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1.2 cell structure and organisation Flashcards

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1
Q

which microscope has a greater magnification and higher resolving power?

A

electron microscope because it uses electrons (rather than light), which have a much shorter wavelength

(so electron microscopes can see many more structures called organelles in eukaryotic cells)

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2
Q

organelle definition

A

a specialised structure with a specific function inside a (eukaryotic) cell

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3
Q

eukaryotic cells (eukaryotes) definition

A

they contain DNA in chromosomes in a nucleus, and possess membrane-bound organelles e.g plants and animals

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4
Q

resolving power definition

A

the minimum distance by which two points must be separated in order for them to be seen as two distinct points rather than a single focused image

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5
Q

what surrounds organelles?
and what are the advantages of this?

A

a membrane

potentially harmful chemicals, such as enzymes, are isolated, and molecules with particular functions, such as chlorophyll, can be concentrated in one area

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6
Q

what do membranes provide for organelles?

A

a large surface area for the transport of molecules and attachment of enzymes

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7
Q

what are the different units of measurements in biology? and what are they used to measure?

A
  • metre (m) = used to measure larger organisms
  • millimetre (mm) = used to measure tissues and organs
  • micrometre = cells and organelles (10^-6m)
  • nanometre (nm) = molecules (10^-9m)
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8
Q

what is the most convenient unit for measuring cells and organelles?

A

micrometres

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9
Q

what is the nucleus?

A
  • the largest organelle of the cell, bounded by a double membrane
  • present in the cytoplasm of a eukaryotic cell
  • CONTAINS DNA WHICH CODES FOR PROTEIN SYNTHESIS
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10
Q

what are the different components in a nucleus?

A
  • nucleolus
  • chromatin
  • nucleoplasm
  • (nuclear) pore
  • nuclear envelope
  • endoplasmic reticulum
  • ribosome
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11
Q

what is the nucleolus?

A
  • a small spherical body found within the nucleus
  • responsible for the production of rRNA and ribosomes
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12
Q

what is the nucleoplasm?

A
  • like the cytoplams of a cell, but for a nucleus
  • contains chromatin (which condenses to form chromosomes during cell division)
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13
Q

what is the nuclear envelope?

A
  • the double membrane which encloses the genetic material
  • has pores (to allow movement)
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14
Q

what are nuclear pores?

A
  • gaps in the nuclear envelope that allow movement
  • allows the passage of large molecules, such as mRNA and ribosomes
  • allows transport of messenger/mRNA/nucleotides/ribosomes
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15
Q

where is the endoplasmic reticulum in the nucleus?

A

the outer membrane of the double membrane is continuous with the endoplasmic reticulum

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16
Q

what is chromatin?

A
  • made of coils of DNA bound to protein (DNA-protein complex) but uncoils (is linear) when not during cell division
  • condenses to form chromosomes during cell division
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17
Q

what are the main functions of the nucleus?

A
  • enable protein synthesis (by creating ribosomes), cell division, growth and differentiation into specialised cells
  • stores genetic material in the form of chromatin
  • exchange of RNA with the rest of the cell
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18
Q

what is the endoplasmic reticulum?

A
  • a network of membranes connected to the nucleus of the cell by the nuclear envelope
  • has two types: rough and smooth
  • main role is concerned with the transport of material through the cell
  • a continuous membrane with many folds
  • form interconnected flattened fluid-filled sacs called cisternae
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19
Q

what is the smooth endoplasmic reticulum?

A
  • more tubular (tubular membrane)
  • lacks ribosomes
  • involved with the synthesis and transport of lipids
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20
Q

what is the rough endoplasmic reticulum?

A
  • has ribosomes on the outer surface
  • transports the proteins once they’ve been synthesised at the ribosomes (via the cisternae)

packages and transports proteins

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21
Q

what are cisternae?

A

interconnected flattened fluid-filled sacs in the endoplasmic reticulum

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22
Q

vesicle definition

A

a ‘bubble’ that can contain and transport molecules inside of it

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23
Q

what is the golgi body?

A
  • stack of curves cisternae
  • vesicles containing polypeptides (building blocks of protein) pinch off from the rough endoplasmic reticulum, and fuse with the golgi
  • proteins are modified and packed into vesicles by the golgi body for export
  • also involved in the transport and storage of lipids, and the production of glycoproteins and lysosome
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24
Q

what are the components of a mitochondria?

A
  • circular DNA
  • matrix
  • outer membrane
  • inter-membrane space
  • inner membrane
  • crista (cristae)
  • 70s ribosomes
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25
Q

what is the usual size and shape of a nucleus?

A

usually spherical
and 10-20 micrometres in diameter

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26
Q

what is the usual size and shape of a mitochondria?

A

often cylindrical
1-10 micrometers in length

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27
Q

what type of cells have extensive endoplasmic reticulum?

A

cells that store large quantities of carbohydrates, proteins and fats, including liver and secretory cells

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28
Q

why type of cells contain lots of mitochondria?

A

they are present in all cells, but are found in much higher number in metabolically active cells e.g in muscle cells, that need a plentiful supply of ATP

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29
Q

what is the mitochondria?

A
  • the site of aerobic respiration/ ATP production (energy)
  • RELEASES energy
  • has a double membrane
  • being cylindrical, has a larger surface area than a sphere of the same volume (big surface area to volume ratio) + reduces the diffusion distance b/w the edge and the centre, making aerobic respiration more efficient
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30
Q

what is the cristae?
why is this useful?

A
  • the inner membrane of the mitochondria is folded into structures called cristae
  • it PROVIDES A LARGE SURFACE AREA for the attachment of enzymes involved in respiration
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31
Q

what is the inter-membrane space?

A
  • the space in between the two membranes (outer membrane and the inner membrane) in a mitochondria
  • fluid-filled
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32
Q

what is the matrix?

A
  • the volume enclosed by the inner membrane in a mitochondria
  • a solution containing many compounds, including lipids and proteins, 70s ribosomes and a small circle of DNA
  • contains the enzymes we need for respiration
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33
Q

what are the 70s ribosomes and the small circle of DNA for in a mitochondria?

A

they enable mitochondria to make some of their own proteins and self-replicate

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34
Q

in a mitochondria, where do the reactions occur?

A

some occur in the matrix and others on the inner membrane

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35
Q

what are the components of a chloroplast?

A
  • double membrane
  • thylakoid
  • thylakoid membrane
  • inter-granal lamella
  • granum
  • 70s ribosomes
  • starch grain
  • stroma
  • circular DNA
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36
Q

what are the chloroplasts?

A
  • the site of photoynthesis
  • absorbs sunlights and converts into sugar molecules
  • found in photosynthetic plants
  • surrounded by two membranes, comprising the chloroplast envelope
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37
Q

what is the thylakoid?

A
  • a flattened membrane
  • site of light absorption in the chloroplasts
  • stacks of thylakoid contain the photosynthetic pigments, which include chlorophyll
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38
Q

what is the granum?

A
  • stacks of thylakoids (between two and a hundred parallel stacks) in a chloroplast
  • this arrangement produces a large surface area, efficient for trapping light energy
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39
Q

what is the lamella?

A
  • they connect the stacks of thylakoids together and allow transport between the stacks in a chloroplast
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40
Q

what is the stroma?

A
  • fluid-filled
  • got enzymes used in photosynthesis
  • filled with starch grains, 70s ribosomes and a circle of DNA
  • like the cytoplasm/nucleoplasm but in a chloroplast
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41
Q

in chloroplasts, what do the 70s ribosomes and circular DNA enable them to do?

A

enable them to make some of their own proteins and self-replicate

(like mitochondria)

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42
Q

in chloroplasts, is the inner membrane folded?

A

no
(only in mitochondria)

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43
Q

why are thylakoids arranged how they are in chloroplasts?

A

it produces a large surface area so is efficient for trapping light energy

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44
Q

prokaryotes definition

A

a single-celled organism lacking membrane-bound organelles, such as a nucleus, with its DNA free in the cytoplasm

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45
Q

what are the components of a ribosome (when drawing a diagram)?

A
  • 2 tRNA attachment sites
  • mRNA attachment site
  • large subunit
  • small subunit
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46
Q

what are ribosomes made from? and where are they found?

A
  • made from rRNA and protein
  • found within the cytoplasm
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47
Q

are ribosomes surrounded by a membrane?

A

no

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48
Q

what is the role of ribosomes?

A
  • the assembly of proteins during translation
  • they are important in protein synthesis, as they are the site of translation, where mRNA is used to assemble the polypeptide chain
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49
Q

what is the size of ribosomes in prokaryotic cells? in eukaryotic cells?

A
  • prokaryotic cells = 70s in size
  • in the cytoplasm of eukaryotic cells = 80s, where they occur singly or attached to membranes on the RER (except 70s in mitochondria and chloroplasts)
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50
Q

what does the small subunit contain? the large subunit? in a ribosome

A
  • the small subunit contains a mRNA attachment site
  • the large subunit contains two tRNA attachment sites
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51
Q

how do ribosomes compare in size between nucleus and mitochondria?

A

ribosomes are much smaller than the nucleus and mitochondria

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52
Q

what is the endosymbiotic theory?

A

the theory that describes the origin of chloroplasts and mitochondria

  • it has been suggested that these organelles arose from a symbiotic relationship between early cells that engulfed photosynthetic and respiratory bacteria over 1.5 billion years ago
  • they both have 70s ribosomes and circular DNA (which are the type found in prokaryotes including bacteria)
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53
Q

what are lysosomes? what is their role?

A
  • vesicles with (hydrolytic/digestive) enzymes inside to break down waste product
  • their role is to digest worn out organelles within the cell, and foreign material that has been engulfed by phagocytosis e.g bacteria engulfed by a white blood cell

(also contain digestive enzymes that break down/recycle worn out organelles or cells)

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54
Q

how are lysosomes formed?

A

formed by being pinched off from the golgi body

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55
Q

what enzyme do lysosomes contain?

A

the digestive enzyme lysozyme

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56
Q

what are centrioles?

A
  • present in all animal cells and most protoctistans (but not in the cells of higher plants)
  • consist of two rings of microtubules (making cylinders) positioned at right angles to each other
  • they organise the microtubules that make the spindle during cell division
  • located just outside the nucleus
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57
Q

what is the function of a vacuole?

A
  • supporting soft plant tissues
  • but also store chemicals such as glucose and amino acids in the cell sap
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58
Q

what are vacuoles?

A
  • fluid-filled sac bounded by a single membrane, the tonoplast
  • most are large and permanent
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59
Q

in plants, what is the cell wall mostly made from?

A

cellulose

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60
Q

what are the functions of the cell wall?

A
  • STRENGTH = providing strength to the cell wall, which resists the expansion of the vacuole due to osmosis, and so the cell becomes turgid, supporting the plant
  • TRANSPORT = transports water and dissolved molecules and ions through gaps in the cellulose fibres (known as the apoplast pathway - the main way that water crosses the plant root)
  • COMMUNICATION BETWEEN CELLS = communication between cells via pores in the cell wall which allow strands of cytoplasm called plasmodesmata to pass. this allows water to pass via the symplast pathway (important in the transport of water through a plant)
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61
Q

what is plasmodesmata?

A
  • strands of cytoplasm
  • they pass through the pores in the cell wall
  • plasmodesma occurs where there is no cellulose thickening between two cells
  • they run from one cell to the next

(this network of cytoplasm in connected cells is called the symplast)

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62
Q

do all plant cells contain chloroplasts?

A

no - root cells for example, being underground, would have no use for them

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63
Q

are cell walls found in animal cells? plant cells?

A

animals cells - absent
plant cells - present = it surrounds the cell membrane

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64
Q

are chloroplasts found in animal cells? plant cells?

A

animal cells - absent
plant cells - present = in cells above ground

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65
Q

are plasmodesmata found in animal cells? plant cells?

A

animal cells - absent
plant cells - present

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66
Q

are vaculoes found in animal cells? plant cells?

A

animal cells - present = but small, temporary; scattered throughout cell
plant cells - present = large, permanent, central; filled with cell sap

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67
Q

are centrioles found in animal cells? plant cells?

A

animals cells - present
plant cells - absent

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68
Q

what energy store is found in animal cells? plant cells?

A

animal cells - glycogen
plant cells - starch

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69
Q

what does the nucleus contain and what does it do?

A
  • contains chromosomes
  • in which the DNA encodes proteins
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70
Q

what do the nuclear pores in the nuclear envelope allow?

A

it allow mRNA molecules, transcribed off the DNA, to leave the nucleus and attach ribosomes in the cytoplasm or on the rough ER

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71
Q

what do ribosomes contain?

A

rRNA, transcribed from DNA located at the nucleolus

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72
Q

where does protein synthesis occur? what does it produce?

A
  • occurs on ribosomes
  • produces proteins in their primary structure
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73
Q

where are polypeptides made? where are they then moved to?

A
  • polypeptides made on the ribosomes are moved through the RER and are packaged into vesicles
  • the vesicles bud off the RER and carry polypeptides to the Golgi body, where they are chemically modified and folded
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74
Q

what does the Golgi body produce? what may they be?

A
  • produces vesicles containing newly synthesised proteins
  • these may be lysosomes, containing digestive enzymes, used within the cell
  • they may be secretory vesicles, which carry the proteins to the cell membrane for exocytosis
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75
Q

what do secretory vesicles do?

A

carry the proteins to the cell membrane for exocytosis

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76
Q

what do phospholipids and triglycerides move through? where do they go?

A
  • they move through the smooth endoplasmic reticulum
  • to various destinations in the cell
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77
Q

what have eukaryotic cells?

A
  • fungi
  • protoctista
  • plants
  • animals
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78
Q

are viruses made of cells?

A

no - they are not made of cells and they are not classified with living organisms
- they seem to exist at the interface between living and non-living systems

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79
Q

prokaryote definition

A

a single-celled organism lacking membrane-bound organelles, such ad a nucleus, with its DNA free in the cytoplasm

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80
Q

eukaryote definition

A

an organism containing cells that have membrane-bound organelles, with DNA in chromosomes within the nucleus

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81
Q

what is an example of a prokaryotic cell?

A

a bacterium

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82
Q

what is the major distinguishing feature of prokaryotic cells?

A
  • they have no nucleus
  • or any internal membrane

so unlike eukaryotic cells, they have no membrane-bound organelles

  • also they are unicellular and rarely form multicellular structures
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83
Q

in some prokaryotes, what increases the surface area of the cell’s membrane?

A

the infolding of the cell membrane in a mesosome or photosynthetic lamellae

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84
Q

for each one, state whether it’s in all prokaryotes or only some prokaryotes?
- DNA molecule loose in cytoplasm
- peptidoglycan (murein) cell wall
- slime coat
- 70S ribosomes
- flagella (one, some or many)
- photosynthetic lamellae holding photosynthetic pigments
- cytoplasm
- cell membrane
- mesosomes - possible site of aerobic respiration
- plasmids

A
  • DNA molecules loose in cytoplasm - ALL
  • peptidoglycan cell wall - ALL
  • slime coat - SOME
  • 70S ribosomes - ALL
  • flagella - SOME
  • photosynthetic lamellae - SOME
  • cytoplasm - ALL
  • cell membrane - ALL
  • mesosome - SOME
  • plasmids - SOME
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85
Q

what is the difference between prokaryotes and eukaryotes?

A

prokaryotes:
- smaller
- no organelles
- DNA free in cytoplasm
- no nuclear envelope
- plasmids may be present
- peptidoglycan (murein) cell wall
- no chloroplasts (but may use photosynthetic lamella for photosynthesis)
- no mitochondria (but may use mesosome for respiration)
- 70s ribosomes, free in cytoplasm

eukaryotes
- larger
- membrane-bound organelles
- DNA combined with protein in chromosomes
- double membrane nuclear envelope
- plasmids absent
- cellulose cell wall in plants, chitin in fungi
- chloroplasts in plants and some protoctista
- mitochondria present
- mesosome absent
- 80s ribosomes, free in cytoplasm or attached to ER

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86
Q

why can’t viruses be seen in the light microscope?

A

they are so small

87
Q

what does being small allow viruses to do?

A

pass through filters that can trap bacteria

88
Q

why are viruses described as ‘acellular’?

A

they are not made of cells

  • there are no organelles, no chromosomes and no cytoplasm
89
Q

what happens when a virus invades a cell?

A

they are able to take over the cell’s metabolism and multiply inside the host cell

90
Q

what is each virus particle made up of?

A
  • a core of nucleic acid, either DNA or RNA surrounded by a protein coat, the capsid
  • in some viruses, a membrane derived from the host cell surrounds the capsid
91
Q

what cells can be infected with viruses?

A

cells of all groups of organisms

92
Q

what is the virus that attacks bacteria called?

A

bacteriophages

93
Q

what is an example of a well-known bacteriophage?

A

T2, which attacks Escherichia coli (E.coli)

94
Q

what is the only characteristic of life that viruses show?

A

their ability to reproduce

95
Q

can viruses be crystallised?

A

yes - not a property associated with living organisms

96
Q

what are examples of infective viruses in human hosts?

A
  • flu
  • chickenpox
  • cold
  • HIV
  • mumps
  • rubella
  • Ebola
97
Q

what are examples of infective viruses in plants hosts?

A
  • tobacco mosaic virus
  • cauliflower mosaic virus
98
Q

what are examples of infective viruses in bird hosts?

A
  • avian flu
99
Q

what are examples of infective viruses in other mammal hosts?

A
  • swine flu
  • cow pox
  • feline leukaemia virus
100
Q

in an exam, read the question very carefully. notice if you are asked for the name of a virus or the name of the disease it causes

A

e.g tobacco mosaic virus causes tobacco mosaic disease
HIV causes HIV-AIDS

101
Q

what is the function of single-celled organisms?

A

single-celled organisms carry out all life functions within a single cell

102
Q

what is the function of multicellular organisms?

A

multicellular organisms have specialised cells, forming tissues and organs, which have various structures and roles

103
Q

what do stem cells have the potential to do?

A

to become any cell type in the body

104
Q

what is differentiation?

A

the development of a cell into a specific type

105
Q

what happens when cells differentiate?

A

they become specialised in structure and in the chemical reactions that they perform

106
Q

tissue definition

A

group of cells with the same structure and function working together

(a group of one type of cell/ similar/same cells working together to perform a function)

107
Q

what do cells near each other in the embryo, that often differentiate in the same way, group together as?

A

a tissue

108
Q

do mammals have several tissue types?

A

yes

109
Q

what are 3 examples of mammalian tissues?

A
  • epithelial tissue
  • muscular tissue
  • connective tissue
110
Q

epithelial tissue properties:

A
  • forms a continuous layer, covering/lining the internal and external surfaces of the body
  • have no blood vessels (but may have nerve endings)
  • the cells sit on a basement membrane (made of collagen and protein) and they vary in shape and complexity
  • often have a protective or secretory function (also often the sites of absorption of substances)
111
Q

do epithelial tissues have blood vessels?

A

no (but they may have nerve endings)

112
Q

what do epithelial tissue cells sit on?

A

a basement membrane

113
Q

what are basement membranes made of?

A

collagen and protein (and they vary in shape and complexity)

114
Q

what function does epithelial tissue usually have?

A

protective or secretory function

115
Q

what are the three types of epithelial tissue?

A
  • cuboidal epithelium
  • columnar epithelium
  • squamous epithelium
116
Q

cuboidal epithelium properties?

A
  • cells have a cube shape
  • tissue is just one cell thick
  • occurs in the proximal convoluted tubule of the kidney nephron and the ducts of salivary glands
  • they reabsorb useful substances that are filtered out of the blood
117
Q

how thick are cuboidal epitheliums?

A

just one cell thick (simple)

118
Q

where do cuboidal epithelium occur?

A

in the proximal convoluted tubule of the kidney nephron and the ducts of salivary glands

119
Q

columnar epithelium properties:

A
  • elongated cells
  • those lining tubes that substances move through, such as the oviduct (fallopian tube) and trachea, have cilia
  • the cilia move and sweep substances along
120
Q

squamous epithelium properties:

A
  • consist of flattened cells on a basement membrane
  • they form the walls of the alveoli and line the renal (bowman’s) capsule of the nephron
  • short diffusion distance
121
Q

what do squamous epithelium form? what do they line?

A
  • they form the walls of the alveoli
  • they line the renal (bowman’s) capsule of the nephron
122
Q

what are the three main muscle tissue types?

A
  • skeletal muscle
  • smooth muscle
  • cardiac muscle
123
Q

skeletal muscle properties:

A
  • attached to bones
  • generates locomotion in mammals
  • has bands of long cells, or fibres, which give powerful contraction, but these muscles tire easily
  • you can choose whether to contract these muscles of not, so they are called voluntary muscles
  • because you can see stripes on them in the microscope, they are also called striped or striated muscle
124
Q

what enables skeletal muscles to give powerful contractions?

A
  • it has bands of long cells, or fibres, which give powerful contraction
125
Q

do skeletal muscles tire easily?

A

yes

126
Q

why are skeletal muscles called striped or striated muscle?

A

because you can see stripes on them in the microscope

127
Q

what are skeletal muscles attached to?

A
  • they are attached to bones
128
Q

smooth muscle properties:

A
  • have individual spindle-shaped cells that can contract rhythmically, but they contract less powerfully than skeletal muscle
  • they occur in the skin, in the walls of blood vessels and in the digestive and respiratory tracts
  • you cannot control these muscles, so they are called involuntary muscles
  • they do not have stripes and so are called unstriped or unstriated muscle
129
Q

are skeletal muscles called voluntary or involuntary muscles?

A

voluntary - because you can choose whether or not to contract these muscles

130
Q

do smooth muscles contract powerfully?

A
  • they contract less powerfully than skeletal muscles
131
Q

what makes smooth muscles contract?

A
  • they have individual spindle-shaped cells that can contract rhythmically

(but they contract less powerfully than skeletal muscles)

132
Q

where do smooth muscles occur?

A

in the skin, in the walls of blood vessels and in the digestive and respiratory tracts

133
Q

are smooth muscles called voluntary or involuntary muscles?

A

involuntary - you cannot control these muscles

134
Q

do smooth muscles have stripes?

A

no - so they are called unstriped or unstriated muscle

135
Q

cardiac muscle properties:

A
  • only found in the heart
  • its structure and properties are somewhat in between skeletal and smooth muscle
  • have stripes
  • but lack the long fibres of skeletal muscle
  • they contract rhythmically, without any stimulation from nerves or hormones, although these can modify their contraction
  • do not tire
136
Q

where are cardiac muscles found?

A

only in the heart

137
Q

are cardiac muscles similar to skeletal and smooth muscles in terms of structure and properties?

A
  • they are somewhat in between skeletal and smooth muscles
  • the cells have stripes, but lack the long fibres of skeletal muscle
138
Q

do cardiac muscles contract rhythmically?

A

yes - without any stimulation from nerves and hormones, although these can modify their contraction

139
Q

do cardiac muscles tire?

A

no

140
Q

connective tissue properties:

A
  • connects, supports or separates tissues and organs
  • contains elastic and collagen fibres in an extracellular fluid or matrix
  • between the fibres are fat-storing cells (adipocytes) and cells of the immune system
141
Q

what does connective tissue do?

A
  • connect, support or separates tissues and organs
142
Q

what does connective tissue contain?

A

elastic and collagen fibres in an extracellular fluid or matrix

143
Q

what are between the fibres of connective tissue?

A

fat-storing cells (adipocytes) and cells of the immune system

144
Q

organ definition

A

a group of tissues in a structural unit, working together and performing a specific function

145
Q

what does an organ do?

A

comprises of several tissues working together, performing a specific function

146
Q

what is an example of on organ?

A

in humans e.g the eye contains nervous, connective, muscle and epithelial tissues and is the organ of sight

147
Q

what is an organ system?

A

a group of organs working together with a particular role

148
Q

what is an example of a mammalian organ system?

A

the circulatory system consists of the heart and aorta

149
Q

what is an organism?

A
  • is a discrete individual
  • when all of the systems of the body are working together, making an organism
150
Q

where are prokaryotic cells found?

A

in bacteria and cyanbacteria

151
Q

in what kingdom are prokaryotic cells?

A

prokaryotae

152
Q

where are eukaryotic cells found?

A

in all organisms apart from bacteria

153
Q

in what kingdoms are eukaryotic cells?

A
  • protoctista
  • fungi
  • plantae
  • animalia
154
Q

do prokaryotes have any membrane bound organelles?

A

no

155
Q

how are ribosomes different in prokaryotic cells than eukaryotic cells?

A

in prokaryotic cells:
- the site of photosynthesis
- BUT not attached to any membranes
- also slightly smaller (70s not 80s)

156
Q

what is the mesosome in prokaryotic cells?

A
  • site of respiration
  • in-foldings of the cell membrane
  • for enzymes to attach
  • large surface area
157
Q

what are the plasmids in prokaryotic cells?

A
  • tiny loops of DNA
  • carrying only a few genes
  • occur though out the cytoplasm
158
Q

what is the flagellum in prokaryotic cells?

A
  • the ‘tail’
  • it rotates
  • allowing the bacteria to move
  • not all bacteria have one (and some have more than one)
159
Q

what is the capsule (slime layer) in prokaryotic cells?

A
  • type of protein
  • stops cell drying out (helps it to retain moisture)
  • protects the cell
  • helps the cell adhere to surfaces
160
Q

how is the cell wall different in prokaryotic cells than eukaryotic cells?

A

in prokaryotic cells:
- made of a protein called murein

161
Q

how is the cell membrane different in prokaryotic cells than eukaryotic cells?

A

it’s not - they are the same

162
Q

what is the nucleoid/DNA in prokaryotic cells?

A
  • single circular piece of DNA
  • forming the bacterial chromosomes
  • but no nuclear membrane
163
Q

what do all eukaryotic cells contain?

A

a nucleus and membrane bound organelles

164
Q

what does the rough endoplasmic reticulum do?

A

folds and processes proteins made on the ribosomes

165
Q

what does the nucleolus do?

A

it’s the site of ribosome production

166
Q

what does the smooth endoplasmic reticulum do?

A

produces, packages and transports a lipids

167
Q

what does the golgi apparatus do?

A

processes and packages proteins and lipids.
it also produces lysosomes

168
Q

what are viruses?

A

non-living structures which consist of nucleic acid (DNA or RNA) enclosed in a protective protein coat called the capsid, sometimes covered with a lipid layer called the envelope

169
Q

are centrioles found in pairs?

A

yes
they are found in pairs in centrosomes

170
Q

what is the function of centrioles?

A
  • they migrate to opposite poles of the cell during prophase
  • they are involved in the organisation of spindle fibres
171
Q

what is the function of pili in prokaryotic cells?

what is the structure of pili in prokaryotic cells?

A

they enable the attachment of bacteria to each other and to other surfaces

they are hair-like microfibres made of pilin that extend through the cell wall

172
Q

what is cell theory?

A
  • new cells can be formed from other existing cells
  • the cell is a fundamental unit of structure, function and organisation in all living organisms
  • cells contain genetic information which can be transferred to daughter cells
  • organisms can be unicellular e.g amoeba or multicellular e.g animals
173
Q

why do scientists not believe that viruses are cells or even alive?

A

because:
- they have no cell membrane
- they have no cytoplasm
- they cannot carry out respiration and synthesise ATP
- they do not grow
- they cannot replicate or reproduce on their own - they must invade a host cell and use the cell’s metabolic processes to produce more viruses particles

174
Q

what components of prokaryotic cells are not present in ALL prokaryotic cells?

A
  • pili
  • capsule
  • flagellum
175
Q

are centrioles found in animal cells, plant cells or both?

A

only animal cells

176
Q

what is found in only prokaryotic cells?

A
  • mesosome
  • plasmids and nucleoid
  • peptidoglycan (murein) cell wall
177
Q

what is found in only plant cells?

A
  • chloroplasts
  • plasmodesmata
  • vacuoles
  • cellulose cell wall
178
Q

what does the process of protein synthesis involve at every component?

A
  • in the nucleus = the transcription of the genetic code in DNA into messenger RNA (mRNA)
  • in the nucleolus = production of ribosomes
  • the nuclear pores = the mRNA leaves the nucleus and enters the cytoplasm through nuclear pores
  • in the cytoplasm = ribosomes translate of the code in mRNA into polypeptides (amino acids are bonded together by peptide bonds t form a polypeptide)
  • in RER = a vesicle pinches off the RER and transports the polypeptide to the golgi body
  • in Golgi bodies = the processing of the polypeptide to produce functional proteins (folding to give secondary/tertiary structure, adding carbohydrate chains, combining polypeptides) and packaging of the proteins into secretory vesicles for secretion
179
Q

what is an advantage of squamous epithelium being very thin?

A

because they line the alveoli in the lungs, being very thin reduces the diffusion distance for the exchange of gases

180
Q

what are muscle tissues responsible for?

A

moving parts of the body through contractions

181
Q

what are the main differences between a light microscope and an electron microscope?

A

light microscope:
- uses a beam of light (longer wavelength)
- can see colour images
- can observe live specimens
- resolution power is lower
- magnification is lower

electron microscope:
- uses a beam of electrons (shorter wavelength)
- can only see black and white images
- specimens must be dead
- resolution power is higher
- magnification is higher

182
Q

because electron microscopes use beams of electrons rather than light, they can…?

A
  • produce images at a higher magnification
  • produce images which are clearer and with greater detail - they have greater resolution
183
Q

what is used to give more contrast between cell structures and make them easier to see when using microscopes? what is a disadvantage with this?

A

staining
however, staining cells kills them so cannot be used when observing live cells

184
Q

how do you work out the magnification?

A

magnification = image/actual

185
Q

resolution definition

A

the smallest distance between two points that can be separately distinguished

186
Q

why do electron microscopes have greater resolution than light microscopes?

A

because electrons have a much shorter wavelength than visible light so they distinguish objects that are smaller and closer together

187
Q

what does the resolution of a microscope tell you?

A

how close two points can be and still be separately distinguished, rather than being seen as a single image

it tells you the detail which can be seen

188
Q

what is the cell wall of prokaryotic cells made from?

A

peptidoglycan

189
Q

do viruses possess a cytoplasm, organelles or any chromosomes?

A

no - just a core of nucleic acid surrounded by a protein coat, called the capsid

190
Q

how do you work out the size of object, using magnification and size of image?

A

size of object = size of image/magnification

191
Q

how can mitochondria differ in appearance when looking at a diagram?

A
  • cut in different plane

(another reason that could account for the difference in their appearance : self-replication / stage (of division) / stage of development/ size / not fully formed / age)

192
Q

what kingdom has eukaryotic characteristics, has a nucleus and in some species have chloroplasts and a cell wall?

A

protoctista

193
Q

what is an example of a cell that contains lots of mitochindria?

A

muscles/secretory cell

194
Q

what is the function of mitochondria? (exam question)

A
  • site of respiration
  • RELEASES energy in the form ATP
195
Q

what is the function of the nucleus?

A
  • contains DNA coiled around chromatin into chromosomes
  • coordinates cellular activities
196
Q

describe the sequence of events that lead to the production of digestive enzymes in a cell (using the nucleus, nuclear pores and ribosomes)

A

nucleus : contains DNA which codes for the production of proteins/polypeptides - production of mRNA (1)
nuclear pores : allow mRNA/rRNA to leave the nucleus
ribosomes : carry out protein synthesis

197
Q

describe the sequence of events that lead to the secretion of digestive enzymes from a cell (by RER, golgi body and vesicles)

A

RER: transports proteins through the cell to golgi body where it packages proteins into vesicles
golgi body : packaging/modification of protein
vesicles : transports proyeins to the cell membrane

exocytosis (of enzymes from the cell)

198
Q

what is the role of mitochondria in the production and secretion of digestive enzymes?

A
  • provide ATP for protein synthesis/transcription/translation
  • exocytosis
199
Q

where are cuboidal tissues found in the body?

A

kidney tubule

200
Q

where are cilliated tissues found in the body?

A

trachea/bronchi

201
Q

what are two differences between the ribosomes found in animal cells and those found in prokaryotic cells?

A
  • ribosomes are not attachrd to membranes/ER in prokaryoyes - (some) are in animal cells
  • ribosomes larger (80s) in animal cells than prokaryotes (70s)
202
Q

state which 2 structures found in prokaryotic cells are also found in mitochondria

A
  • (loop of) DNA
  • 70s ribosomes
203
Q

explain why e.g liver cells have large numbers of mitochondria present

A

they are metabolically active so large amounts of ATP required

204
Q

what is the edge of the vacuole in a plant cell called?

A

tonoplast

205
Q

what is the gap in the cell wall and cell membrane in a plant cell called?

A

plasmodesmata

206
Q

describe the structure and function of lysosomes

A
  • fluid-filled vesicles surrounded by a single membrane, contain enzymes
  • role in phagocytosis, digest unwanted materials in the cytoplasm
207
Q

describe the functions of the permanent vacuole in plants

A
  • control turgor pressure
  • water storage
  • isolates harmful waste products
  • maintained pH
208
Q

how is genetic information stored in prokaryotes?

A
  • plasmids - small rings of DNA that carry non-essential genes, exchanged between bacterial cells via conjugation
  • loop of DNA - circular DNA stored in the nucleoid region of the cell
209
Q

describe the structure and function of mesosome

A
  • infolds of the cell membrane
  • increase the surface area of the cell, aiding cellular respiration
210
Q

by what do prokaryotes reproduce?

A

binary fission

211
Q

in viruses, what is the genetic material in the form of?

A

DNA or RNA

(while prokaryotes and eukaryotes’s genetic material is only in the form of DNA)

212
Q

what is the function of the double nuclear membrane/nuclear envelope in nuclei?

A

separates the DNA from the rest of the cellular contents/hold DNA/chromosomes

213
Q

following processing by the golgi body, describe how proteins are secreted from the cell [3]

A
  • MEMBRANE of (secretory vesicles/vesicles containing product), fuses with cell membrane
  • contents released from cell (secreted is neutral)
  • exocytosis

as level biology (13 decks)

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