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Alevel Biology > 2.1 > Flashcards

2.1 Flashcards

1
Q

Electron micrograph

A

Photograph of an image seen using an electron microscope

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2
Q

Magnification

A

Number of times larger an image appears, compared with size of object

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3
Q

Organelles

A

Small structure within cells, each of which has specific function

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4
Q

Photomicrograph

A

Photograph of an image seen using optical microscope

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5
Q

Resolution

A

Clarity of an image, higher the resolution, the clearer the image

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6
Q

What is magnification

A

How much bigger ab image appears compared to original object

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7
Q

What type of magnification do microscopes produce

A

Linear magnification

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8
Q

Why do we say that microscopes magnification is linear

A

Is specimen is magnified by x100, then it is seen as 100times wider and longer than it is

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9
Q

What is resolution

A

Ability of optical instruments to see/ produce an image that shows fine detail clearly

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10
Q

Give an example of something with high resolution

A

UHD television is extremely clear and sharp images on the screen

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11
Q

What are optical microscopes useful in understanding

A

Basic cell structure

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12
Q

Where are optical microscopes used

A

Schools, hospitals and research labs

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13
Q

Why are optical microscopes used in schools and hospitals

A

Cheap, easy to use, portable and able to study a living specimen

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14
Q

What does optical microscope rely on to work

A

Lenses focusing a beam of light

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15
Q

What is an optical microscope magnification

A

x1500-x2000

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16
Q

What does optical microscope enable use to see

A

Larger cell structures

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17
Q

What does optical microscopes limited resolution mean

A

They can’t magnify more whilst producing a clear image

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18
Q

How does an optical microscope work

A

They use visible light on electromagnetic spectrum (400-700nm), so structures closer together than 200nm will appear one object such as ribsomes which are only 20nm

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19
Q

How would you analyse a specimen on a light microscope

A

1.put specimen on slide and clip into place with stage clips 2.rotate nose piece till low power objective lens is over specimen 3.adjust coarse focus knob and fine focus knob whilst looking into eyepiece until image is clear and focused 4.adjust iris diaphragm for optimum light 5.make sure specimen is directly over hole on the stage and turn to x10 lens and refocus with knobs 6.repeat step 5 with x40 objective lense

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20
Q

What is the equation for total magnification

A

Magnifying power of objective lens x magnifying power of eyepiece lense

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21
Q

What is a photomicrograph

A

Photo of image seen using optical microscope

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22
Q

How does a laser scanning microscope work

A

Uses laser to scan object point by point and assemble by computer pixel information into one image, displayed on a computer screen

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23
Q

Are image high or low resolution on laser scanning microscope and do they show contrast

A

High resolution and show contrast

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24
Q

How can laser scanning microscopes observe whole living specimen as well as individual cells

A

They have depth selectivity so can focus on structures at different depths in specimen

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25
Q

Where and when are laser scanning microscopes used

A

Used in medical professions, to observe fungal filament within cornea of eye in patients who have fungal infection, used in branches of biological research

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26
Q

What must be done to the specimen before using it in a transmission electron microscope

A

Specimen must be chemically fixed by being dehydrated and stained

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27
Q

How does transmission electron microscope work

A

Beam of electrons pass through specimen (stained with metal salts which can harm user) some electrons pass through and are focused on screen or photographic plate

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28
Q

What kind of image does a transmission electron microscope form

A

A 2D b&w image, when photographed called an electron micrograph

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29
Q

What magnification does transmission electron microscope have

A

x2,000,000 - x50,000,000

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30
Q

What happens in scanning electron microscope

A

Electrons don’t pass through specimen but causes secondary electrons to reflect off specimen surface and then be focused onto a screen

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31
Q

Does scanning electron microscope produce 2/3D image

A

3D

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32
Q

What is magnification of scanning electron microscope

A

x15 - x200 000

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33
Q

In scanning electron microscope what colour is the image

A

B&w but computer software adds false colours to make it easier to see different structures

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34
Q

What must specimen be dead before being used in scanning electron microscope

A

As specimen must be placed in a vacuum and often coated with a fine film of metal

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35
Q

How does an electron microscope work

A

Beams fast travelling electrons with wavelength of 0.004nm, electrons fired from cathode and focused by magnet rather than glass lenses onto screen or photographic plate

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36
Q

Why is electron microscope better than optical microscope

A

Greater resolution so used to giver clear and highly magnified images

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37
Q

Why is fast travelling electrons have better resolution than optical microscope

A

They have x125000 smaller wavelength than central part of visible light spectrum

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38
Q

Why are electron microscopes not as commonly used

A

Both types require lots of training, are expensive and large so cannot be moved easily

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39
Q

What size is an atom and what microscope can see it

A

0.1nm and electron microscope

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40
Q

What size is lipid and what microscope can see it

A

1nm and electron microscope

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41
Q

What size is ribosomes and what microscope can see It

A

10nm and electron microscope

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42
Q

What size if influence virus and what microscope can see it

A

100nm and light and electron microscope

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43
Q

What size are mitochondria, chloroplast and bacterium and what microscope can see it

A

1um and electron and light microscope

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44
Q

What size is human cheek cell and human ovum and what can see it

A

10um and electron and light microscope

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45
Q

Down to what size can the human eye see

A

1m - 1mm

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46
Q

What is the smallest thing human eye could see

A

Amoeba

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47
Q

What is the resolving power

A

Minimum distance two points must be separated in order for them to be seen as two separate points like microscope resolution is 0.2um

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48
Q

Advantages of electron microscope

A

Use electron beam instead of light and use electromagnets instead of glass lenses

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49
Q

Resolution of electron microscope

A

1nm

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50
Q

Disadvantage of electron microscope

A

Material must be dead as it is done in a vacuum

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51
Q

What specimen can you view under light microscope

A

Living organisms like paramecium and amoeba and smear preparations of human blood and cheek cell and thin sections of animal, plant and fungi tissue such as bone, muscle, leaf, root, or fungal hayphae

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52
Q

Why must biological structures be stained before viewing

A

Many structures are colourless and transparent, such as single felled organisms (paramecium)

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53
Q

What do some light microscopes use instead of staining

A

Light interference such as using a dark background to illuminate specimen

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54
Q

When is light interference most useful

A

Useful for studying living specimens and you can observe this with school light microscopes by adjusting iris diaphragm to reduce illumination of specimen

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55
Q

What are stains

A

Coloured chemicals that bind to molecules or on the specimen that makes them easy to see

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56
Q

Give an example of an all purpose stain

A

Methylene blue

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57
Q

What is differential staining

A

Where some stains bind to specific cell structures, staining each differently so structure can be easily identified within a single preparation

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58
Q

What stain binds to DNA and stains chromosomes dark red

A

Acetic stains

59
Q

What is eosin stain

A

Stains cytoplasm

60
Q

What does Sudan red stain

A

Lipids

61
Q

What stains cellulose yellow and starch granules blue/black which look violet under microscope

A

Iodine in potassium iodine

62
Q

How do scientists in a lab make a prepared fixed slide for schools

A

Dehydrate the specimen, then embed them with wax preventing distortion during slicing, create sections(very thin slices) using special instruments, then stain and mount them onto special chemical which will preserve them

63
Q

How do you work out actual size of object from a photosmicrogram if you know the magnification

A

Measure with of specimen on diagram in mm, convert to um by x1000, and divide by magnification

64
Q

Equation for magnification

A

Image size/actual size

65
Q

How do you draw biological drawing

A

Use sharp pencil, title drawing and write magnification, indicate how much bigger it is than actual size, use clear unbroken lines and no shading, label areas on low power plan, then draw high power of 2-3 cells and identify structures you can see, use a ruler to label

66
Q

What is 2mm in um

A

2000um

67
Q

What is 30 000um in mm

A

30mm

68
Q

What is the microscope eye piece fitted with

A

A graticule

69
Q

What is a graticule look like

A

Transparent with small ruler etched on it

70
Q

Can you still see the eyepiece graticule when viewing specimen

A

Yes, it is superimposed on it and can measure diameter of specimen in eye piece unit

71
Q

Why is the scale of the eyepiece graticule described as arbitrary

A

Represents different lengths as different magnifications, image of specimen looks bigger if magnification is higher but actual size doesn’t change

72
Q

What must be done to each objective lens before measuring a specimen

A

Must be calibrated with the eyepiece graticule

73
Q

How do you calibrate eyepiece graticule with stage graticule

A

Place stage graticule on microscope stage and focus using low power objective lens so magnification is x40, align eyepiece and stage graticule, ensure stage and eyepiece graticule correspond(1mm to 40eyepiece divisions), so each eyepiece division would be 1000/40=0.025mm, then use x10 (x100) and focus and align graticules (100eyepiece division is now 1mm) =0.01mm is one eyepiece division

74
Q

What safety precaution should you take when observing and measuring starch grains in potato tubular cells

A

Wear eye protection

75
Q

How would you observe and measure starch grains(amyloplats) In potato tubular cells

A

1.use sharp knife to scrape little material from surface of peeled potato and place in microscope slide (need very thin layer and will have tubular cells) 2. place 2 drops of iodine solution on them and add coverslip 3.examine under microscope starting with low power and going higher, amyloplats stained with iodine will appear violet 4.measure length and with of 3 amyloplats

76
Q

What cells are eukaryotic

A

All animal, plant, fungal and protoctist cells

77
Q

Features of eukaryotic cells nucleus

A

Nucleus surrounded by nuclear envelope and containing DNA organised and wound to linear chromosomes, inside nucleus there is nucleolus containing RNA where chromosomes unwind and also involved in making ribosomes

78
Q

Features in eukaryotic cell

A

cytoskeleton:network of protein filaments within cytoplasm that move organelles around cell, plasma membrane, membrane bound organelles like nucleus, mitochondria, golgi, endoplasmic reticulum, secretory vesicles, ribosomes

79
Q

Extra features in a plant cell

A

Amyloplats containing starch, chloroplast, vacuole, cell wall

80
Q

Extra features in animal cells

A

Lysosomes containing digestive enzymes

81
Q

Definition of cells

A

Cell are fundamental building blocks of all living organisms

82
Q

What is within every cell

A

Organelles with a specific function

83
Q

What does a membrane bound organelle mean

A

Keeps organelle separate from rest of the cell

84
Q

Under what microscope can you see organelle membranes

A

Electron microscope

85
Q

Do prokaryotes have membrane bound organelles

A

No

86
Q

What is the nucleus structure (eularyotes)

A

Nucleus surrounded by double membrane called nuclear envelope which has pores and nucleus contains DNA, but the nucleolus doesn’t have a membrane around it

87
Q

What is chromatin

A

Genetic material, consists of DNA wound linearly around histone proteins and when cell doesn’t divide chromatin is spread out or extended but when cell about to divide chromatin bonds tightly into chromosomes, chromatin makes up nearly all organisms genome

88
Q

What is nuclear envelope function

A

Separates content of nucleus from rest of the cell, in some regions outer and inner nuclear membranes fuse together, then some dissolve substances and ribosomes can pass through as pores allow larger substances (mRNA) to leave nucleus and steroid hormones may enter nucleus from cytoplasm via these pores

89
Q

What is overall function of nucleus

A

Is the control centre of cells, stores organisms genome, transmits genetic information, provides instructions for protein synthesis

90
Q

Structure of rough endoplasmic reticulum

A

System of membranes with fluid filled caverties called cisternae that are continuous with nuclear membrane and coated with ribosomes

91
Q

Function of rough endoplasmic reticulum

A

It is a ultra cellular transport system, cisterns form channels for transport in cells and provide large SA for ribosomes which turn amino acids to proteins which then actively pass through membrane into cisternae and transported to Golgi apparatus

92
Q

Structure of smooth endoplasmic reticulum

A

System of membranes containing fluid filled cavities called cisternae that are continuous with nuclear membrane but has no ribosomes on it surface

93
Q

Function of smooth endoplasmic reticulum

A

Contains enzymes that catalyse reactions involved with lipid metabolism like synthesis of cholesterol, lipids and phospholipids needed by cell and synthesis of steroid hormones, involved with absorption, synthesis and transport of lipids from gut

94
Q

Structure of Golgi apparatus

A

Consists of stack of membrane bound flattened sacs, secretory vesicles bring materials to and from Golgi apparatus

95
Q

Function of Golgi apparatus

A

Protein modified by adding sugar molecules to make glycoproteins, or adding lipids to make lipoproteins or being folded into their 3D shape, proteins are packed into vesicles which are pinched off and then stored in cell or moved to plasma membrane to be incorporated in membrane or exported outside of cell

96
Q

Structure of mitochondria

A

Spherical rod shaped or branched, surrounded by two membranes with fluid filled space between them, inner membrane highly folded into cristae making inner part of mitochondria a fluid filled matrix

97
Q

Function of mitochondria

A

Site of ATP produced in aerobic respiration, self-replicating, so more can be made if cells energy needs increasing, abundant in cells where much metabolic activity takes place such as liver cells and at synapsis between neurone where neurotransmitter is synthesised and released

98
Q

Structure of chloroplast

A

Large organelle, found in plants and some protoctists, surrounded by double membrane/ envelope, inner membrane continuous with stacks of flattened membrane stacks called thylakoids which contain chlorophyll(each stack called granum, fluid filled matrix called stroma, also contains loops of DNA and starch grains

99
Q

Function of chloroplast

A

Site of photosynthesising, 1st stage of photosynthesis when light energy trapped by chlorophyll and used to make ATP which occurs in the grana. Water also split to supply hydrogen ions, 2nd stage, hydrogen reduces CO2 using energy from ATP to make carbohydrates which occurs in stroma, chloroplast abundant in leaf cells usually in palisade mesophyll layer

100
Q

Structure of vacuoles

A

Surrounded by membrane called tonoplast and contains fluid

101
Q

Function of vacuoles

A

Only plant cells have large permeant vacuoles, filled with water and solutes and maintains cells stability, as when it is full it pushes against cell wall making it turgid, if all plant cells turgid it helps to support plants, especially non woody ones

102
Q

What is the structure of lysosomes

A

Small bags formed from Golgi apparatus each surrounded by a single membrane, contains powerful hydrolytic (digestive) enzymes, abundant in phagocyte cells (wbc) that can ingest and digest invading pathogens like bacteria

103
Q

Function of lysosomes

A

Keep powerful hydrolytic enzymes from rest of the cell, can engulf old cell organelles and foreign matter, digest them and return digested components to cell for reuse

104
Q

Structure of cilia and undulipodia

A

Protrusions from cell and surrounded by cell surface membrane, each contain microtubules and are formed from centrioles

105
Q

Examples of organelles without membranes

A

Ribosomes and cytoskeletons like centrioles

106
Q

Structure of ribosomes

A

Small spherical organelles made of ribosomal RNA, made in nucleolus as two separate subunits, which pass through nuclear envelope into cell cytoplasm then combine, but some remain free in cytoplasm and some attach to endoplasmic reticulum

107
Q

Ribosomes function

A

Bound to exterior of rough endoplasmic reticulum for synthesising proteins that will be exported outside the cell, ribosomes free in cytoplasm, single or cluster, primarily site of assembly of proteins that will be used inside the cell

108
Q

Structure of centrioles

A

Consists of 2 bundles of microtubules at right angle to each other, microtubules made of tubulin protein subunits and arranged to form cylinders

109
Q

Centrioles function before cells divide

A

Spindle made of thread of tubulin forms from centrioles, chromosomes attach to middle part of spindle and motor protein walks along tubulin threads which pulls chromosomes to opposite ends of the cell

110
Q

Centrioles function in formation of cilia and undulipodia

A

Before cilia forms, centrioles multiply and line up beneath cell surface membrane, microtubules then spout outwards from each centriole forming cilia or undulipodium

111
Q

Are centrioles found In plant cells

A

Not usually but sometimes in unicellular algae like chlamydomas

112
Q

Structure of cytoskeleton

A

Network of protein structure within cytoplasm consisting of rod like micro filaments made of subunits of protein actin, polymers of actin(7nm diameter) with intermediate filaments 10nm diameter, straight cylindrical microtubules made of protein subunits called tubulin(18-30nm diameter)

113
Q

Structure of cytoskeletal motor proteins

A

Myosins, kinesins, and dyneins are molecular motors, they are also enzymes which have a site that binds to and allows hydrolysis of ATP as an energy source

114
Q

Function of cytoskeletons

A

Protein micro filaments within cell wall give support and mechanical strength to keep cel shape stable and allows cell movement, microtubules also provide shape and support and help substances and organelles move across cytoplasm by forming tracks along which motor proteins can walk/drag organelles from one to another part of a cell which forms spindle before cell divides enabling chromosomes to move within cell, microtubules also make up cilia, undulipodia and centrioles

115
Q

Cytoskeleton intermediate filaments function

A

Made of a variety of proteins which anchor nucleus within cytoplasm, and extend between cells in some tissues between species junctions, enabling cell to cell signaling and allows cells to adhere to a basement membrane, therefore stabilising tissues

116
Q

Cellulose in cell wall structure

A

Outside of plasma membrane and made from bundles of cellulose fibres

117
Q

Function of cellulose in cell wall

A

Absent from animal cells but cell wall is strong and prevent plant cells bursting when turgid, the cell wall of plants provide strength and support, maintain cell shape, contribute to strength and support of whole plant and permeable and allows solutions (solutes and solvent) to pass through

118
Q

What is fungi cell wall made of

A

Chitin

119
Q

What is the first step in making a protein

A

The gene that has coded instructions for a protein such as insulin (housed in chromatin) in nucleus is transcribed to RNA called messenger RNA (mRNA)

120
Q

What happens after mRNA is made in protein synthesis

A

Many copies of mRNA are made and passed out of pores in nuclear envelope to ribosomes

121
Q

What happens at ribosomes in protein synthesis

A

Instructions are translated and insulin molecules are assembled

122
Q

What happens after ribosomes translate mRNA to insulin

A

Insulin molecule passes to cisternae of rough endoplasmic reticulum and along hollow sacs

123
Q

What happens in protein synthesis after protein molecule is in RER cisternae

A

Vesicles fuse with Golgi apparatus where insulin protein molecules may be modified for rerelease

124
Q

What happens to vesicles at Golgi apparatus after protein has been processed and packaged

A

Inside vesicles pinched off from Golgi apparatus, then these molecules pass to plasma membrane and the vesicles and plasma membrane fuse and insulin is released outside of the cell

125
Q

Where is mRNA copy of the instructions/gene for insulin made

A

The nucleus

126
Q

How does mRNA leave nucleus

A

Nuclear pores in nuclear envelope

127
Q

Where does mRNA attach to after it left nucleus

A

Ribosomes

128
Q

What happens to protein molecule in Golgi apparatus

A

Processed and packages protein molecule ready for release

129
Q

What is exocytosis

A

Type of bulk process which is active so energy is needed, to move protein molecule out of the cell

130
Q

Where does exocytosis occur

A

Plasma membrane

131
Q

What are bacteria and what cell do they have

A

Microorganisms with prokaryote cells

132
Q

how are prokaryotes similar to eukaryotes

A

Have plasma membrane, cytoplasm, ribosomes for assembling amino acids to proteins, DNA and RNA

133
Q

How are prokaryotes different from eukaryotes

A

Much smaller and less developed cytoskeleton with no centrioles, don’t have nucleus, don’t have membrane bound organelles like mitochondria, ER, chloroplasts or Golgi apparatus, they also have a peptidoglycan cell wall instead of cellulose, smaller ribosomes and naked DNA that isn’t wound around histone proteins but floats free in cytoplasm as a loop (not linear)

134
Q

What are other extra features of prokaryotes

A

Have a waxy capsule surrounding cell wall, small loops of DNA called plasmids, flagella so they can move, pili which are smaller hair like structures so bacteria can adhere to host cell and to each other and allows passage of plasmid DNA from one cell to another

135
Q

How do prokaryotes divide

A

Binary fission

136
Q

Why don’t prokaryotes carry out mitosis

A

As they don’t have linear chromosomes

137
Q

What happens before prokaryotes divide

A

Before they divide there DNA is copied so each new cell gets a large loop of DNA and any smaller plasmids

138
Q

Do prokaryotes in bacteria have membrane bound organelles

A

No but they have non membrane bound organelles like ribosomes

139
Q

Why are bacteria microorganisms

A

As they are small and prokaryotes due to their cell structure

140
Q

Are all microorganisms prokaryotes

A

No, yeast is a single called fungus and amoeba have eukaryote cells

141
Q

Why are viruses different

A

They are microscopic but do not have cells

142
Q

What do plasmids serves as

A

Additional chromosomes to the nucleotoid and in many disease causing bacteria these plasmids are associated with resistance to antibiotics

143
Q

How is a mesosome formed in prokaryotes cells

A

Formed by unfoldings in plasma membrane

144
Q

What is function of waxy capsule on prokaryotes

A

To prevent phagocytes ingesting them or dehydration

Alevel Biology (25 decks)

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