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Biology 3.2 Cells Mr Dawson Keywords > 3.2.1 Cell Structure > Flashcards

3.2.1 Cell Structure Flashcards

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1
Q

3.2.1.3 What is the cell theory?

A

The unifying concept in biology- theory that all living organisms are composed of one or more cells, the cell is the basic organisational unit of life and all cells arise from pre-existing cells

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2
Q

3.2.1.3 What is compartmentalisation?

A

refers to the way organelles in eukaryotic cells live and work in separate areas within the cell in order to perform their specific functions more efficiently

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3
Q

3.2.1.3 Magnification equations

A

objective lens x eyepiece lens and image size/actual size

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4
Q

3.2.1.3 How does a light microscope work?

A

Visible light passes and is bent through the lens system to enable the user to see the specimen

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5
Q

3.2.1.3 Why must specimens be stained and what does it cause?

A

Individual cells are generally transparent and their components are not distinguishable unless they are coloured with special stains. Staining does kill the cells.

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6
Q

3.2.1.3 Why do the specimens have to be thin when using a light microscope?

A

To enable the light to pass through it easily and to get a clear image without layers of the cell overlapping and making the image produced blurry

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7
Q

3.2.1.3 What is the maximum resolution of a light microscope?

A

0.2 micrometers-quite low

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8
Q

3.2.1.3 What organelles are visible when using a light microscope?

A

nucleus, cytoplasm, cell membrane, chloroplasts and cell wall (mitochondria but detailed study not possible)

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9
Q

3.2.1.3 What is the maximum magnification of a light microscope?

A

x2,000

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10
Q

3.2.1.3 How do electron microscopes work?

A

By using a beam of electrons which gives EMs a higher resolution due to the shorter wavelengths of electrons

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11
Q

3.2.1.3 What is the maximum resolution of an electron microscope?

A

0.0002 micrometers-100 times more than light microscope

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12
Q

3.2.1.3 What is the maximum magnification?

A

x1.5million

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13
Q

3.2.1.3 What are the two types of electron microscopes?

A

Transmission (TEM) and Scanning (SEM)

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14
Q

3.2.1.3 How does a TEM work?

A

Beam of electrons sent down the column which then pass through the specimen and scatter. Magnetic lenses then focus the image onto a flourescent screen.

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15
Q

3.2.1.3 Why must the column be a vaccum?

A

Because other molecules in the air are far bigger than electrons and would disrupt the beam

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16
Q

3.2.1.3 Why must the (TEM) sample be dehydrated

A

The water would evaporate in a vaccum and damage the sample

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17
Q

3.2.1.3 Why must the (TEM) sample be extremely thin (40-80nm)? What is the machine used to cut them called?

A

Electrons are extremely small so need a sample thin enough for them to pass through. Machine is called ultramicrotome.

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18
Q

3.2.1.3 Why must the sample be stained with heavy metals(give examples)?

A

heavy metals like uranium, lead, or tungsten are used to increase the contrast between different structures in the specimen, and also to scatter the electron beams

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19
Q

3.2.1.3 Basic properties of light microscope

A

Uses light, low magn, low resol, cheaper, glass lens to focus, easy to use, colour, can view living cells

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20
Q

3.2.1.3 Basic properties of electron microscope

A

Uses electrons, high magn, high resol, expensive, electromagnets to focus, needs training-controlled temps/press/humid. Requires vaccum

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21
Q

3.2.1.3 What does resolution mean?

A

the minimum distance between two points at which they can be distinguished from one another.

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22
Q

3.2.1.3 How does a Scanning Electron Microscope work?

A

Sample is coated with a thin layer of gold and abeam of electrons is scanned over the image. Electrons are scattered as they hit the sample. The pattern of scattered electrons is used to create a 3D image.

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23
Q

3.2.1.3 Basic differences between TEM and SEM

A

TEM-Higher Magnification SEM- Lower magnification

2D image 3D image

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24
Q

3.2.1.3 1mm=?μm

A

1000

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25
Q

3.2.1.3 1μm=?nm

A

1000

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26
Q

3.2.1.3 1nm=?μm

A

0.001

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27
Q

3.2.1.3 1μm=?mm

A

0.001

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28
Q

3.2.1.1 Nucleus description

A

A large organelle surrounded by a nuclear envelope (double membrane), which contains many pores. The nucleus contains chromosomes (which are made from protein-bound linear DNA and one or more structure(s) called a nucleolus

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29
Q

3.2.1.1 What are the functions of the nucleus?

A

1)Contains DNA, the information needed to make proteins 2)Replicates DNA in preparation for cell division 3)Makes mRNA for protein synthesis 4)Nucleolus produces rRNA for manufacture of ribosomes

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30
Q

3.2.1.1 Name some of the different parts of the nucleus

A

The nuclear envelope, nuclear pores, nucleoplasm, chromosomes, nucleolus, ribosomes, chromatin

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31
Q

3.2.1.1 What is the nucleolus ?

A

a small spherical region within the nucleoplasm. It manufactures ribosomal RNA and assembles the ribosomes. There may be more than one nucleolus in a nucleus

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32
Q

3.2.1.1 What is the nuclear envelope?

A

is a double membrane that surrounds the nucleus. lts outer membrane is continuous with the endoplasmic reticulum or the cell and often has ribosomes on its surface. It controls the entry and exit of materials in and out of the nucleus and contains the reactions taking place within it

33
Q

3.2.1.1 Nuclear pores

A

allow the passage of large molecules, such as messenger RNA, out of the nucleus. There are typically around 3000 pores in each nucleus. each 40- lOOnm in diameter

34
Q

3.2.1.1 Nucleoplasm

A

is the granular, jelly-like material that makes up the bulk of the nucleus

35
Q

3.2.1.1 Chromosomes

A

condensed DNA formed during cell division/ consists of protein bound, linear DNA

36
Q

3.2.1.1 Chromatin

A

DNA coiled around proteins (histones)

37
Q

3.2.1.1 Ribosomes

A

made of ribosome RNA (rRNA) and proteins, found outside the cell, often stuck to nuclear membrane

38
Q

3.2.1.1 Mitochondrion description

A

Usually oval shaped and 1- 10 pm in length, consists of an outer smooth membrane and an inner folded membrane, forms structures called cristae. Central fluid filled space is called the matrix. Matrix contains enzymes used in respiration.

39
Q

3.2.1.1 Why so many folds (cristae) in the mitochondria?

A

To increase SA to increase rate of respiration

40
Q

3.2.1.1 Mitochondria function

A

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

41
Q

3.2.1.1 Double membrane

A

Controls entry and exit of material. The inner of the two membranes is folded to form extensions known as cristae.

42
Q

3.2.1.1 Cristae

A

extensions or the inner membrane, which in some species extend across the whole width of the mitochondrion. These provide a large surface area For the attachment of enzymes and other proteins involved in respiration.

43
Q

3.2.1.1 What is the endosymbiotic theory (in relation to mitochondria)?

A

Started as bacteria with rough, spiky surface but then phagocytised by simpler organism, smooth membrane then on the outside and folded membrane inside- mutualistic relationship as energy and safe space is provided. Further proof- mitochondria has circular DNA (like plasmids in bacteria) and ribosomes to make own proteins.

44
Q

3.2.1.1 What is the Rough Endoplasmic Membrane?

A

(Reticulum = “network”)

RER is continuous with the nuclear membrane.
Covered in Ribosomes =site of protein synthesis.
The protein collects inside the RER and is transported throughout the cell.

45
Q

3.2.1.1 Why RER not continuous under microscope?

A

Slicing of sample

46
Q

3.2.1.1 What cells would require more RER?

A

Cells that make lots of protein e.g pancreas making insulin

47
Q

3.2.1.1 Magn of RER?

A

x33,000

48
Q

3.2.1.1 Magn of Nucleus?

A

x3000 (largest)

49
Q

3.2.1.1 Magn of Mitochondrion?

A

x33,000

50
Q

3.2.1.1 ER Structure

A

A complex network of flattened, membrane-bounded sacs called cisternae. Often has ribosomes on the cytoplasmic side.

51
Q

3.2.1.1 ER Function

A

Forms a system of channels for trans porting materials through the cytoplasm. One type has ribosomes on its surface and is the site of protein synthesis. The other type has no ribosomes and is where steroids and other lipids are synthesised.

52
Q

3.2.1.1 What are cisternae and what consist of them?

A

A complex network of flattened, membrane bound sacs. Make up RER and SER

53
Q

3.2.1.1 What is the Endoplasmic Reticulum and the two types?

A

(ER) is an elaborate, three-dimensional system of sheet-like membranes, spreading through the cytoplasm of the cells. It is continuous with the outer nuclear membrane. The membranes enclose a network of tubules and flattened sacs called cisternae

Rough endoplasmic reticulum (RER) has ribosomes present on the outer surfaces of the membranes. Mainly transporting proteins and protein synthesis

Smooth endoplasmic reticulum (SER) lacks ribosomes on its surface and is often more tubular in appearance.

synthesise, store and transport lipids/carbohydrates.

54
Q

3.2.1.1 Smooth Endoplasmic Reticulum

A

Similar to RER but without ribosomes.

Found on the periphery of the cell and is not connected to the nuclear membrane.

Closer to cell membrane (cm made of lipids)
Synth + transport lipids and steroids

Memb bound sacs all joined together, more tubular

55
Q

3.2.1.1 Golgi Apparatus and general

A

It consists of a stack of membranes that make up flattened sacs, or cisternae, with small rounded hollow structures called vesicles
The proteins and lipids produced by the ER are passed through the Golgi apparatus in strict sequence. The Golgi modifies these proteins often adding non-protein components, such as carbohydrate, to them. It also ‘labels’ them, allowing them to be accurately sorted and sent to their correct destinations. Once sorted, the modified proteins and lipids are transported in Golgi vesicles which are regularly pinched off from the ends of the Golgi cisternae (Figure 6). These vesicles may move to the cell surface, where they fuse with the membrane and release their contents to the outside.

56
Q

3.2.1.1 Golgi Apparatus and general simple

A

Distribution of substances through out the cell.
Consists of a stack of cisternae.
Surrounding the GA are separated golgi vesicles.
Exists as stack of closely packed but not continuous membrane bound sacs/cisternae- ‘pinched off’ portions of Golgi body

57
Q

3.2.1.1 Golgi Apparatus function

A

add carbohydrate to proteins to form glycoproteins
• produce secretory enzymes, such as those secreted by the pancreas
• secrete carbohydrates, such as those used in making cell walls
in plants
• transport, modify and store lipids
• form lysosomes.

58
Q

3.2.1.1 Golgi Apparatus function simple

A

receives proteins synthesised at ER and prepares them for secretion from the cell. Often involves adding carbohydrates to proteins to make glycoproteins.

59
Q

3.2.1.1 Golgi Apparatus structure

A

Stack of membrane bound, flattened sacs in the cytoplasm, looking like a pile of pitta bread

60
Q

3.2.1.1 Ribosomes Function

A

Uses the information in nucleic acid to synthesise proteins

61
Q

3.2.1.1 Ribosomes Structure

A

Very small organelle not bounded by a membrane. Consists of a large and a small subunit. Made of protein and RNA.

62
Q

3.2.1.1 Two types of Ribosomes

A

8OS - found in eukaryotic cells, is around 25 nm in diameter.
70S - found in prokaryotic cells, mitochondria and chloroplasts, is slightly smaller.

63
Q

3.2.1.1 Ribosome diameter

A

20nm

64
Q

Chloroplasts structure

A

Surrounded by a double membrane called the chloroplast envelope.
Filled with “jelly like” fluid called stroma. The stroma is the site of the light independent stage of photosynthesis. Stroma also contains circular DNA and ribosomes, starch grains
Membranes form fluid filled discs called thylakoids arranged into stacks called granum.
Granum are interconnected by lamellae. This membranes contain the photosynthetic pigments (e.g. chlorophyll).

65
Q

How chloroplasts are adapted to their function of harvesting sun light and carrying out photosynthesis

A

The granal membranes provide a large surface area for the attachment of chlorophyll, electron carriers and enzymes that carry out the first scage of photosynthesis. These chemicals are attached to the membrane in a highly ordered fashion.

  • The fluid of the stroma possesses all the enzymes needed to make sugars in the second stage of photosynthesis.
  • Chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis.
66
Q

Lysosomes structure and how they are formed and how they appear on microscopes

A

Round, single membrane bound sac-They contain digestive enzymes.
Formed when the vesicles produced by the Golgi
apparatus contain enzymes such as proteases and lipases. They also contain lysozymes, enzymes that hydrolyse the cell walls of certain
bacteria.

Light, plain sacs as they contain soluble substances

67
Q

Lysosome function- given this, where are they most abundant?

A

Breakdown of food, bacteria or other materials taken into the cell.
Breakdown of redundant, ageing organelles.
Breakdown of the whole cell (autolysis)
Release of enzymes outside of cell.

secretory cells, such as epithelial cells, and in phagocytic cells

68
Q

Advantage of cells having mitochondria?

A

Mitochondria are advantageous as they allow the cell to respire aerobically, without them they can only respire anaerobically. As a result of this aerobic respiration due to the mitochondria’s presence they can produce more ATP

69
Q

Endosymbiotic theory and evidence

A

The endosymbiotic theory states that some of the organelles in eukaryotic cells were once prokaryotic microbes.
Evidence: Mitochondria and chloroplasts are the same size as prokaryotic cells
divide by binary fission.
Mitochondria and chloroplasts have their own DNA which is circular, not linear
Have ribosomes same size as those in prokaryotes

70
Q

Compare/contrast eukaryotes and prokaryotes

A

P- no nucleus, no membrane bound organelles,
very small (1-10microm),
smaller ribosomes(70S),
some DNA in plasmids,
no chloroplasts, only bacterial chloroplasts present in plants chlorophyll associated with the cell,
cell wall made of murein (peptidoglycan),
capsule layer
Asexual Binary Fission
Respration- Mesosome and an in cyct

E-DNA bound in nucleus, membrane bound organelles
larger (100s of micrometers)
80S ribosomes
No plasmids, DNA linear
When present, wall mad of cellulose (chitin in fungi)
No capsule
Asexual Mitosis/Sexual Meiosis (Gamete Production)
Resp- An in cyctp and aer in mitochondria

Both-Plasma membrane-a barrier between the inside of the cell and the outside.
Ribosomes
Anaerobic respiration in the cytoplasm
Cell Wall

71
Q

What are mesosomes?

A

Mesosomes are areas in the cell membrane of prokaryotic (bacterial) cells that fold inward to provide internal membrane surfaces for special purposes. They play a role in cellular respiration, the process that breaks down food to release energy.

72
Q

How do bacteria exchange genetic material(also causes genetic variation)?

A

The joining of pili which forms a narrow tube which plasmids can pass through

73
Q

Why are eukaryotes larger?

A

Eukaryotic cells are larger than prokaryotic cells because they are compartmentalized. Eukaryotic cells contain many different membrane-bound structures called organelles, each of which carries out a specific function within the cell.

74
Q

What does S stand for?

A

S stands for Svedberg units and is a measure of how rapidly the ribosomes sediment in a centrifuge. 80S ribosomes sink quickest because they are heaviest

75
Q

What domains are prokaryotes and eukaryotes a part of?

A

Archaea, Bacteria and Eukarya. The first two domains consist of primarily prokaryotes, while as the name suggests, Eukarya consists of eukaryotes

76
Q

Viruses: Structure and stuff

A

Viruses are acellular, non-living particles. They
are smaller than bacteria, ranging in size from
20-300nm. They contain nucleic acids such
as DNA or RNA as genetic material but can only multiply inside living host cells. The nucleic acid is
enclosed within a protein coat called the capsid. Some viruses, like the human immunodeficiency
(enzyme) virus, are further surrounded by a lipid envelope. The
matrix lipid envelope, or if this is not present, the capsid, have attachment proteins which are essential to allow the virus to identify and attach to a host cell

77
Q

Describe how cell fractionation works- two steps and conditions

A

1)Homogenisation using
Mortar and pestel OR liquidiser
Break down cells releasing organelles- remaining is homogenate

2) Centrifugation- H spun at high speeds, causing different organelles to fall and from pellet. Bigger ones first then as speed increases, smaller ones

Conditions- Ice cold- lowers enzyme activity
pH buffer- stops enzyme denaturing
Isotonic- stops osmosis

78
Q

Cell wall structure and function

A
  • They consist or a number of polysaccharides, such as cellulose and/or glycoproteins- chitin in fungi
  • There is a thin layer, called the middle lamella, which marks the boundary between adjacent cell walls and cements adjacent cells together.

The functions of the cellulose cell wall are:
• to provide mechanical strength in order to prevent the cell bursting under the pressure created by the osmotic entry of water
• to give mechanical strength to the plant as a whole
• to allow water to pass along it and so contribute to the movement of water through the plant.

79
Q

Vacuoles and function

A

A fluid-filled sac bounded by a single membrane may be termed a vacuole. Within mature plant cells there is usually one large central vacuole. The single membrane around it is called the tonoplast. A plant vacuole contains a solution or mineral salts, sugars, amino acids, wastes and sometimes pigments such as anthocyanins.

Plant vacuoles serve a variety of functions: • They support herbaceous plants, and herbaceous parts of woody plants, by making cells turgid.
• The sugars and amino acids may act as a temporary food store.
• The pigments may colour petals to attract pollinating insects.

Biology 3.2 Cells Mr Dawson Keywords (4 decks)

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