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Biology Alevel > Cell Structure (cells) > Flashcards

Cell Structure (cells) Flashcards

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1
Q

In which cells is the nucleus present

A

All eukaryotic cells

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2
Q

What is the structure of the nucleus

A

It is relatively large and separated from the cytoplasm by a double membrane (the nuclear envelope) which has many nuclear pores . These nuclear pores are important channels for allowing mRNA and ribosomes to travel out of the nucleus . As well as allowing enzymes to travel in it also contains chromatin and a nucleolus

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3
Q

In which cells is the rough endoplasmic reticulum present

A

Eukaryotic cells

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4
Q

What is the structure and function of the rough endoplasmic reticulum

A

Surface covered in ribosomes , formed from continuous folds of membrane continuous with the nuclear envelope. It processes proteins made by the ribosomes

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5
Q

In which cells is the smooth endoplasmic reticulum present

A

Eukaryotic cells

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6
Q

What is the structure and function of the smooth endoplasmic reticulum

A

Does not have ribosomes on the surface,it is involved in the production , processing and storage of lipids and carbohydrates

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7
Q

In which cells is the Golgi apparatus present

A

Eukaryotic cells

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8
Q

What is the structure and function of the Golgi apparatus

A

Flattened sacs of membrane similar to the smooth endoplasmic reticulum.
It processes proteins and lipids before packing them into the Golgi vesicles (membrane bound sac for transport and storage) the vesicles then transport the proteins and lipids to their required destination eg. Exported out of the cell , put into lysosomes or delivered to other membrane bound organelles
- modifies triglycerides and combines them with proteins packaged for release exocytosis

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9
Q

In which cells is mitocondria present

A

Eukaryotic ( animal and plant) as too large to fit inside a bacterial cell

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10
Q

What is the structure and function of mitochondria

A

The site of aerobic respiration,and where ATP is made

surrounded by double membrane , with the inner membrane folded to form Cristae and the matrix formed by the cristae contains enzymes needed for aerobic respiration producing ATP . Also small circular pieces of DNA and ribosomes are also found in the matrix ( needed for replication)

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11
Q

In which cells are chloroplasts present

A

Plant cells (eukaryotic)

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12
Q

What is the structure and function of chloroplasts

A

chloroplasts absorb light for photosynthesis and produce carbohydrates/sugars They are surrounded by a double membrane . Have membrane bound compartments , called thylakoids containing chlorophyll stack to form structures called grana (joined together by lamellae- thin and flat thylakoid membranes ) chloroplasts are the site of photosynthesis. They also contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis

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13
Q

In which cells are vacuoles present

A

Present in plant cells ( if present in animal cells , not permanent and small)

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14
Q

What is the structure and function of vacuoles

A

Holds cell Sap- a dilute fluid consisting of water , amino acids , glucose and salts , and it is surrounded by the tonoplast - a specialised selectively permeable membrane

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15
Q

In which cells are lysosomes present

A

Animal and plant

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16
Q

What is the structure and function of lysosomes

A

Specialist forms of vesicles which contain hydrolytic enzymes ( enzymes that break down biological molecules ) and break down waste materials such as worn - out organelles . used extensively by cells of the immune system and in apoptosis ( programmed cell death)

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17
Q

In which cells is the cell wall present

A

Plant and bacterial

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18
Q

What is the structure and function of the cell wall

A

Cell walls are formed outside of the cell membrane and offer structural support to cell , this is provided by the polysaccharide cellulose in plants and peptidoglycan (murein) in most bacterial cells

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19
Q

In which cells are ribosomes found

A

All cells ( eukaryotic and prokaryotic )

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20
Q

What is the structure and function of ribosomes

A

Found freely in the cytoplasm or as part of the rough endoplasmic reticulum in eukaryotic cells. Each ribosome is a two part complex of ribosomal RNA and proteins . 80S ribosomes (composed of 40S and 60S ) subunits are found in eukaryotic cells . Ribosomes are the sight of translation ( protein synthesis )

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21
Q

In which cells is the cell membrane present

A

All eukaryotic cells

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22
Q

What is the structure and function of the cell membrane

A

All cells are surrounded by a cell surface membrane which controls the exchange of materials between the internal cell environment and the external environment . The membrane is described as being partially permeable and is formed from a phospholipid bilayer of phospholipids spanning a diameter of around 10nm

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23
Q

In which cells are centrioles found

A

Not found in flowering plants or fungi

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24
Q

What is the structure and function of centrioles

A

Hollow fibres made of microtubules . Two centrioles at right angles to each other form a centro some which organises the spindle fibres during cell division ( mitosis )

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25
Q

What is the smaller knob on the light microscope called

A

Fine adjustment screw

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26
Q

What is the larger knob on the microscope called

A

Coarse adjustment screw

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27
Q

What’s the long piece attached to the eyepiece called

A

Body tube

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28
Q

What are the objective lens called

A

High power objective lens and low power objective lens

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29
Q

What is the thing below the stage

A

Condenser

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30
Q

What is the max magnification for a light microscope

A

X1500

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31
Q

What is the max magnification for an electron microscope

A

1,000,000

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32
Q

What is the smallest resolution on a light microscope

A

250 nm

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33
Q

What is the smallest resolution on a electron microscope

A

0.25nm

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34
Q

What type of radiation is used for a light microscope

A

Light

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35
Q

What type of radiation is used for an electron microscope

A

Electrons

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36
Q

How is a light microscope focussed

A

Glass lenses

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37
Q

How is an electron microscope focussed

A

Electromagnets

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38
Q

What specimen can be used on a light microscope

A

Living / moving / dead / abiotic

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39
Q

What type of specimen can be used for an electron microscope

A

Dead / abiotic

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40
Q

What is the size of a light microscope

A

Small and portable

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41
Q

What is the size of an electron microscope

A

Large and static

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42
Q

What is the preparation and cost of light microscopes

A

Cheap and easy

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43
Q

What is the preparation and cost of material on electron microscope

A

Large and static

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44
Q

How do light microscopes work

A

Light microscopes use light and lenses to form to form an image of a specimen and magnify it to look bigger

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45
Q

What is the magnification and resolution of light microscopes

A

Low

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46
Q

What images do light microscopes give

A

They give coloured images of cells

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47
Q

Why do light microscopes have a low resolution

A

Light has a long wavelength

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48
Q

How do electron microscopes work

A

Electron microscopes use a beam of electrons instead of beams or rays of light

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49
Q

What is the magnification of electron microscopes

A

High

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50
Q

What is the resolution of electron microscopes and why

A

High as the electron beam has a very short wavelength

51
Q

What is an advantage of electron microscopes

A

They let us see much smaller organelles than light microscopes eg mitocondria

52
Q

What images do electron microscopes give

A

Black and white images

53
Q

What does the specimen have to be to use an electron microscope

A

Dead

54
Q

What are the two types of electron microscopes

A

Transmission electron microscopes (TEM) and scanning electron microscopes (SEM)

55
Q

How do TEM microscopes work

A

A microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. Which is focused onto the specimen by a condenser electromagnet. Parts of the specimen absorb electrons ( the denser parts) and therefore appear darker and bright sections where electrons were passed through

56
Q

What is a limitation of TEM microscopes

A

Has to be very thin and images formed are in black and white

57
Q

How does a SEM microscope work

A

A type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons

58
Q

What is an advantage of SEM microscopes

A

The specimens do not need to be as thin as TEM and can show 3D images whereas TEM only show 2D images

59
Q

Why can the resolving power on TEM microscopes not always be achieved

A

Difficulties preparing the specimen can limit the resolution and also a higher energy electron beam is required and this may destroy the specimen

60
Q

What is a limitation of the TEM microscope

A

Image may contain artefacts

61
Q

how do you convert mm - um

A

X1000

62
Q

magnification =

A

image size / actual size

63
Q

What is the definition for cell fractionation

A

Cell fractionation is the process used to separate cellular components while preserving individual functions of each component.

64
Q

What are the two stages of cell fractionation

A

Homogenation and ultracentrifugation

65
Q

What needs to happen before cell fractionation can begin

A

Tissue placed in cold , isotonic , buffer solution .

66
Q

Why is the tissue placed in cold solution

A

To reduce enzyme activity that might break down organelles

67
Q

What does isotonic mean

A

Two solutions ( buffer and tissue ) are at the same concentration

68
Q

Why is the solution isotonic

A

Isotonic (same water potential as original tissue) to prevent organelles bursting /shrinking due to osmotic gain/loss os water

69
Q

Why is the solution buffered

A

To maintain a constant ph as any change in ph could denature enzymes or alter organelle structure

70
Q

Describe stage 1 of cell fractionation - homogenation

A

1) tissue is cut into small peices and placed in a cold , isotonic , buffered solution
2) these are then ground into smaller pieces using a homogeniser which releases the organelles from the cell . The resultant fluid is called the homogenate
3) the homogenate is filtered to remove any complete cells and large debris eg cell wall / membrane

71
Q

Describe stage 2 - ultracentrifugation

A

1) ultracentrifugation is the process by which fragments in the filtered homogenate are separated in a machine called a centrifuge
2) the filtrate is placed in the centrifuge and spun at a slow speed
3) the heaviest organelles , the nuclei , are forced (by centrifugal force ) to the bottom of the tube , where they form a thin sediment or pellet .
4) the fluid at the top of the tube (supernatent) is removed , leaving just the sediment behind the nuclei
5) the supernatent is transferred to another tube and spun in the centrifuge at a faster speed
6) the next heaviest organelles the mitocondria are forced to the bottom of the tube
7) the process is continued in this way so that at each increase in speed the next heaviest organelle is separated out

72
Q

What does homogenise mean

A

Break down ( tissue )

73
Q

What is the size order of the organelles

A

Nucleus -> chloroplasts —> mitocondria -> lysosomes -> endoplasmic reticulum—>ribosomes

74
Q

What is the supernatent

A

Remaining organelles (liquid left after centrifugation)

75
Q

What are the problems with ultracentrifugation

A
  • difficult to separate organelles fully . Other organelles may be present
  • cannot separate all organelles
  • cannot be sure that the pellet contains one singular organelle
76
Q

What is the homogenate

A

The tissue once broken down

77
Q

What is used to keep it cold

A

Ice

78
Q

What is the definition for magnification

A

Magnification is how many times bigger the image of a specimen observed is in compared to the actual (real - life ) size of the specimen

79
Q

What is the definition for resolution

A

A measure of the microscopes ability of to distinguish between two points which are close together on an object

80
Q

What is the cell cycle

A

The cell cycle is the series of events that take place in a cell leading to its division to produce two daughter cells.

81
Q

What is the average time of the cell cycle

A

A typical human cell might take about 24 hours to divide but fast cycling cells eg the ones that line the intestine can take 9-10 hours this is because they are some of the most hard working cells and need to be replaced rapidly

82
Q

What are the two stages in the cell cycle

A

Interphase and mitosis

83
Q

What is the interphase

A

A time of organised activity during which the cell synthesises new cell components, such as organelles and membranes and new DNA

84
Q

What is mitosis

A

Cell division in body cells

85
Q

What causes cancer

A

Uncontrolled cell growth

86
Q

What percentage of a cells life is spent in interphase

A

90%

87
Q

What is a cell checkpoint

A

To check the cell is working properly . Regulation / check it’s carrying out correct function

88
Q

What type of cells does chemotherapy target

A

Cells that go through the cell cycle quickly

89
Q

What happens at G1. In the interphase

A

Cell organelles are duplicated - chemical reactions and cell process take place

90
Q

What happens at s in the interphase

A

Each of the 46 chromosomes are duplicated

91
Q

What happens at G2 in the interphase

A

A period of rapid cell growth and protein synthesis during which the cell readies itself for mitosis . During g2 the cell checks the duplicated chromosomes for errors and duplicates enzymes

92
Q

what is mitosis

A

mitosis is the process by which cells divide to achieve growth and repair by simply increasing cell number eg cloning B cells

93
Q

what is the dividing cell and resulting cells called

A

the dividing cell is called the parent cell. the resulting two cells are called daughter cells

94
Q

why are the daughter cells genetically identical

A

because they contain copies of the parents cells DNA

95
Q

what is the interphase nucleus

A

the interphase nucleus looks fairly uniform in images . DNA in interphase is loosely packed - this is called chromatin

96
Q

what happens to the DNA during mitosis

A

the nucleus breaks dowbnand the chromosomes condense. chromosomes are made up of DNA associated with proteins called histones

97
Q

what are the stages in mitosis

A

prophase , metaphase , anaphase and telophase and cytokinesis

98
Q

what happens during interphase

A

the nucleus is in a uniform shape and the chromatin is in its least condensed state. the chromosomes double

99
Q

what happens during prophase

A

the nuclear envelope breaks down and the chromosomes begin to appear visible under a microscope due to dna condensing . . organelles known as centrioles migrate towards te poles of the cell to release spindle fibres

100
Q

what happens when dna doubles

A

chromatids double and join together at their centres called centromeres they are then called homologous chromosomes

101
Q

what happens during metaphase

A

chromosomes are aligned at the cell equator by spindle fibres. this area is called the metaphase plate

102
Q

what happens during anaphase

A

the chromatids split at their centromeres and are pulled towards opposite poles of the cell by the spindle fibres

103
Q

what happens at telophase

A

nuclear envelopes reform around the two new nuclei . the chromosomes become indistinguisible again under a microscope and the spindle fibres spread out

104
Q

what happens during cytokinesis

A

this is the final step of mitosis when the cytoplasm of the parent cell divides to complete the cell division , resulting in two brand new and genetically identical daughter cells . these cells then go through interphase

105
Q
A
106
Q

Describe the role of the spindle during mitosis

A

Spindle fibres attach to chromatids and then pull chromostids to opposite poles of the cell

107
Q

Why are viruses described as acellular and non living

A

They have no cell surface membrane , they have no metabolic reactions and they cannot independently respire or replicate

108
Q

A student prepared a plant root to observe cells undergoing mitosis . He put the root in a small bottle of hydrochloric acid why

A
  • to soften the cells so soften the root top so the root tip can be more easily squashed . Also stop mitosis / stop mitosis continuting and allowing stain to pass through cells
109
Q

A student prepared a plant root to observe cells undergoing mitosis . He put the root in a small bottle of hydrochloric acid why

A
  • to soften the cells so soften the root top so the root tip can be more easily squashed . Also stop mitosis / stop mitosis continuting and allowing stain to pass through cells
110
Q

State two precautions when working with hcl

A
  • eye protection
    -gloves
    -add water to spills
    -do not pour down sink
111
Q

State two precautions when working with hcl

A
  • eye protection
    -gloves
    -add water to spills
    -do not pour down sink
112
Q

Describe one difference between SEM and TEM images

A

3D with SEM and 2D with TEM

113
Q

What does a colorimeter do

A

Measures the light absorbance , a calibration curve can be used to draw a line to curve and then read against po2 value obtained

114
Q

Is po2 pressure or volume

A

Pressure

115
Q

do mitocondria contain starch grains

A

no

116
Q

name one organelle that you would expect to find in large numbers in a mucus secreting cell and describe its role in the production of mucus

A

golgi apparatus - packages / processes proteins

or rough endoplasmic reticulum as it makes proteins on ribosomes

117
Q

give one function of the cell wall

A

prevents lysis
provides strength and support
protection

118
Q

describe how tempory mounts are made

A

place a thin slice of specimen onto a slide and add water and a coverslip

119
Q

give two reasons why mitosis is important

A
  • replaces cells and tissues
    -produces genetically identical cells
  • cloning
120
Q

why are chromosomes stained when doing the root tip squash

A

to distinguish chromosomes / they are not visible without the stain

121
Q

describe how bacteria divide

A

they divide by binary fission first - plasmids and circular dna replicate and then the cytoplasm divides producing two daughter cells , each with a single copy of circular dna

122
Q

how do viruses divide

A

not living so no cell division , they inject their DNA into a hosts cell and the host cell replicates the virus particles

123
Q

how does a tumour cause harm to the body

A

it may exert pressure on other organs or cause obstruction

124
Q
A

Biology Alevel (18 decks)

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