a2.2- cell structure

Question 1

disadvantages of electron microscopy

Answer 1

• specimen needs to die

Question 2

advantages of electron microscopy [2]

Answer 2

• higher range of magnification (can detect smaller structures)
• higher resolution

Question 3

why electron microscopy have higher resolution

Answer 3

shorter wavelength

Question 4

freeze fracture

Answer 4

cut in half → spray metal
- see inside of membrane

Question 5

cryogenic electron microscopy

Answer 5

see proteins with atomic precision- can design drugs that fit into them

Question 6

florescent stains

Answer 6

bright colours- see it clearer

Question 7

immunofluorescence

Answer 7

tag antibodies

Question 8

structures common to cells in all living organisms [2]

Answer 8

1. dna as genetic material
2. cytoplasm enclosed by plasma membrane composed of lipids

Question 9

use of plasma membrane

Answer 9

separating interior from its surrounding

Question 10

functions of cytoskeleton [3]

Answer 10

1. maintain cell shape
2. organises cell parts
3. enables cells to move and divide

Question 11

components of cytoskeleton

Answer 11

1. microtubules (movement)
2. actin filaments (movement)
3. intermediate filaments (structural)

Question 12

process of life in unicellular organisms

Answer 12

metabolism
reproduction
homeostasis
growth
response to stimuli
excretion
nutrition

Question 13

difference between eukaryotes [6]

Answer 13

1. cell wall
   animals- none
   plants- cellulose
   fungi- chitin
2. vacuole
   animals- many small
   plant and fungi- large (central in plant)
3. chloroplasts only present in plants
4. centrioles only present in animals
5. cilia only present in animals and plants
6. flagella only present in animals and plants

Question 14

endosymbiotic theory

Answer 14

• Eukaryotic cells are believed to have evolved from early prokaryotes that were engulfed by phagocytosis
• originated as symbioses between separate single-celled organisms
• eukaryotic organisms engulfed by a prokaryotic cell, was not digested because of symbiotic relationship
• remained inside host cell, carrying out aerobic respiration and providing energy to their host cells, evolving into mitochondria.

Question 15

what does evidence suggest about eukaryotes

Answer 15

• all eukaryotes evolved from common ancestor that had a nucleus and reproduced sexually

Question 16

evidence of endosymbiotic theory [5]

Answer 16

1. double membrane
   - inner membrane has proteins similar to prokaryotes
   - organelles may have bacterial origins
2. able to replicate
   - reproduction occurs via a fission-like process
   - only through division of pre-existing mitochondria and chloroplasts
3. naked and circular DNA
4. Ribosomes
   - 70S
   - similar to prokaryotes
5. Size
   - similar size to prokaryotes

Question 17

cell differentiation + caused by

Answer 17

• development of a cell to carry out specific function
• different patterns of gene expression: often triggered by changes in the environment

Question 18

advantages to multicellularity

Answer 18

1. larger body size
2. cell specialisation

Question 19

polymer that forms part of cytoskeleton

Answer 19

tubulin

Question 20

doesnt conform to the idea of standard notions of a cell [5]

Answer 20

1. striated muscle fibres
2. aseptate fungal hyphae
3. red blood cell
4. phloem sieve tube
5. giant algae

Question 21

striated muscle fibres

Answer 21

multiple nuclei surrounded by a single, continuous plasma membrane
challenges: cells always function as autonomous units

Question 22

aseptate fungal hyphae

Answer 22

each aseptate hyphae is an uninterrupted tube-like structure with many nuclei spread along it

Question 23

red blood cell

Answer 23

no nucleus

Question 24

phloem sieve tube element

Answer 24

• considered living cels without a nucleus
  nucleus of companion cells
• controls their functional activities

Question 25

giant algae

Answer 25

may grow to very large sizes challenges- larger organisms are always made of many microscopic cells

Question 26

why growing cells tend to divide and remain small

Answer 26

maintain high sa : vol ratio - fast exchange of nutrients

Question 27

emergent properties

Answer 27

- a property in which a collection or complex system had but the individual members do not have - interaction between parts produce more complex function than individually work together eg. grped cells → tissues, grped tissues → organs

Question 28

protista

Answer 28

- eukaryote - uni/multi cellular - no specialised tissue

Question 29

fungi: cell wall and how it obtains nutrients

Answer 29

- cell wall made of chitin - obtain nutrition via heterotrophic absorption

Question 30

plantae: cell wall and how it obtains nutrients

Answer 30

- call wall made of cellulose - obtain nutrients autotrophically

Question 31

animalia: cell wall and how they obtain nutrients

Answer 31

- no cell wall - nutrition via heterotrophic ingestion

Question 32

factors that determine how a cell develops [4]

Answer 32

1. position 2. hormones 3. cell to cell signals 4. chemicals

Question 33

why is cell division necessary [4]

Answer 33

1. more cells needed for growth 2. replacement 3. cells specialise 4. cells have to divide when they reach a certain size SA:vol ratio + nutrients cant be absorbed quickly enough

Question 34

nucleosome

Answer 34

DNA molecule wrapped around a core of eight histone proteins held together by an additional histone protein attached to linker DNA

Question 35

evidence that living organisms are composed of cells

Answer 35

1. living organisms are multicellular 2. organelles are specialised and contribute to the functions for the whole cell 3. cells multiply through cellular division

Question 36

resolution definition

Answer 36

ability to differentiate two objects in a microscope, distinguishing the details of the specimen

Question 37

ultrastructure definition

Answer 37

structure of the cell as observed under the electron microscope

Question 38

formation of the nucleus

Answer 38

nucleoid region enclosed in the internal membrane

Question 39

advantages of cell differentiation [2]

Answer 39

1. helps the body to carry out very specific functions efficiently 2. helps the organisms acquire specialisation for survival

Question 40

in which type of cells is the entire genome active

Answer 40

embryotic cell

Question 41

how newly formed cells become specialised

Answer 41

transcription regulators - some genes turned on or off - depends on the specialisation and location of cell during embryotic stage

Question 42

organelles both prokaryotes and eukaryotes have [4]

Answer 42

1. cell membrane 2. cytoplasm 3. ribosomes 4. genetic material