cell structure

Question 1

What processes do all living organisms carry out?
MRS HENG

Answer 1

• Metabolism (respiration)
• Reproduction (sexual or asexual)
• Sensitivity (responsive to both internal + external stimuli)
• Homeostasis (stable internal environment)
• Excretion (removal of waste products)
• Nutrition (exchange of materials + gases with environment)
• Growth (moving + change in shape and size)

Question 2

What is the process of endosymbiosis in mitochondria/ chloroplasts?

Answer 2

• one free living prokaryotes
• aerobically respire or can photosynthesize
• larger prokaryotes only aerobically respire
• took in smaller prokaryotes
• did not kill and ingest them
• engulfed cells live in cytoplasm as endosymbionts
• aerobic respiration supplies energy to host
• ∴ more efficient than anaerobic respiration of host
• endosymbiont supplied with food by host
• ∴ mutualistic relationship
• natural selection ∴ favoured cells that had developed in this way
• anaerobically respiring endosymbiont evolved to mitochondria of eukaryotic cells today

Question 3

evidence in chloroplasts and mitochondria for Endosymbiotic theory

Answer 3

• 70 s ribosomes
• double membrane
• own circular DNA and make their
  own proteins
• new mitochondria and chloroplasts
  only be produced by binary fission
  of the pre-existing organisms

Question 4

how does a double membrane support the endosymbiotic theory?

Answer 4

• engulfed prokaryotes had its own
  membrane (inner membrane)
• then enclosed by a vesicle from host cell (outer membrane)

Question 5

what are fungal cell walls composed of?

Answer 5

chitin

Question 6

which organisms out of plants, animals and fungi, have cells containing chloroplasts?

Answer 6

only plant cells

Question 7

which organisms out of plants, animals and fungi, have cells containing small and numerous vacuoles?

Answer 7

Animal (temporary too)
Fungal

Question 8

which organisms out of plants, animals and fungi, have cells containing large, centrally located vacuoles? what do they store

Answer 8

Plant cells
store carbohydrates/ sugars

Question 9

which organisms out of plants, animals and fungi, store carbohydrates as glycogen?

Answer 9

Fungal and animal cells

Question 10

which organisms out of plants, animals and fungi, store carbohydrates as starch?

Answer 10

plant cells

Question 11

What are basal bodies?

Answer 11

Essentially modified centrioles, they anchor the microtubule core
of these hair-like appendages, dictating their orientation and function

Question 12

Do plant cells usually contain cilia, flagella or basal bodies?

Answer 12

no

Question 13

Do animal cells usually contain cilia, flagella or basal bodies?

Answer 13

may have cilia or flagella, with associated basal bodies

Question 14

Do fungal cells usually contain cilia, flagella or basal bodies?

Answer 14

may have cilia or flagella but no associate basal bodies

Question 15

how does the cell wall in plant cells affect its shape?

Answer 15

rigid cell wall ∴ fixed often angular shape

Question 16

how does the cell wall in fungal cells affect its shape?

Answer 16

degree of flexibility + support
cell shape varies

Question 17

do plant cells have centrosomes and centrioles?

Answer 17

centrosomes no centrioles

Question 18

do animal cells have centrosomes and centrioles?

Answer 18

both centrosomes and centrioles

Question 19

do fungal cells have centrosomes and centrioles?

Answer 19

centrosomes no centrioles

Question 20

what are centrosomes and centrioles? what can they form?

Answer 20

centrosomes are made of microtubules and contain centrioles
- can mature into basal bodies and
form cilia and flagella

Question 21

why are skeletal muscle cells considered atypical?

Answer 21

• very long cells have multiple nuclei despite being surrounded by a single, continuous plasma membrane
• challenges idea of discrete cells

Question 22

why are aseptate hyphae cells considered atypical?

Answer 22

• not partitioned by septa
• have a continuous cytoplasm
• challenges idea of discrete cells
• multinucleated structure with continuous cytoplasm

Question 23

why are phloem cells considered atypical?

Answer 23

• formed of cells called sieve elements
• lie end to end
• have no nucleus or other cell components
• connected to companion cells which keep them alive, carrying out metabolic functions

Question 24

why are RBCs considered atypical?

Answer 24

• have no nucleus
• nucleus breaks down in late stage of
  development
• cannot repair themselves
• cannot reproduce

Question 25

prokaryotic cells

Answer 25

- smaller than eukaryotic cells - no membrane bound organelles - DNA free in cytoplasm - cell wall = peptidoglycan - 70 s ribosomes - divide by binary fission