MOLECULES AND CELLS

Question 1

Monosaccharide examples

Answer 1

a glucose (OH low) and b glucose (OH high), fructose

Question 2

Disaccharides definition

Answer 2

Formed when two monosaccharides join by condensation reaction (broke down by hydrolysis)

Question 3

Disaccharides example

Answer 3

maltose (2 a glucose with a a1,4-glycosidic bond) and sucrose (a gluocse and fructose)

Question 4

Polysaccharides examples

Answer 4

Starch, glycogen and cellulose

Question 5

Starch types

Answer 5

Amylose- (a1,4-glycosidic bonds) chains are coiled to form a spiral, held together by H bonds, branched
Amylopectin- ( a1,4-glycosidic bonds and a1,6-glycosidic bonds) much more branched than amylose

Question 6

Why is starch such a good storage molecule

Answer 6

-Compact
-Insoluable
Large molecule (will not easily pass through the cell membrane)
-branching= many terminal ends= easily hydrolysed when in high demand

Question 7

Glycogen structure

Answer 7

The same as amylopectin, just more branched and much shorter. stored in the form of small granules

Question 8

Glycogen function and location

Answer 8

-Found in animal and fungal cells
-Stored in the liver and muscle cells in mammals for fast hydrolysis= faster energy can be supplied

Question 9

Cellulose structure

Answer 9

Two b glucose molecules, with every other molecule being inverted (b1,4-glycosidic bonds)

Question 10

Effects of flipping the monomers in cellulose

Answer 10

-Unbranched chains are straighter
-Hydrogen bonds can form cross-linkages between adjacent chains

Question 11

Cellulose location

Answer 11

Cellulose chains are grouped together in microfibrils (plant cell walls) increases tensile strength

Question 12

Lipid properties and types

Answer 12

-Hydrophobic
-triglycerides(fats and oils), phospholipids waxes and steriods

Question 13

Triglycerides structure

Answer 13

One glycerol is joined to 3 fatty acids by 3 condensation reactions, ester bonds are formed

Question 14

Saturated fatty acid

Answer 14

Contains the maximum number of hydrogen atoms, carbons are linked by C-C bonds (no double bonds)

Question 15

Unsaturated fatty acids

Answer 15

Have at least one C=C bond in the chain
-Monounsaturated (1 C=C)
-Polyunsaturated (>1 C=C)

Question 16

Triglyceride functions

Answer 16

-Energy store
-Insulation
-Buoyancy

Question 17

Phopholipid structure

Answer 17

Instead of 3 fatty acids (hydrophobic), one is a phosphate group (hydrophillic)

Question 18

Protein structure

Answer 18

-Amino acids are linked by peptide bonds by condensation reactions between the amino and carboxyl group
-Two amino acids joined is a dipeptide
-Many amino acids is a polypeptide

Question 19

Primary protein structure

Answer 19

Sequence of amino acids in the polypeptide chain

Question 20

Secondary protein structure

Answer 20

a-helix or b-pleated sheets

Question 21

Tertiary protein structure

Answer 21

Further folding of the secondary structure, this gives it it’s 3D shape
-Hydrogen bonds
-Ionic bonds
-Disulfide bonds
-Hydrophobic interactions

Question 22

Quaternary structure

Answer 22

Two or more polypeptide chains bonded together

Question 23

Fibrous proteins

Answer 23

-Collagen
-Found intendons that link muscle to bone

Question 24

Globular proteins

Answer 24

Have a metabolic role and include enzymes and antibodies. Haemoglobin is an example

Question 25

Prions

Answer 25

A particular type of protein found in mammals. Found in the nervous system and they are involved in synaptic transmission.

Question 26

How does prion disease work?

Answer 26

Normal form of prion protein can convert to a disease causing form. this form has a higher proportion of b-pleated sheets which causes a chain reaction. Once the amount of b-sheets are over a certain threshold, this causes neurodegenerative disorders, and eventually death.

Question 27

How can diseases with prions arise?

Answer 27

-Normal prion protein ‘spontaneously’ adopting the disease form
-Mutations that code for the prion protein
-Eating contaminated food that contains the disease form

Question 28

Prion diseases examples

Answer 28

-Scrapie (sheep)
-Bovine spongiform encephalopathy (BSE, cattle)
-Variant Creutzfeldt-Jakob disease (vCJD, humans)

Question 29

Nucleic acids structure

Answer 29

Made up of nucleotides which are made up of:
- Pentose sugar
-Phosphate group
-Nitrogenous base
Phosphodiester bonds are formed between the pentose sugar and phosphate group, and also between adjacent nucelotides (nucleic acid)

Question 30

DNA defintion

Answer 30

A molecule of DNA consists of two anti-parallel strnds with the two strands being held together by ydrogen bonds between adjacent bases.

Question 31

DNA structure

Answer 31

The DNA molecule is organisee as a double helix. Each strand of the DNA is wound rounch each other like a twisted ladder, linked and held together by the bases, following base pairing rules (A-T G-C)

Question 32

RNA structure

Answer 32

-It’s sugar is ribose
-Single stranded and shorter than DNA
-The base uracil replaces thymine (A-U, G-C)

Question 33

Functions of DNA

Answer 33

-Regulates the development of living organisms through the control of protein syntheis.

Question 34

Messenger RNA

Answer 34

Carries the code from the DNA in the nucleus to a ribosome in the cytoplasm where protein synthesis takes place

Question 35

Transfer RNA

Answer 35

Carriesthe amino acids to the mRNA/ribosome where protein synthesis takes place. It is a single chain folded into a ‘clover leaf’ shape

Question 36

Ribosomal RNA

Answer 36

Made in the nucleolus and formsover half the mass of each ribosome

Question 37

DNA replication

Answer 37

The enzyme DNA helicase unzipsthe two strands of DNA by breaking the hydrogen bonds between the bases. this allows each of the original strands to become a template for the formation of two DNA molecules.Free nucleotides are linked to the template strands by base pairing rules. The nucleotides of each strand are joined together by the enzyme DNA polymerase. Each of the new DNA molecules contains one original strand and one new strand,this is known as semi-conservative replication