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IB Biology > 1.2 Cell Structure > Flashcards

1.2 Cell Structure Flashcards

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1
Q

What organelle (main) do prokaryotes lack?

A

Prokaryotes are organisms whose cells lack a nucleus

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2
Q

What 2 domains are prokaryotes divided into?

A

Eubacteria and Archaebacteria (bacteria and archae)

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3
Q

Where are archaebacteria found?

A

extreme environments [ high temperatures, salt concentrations or pH] ( = extremophiles)

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4
Q

What are eubacteria?

A

traditional bacteria including most known pathogenic forms (e.g. E. coli, S. aureus, etc.)

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5
Q

What different organelles do prokaryotes have (from eukaryotes)?

A
  • nucleoid
  • plasmids
  • slime capsule
  • flagella
  • pilli
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6
Q

What is a nucleoid?

A

region of the cytoplasm where the DNA is located (DNA strand is circular and called a genophore)

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7
Q

What are plasmids?

A

autonomous circular DNA molecules that may be transferred between bacteria (horizontal gene transfer)

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8
Q

What size is a prokaryote ribosome?

A

70S

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9
Q

How does the cell wall in a prokaryote differ from a eukaryote?

A

rigid outer covering made of peptidoglycan

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10
Q

What is a slime capsule?

A

a thick polysaccharide layer

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11
Q

What is the function of a slime capsule?

A

used for protection against dessication (drying out) and phagocytosis

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12
Q

What is a flagella?

A

Long, slender projections containing a motor protein that enables movement

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13
Q

What are pili?

A

Hair-like extensions

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14
Q

What are the function of pili?

A

enable adherence to surfaces (attachment pili) or mediate bacterial conjugation (sex pili)

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15
Q

How do prokaryotic cells reproduce?

A

Binary fission

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16
Q

What are the 3 steps of binary fission?

A
  1. The circular DNA is copied in response to a replication signal
  2. The two DNA loops attach to the membrane
  3. The membrane elongates and pinches off (cytokinesis), forming two cells
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17
Q

What do eukaryote cells have that prokaryotes don’t?

A

a nucleus

compartmentalised by membrane-bound structures (organelles) that perform specific roles

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18
Q

What 4 kingdoms can eukaryotes be categorised into?

A
  • protista
  • fungi
  • plantae
  • animalia
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19
Q

What are protista?

A

unicellular organisms; or multicellular organisms without specialised tissue

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20
Q

What are fungi?

A

have a cell wall made of chitin and obtain nutrition via heterotrophic absorption

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21
Q

What are plantae?

A

have a cell wall made of cellulose and obtain nutrition autotrophically (via photosynthesis)

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22
Q

What are animalia?

A

no cell wall and obtain nutrition via heterotrophic ingestion

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23
Q

What are organelles?

A

Organelles are specialised sub-structures within a cell that serve a specific function

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24
Q

What are 3 universal organelles (pro and eukaryote)?

A
  • ribosomes
  • cytoskeleton
  • plasma membrane
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25
Q

What is the structure of a ribosome?

A

Two subunits made of RNA and protein; larger in eukaryotes (80S) than prokaryotes (70S)

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26
Q

What is the function of a ribosome?

A

Site of polypeptide synthesis (this process is called translation)

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27
Q

What is the structure of the cytoskeleton?

A

A filamentous scaffolding within the cytoplasm (fluid portion of the cytoplasm is the cytosol)

28
Q

What is the function of the cytoskeleton?

A

Provides internal structure and mediates intracellular transport (less developed in prokaryotes)

29
Q

What is the structure of the plasma membrane?

A

Phospholipid bilayer embedded with proteins (not an organelle per se, but a vital structure)

30
Q

What is the function of the plasma membrane?

A

Semi-permeable and selective barrier surrounding the cell

31
Q

What is the structure of the nucleus?

A

Double membrane structure with pores; contains an inner region called a nucleolus

32
Q

What is the function of the nucleus?

A

Stores genetic material (DNA) as chromatin; nucleolus is site of ribosome assembly

33
Q

What is the structure of the endoplasmic reticulum?

A

A membrane network that may be bare (smooth ER) or studded with ribosomes (rough ER)

34
Q

What is the function of the ER?

A

Transports materials between organelles

smooth ER = lipids ; rough ER = proteins

35
Q

What is the structure of the golgi apparatus?

A

An assembly of vesicles and folded membranes located near the cell membrane

36
Q

What is the function of the golgi apparatus?

A

Involved in the sorting, storing, modification and export of secretory products

37
Q

What is the structure of the mitochondrion?

A

Double membrane structure, inner membrane highly folded into internal cristae

38
Q

What is the function of the mitochondrion?

A

Site of aerobic respiration (ATP production)

39
Q

What is the structure of the peroxisome?

A

Membranous sac containing a variety of catabolic enzymes

40
Q

What is the function of the peroxisome?

A

Catalyses breakdown of toxic substances (e.g. H2O2) and other metabolites

41
Q

What is the structure of the centrosome?

A

Microtubule organising centre (contains paired centrioles in animal cells but not plant cells)

42
Q

What is the function of the centrosome?

A

Radiating microtubules form spindle fibres and contribute to cell division (mitosis / meiosis)

43
Q

What are 3 organelles unique to plant cells?

A
  • chloroplast
  • vacuole (large, central and permanent)
  • cell wall
44
Q

What is the structure of a chloroplast?

A

Double membrane structure with internal stacks of membranous discs (thylakoids)

45
Q

What is the function of the chloroplast?

A

Site of photosynthesis – manufactured organic molecules are stored in various plastids

46
Q

What is the structure of a vacuole?

A

Fluid-filled internal cavity surrounded by a membrane (tonoplast)

47
Q

What is the function of a vacuole?

A

Maintains hydrostatic pressure (animal cells may have small, temporary vacuoles)

48
Q

What is the structure of the cell wall?

A

External outer covering made of cellulose (not an organelle per se, but a vital structure)

49
Q

What is the function of the cell wall?

A

Provides support and mechanical strength; prevents excess water uptake

50
Q

What is the structure of the lysosome?

A

Membranous sacs filled with hydrolytic enzymes

51
Q

What is the function of the lysosome?

A

Breakdown/hydrolysis of macromolecules (presence in plant cells is subject to debate)

52
Q

How do electron microscopes work?

A

Electron microscopes use electron beams focused by electromagnets to magnify and resolve microscopic specimens

53
Q

What 2 types of electron microscopes are there?

A

Transmission electron microscopes (TEM)

Scanning electron microscopes (SEM)

54
Q

What do TEM produce? (image type)

A

generate high resolution cross-sections of objects

55
Q

What do SEM produce? (image type)

A

display enhanced depth to map the surface of objects in 3D

56
Q

What are 2 key advantages of electron microscopes compared to light microscopes?

A

They have a much higher range of magnification (can detect smaller structures)

They have a much higher resolution (can provide clearer and more detailed images)

57
Q

What is a disadvantage of an electron microscope?

A

Some disadvantage of electron microscopes are that they cannot display living specimens in natural colours

58
Q

What is a micrograph?

A

A micrograph is a photo or digital image taken through a microscope to show a magnified image of a specimen

59
Q

How could we guess cell function from a micrograph?

A

Attempts can be made to deduce cell function based on the relative abundance of various organelles

60
Q

What does it suggest about the cell if it has a large number of mitochondria?

A

Cells with many mitochondria typically undertake energy-consuming processes (e.g. neurons, muscle cells)

61
Q

What does it suggest about the cell if it has a large ER network?

A

Cells with extensive ER networks undertake secretory activities (e.g. plasma cells, exocrine gland cells)

62
Q

What does it suggest about the cell if it has a large number of lysosomes?

A

Cells rich in lysosomes tend to undertake digestive processes (e.g. phagocytes)

63
Q

What does it suggest about the cell if it has a large number of chloroplasts?

A

Cells with chloroplasts undergo photosynthesis (e.g. plant leaf tissue but not root tissue)

64
Q

What 4 features of a prokaryotic cell are not found in a eukaryote?

A
  • pili
  • flagella (except sperm)
  • slime capsule
  • plasmid
65
Q

What size are ribosomes in a prokaryote?

A

labelled as 70S

66
Q

What is the cell wall in a prokaryote composed of?

A

peptidoglycan, (thicker than cell membrane)

IB Biology (38 decks)

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