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A Level Biology OCR A > 2 - Basic components of living systems > Flashcards

2 - Basic components of living systems Flashcards

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1
Q

What is a microscope?

A

instrument that enables you to magnify an object

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2
Q

What do microscopes allow us to discover?

A

how details of their structure relate to their function

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3
Q

When was the light microscope developed?

A

16th/17th century

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4
Q

What was the first microscope to be developed?

A

light microscope

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5
Q

Why could microscopes in the 19th century see individual cells?

A

had a high enough resolution

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6
Q

What does the cell theory state that both plant and animal tissues are composed of?

A

cells

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7
Q

What do cells only develop from?

A

existing cells

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8
Q

How was cell theory developed?

A

as microscopes had higher magnification/resolution

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9
Q

What is the availability like for light microscopes?

A

easily available

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10
Q

How expensive is the light microscope?

A

relatively cheap

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11
Q

What organisms can be observed under a light microscope?

A

living organisms as well as dead, prepared specimens

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12
Q

How many 2 lenses does a compound light microscope have?

A

objective and eyepiece lens

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13
Q

Where is the objective lens found on a compound light microscope?

A

near to the specimen

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14
Q

What is the eyepiece lens?

A

where specimen is viewed

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15
Q

How does a compound light microscope work?

A

objective lens produces a magnified image, which is then magnified again by eyepiece lens

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16
Q

What does the objective/eyepiece lens configuration allow for?

A
  • higher magnification

- reduced chromatic aberration

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17
Q

Where is illumination usually provided by in a compound microscope?

A

light underneath the sample

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18
Q

What is sectioning?

A

specimens cut into very thin slices with a sharp blade

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19
Q

What is dry mount?

A

specimen placed on centre of slide and cover slip placed over sample

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20
Q

What are some examples of specimens that can be viewed using dry mount?

A

hair, pollen, dust (muscle tissue have to be sectioned first)

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21
Q

What is wet mount?

A

specimens suspended in a liquid e.g. water or immersion oil

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22
Q

How is the cover slip placed on wet mount?

A

at an angle

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23
Q

What specimens can be viewed using wet mount?

A

aquatic samples + other living organisms

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24
Q

What are squash slides?

A

wet mount first prepared, then lens tissue used to press down cover slip

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25
Q

How can potential damage of the cover slip be avoided with squash slides?

A

squashing sample between two slides

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26
Q

What specimens can be used for squash slides?

A

soft samples e.g. root tip squashes

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27
Q

What is a smear slide?

A

edge of slide used to smear sample, creating thin, even coating on another slide. cover slip then placed over

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28
Q

What samples can be used for a smear slide?

A

blood

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29
Q

How is the sample illuminated in a light microscope?

A

from below with white light and observed from above

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30
Q

Why do light microscopy images tend to have a low contrast?

A

most cells don’t absorb a lot of light

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31
Q

What is resolution limited by?

A

wavelength of light and diffraction of light as it passes through sample

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32
Q

What is diffraction?

A

bending of light as it passes close to the edge of an object

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33
Q

What is the cytosol of cells?

A

aqueous interior

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34
Q

What is the cytosols and other cells structures like?

A

transparent

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35
Q

What do stains do?

A

increase contrast

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36
Q

Why do stains increase contrast?

A

different components within cell take up stains to different degrees

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37
Q

What does the increase in contrast allow components to do?

A

become visible so they can be identified

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38
Q

What is the 1st step for preparing a sample for staining?

A

placed on slide and air dried

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39
Q

What is the 2nd step for preparing a sample for staining?

A

heat-fixed by passing through a flame

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40
Q

What is the 3rd step for preparing a sample for staining?

A

specimen will adhere to the microscope slide and take up stains

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41
Q

What is crystal violet and methylene blue?

A

positively charged dyes

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42
Q

How does the crystal violet and methylene dyes work?

A

attracted to negatively charged materials in cytoplasm leading to the staining of cell components

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43
Q

What is nigrosin and congo red dyes?

A

negatively charged and repelled by negatively charged cytosol

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44
Q

How do nigrosin and congo red dyes work?

A

stay outside cells, leaving cells unstained, which stand out against stained background (negative stain technique)

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45
Q

What can differential staining do?

A

distinguish between two types of organisms that would otherwise be hard to identify

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46
Q

What can differential staining also differentiate between?

A

different organelles of a single organism within a tissue sample

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47
Q

Differential staining: What is the gram stain technique used for?

A

separate bacteria into two groups, Gram-positive and Gram-negative bacteria

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48
Q

How do you use the Gram stain technique?

A

crystal violet first applied to bacterial specimen on a slide, then iodine, which fixes the dye. Slide then washed with alcohol

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49
Q

Gram stain technique: What happens when the gram positive bacteria is stained with the crystal violet dye?

A

retain crystal violet stain and will appear blue or purple under a microscope

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50
Q

Gram stain technique: What happens when the gram negative bacteria is stained with the crystal violet dye?

A

have thinner cell walls and therefore lose the stain

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51
Q

Gram stain technique: What is the gram negative bacteria then stained with?

A

safranin dye, called counterstain. these bacteria will then appear red

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52
Q

What is the acid-fast technique used for?

A

differentiate species of Mycobacterium from other bacteria

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53
Q

What happens in the acid-fast technique?

A

lipid solvent used to carry carbolfuchsin dye into cells being studied. cells then washed with dilute alcohol solution

54
Q

What happens to the Mycobacterium during the acid-fast technique?

A

not affected by the acid-alcohol and retain the carbolfuchsin stain which is bright red

55
Q

What happens to the other bacteria during the acid-fast technique?

A

lose stain and exposed to methylene blue stain, which is blue

56
Q

Pre-prepared slides: What happens during fixing? (1)

A

chemicals like formaldehyde are used to preserve specimens in as near-natural state as possible

57
Q

Pre-prepared slides: What happens during sectioning? (2)

A

specimens dehydrated with alcohols then placed in mould with wax or resin to form hard block. then sliced thinly with knife called microtome

58
Q

Pre-prepared slides: What happens during staining? (3)

A

specimens often treated with multiple stains to show different structures

59
Q

Pre-prepared slides: What happens during mounting? (4)

A

specimens then secured to microscope slide and cover slip placed on top

60
Q

What is the function of the nucleus?

A

It contains genetic information in the form of DNA

61
Q

What does DNA do?

A

Directs synthesis of proteins required by the cell

62
Q

What is the nuclear envelope?

A

A double membrane that surrounds the nucleus to protect it from damage

63
Q

How are chromosomes formed?

A

DNA assosciates with histones to form a complex called chromatin, which then coils and condenses to form chromosomes.

64
Q

What is the function of the nucleolus?

A

To produce ribosomes. RNA is used to makes ribosomal RNA, which then combines with proteins to form ribosomes

65
Q

How do substances enter and leave the nucleus?

A

Through nuclear pores

66
Q

How is DNA removed from the nucleus?

A

It is transcribed to smaller RNA molecules and leaves through the nuclear pores

67
Q

What is the function of mitochondria?

A

They are the site of the production of ATP, the final stage of aerobic respiration

68
Q

What does it mean if there are more mitochondria in a cell?

A

It would likely be more active

69
Q

What are the 4 components of mitochondria?

A

Inner and Outer membrane, cristae, matrix

70
Q

Why do mitochondria contain a very small amount of DNA?

A

So they can produce their own enzymes and reproduce themselves

71
Q

Where are the enzymes used in aerobic respiration found in mitochondria?

A

The cristae

72
Q

What is the structure of a vesicle?

A

A membranous sac (with a single membrane) with fluid inside

73
Q

What is the function of vesicles?

A

To store materials and transport them around the cell

74
Q

What is a lysosome?

A

A specialised vesicle containing hydrolytic enzymes

75
Q

What is the function of a lysosome?

A

They break down waste in cells, including old organelles and pathogens ingested by phagocytes. Also play a role in programmed cell death.

76
Q

What are centrioles?

A

A component of the cytoskeleton made up of bundles of microtubules

77
Q

In what eukaryotic cells are centrioles not found?

A

Flowering plants and most fungi

78
Q

What is the function of centrioles?

A

They are involved in the assembly and organisation of spindle fibres, which separate chromosomes during cell division.

79
Q

What are the 3 components of the cytoskeleton?

A

Microtubules, microfilaments and intermediate fibres

80
Q

What is the structure and function of microfilaments?

A

They are contractile fibres made up of the protein actin. They are responsible for cell movement and contraction during cytokinesis (the division of cytoplasm during cell division)

81
Q

What are the functions of the cytoskeleton?

A

Necessary for the shape and stability of the cell, holds organelles in place, controls the movement of organelles and cell movement.

82
Q

What is the function of intermediate fibres?

A

Give mechanical strength to cells and help maintain integrity in the cell.

83
Q

What is the structure of microtubules?

A

Polymerised proteins which form tubes.

84
Q

What are the functions of microtubules?

A

Act as tracks for the movement of organelles around the cell, form a scaffold-like structure which determines cell shape, make up centrioles.

85
Q

What is the structure of the Smooth and Rough ER?

A

A network of membranes enclosing cisternae (flattened sacs). Connected to nuclear membrane.

86
Q

What is the function of the Smooth ER?

A

Lipid and carbohydrate synthesis and storage

87
Q

What is the function of the Rough ER?

A

Ribosomes bound to its surface make it responsible for the synthesis and transport of proteins.

88
Q

What do secretory cells have more of than others?

A

Rough ER and ribosomes bound to it

89
Q

Where are ribosomes found in the cell?

A

Either on the Rough ER or free-floating in the cytoplasm

90
Q

Are ribosomes surrounded by a membrane?

A

No

91
Q

What is the structure of a ribosome?

A

A large and a small sub-unit

92
Q

What is the function of a ribosome?

A

It is the site of protein synthesis.

93
Q

What is the difference between free floating ribosomes and those found on the ER?

A

Free floating ones tend to produce proteins for use within the cell, whilst ones on the Rough ER tend to produce proteins to be transported out of the cell

94
Q

What is the structure of the Golgi Apparatus?

A

Similar to the Smooth ER- compact structure made up of cisternae

95
Q

What are cisternae?

A

Flattened sacs

96
Q

What is the function of the Golgi Apparatus?

A

Modifies proteins and packages them into vesicles (can be secretory vesicles if the proteins ar leaving the cell or lysosomes)

97
Q

What are flagella and cilia?

A

Extensions which produce from some cell types

98
Q

What are the main differences between flagella and cilia?

A

Flagella whip-like, longer, cilia hair-like and found in greater numbers

99
Q

What are the functions of flagella?

A

Enable some cells’ (i.e sperm cells or prokaryotes) mobility, in some cells act as a sensor detecting chemical changes in the environment

100
Q

What are the two types of cilia?

A

Mobile and stationary

101
Q

What are stationary cilia?

A

Found on the surface of many cells and provide important function in many sensory organs i.e nose

102
Q

What do mobile cilia do?

A

Beat in a rhythmic manner in order to create a current and cause fluids or objects near the cell to move

103
Q

What are some functions of mobile cilia?

A

Keeping air passages such as the trachea clear by moving mucus away from the lungs, moving eggs down the fallopian tubes

104
Q

What is the structure of a cilium (singular cilia)?

A

Two central microtubules surrounded by 9 microtubules in a wheel-like arrangement (the 9+2 areangement). Parallel microtubules move over each other, causing beating

105
Q

Where are cellulose cell walls found?

A

Surrounding the cell surface membrane in plant cells.

106
Q

How permeable is a cellulose cell wall?

A

Freely permeable to allow all substances to move

107
Q

What are the functions of a cellulose cell wall?

A

Act as a defence against pathogens, give the cell a shape, allow cel, contents to press against it to keep the cell rigid, supports the cell and plant as a whole

108
Q

What is the structure of a vacuole?

A

A membrane lined sac containing cell sap

109
Q

Why do most plant cells have a permanent vacuole?

A

Important in maintaining rigidity

110
Q

What Is the membrane of a vacuole called and how permeable is it?

A

The tonoplast, and it is selectively permeable (allows some small molecules through)

111
Q

Do animal cells have vacuoles?

A

Some have a small, non-permanent one

112
Q

What is the function of a choloroplast?

A

Site of photosynthesis in plants

113
Q

Where are chloroplasts found?

A

The green parts of plants

114
Q

What are the 7 components of chloroplasts?

A
  1. Outer & Inner Membrane 2. Stroma (fluid inside it) 3. Granum (several thylakoids stacked) 4. Lamellae (membranes which join grana 5&6. DNA and ribosomes (used to make own proteins) 7. Starch grains (from photosynthesis)
115
Q

What do grana contain?

A

Chlorophyll pigments

116
Q

What is the advantage of the internal membrane in chloroplasts?

A

Give a large surface area for photosynthesis?

117
Q

What is the main difference between prokaryotic and eukaryotic cells?

A

Prokaryotic cells lack a membrane-bound nucleus and organelles, while eukaryotic cells contain both.

118
Q

What is the size difference between prokaryotic and eukaryotic cells?

A

Prokaryotic cells tend to be smaller.

119
Q

What type of ribosomes are found in prokaryotic and eukaryotic cells?

A

70s in prokaryotes, 80s in eukaryotes

120
Q

What 2 things can prokaryotic cells’ cell membranes be made of?

A

Murein or peptidoglycan

121
Q

What is the structure of free chromosomal DNA in a prokaryotic cell?

A

1 molecule of DNA supercoiled, with the genes grouped into operons so some can be turned on or off

122
Q

What is the difference between flagella in prokaryotic and eukaryotic cells?

A

Thinner in prokaryotes, energy provided by chemiosmosis rather than aerobic respiration in prokaryotic cells

123
Q

What is the function of pili?

A

Used to manoeuvre the cell, can be used for attachment

124
Q

What does a flagellum contain in prokaryotic cells to help it move?

A

Microfilaments

125
Q

What is the purpose of cytosol?

A

Site of most chemical reactions in a cell

126
Q

What is the function of free chromosomal DNA?

A

Contains genetic information, controls cell including which proteins are synthesised

127
Q

What is the function of the cell surface membrane?

A

Controls the movement of some substances in and out of the cell

128
Q

What is the purpose of a plasmid in a prokaryotic cell?

A

Contains genetic information

129
Q

What is the function of a slime capsule?

A

Provides an extra layer of protection for a cell

130
Q

What is the purpose of a mesosome?

A

Generates ATP via chemiosmosis

A Level Biology OCR A (23 decks)

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