Molecular Composition of Cells

Question 1

What are carbohydrates? What do they do?

Answer 1

Carbohydrates include simple sugars as well as polysaccharides.
They are the major source of nutrients in the cell and are a major structural molecule that plays a role in signalling and cell recognition.

Question 2

What are monosaccharides?

Answer 2

Simple sugars with the basic formula (CH2O)n

Question 3

What are triose sugars?

Answer 3

Breakdown products of glucose from glycolysis and a precursor of pyruvate

Question 4

What is ribose?

Answer 4

A pentose sugar important for forming the backbone of RNA molecules

Question 5

What is glucose?

Answer 5

A hexose sugar which functions as the principle source of the cell’s energy

Question 6

What is a disaccharide?

Answer 6

2 monosaccharides linked together by glycosidic bonds (lactose or sucrose)

Question 7

What is an oligosaccharide?

Answer 7

3 or more monosaccharides linked together by glycosidic bonds

Question 8

What is a polysaccharide?

Answer 8

100s to 1000s of monosaccharides linked together by glycosidic bonds (glycogen or starch)

Question 9

What is glycogen? What is its function?

Answer 9

Branched alpha glucose polymer.

Major storage polysaccharide in animal cells

Question 10

What is starch? What is its function?

Answer 10

Branched or unbranched alpha glucose polymer.

Major storage polysaccharide in plants.

Question 11

What is cellulose? What is its function?

Answer 11

Unbranched polymer of beta glucose molecules.

Structural component component of plant cell walls.

Question 12

What is chitin? What is its function?

Answer 12

Unbranched polymer of beta glucose molecules.

Structural component of fungal cell walls and the exoskeletons of crabs and insects.

Question 13

What is the function of lipids? What are they a major component of?

Answer 13

Lipids provide energy storage and play a role in cell signalling and cell recognition.
Major component of cell membranes.

Question 14

What is the structure of fatty acids?

Answer 14

Fatty acids consist of long hydrocarbon chains. The bonds between carbon and hydrogen are non-polar, resulting in fatty acids being hydrophobic.

Question 15

What is the structure of triacyglycerols? What is their purpose?

Answer 15

Consist of three fatty acids linked to a glycerol molecule. Not soluble in water.
Store fatty acids.

Question 16

What are phospholipids? What do they do?

Answer 16

Consist of two fatty acids joined to a polar head group, and a hydrophobic tail.
Amphipathic. Principal components of cell membranes.

Question 17

What is the function of glycolipids?

Answer 17

Help facilitate cell stability and cellular recognition.

Question 18

What are steroid hormones? What do they do?

Answer 18

Steroid hormones are derivatives of cholesterol and act as signalling molecules both with and between cells.

Question 19

What is deoxyribonucleic acid? Where is it located?

Answer 19

DNA is the genetic molecule of the cell and is located in the nucleus of eukaryote cells.

Question 20

What does messenger RNA do?

Answer 20

Carries information from DNA to the ribosomes.

Question 21

What are ribosomal and transfer RNA involved in?

Answer 21

Protein synthesis.

Question 22

What is the structure of DNA and RNA?

Answer 22

Polymers of nucleotides, which consist of purine and pyrimidine bases linked to phosphorylated sugars.

Question 23

What is the function of purine and pyrimidine bases?

Answer 23

Provide the identity to nucleotides of DNA and RNA that are critical for base-pairing and the genetic code.

Question 24

What are nucleosides?

Answer 24

A nitrogenous base linked to the ribose or deoxyribose sugar.

Question 25

What are nucleotides?

Answer 25

Contain the phosphate group and are the basic building blocks of RNA and DNA

Question 26

Where do phosphodiester bonds form?

Answer 26

Between the 5' phosphate of one nucleotide and the 3' hydroxyl on the sugar of another.

Question 27

What joins amino acids together?

Answer 27

Peptide bonds

Question 28

What are polypeptides?

Answer 28

Linear chains of amino acids

Question 29

What is the primary protein structure?

Answer 29

The linear sequence of amino acids in the protein's polypeptide chain.

Question 30

What is the secondary protein structure? What are 2 types of secondary structures?

Answer 30

The regular arrangement of amino acids within localized regions of the polypeptide. An alpha helix and a beta sheet are two types of secondary structures/

Question 31

What is the tertiary structure of proteins?

Answer 31

The third level which consists of the folding of the polypeptide chain as a result of interactions between the side chains of amino acids that lie in different regions of the primary sequence.

Question 32

What are tertiary structures stabilized by?

Answer 32

- hydrophobic interactions with proteins - hydrophilic interactions on the surface of the protein - disulphide bonds between cysteine residues

Question 33

What is the quarternary structure of proteins?

Answer 33

The fourth level which consists of the interactions between different polypeptide chains in proteins composed of more than one polypeptide.

Question 34

What is the structural organization of the cell membrane?

Answer 34

Bilayer of amphipathic phospholipids with associated proteins and other specialized proteins.

Question 35

How do lipid bilayers behave?

Answer 35

As dynamic, two-dimensional fluids in which individual molecules are free to rotate and move in lateral directions.

Question 36

What characteristics of lipids determine membrane fluidity?

Answer 36

- membranes with short chain fatty acids are less rigid - unsaturated fatty chains increase membrane fluidity - cholesterol makes the membrane less fluid at the region where it is inserted

Question 37

What do channel proteins do?

Answer 37

Form open pores through the membrane, allowing free passage of any molecule of the appropriate size and structure

Question 38

What do carrier proteins do?

Answer 38

Selectively bind and transport specific small molecules, such as glucose

Question 39

What is passive transport?

Answer 39

A process where molecules are transported by either channel or carrier proteins across membranes in the energetically favourable direction

Question 40

What is active transport?

Answer 40

A process where molecules are transported in an energetically unfavourable direction (against the concentration gradient) across a membrane if their transport is coupled to ATP hydrolysis as a source of energy