cell organisation

Question 1

3 divisions of the living world

Answer 1

1. EuBacteria (prokaryotes)
2. archaea (pro)
3. eukaryotes (eukaryotes)

Question 2

role of cells

Answer 2

• grow & divide
• obtain & use energy in specific chemical reactions = metabolism
• move & dynamic
• complex or simple
• whole organism or part

Question 3

features all cells have

Answer 3

• enclosed by a membrane
• all carry nucleic acid
• nucleic acid provides the instructions to direct the construction of specific machinery to obtain energy from the environment
• ATP energy used to duplicate the nucleic acid & the cellular machinery

Question 4

comparison between prokaryotes & eukaryotes

Answer 4

p

• no nuclei
• simple internal organisation
• plasma membrane
• nucleoid - bacteria DNA not in a membrane
• divide by binary fission

e

• more complex
• contain a nucleus
• contain other organelles
• divide by mitosis/meiosis

Question 5

what is common between prokaryotes & eukaryotes

Answer 5

• similar plasma membrane
• same genetic code
• similar mechanisms for ‘decoding’ the genetic code
• many metabolic pathways are the same
• similar use of ATP for energy
• both cells can be unicellular organisms

Question 6

what is contained in a eukaryotic cell

Answer 6

• Defined membrane bound nucleus & organelles
• The nucleus contains the genome (aside
  from mitochondrial and chloroplast DNA),
  and it is the principal site of DNA and RNA
  synthesis
• Extensive internal membranes that
  make up organelles
• Plasma membrane
• Cytoplasm – lies between plasma
  membrane and nucleus

Question 7

structure of nucleus

Answer 7

• contains nearly all DNA
• nuclear envelope formed by two membranes containing nuclear pores
• supported by the nuclear lamina

Question 8

role of nuclear pores

Answer 8

molecules move between the nucleus & cytosol

Question 9

define nuclear lamina

Answer 9

network of intermediate filaments, a thin felt-like mesh just beneath the inner nuclear membrane

Question 10

organelles in eukaryotic cell

Answer 10

• nucleus
• cytoplasm
• cytoskeleton
• ER
• golgi apparatus
• mitochondria
• lysosome
• centrioles
• vesicles and vacuoles

Question 11

role of cytoplasm

Answer 11

= main site of protein synthesis & degradation & also performs most of the cell’s intermediary metabolism

• around 50% of cells volume

Question 12

role of cytoskeleton & its three main components

Answer 12

= gives cell its shape & structure & provides a framework for movement

1. microfilaments
2. intermediate filaments
3. microtubules

Question 13

role of endoplasmic reticulum (ER)

Answer 13

manufacturing system & cellular ‘factory’

Question 14

role of smooth endoplasmic reticulum

Answer 14

• has no ribosomes so no protein synthesis but it produces & stores lipids & steroids

Question 15

role of rough endoplasmic reticulum

Answer 15

• has ribosomes attached to its surface = mediates synthesis & packaging of proteins

ribosomes = where protein synthesis occurs

Question 16

where does ER send proteins

Answer 16

sends newly synthesised proteins to Golgi to be sorted to their final destination

Question 17

structure of endoplasmic reticulum

Answer 17

• smooth & rough ER form sacs called cisternae
• protein molecules are stored in cisternal space/lumen
• when enough proteins are present, they collect & are pinched off in vesicles

Question 18

role of golgi apparatus

Answer 18

receives lipids & proteins from the ER & dispatches them to various destinations, usually covalently modifying them en route

Question 19

role of mitochondria

Answer 19

generate most of the ATP that cells use to drive reactions requiring an input of free energy

Question 20

role of lysosomes

Answer 20

= degrades old organelles & proteins

• lumen pH (4.5-5) for enzymes involved in hydrolysis
• extracellular material taken-up through endocytosis
• intracellular material is digested through autophagy

Question 21

role of endosome system

Answer 21

delivers materials to lysosome or plasma membrane (originates from trans golgi network)

Question 22

structure of centrioles

Answer 22

composed mainly of protein tubulin

• present in many eukaryotes but absent from some plant & fungal cells

Question 23

role of centrosomes

Answer 23

form the microtubule organising centre from which microtubules grow & forms spindles which separates chromosomes during cell divison

Question 24

where are centrioles located & role

Answer 24

centrosomes contain 2 at right-angles surrounded by protein to regulate the cell cycle

Question 25

define vesicles

Answer 25

found within or outside a cell = form naturally during protein secretion (exocytosis) or uptake (endocytosis)

= storage & transport

Question 26

define vacuoles

Answer 26

present in all plant & fungal cells some protist, animal and bacterial cells

storage

Question 27

difference between vesicles & vacuoles

Answer 27

• Vacuoles are much larger
• Vesicles can also fuse with membranes from other organelles whereas
  vacuole membranes do not fuse with the membranes of
  other cellular components.
• Vacuoles used for storage, vesicles for storage and transport
• Many more vesicles present per cell than vacuoles