1.2- Proteins

Question 1

Genome

Answer 1

the total genetic material in a cell

Question 2

Proteome

Answer 2

The entire set of proteins expressed by a genome

Question 3

What is larger, the proteome or the number of genes?

Answer 3

proteome

Question 4

Why is the proteome bigger than the genome?

Answer 4

more than one protein can be produced from a single gene as a result of alternative RNA splicing

Question 5

Genes that do not code for proteins

Answer 5

non-coding RNA genes:
tRNA
rRNA
RNA molecules that control the expression of other genes.

Question 6

Some factors affecting the set of proteins expressed by a given cell type

Answer 6

the metabolic activity of the cell
cellular stress
the response to signalling molecules
diseased versus healthy cells

Question 7

Eukaryotic cells have a ….. membrane

Answer 7

plasma (cell membrane)

Question 8

Plasma membrane in eukaryotic cells

Answer 8

It is the boundary around the outside of the cell.

Question 9

Eukaryotic cells also have a system of …… membranes

Answer 9

internal

Question 10

What does the system of internal membranes in eukaryotes do?

Answer 10

increases the total area of the membrane.

Question 11

Two types of endoplasmic reticulum

Answer 11

Rough endoplasmic reticulum (RER)

Smooth endoplasmic reticulum (SER)

Question 12

The endoplasmic reticulum (ER)

Answer 12

forms a network of membrane tubules with the nuclear membrane.

Question 13

Rough ER (RER)

Answer 13

has ribosomes on its cytosolic face

Question 14

Smooth ER (SER)

Answer 14

lacks ribosomes

Question 15

The Golgi apparatus

Answer 15

a series of flattened membrane discs

Question 16

Lysosomes

Answer 16

membrane-bound organelles containing a variety of hydrolases
digest proteins, lipids, nucleic acids and carbohydrates.

Question 17

Hydrolases

Answer 17

enzymes that catalyse the cleavage of a covalent bond using water.

Question 18

Vesicles

Answer 18

transport materials between membrane compartments.

Question 19

Membranes are made of

Answer 19

lipids and proteins

Question 20

Lipids are synthesised in the

Answer 20

smooth endoplasmic reticulum (SER) and inserted into its membrane.

Question 21

The synthesis of cytosolic proteins (proteins found in the cytoplasm) is completed in the

Answer 21

cytosolic ribosomes, and these proteins remain in the cytosol

Question 22

Transmembrane proteins carry a

Answer 22

signal sequence

Question 23

Transmembrane proteins carry a signal sequence, which

Answer 23

halts translation of the protein at the cytosolic ribosome AND directs the ribosome synthesising the protein to dock with the ER, forming RER.

Question 24

what is a signal sequence

Answer 24

a short stretch of amino acids at one end of the polypeptide that determines the eventual location of a protein in a cell

Question 25

Translation continues after docking, and the protein is inserted into the

Answer 25

membrane of the ER

Question 26

Once a protein has been synthesised at the ER, it can move...

Answer 26

around the cell to where ever it is needed.

Question 27

Once the proteins are in the ER, they are transported by

Answer 27

vesicles

Question 28

Once the proteins are in the ER, they are transported by vesicles that bud off and fuse with

Answer 28

the Golgi apparatus.

Question 29

Molecules move through the Golgi discs in vesicles that

Answer 29

bud off from one disc and fuse to the next one in the stack.

Question 30

As proteins move through the Golgi apparatus they undergo

Answer 30

post-translational modification

Question 31

post-translational modification

Answer 31

``` when the polypeptide chains have carbohydrates or phosphates added to them OR are cleaved (cut) to make them an active protein ```

Question 32

Vesicles that leave the Golgi apparatus take proteins to the

Answer 32

plasma membrane and lysosomes (which has a membrane)

Question 33

Vesicles move along microtubules to other membranes and

Answer 33

fuse with them within the cell.

Question 34

Microtubules

Answer 34

structures that make up the cell’s cytoskeleton and offer support and a means of transport

Question 35

cells often secrete substances

Answer 35

they release substances made inside the cell to the outside

Question 36

secrete substances examples

Answer 36

Peptide hormones eg. Insulin and digestive enzymes eg. Trypsin are examples of secreted proteins.

Question 37

Secreted proteins are translated in

Answer 37

ribosomes on the RER and enter its lumen | They bud off the RER in a vesicle and go to the Golgi apparatus.

Question 38

(secreted substances) | The proteins move through the Golgi apparatus and are then packaged into

Answer 38

secretory vesicles | These vesicles move to and fuse with the plasma membrane, releasing the proteins out of the cell.

Question 39

Many secreted proteins are synthesised as ...........precursors and require ............ clevage to produce active proteins.

Answer 39

Many secreted proteins are synthesised as inactive precursors and require proteolytic cleavage to produce active proteins.

Question 40

Proteolytic cleavage is a type of

Answer 40

post-translational modification where the polypeptide is cut.

Question 41

Digestive enzymes are one example of

Answer 41

secreted proteins that require proteolytic cleavage to become active.

Question 42

Proteins distinguishing feature is their...

Answer 42

folded nature and their ability to bind tightly and specifically to other molecules.

Question 43

peptide bond

Answer 43

a strong covalent bond between a carbon atom of one amino acid and the nitrogen atom of another amino acid C-N water is removed to allow the bond to form

Question 44

Proteins are ...... of of amino acid ...

Answer 44

Proteins are polymers of amino acid | monomers

Question 45

2 functional groups in amino acids

Answer 45

amine group H-N-H | acid group COOH

Question 46

The main categories amino acids are split into (by R group)

Answer 46

- polar - hydrophobic - acidic (negatively charged- carboxyl) - basic (positively charged- amino group)

Question 47

Acidic R groups

Answer 47

end with a negatively charged group (-) hydrophilic carboxylic acid group -COOH

Question 48

Basic R groups

Answer 48

end with a positively charged group hydrophilic amine group -NH2/3

Question 49

Polar R groups

Answer 49

slightly charged hydrophilic carbonyl (CO), hydroxyl (OH), amine (NH) groups

Question 50

Hydrophobic R groups

Answer 50

hydrophobic do not have charges non-polar hydrocarbon group -CH3, long chains of CH and rings