or group of atoms bonded to the central atom known as the R group

Scientists use the name “amino acid” because these acids contain both amino group and carboxyl-acid-group in their basic structure. As we mentioned, there are 20 common amino acids present in proteins. Nine of these are essential amino acids in humans because the human body cannot produce them and we obtain them from our diet. For each amino acid, the R group (or side chain) is different

All amino acids have four identical parts: An amino group, a carboxyl group, a central carbon, and a hydrogen.

They only differ in their fifth part, which has many names.

It can be called a functional group, R group, side chain, or amino acid residue. Let’s go with functional group.

There are 20 amino acids from which all protein molecules are made. Some proteins contain just a few amino acids in a chain. Other proteins are chains of thousands of amino acids.

Question 32

peptide bond

Answer 32

A peptide bond is an amide type of covalent chemical bond linking two consecutive alpha-amino acids from C1 (carbon number one) of one alpha-amino acid and N2 (nitrogen number two) of another, along a peptide or protein chain.

Question 33

Amino acid properties

Answer 33

The products that such linkages form are peptides. As more amino acids join to this growing chain, the resulting chain is a polypeptide. Each polypeptide has a free amino group at one end. This end the N terminal, or the amino terminal, and the other end has a free carboxyl group, also the C or carboxyl terminal. While the terms polypeptide and protein are sometimes used interchangeably, a polypeptide is technically a polymer of amino acids, whereas the term protein is used for a polypeptide or polypeptides that have combined together, often have bound non-peptide prosthetic groups, have a distinct shape, and have a unique function. After protein synthesis (translation), most proteins are modified. These are known as post-translational modifications. They may undergo cleavage, phosphorylation, or may require adding other chemical groups. Only after these modifications is the protein completely functional.

Question 34

Proteins: Secondary Structure

Answer 34

Proteins can have unique secondary structures depending on the functional groups on each amino acid. Secondary structure refers to how these functional groups form hydrogen bonds and interact with each other based on their specific properties like polarity and charge.

This produces two different shapes:
α helix (alpha helix)
β sheet (beta sheet)

There will be many of these shapes varying in size per protein.

The local folding of the polypeptide in some regions gives rise to the secondary structure of the protein. The most common are the α-helix and β-pleated sheet structures Both structures are held in shape by hydrogen bonds. The hydrogen bonds form between the oxygen atom in the carbonyl group in one amino acid and another amino acid that is four amino acids farther along the chain.

Every helical turn in an alpha helix has 3.6 amino acid residues. The polypeptide’s R groups (the variant groups) protrude out from the α-helix chain. In the β-pleated sheet, hydrogen bonding between atoms on the polypeptide chain’s backbone form the “pleats”. The R groups are attached to the carbons and extend above and below the pleat’s folds. The pleated segments align parallel or antiparallel to each other, and hydrogen bonds form between the partially positive nitrogen atom in the amino group and the partially negative oxygen atom in the peptide backbone’s carbonyl group. The α-helix and β-pleated sheet structures are in most globular and fibrous proteins and they play an important structural role.

Question 35

Proteins: Tertiary Structure

Answer 35

The tertiary structure forms when different secondary structures align and fold into a final shape. This level uses many kinds of bonds.

The polypeptide’s unique three-dimensional structure is itstertiary structureThis structure is in part due to chemical interactions at work on the polypeptide chain. Primarily, the interactions among R groups create the protein’s complex three-dimensional tertiary structure. The nature of the R groups in the amino acids involved can counteract forming the hydrogen bonds we described for standard secondary structures. For example, R groups with like charges repel each other and those with unlike charges are attracted to each other (ionic bonds). When protein folding takes place, the nonpolar amino acids’ hydrophobic R groups lie in the protein’s interior; whereas, the hydrophilic R groups lie on the outside. Scientists also call the former interaction types hydrophobic interactions. Interaction between cysteine side chains forms disulfide linkages in the presence of oxygen, the only covalent bond that forms during protein folding.

All of these interactions, weak and strong, determine the protein’s final three-dimensional shape. When a protein loses its three-dimensional shape, it may no longer be functional.

Question 36

Proteins: Quaternary Structure

Answer 36

The quaternary structure is when different protein sub-units come together to make a protein complex. Not all proteins are protein complexes.
Quaternary Structure
In nature, some proteins form from several polypeptides, or subunits, and the interaction of these subunits forms the quaternary structure. Weak interactions between the subunits help to stabilize the overall structure. For example, insulin (a globular protein) has a combination of hydrogen and disulfide bonds that cause it to mostly clump into a ball shape. Insulin starts out as a single polypeptide and loses some internal sequences in the presence of post-translational modification after forming the disulfide linkages that hold the remaining chains together. Silk (a fibrous protein), however, has a β-pleated sheet structure that is the result of hydrogen bonding between different chains.