Cell structure and function

Question 1

What are polymers?

Answer 1

A polymer is a substance or material consisting of very large molecules, or macromolecules, composed of many repeating subunits.

Question 2

What are peptides?

Answer 2

Peptides are short chains of amino acids linked by peptide bonds.
A polypeptide is a longer unbranched peptide chain. A polypeptide that contains more than approx. 50 amino acids is known as a protein.

Question 3

What is a peptide bond?

Answer 3

A type of covalent chemical bond linking two consecutive alpha-amino acids from C1 of one alpha-amino acid and N2 of another, along a peptide or protein chain.

Question 4

What is a protein structure?

Answer 4

A protein structure is the three-dimensional arrangement of atoms in an amino acid-chain molecule. Proteins are polymers - specifically polypeptides, formed from sequences of amino acids, the monomers of the polymer.

Question 5

What is a primary protein structure?

Answer 5

The primary protein structure of a protein refers to the sequence of amino acids in the polypeptide chain. The structure is held together by peptide bonds that are made during the process of protein biosynthesis.

Question 6

What is a secondary protein structure?

Answer 6

Secondary structure refers to highly regular local sub-structures on the actual polypeptide backbone chain. Two main types of secondary structure, the α-helix and the β-strand or β-sheets.

Question 7

What is a tertiary protein structure?

Answer 7

Tertiary structure refers to the three-dimensional structure created by a single protein molecule (a single polypeptide chain). It may include one or several domains. The α-helixes and β-pleated-sheets are folded into a compact globular structure.

Question 8

What is a quaternary protein structure?

Answer 8

Quaternary structure is the three-dimensional structure consisting of the aggregation of two or more individual polypeptide chains (subunits) that operate as a single functional unit (multimer).

Question 9

What is an alpha helix?

Answer 9

The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located four residues earlier along the protein sequence.

Question 10

What is a beta-pleated sheet?

Answer 10

The beta sheet, (β-sheet) (also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet.

Question 11

What is a beta-strand?

Answer 11

A β-strand is a stretch of polypeptide chain typically 3 to 10 amino acids long with backbone in an extended conformation.

Question 12

What are some conditions that damage the structure of a protein?

Answer 12

· Increase in temperature can cause denaturation due to more rapid molecular movements of the protein. This can break the hydrogen bonds and hydrophobic interactions.
· Changes in pH can alter the pattern of ionization in some amino acid side chains.
· Polar or nonpolar substances can disrupt either hydrogen bonds (polar) or hydrophobic interaction within the protein. An example is urea.
· High concentration of hydrophobic liquids (organic solvents)

Question 13

What are prokaryotes?

Answer 13

Prokaryotic cells, with diameters of 1-10 µm.
Prokaryotes have circularized chromosomal DNA.
A prokaryote is a unicellular organism that lacks a nuclear membrane-enclosed nucleus.

Question 14

What are eukaryotes?

Answer 14

Eukaryotic cells, whose diameters are around 10-100 µm, have organelles such as the nucleus, mitochondria, Golgi-apparatus and endoplasmic reticulum.
Eukaryotes have linear chromosomal DNA contained in the nucleus.

Question 15

What is the endosymbiosis theory?

Answer 15

The endosymbiosis theory suggests that the organelles mitochondria and chloroplasts were formed by engulfment of aerobic and photosynthetic bacteria, respectively, by a larger cell, creating mutual benefits. The theory is supported by the fact that mitochondria and chloroplasts carry their own (circular) DNA and have membranes that resemble those of prokaryotes.

Question 16

What are monomeric subunits on a protein?

Answer 16

A monomer is a small molecular subunit that can be combined with similar subunits to form larger molecules. AMINO ACIDS!

Question 17

What are lipids?

Answer 17

Any of a diverse group of organic compounds including fats, oils, hormones, and certain components of membranes that are grouped together because they do not interact appreciably with water.

Question 18

What are lysine residues?

Answer 18

Lysine (symbol Lys or K)[2] is an α-amino acid that is used in the biosynthesis of proteins.
In biochemistry and molecular biology, a residue refers to a specific monomer within the polymeric chain of a polysaccharide, protein or nucleic acid.

Question 19

What are macromolecules in ribosomes?

Answer 19

RNA. As ribosomes translate RNA to protein, it may be smart that they are not composed of protein themselves, as they would then be dependent on other ribosomes.

Question 20

What are lysomes?

Answer 20

Lysosomes are intracellular compartments for the cell’s breakdown of food, other cells, or foreign objects that is taken up by the cell.

Question 21

What happens when a cell expands?

Answer 21

When a cell expands, the internal volume increases faster than the surface area of the cell membrane. When the internal volume becomes much greater than the surface area, transportation of nutrients and waste products across the cell membrane becomes the limiting factor for cell growth, as diffusion becomes rate limiting.

Question 22

What are some structural proteins?

Answer 22

Actin: a structural protein that forms microfilaments, which constitute a major part of the cytoskeleton of eukaryotic cells. The cytoskeleton provides shape of cells and serve as train tracks for vesicle transport.

Collagen: a structural protein abundant in extracellular space of multicellular organisms. In hard tissues like bones and teeth, collagen proteins form fibers that provide strength. In the skin, collagen provides elasticity.

Question 23

What is a net charge?

Answer 23

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be positive or negative (commonly carried by protons and electrons respectively).

Question 24

What are amino acid substitutions?

Answer 24

Amino acid replacement is a change from one amino acid to a different amino acid in a protein due to point mutation in the corresponding DNA sequence. It is caused by nonsynonymous missense mutation which changes the codon sequence to code other amino acid instead of the original.
(Conservative vs radical replacement)

Question 25

What is the mitochondria?

Answer 25

The mitochondria are the powerhouse organelles of cells, responsible for generating chemical energy in the form of ATP by cellular respiration. Here, partially broken-down sugars are used as fuel.
Without mitochondria, cellular respiration cannot be carried out by the cell, and chemical energy cannot be generated efficiently.

Question 26

What are chloroplasts?

Answer 26

The chloroplasts are organelles found in plants and algae and are responsible for producing sugars from CO2 through photosynthesis.Both mitochondria and chloroplasts are essential for plant cell survival, but without chloroplasts, plant cells will starve because no sugars can be made.

Question 27

What is the symbiotic relationship between two organisms/cells?

Answer 27

A symbiotic relationship is when two or more organisms live together. There are six different types of symbiotic interaction.
- Mutualism: both organisms benefit from the interaction.
- Commensalism: one organism benefits and one is not affected by the interaction.
- Neutralism: neither organism benefits or are harmed by the interaction
- Amensalism: one organism is harmed by the interaction while the other is not affected.
- Parasitism: one organism benefits while the other is harmed by the interaction
Competition: both organisms are harmed by the interaction

Question 28

What is a flagella?

Answer 28

A flagellum is a lash-like appendage that protrudes from the cell body of certain cells termed as flagellates.
A flagellate can have one or several flagella.
The presence of flagella makes it possible for a bacterium to effectively reach the intestinal barrier compared to a bacterium without flagella.

Question 29

What is a backbone chain?

Answer 29

In polymer science, the backbone chain of a polymer is the longest series of covalently bonded atoms that together create the continuous chain of the molecule.

Question 30

What is the intestinal barrier?

Answer 30

The intestinal mucosal barrier, also referred to as intestinal barrier, refers to the property of the intestinal mucosa that ensures adequate containment of undesirable luminal contents within the intestine while preserving the ability to absorb nutrients.

Question 31

What are nucleotides?

Answer 31

Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules within all life-forms on Earth. Nucleotides are obtained in the diet and are also synthesized from common nutrients by the liver.

Question 32

What are codons?

Answer 32

A codon is a sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid or stop signal during protein synthesis. The genetic code includes 64 possible permutations, or combinations, of three-letter nucleotide sequences that can be made from the four nucleotides.