B2.2 Organelles and compartmentalisation

Question 1

what are not organelles because they don’t have a membrane

Answer 1

cell wall
cytoskeleton
cytoplasm

Question 2

examples of Eukaryotic cells that have a number of compartmentalised organelles

Answer 2

The nucleus
Vesicles
Ribosomes
The plasma membrane

Question 3

what is the outer membrane of organelles

Answer 3

lysosomes - it encloses their contents and creates a compartment that separates it from the surrounding cytoplasm

Question 4

what does the compartmentalisation of cell allow for

Answer 4

allows for enzymes and substrates to be localised so are available at higher conc
Damaging substances to be kept separated,
Optimal conditions to be maintained for certain processes

Question 5

how can we study organelles

Answer 5

cell fractionation

Question 6

how does cell fractionation happen

Answer 6

sample broken up in blender- in a homogeniser
it is filtered through a gauze
filtrate placed in tube and placed in centrifuge
centrifuge spins material- speed can be altered

Question 7

why does gene transcription and translation occur separately in eukaryotes

Answer 7

due to the compartmentalisation of the nucleus

Question 8

what happens during transcription

Answer 8

mRNA is formed using a template strand of DNA; the mRNA needs some modification before it can be used for translation

Question 9

advantages of compartmentalisation

Answer 9

small volume - enzymes can be concentrated so speeds up their activity
ph can be kept at ideal level
incompatible biochemical processes can be kept separate

Question 10

adaptations of mitochondria

Answer 10

outer membrane smooth and permeable to small molecules
inner membrane is folded and less permeable(site of ATP synthase)
intermembrane space has low ph due to high conc of protons
matrix

Question 11

what does the cristae allow for

Answer 11

a high surface area so membrane can hold many electron transport chain carriers and ATP synthase enzymes

Question 12

matrix

Answer 12

has high conc of enzymes and substrates for krebs cycle

Question 13

thykaloid membrane in chloroplasts

Answer 13

has pigments, enzymes and electron carriers

Question 14

how are grana adapted for photosynthesis

Answer 14

The granal stacks create a large surface area for the presence of many photosystems which allows for the maximum absorption of light
provides more membrane space for electron carriers and ATP synthase enzymes

Question 14

how are stroma adapted for photosynthesis

Answer 14

they contain enzymes that catalyse the reactions of light independent stage
they are compartmentalises for calvin cycle reactions
surrounds grana so transport is quick

Question 15

how is DNA adapted for photosynthesis

Answer 15

contains genes that code for some of the proteins and enzymes used in photosynthesis

Question 16

how are ribosomes adapted for photosynthesis

Answer 16

allows for the translation of proteins coded by the chloroplast DNA

Question 17

what are nuclear pores

Answer 17

important channels that allow mRNA and ribosomes to travel out of nucleus

Question 18

where are ribosomes found in cells

Answer 18

freely in the cytoplasm
Or bound to the endoplasmic reticulum (ER) to form rough ER (only in eukaryotic cells)

Question 19

role of golgi apparatus

Answer 19

modify proteins and lipids before packaging them into Golgi vesicles which then transport them to their required destination

Question 20

what does the cis side of the golgi apparatus do

Answer 20

receive protein or lipid filled vesicles from the endoplasmic reticulum

Question 21

what does the trans side of the golgi apparatus do

Answer 21

Once the received proteins or lipids have been modified the final products are sent out via the trans side

Question 22

what are vesicles

Answer 22

membrane-bound sacs used for transport and storage

Question 22

types of vesicles

Answer 22

peroxisomes
lysosomes
transport vesicles
secretory vesicles

Question 23

role of peroxisomes

Answer 23

these contain enzymes which digest fatty acids

Question 24

role of lysosomes

Answer 24

these contain lytic enzymes which digest cellular waste or harmful substances

Question 25

what are clathrins

Answer 25

proteins that help with the formation of vesicles

Question 26

how is a vesicle formed

Answer 26

A clathrin coated pit is formed on the surface of cell membrane
Receptor proteins on surface bind to the target molecules
Once enough target molecules are attached, cytoskeleton proteins help the clathrin pit to deepen and seal off, trapping the target molecules inside- vesicle