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A-Level Biology🌼 > Mod 2 Chap 2: Basic components of living systems > Flashcards

Mod 2 Chap 2: Basic components of living systems Flashcards

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1
Q

What is the function of cell surface (plasma) membranes?

A

Cell surface (plasma) membranes regulate the movement of substances into and out of the cell. it also has receptor molecules on it, which allow it to respond to chemicals like hormones

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2
Q

What is the function of the nucleus?

A

The nucleus controls the cell’s activities (by controlling the transcription of DNA - DNA controls the instructions to make proteins.) The pores allow substances eg RNA to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes.

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3
Q

What is the function of mitochondrion?

A

Mitochondrion is the site of aerobic respiration, where ATP is produced. They’re found in large numbers in cells that are very active and require a lot of energy.

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4
Q

What is the function of chloroplast?

A

Chloroplast is the site where photosynthesis take place. Some parts of photosynthesis happen in the grana, and other parts happen in the stroma (a thick fluid found in chloroplast)

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5
Q

What is the function of the Golgi apparatus?

A

Golgi apparatus processes and packages new lipids and proteins. It also makes lyosomes.

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6
Q

What is the function of the golgi apparatus?

A

Golgi apparatus stores lipids and proteins transports them out of the cell via the cell surface membrane

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7
Q

What is the function of the lyosome?

A

The lyosomes contain digestive enzymes called lysozymes. These are kept separate from the cytoplasm by the surrounding membrane, and can be used to digest invading cells or to break down worn out components of the cell.

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8
Q

What is the function of the ribosome?

A

The ribosome is the site where proteins are made

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9
Q

What is the function of the rough endoplasmic reticulum?

A

The rough endoplasmic reticulum folds and prcesses proteins that have been made at the ribosomes

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10
Q

What is the function of the smooth endoplasmic reticulum?

A

The smooth endoplasmic reticulum synthesises and processes lipids

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11
Q

What is the function of the cell wall?

A

The cell wall supports cells and prevents them from changing shape

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12
Q

What is the function of the cell vacuole?

A

The cell vacuole helps to maintain pressure inside the cell and keep the cell rigid. This stops plants wilting. Also involved in the isolation of unwanted chemicals inside the cells.

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13
Q

What is the nuclear envelope?

A

A nuclear envelope the double membrane that DNA is contained in to protect it from damage in the cytoplasm. It contains nuclear pores that allow molecules to move in and out of the nucleus.

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14
Q

How are chromosomes formed?

A

Chromosomes are formed when chromatin coils and condenses

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15
Q

What is chromatin?

A

Chromatin is a complex formed when DNA associates with proteins called histones

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16
Q

How are christae formed in mitchondria?

A

Christae is formed when the inner membrane of mitochondria is highly folded

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17
Q

What is the fluid interior of the inner membrane of mitochondria called?

A

The fluid interior of the inner membrane of mitochondria is called the matrix

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18
Q

What are the functions of the vesicles in prokaryotic cells?

A

Vesicles in prokaryotic cells are membranous sacs that have storage and transport roles. They transport material inside the cell.

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19
Q

What is the cytoskeleton?

A

The cytoskeleton is present throughout all cytoplasms of eukaryotic cells. It is a network of fibres necessary for shape and stability of a cell

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20
Q

What are the three components of the cytoskeleton?

A

The three components of the cytoskeleton:
-Microfilaments
-Microtubules
-Intermediate fibres

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21
Q

What are thylakoid membranes called when stacked in chloroplasts?

A

Stacked thylakoid membranes are called grana. The links between them are called intergranel lamellae.

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22
Q

What is the membrane that the permanent vacuole is contained in?

A

Permanent vacuole is contained with the tonoplast which is filled with cell sap (a watery solution of different substances). This keeps the cell firm and turgid.

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23
Q

What are the pores within the cell wall called?

A

The pores within the cell wall are plasmodesmata. They connect cells together by their cytoplasm, enabling the exchange and transport of substances.

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24
Q

How are proteins produced and moved in a cell?

A

1) mRNA copy of hormone is made in nucleus
2) mRNA leaves through nucleus pore
3) mRNA attaches to ribosome. The ribosome reads the instructions to assemble the protein.
4) Protein is pinched off in vesicles and go to golgi apparatus
5) Vesicle fuses with golgi apparatus
6) Golgi apparatus processes and packages protein
7) Packaged protein move towards cell surface membrane
8) Vesicle fuses with plasma membrane
9) Plasma membrane opens to release protein (exocytosis)

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25
Q

What is a eukaryote?

A

A eukaryote is an organism consisting of one or more cells that contain DNA in a membrane bound nucleus

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26
Q

What are histones?

A

A histone is a protein that provides structural support for a chromosome. Each chromosome contains a long molecule of DNA, which must fit into the cell nucleus. To do that, the DNA wraps around complexes of histone proteins, giving the chromosome a more compact shape.

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27
Q

Roles of membranes

A

Roles of membranes:
-Site for attachment of enzymes
-Formation of organelles
-Selectively permeable

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28
Q

Resolution of light microscope

A

Resolution of light microscope = 200nm

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29
Q

Resolution of electron microscope

A

Resolution of electron microscope = 0.5nm

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30
Q

Benefits of staining for light microscopy

A

Benefits of staining for light microscopy:
-More organelles can be seen - specific organelles - organelles bind to stain

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31
Q

Evidence for endosymbiotic theory

A

Evidence for endosymbiotic theory - mitochondria contain ribosomes that are smaller than those found in the cell cytoplasm

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32
Q

Roles of cytoskeleton

A

Roles of cytoskeleton:
-Maintains shape of cell
-Keeps organelles in place
-Transport ie cell division, vesicles, cillia
-Movement of chromosomes and chromatids

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33
Q

What provides structural support in plants other than cell wall?

A

In leaves, air spaces give buoyancy, supported by surrounding water

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34
Q

Roles of lignin in xylem

A

Roles of lignin in xylem:
-Strengthens/Thickens cell wall
-Waterproof cell > reduces loss of water
-Allows for flexibility
-Improves adhesion of water-

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35
Q

What is the size of each division in the following microscopes?:
4x
10x
20x
40x
100x

A

4x = 25 micrometers
10x = 10 micrometers
20x = 5 micrometers
40x = 2.5 micrometers
100x = 1 micrometer

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36
Q

How do you calculate 1 graticule division?

A

1 graticule division = 0.1 divided by objective magnification

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37
Q

Light microscope resolution

A

Light microscope resolution is 200nm

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38
Q

TEM resolution

A

TEM resolution = 0.005-1nm

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39
Q

Features not visibile using medium power of light microscope

A

Features not visible using medium power of a light microscope:
-Ribosomes
-Golgi
-Mitochondria
-Vesicles

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40
Q

Roles of cytoskeleton

A

-Movement of molecules eg chromosomes
-Provides support and shape
-Holds organelles in place

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41
Q

Features of ultrastructure of phagocytic blood cells that enable it to perform its function

A

Ultrastructure features:
-Microfilaments and microtubules
-Many lysosomes (for digestive enzymes)
-Many ribosomes
-Many mitochondria

42
Q

Role of mesosome in bacterial cells

A

Mesosome roles:
-Increases SA of plasma membrane
-Releases ATP
-Helps in secretion processes

43
Q

Why does single celled organisms not need a specialised area to carry out gaseous exchanges

A

-Large SA:Vol ratio
-Small, so oxygen demands are low
-Short diffusion distance

44
Q

Function of the squamous epithelium in the gas exchange system of cells

A

Squamous epithelium - provides a thin surface for a short diffusion distance

45
Q

Function of the elastic tissue in the gas exchange system of cells

A

Elastic tissue - allows for recoiling/returning to original shape

46
Q

Function of the ciliated epithelium in the gas exchange system of cells

A

Ciliated epithelium - wafts mucus

47
Q

Function of the goblet cells in the gas exchange system of cells

A

Goblet cells - secretes mucus

48
Q

Function of the smooth muscle in the gas exchange system of cells

A

Smooth muscle - constricts airway/narrows the lumen

49
Q

Microtubules

A

Microtubules - large diameter, tubulin subunits form tubulin polymers which form the hollow microtubules, involved in movement of organelles, forms spindle fibres in mitosis and meiosis, helps determine shape of cells

50
Q

Microfilaments

A

Microfilaments -narrow fibres, contains actin which contracts, involved in cell movement, plays role in cell division - its action helps divide cells into two in cytokenisis

51
Q

Intermediate fibres

A

Intermediate fibres - strengthens the cell, lots of diff proteins - eg preventing stress from damagingskin cells

52
Q

Centrioles

A

Centrioles: not found in flowering plant cells, made of microtubules, comes in pairs at right angles to eachother, pairs of centrioles are called centrosome, during mitosis and meiosis they assemble spindle fibres, they form the cillia and flagellum

53
Q

Cilia

A

Cilia: hairlike organelles, wafts particles eg dust in trachea, ones that don’t move sense chemicals around the cells eg in nose

54
Q

Flagellum

A

Flagella: moves the cell, 9+2 structure - nine pairs of microtubules arranged in a circle with another pair of microtubules in the centre (same in cilia), atp creates bending motion

55
Q

What is the ‘9+2’ structure found in cillia and flagellum?

A

The 9+2 structure is nine pairs of microtubules arranged in a circle with another pair of microtubules in the centre

56
Q

Microtubules

A

Microtubules - formed from subunits of tubulin protein (the subunits assemble to form tubulin polymers, which then form hollow microtubules), involved in the movement of organelles eg vesicle movements, forms spindle fibres, helps determine cell shape by forming networks

57
Q

Cellulose cell walls in plants

A

Cellulose cell walls in plants:
-Strengthens the plant to resist high hydrostatic pressure caused by greater water potential outside plant than inside creating a net inflow of water molecules by osmosis
-Permeable to water molecules
-Middle lamella between cell wall - consists of polysaccharides, calcium and magneisium ions - acts as glue between plant cells

58
Q

Algae and fungi cell walls

A

-Cell walls provide them with mechanical strength
-Algae cell walls contain cellulose and glycoproteins
-Fungi - made up of chitin as well as glycoproteins and other polysaccharides

59
Q

Cell theory

A

Cell theory states that:
-Both plant and animal tissue is composed of cells
-Cells are the basic unit of all life
-Cells only develop from existing cells

60
Q

Objective lens

A

Objective lens - produces a magnified image, which is magnified again by the eyepiece lens

61
Q

4 types of sample preparation in microscopy

A

4 types of sample preparation in microscopy:
-Dry mount
-Wet mount
-Squash slides
-Smear slides

62
Q

Dry mount sample preparation:

A

Dry mount sample preparation:
Solid specimens cut into thin slices - placed on centtre - cover slip added
-Examples: muscle or plant tissue

63
Q

Wet mount sample preparation

A

Wet mount sample preparation:
Specimens suspended in a liquid eg water or immersion oil, coverslip placed from an angle
-Eg aquatic organisms

64
Q

Squash slide sample preparation

A

Squash slide sample preparation:
Wet mount prepared, lens tissue used to gently press down cover slip

65
Q

Smear slide sample preparation

A

Smear slide sample preparation:
Edge of slide used to smear sample to create a thin even coating on another slide, cover slip placed over the sample

66
Q

Why are stains used in microscopy?

A

Stains are used in microscopy to increase contrast as different components within a cell take up the stains to different degrees - the increase in contrast allows components to become visible so they can be identified

67
Q

Crystal violet or Methylene blue as stains

A

Crystal violet/Methylene blue are positively charged dyes, which are attracted to negatively charged materials in cytoplasm leading to staining of cell components

68
Q

Differential staining

A

Differential staining can distinguish between two types of organisms that would otherwise be hard to identify, it also differentiates organelles of a single organism within a tissue sample

69
Q

Magnification definition

A

Magnification: how many times large the image is than the actual size of the object being observed

70
Q

Resolution definition

A

Resolution: the ability to see individual objects separately in detail

71
Q

What can limit resolution?

A

Resolution is limited by the diffraction of light as it passes through the sample and lenses, which results in structures being harder to distinguish from one another

72
Q

How can resolution be increased?

A

Resolution can be increased by using beams of electrons which have a wavelength thousands of times shorter than light - short wavelength means individual beams can be much closer before they overlap - means objects small and close together can be seen seperately without being affected by diffraction

73
Q

Magnification formula

A

Magnification formula = size of image/actual size of object (MIA)

74
Q

Problems associated with electron microscopes

A

Problems associated with electron microscopes:
-Expensive
-Can only be used inside carefully controlled environment
-Specimens can be damaged by the electron beam
-Complex preparation process can introduce artefacts

75
Q

Artefacts

A

Artefacts: visible structures/distorted cell structures that are produced due to the preparation process

76
Q

Transmission Electron Microscopes (TEM)

A

TEM:
-Beam of electrons transmitted through a specimen and focused to produce an image
-Similar to light microscopy
-Best resolution (0.5nm)

77
Q

Scanning Electron Microscope (SEM)

A

SEM:
-Beam of electrons sent across surface of the specimen and reflected electrons are collected
-Resolution 3-10nm
-Produces 3D images

78
Q

Differences between light and electron microscopes

A

Light microscopes: inexpensive, small, simple sample preparation, vacuum not required, natural colour of sample or seen, up to 2000x mag, resolving power 200nm, specimens living or dead
Electron microscopes: expensive, large, complex sample preparation, vacuum required,black and white images, resolving power 0.5nm for tem and 3-10nm for sem, up to 500 000 mag, specimens dead

79
Q

Mesosomes

A

Mesosome - inward foldings of cell membranes

80
Q

Laser scanning confocal microscopes

A

Laser scanning confocal microscopes - moves a single spot of focused light across a specimen - causes fluorescence from the components labelled with a dye - emitted light from specimen filtered through a pinhole aperture

81
Q

Purpose of the pinhole in laser scanning confocal microscopes

A

The pinhole in laser scanning confocal microscopes does not allow unwanted radiation through, a laser is used instead of light to get higher intensities which improves illumination

82
Q

Positive of using fluorescent tags

A

Fluorescent tags - specific features can be targetered and studied by confocal microscopy with more precision than staining and light microscopy

83
Q

Histones

A

Histones are the proteins that DNA associates with, and they form a complex called chromatin, which coils and condenses to form chromosomes

84
Q

Features of mitochondria

A

Mitochondria features:
-Double membrane - inner membrane folded to form structures called cristae - fluid interior is called the matrix
-Their own DNA - called mitochondria (mt) DNA

85
Q

Process of protein synthesis

A

Proteins are synthesised on ribosomes bound to endoplasmic reticulum -> pass into its cisternae and is packaged into vesicles -> vesicles move toward golgi apparatus via transport funciton of the cytoskeleton -> vesicles fuse with golgi and proteins enter (they are structurally modified) -> vesicles move from golgi to cell surface membrane -> releases their contents by exocytosis (some vesicles form lysosomes)

86
Q

Why is it more likely for artefacts to be introduced in electron microscopy?

A

Artefacts are likely to be introduced in electron microscopy due to the long, complex staining process involved which makes it more likely for the specimen to be damaged and therefore increases likelihood of artefacts

87
Q

Advantages and disadvantages of SEM:

A

Advantages and disadvantages of SEM:
-Adv = specimens doesn’t need to be thin, 3D images produced
-Disadv = resolution and magnification lower than TEM

88
Q

Advantages and disadvantages of TEM:

A

Advantages and disadvantages of TEM:
-Adv = greater magnification, resolution and detail
-Disadv = 2D, specimens need to be thin

89
Q

Fluorescence definition

A

Fluorescence = the absorption and re-radiation of light, of which light is emitted with a longer wavelength

90
Q

Why is confocal microscopy not used for deep tissue imaging?

A

Confocal microscopy is not used for deep tissue imaging due to the light penetration of sample being limited

91
Q

Intermediate fibres

A

Intermediate fibres - these fibres give mechanical strength to cells and help maintain their integrity

92
Q

What controls cell movement?

A

Cell movement is controlled by the cytoskeleton, via cillia and flagella, which are hair-like structures containing microtubules which are responsible for moving them

93
Q

Purpose of the cytoskeleton

A

The cytoskeleton:
-Provides strength and support: supports organelles and keeps them in place
-Intracellular movement: forms ‘tracks’ of which organelles can move along eg movement of vesicles and chromosomes
-Cellular movement via flagella and cilia

94
Q

Why is the membrane that surrounds the lysosome important?

A

The membrane that surrounds the lysosome is important because of compartmentalisation - enzymes are kept away from cell structures as they could cause damage to them by the enzyme activity

95
Q

Why do cells needs to be compartmentalised with examples?

A

Compartmentalisation:
-Reactions of cell structures require different conditions - prevents them fro being damaged by enzymes - eg nucleus, lysosomes, endoplasmic reticulucm, golgi apparatus body

96
Q

How can DNA be packed in a cell with a small diameter?

A

DNA coils around histones, further coiling causes formation of chromatin

97
Q

DNA structure in prokaryotes

A

DNA structure in prokaryotes:
-One molecule of DNA (a chromosome) - supercoiled to become compact - genes on chromosome grouped into operans so only a number of genes are switched on or off at the same times

98
Q

Ribosomes in prokaryotes

A

Ribosomes of prokaryotes:
-70S, smaller than eukaryotes, their relative size is determined by the rate at which they settle

99
Q

Prokaryotic cell wall

A

Prokaryotic cell wall:
-Made up of peptidoglycan, known as murein - complex polymer formed from amino acids and sugars

100
Q

How to add a stain to a wet mount slide?

A

Adding stain to a wet mount slide:
-Put a drop of stain on the edge of the coverslip and paper towel on opposite edge
-Paper towel will draw stain under the coverslip and across the specimen

101
Q

Why do you need to recalibrate the graticule in microscopy?

A

Recalibrating the graticule:
The stage micrometer will appear larger, so each eyepiece division will be smaller measurement

A-Level Biology🌼 (25 decks)

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