2.1 Eukaryotic and prokaryotic cell structure + function Flashcards

1
Q

What is the unifying concept of cell theory?

A

1) Cells - smallest unit of life.
2) All cells derived from division of pre-existing cells.
3) Within cells are the sites of all chem reactions of life.

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2
Q

What is the meaning of cell theory?

A
  • Cells fundamental unit of structure, function + organisation in all living organisms.
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3
Q

What is the definition of a unicellular organism?

A
  • Organism composed of a single cell.
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4
Q

What are cells organised into in complex organisms?

A
  • Tissues, organs + organ systems.
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5
Q

What is the definition of a multicellular organism?

A
  • Organism composed of many cells.
  • Cells differentiate to become arranged into tissues, organs + systems that carry out different functions.
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6
Q

What is the process of differentiation?

A
  • Developmental process - structure of cells in a multicellular organism specialise, becoming adapted for a specific function.
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7
Q

What happens to specialised cells?

A
  • No longer able to divide.
  • Cells show great variety in shape + structure.
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8
Q

What is the definition of a tissue?

A
  • Group of cells w common origin + similar structure that work together to perform a single function.
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9
Q

What is an example of an animal tissue and an example of a plant tissue?

A
  • Animal tissue –> blood.
  • Plant tissue –> xylem.
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10
Q

What is the definition of an organ?

A
  • Structure made of more than one type of tissue, that work together to perform a specific function.
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11
Q

What is the definition of an organ system?

A
  • A group of organs + tissues that perform a particular function.
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12
Q

What is an example of an organ system?

A
  • Circulatory system –> heart, together with blood vessels + blood.
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13
Q

What is the definition of a prokaryotic cell?

A
  • Microorganisms, typically unicellular + have fundamentally different structure to eukaryotes.
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14
Q

What are the examples of prokaryotes?

A
  • Bacteria + Cyanobacteria (photosynthetic bacteria).
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15
Q

What are the distinctive features of prokaryotes?

A
  • Size –> exceedingly small - about size of ribosomes/chloroplasts in eukaryotic cells.
  • Absence of (membrane-bound) nucleus.
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16
Q

Do prokaryotic cells have a membrane-bound nucleus?

A
  • Single circular DNA molecule molecule (nucleoid).
  • Unlike eukaryotic, DNA in nucleoid is not associated w protein.
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17
Q

What is the definition of a nucleoid?

A
  • Circular DNA molecule found in prokaryotic cells.
  • Don’t refer to as chromosome - the DNA in neither linear nor associated w histones.
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18
Q

Which structures are found in all prokaryotic cells?

A
  • Cytoplasm, plasma membrane, ribosomes, nucleoid, cell wall.
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19
Q

Which two structures are only found in some prokaryotic cells?

A

Pili + Flagella.

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20
Q

What are plasmids + what is their function?

A
  • Circular DNA molecules (in addition to nucleoid).
  • usually only contain a few genes - usually conferring resistance to antibiotics.
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21
Q

What are 70s ribosomes?

A
  • Involved in protein synthesis, but smaller than 80s ribosomes in eukaryotic cells.
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22
Q

What is found in the cytoplasm of prokaryotic cells?

A
  • Lack of membrane-bound organelles.
  • No mitochondria, chloroplasts, golgi apparatus or endoplasmic reticulum.
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23
Q

What are the functions of cell walls in all prokaryotic cells?

A
  • Protects cells from rupture caused by osmosis + possible harm from other organisms.
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24
Q

What does a mesosome look like?

A
  • In-tuckings of the cell membrane.
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25
What actually is a mesosome?
- An artefact.
26
What is an artefact?
- Part of specimen viewed under microscope that wasn't part of original cell. - Damage caused by processing tissue for examination.
27
What are cell walls made up from in prokaryotic cells?
- Not cellulose as plant cells, instead they are **PEPTIDOGLYCAN**.
28
What is the function of Pili?
- Enable attachment to surfaces + other bacteria.
29
What is the function of Flagella?
- Bring about movement of the bacterium.
30
What is peptidoglycan in cell walls made of?
- Polymers of amino acids + sugars.
31
How are gram positive cell walls compromised and how does this affect staining?
- Thick walls made almost entirely of peptidoglycan. - Wall becomes purple when stained w crystal violet.
32
How are gram negative walls compromised and how does this affect staining?
- Thin peptidoglycan walls w additional outer-membrane w high lipid content. - Prevents crystal purple from getting to cell wall, so bacteria do not become purple.
33
What is the outer-layer of gram negative bacteria made of?
- Lipid + polysaccharide.
34
What happens in stage 1 of gram staining?
- Bacteria in an air-dried smear on a microscope slide appears colourless.
35
What happens in stage 2 of gram staining?
- Smear is treated w **crystal violet**. - cells all appear violet when stain is washed from the slide.
36
What happens in stage 3 of gram staining?
- Smear is flooded w **Lugol's iodine** (mordent treatment to combine dye to bacteria).
37
What happens in stage 4 of gram staining?
- Smear now treated w **decolourising solution** of **acetone + alcohol**. - Removes violet dye from cells not reacted. - Gram positive bacteria remain purple.
38
What happens in stage 5 of gram staining?
- Red dye **Safranin** is added as counter-stain. - Taken up by colourless bacteria of the treatment smear.
39
What are the final results of gram staining?
- Gram positive --> Purple. - Gram negative --> Red.
40
When and who discovered gram staining?
- The Dane, Hanz Gram. - 1884.
41
Why was gram staining devised?
- To differentiate between the two types of bacteria.
42
How does antibiotics affect gram positive + gram negative bacteria? and why does this difference happen?
- Gram positive - susceptible to penicillin. - Gram negative - resistant to many types of antibiotics. - Outer, lipid-rich membrane of gn bacteria is relatively impermeable to antibiotics + antigens are hidden.
43
What is an organelle?
- A structure within cytoplasm of a eukaryotic cell that performs a discrete function.
44
Which organelles are membrane-bound in prokaryotic cells?
- All with the exception of ribosomes.
45
What is the solution around organelles called?
- Aqueous solution of chemicals - cytosol.
46
What are the cytosol and organelles contained in in eukaryotic cells?
- Cell surface membrane.
47
How have images of the ultrastructure of eukaryotic cells been made?
- With TEM's (Transmission Electron Micrographs).
48
What is the role and structure of the nucleus in eukaryotic cells?
- Role in protein synthesis. - Largest organelle in eukaryotic cell (10-20 μm diameter). - Surrounded by double nuclear membrane w pores.
49
What is the size and purpose of nuclear pores in eukaryotic cells?
- 100nm. - Allow movement of molecules between cytoplasm + nucleus e.g. mRNA.
50
What are the chromosomes in nuclei in eukaryotic cells?
- Each chromosome contains long strand DNA wound around beads of histone (type of protein).
51
When can chromosomes be seen in eukaryotic cells?
- Only visible w light microscope when nucleus divides. - At other times, appear dispersed as a diffuse network, called **chromatin**.
52
What is a nucleoli?
- Single nucleolus, present in nucleus. - Rounded, dark-staining bodies - sites of ribosome synthesis.
53
Which parts of the nucleus can only be seen when stained with certain dyes?
- Chromatin, chromosomes + the nucleolus.
54
What are some examples of eukaryotic cells that don't contain one nucleus?
- Mature RBCs (mammals) - 0. - Mature sieve elements in phloem of flowering plants - 0. - Voluntary muscle cells + mycelia of fungi - both contain many nuclei.
55
What are features of mitochondria?
- Rod-shaped, 0.5-1.5μm diameter, 3.0-10.0μm long. - Each has double membrane.
56
What are the features of the double membrane of the mitochondria in eukaryotic cells?
- Outer membrane, smooth boundary. - Inner membrane, infolded to form cristae
57
What is in the middle of the mitochondria?
- Aqueous solution of metabolites + enzymes, called the **matrix**. - Small circular molecules of DNA in matrix.
58
What do chloroplasts look like?
- Biconvex shape. - 4-10μm long + 2-3μm wide.
59
Where are chloroplasts found?
- Cells of green plants + photosynthetic protoctists. - Plants --> found in mesophyll.
60
What are chlororplasts?
- The site of photosynthesis.
61
What are the two layers of the double membrane of chloroplasts?
- Outer - smooth continuous boundary. - Inner - in-tucked to form system of of branching membranes - **lamellae** or **thylakoids**. - These are arranged in flattened circular piles called **grana** (singular granum).
62
What is located in the stroma of chloroplasts?
- Pigments including chlorophyll. - Lots of grana. - branching membranes in aqueous solution w enzymes + starch grains.
63
What are plastids?
- Organelles found in plant cells but not animal cells.
64
What are amyoplasts?
- Colourless plastids in which starch is stored.
65
What are chromoplasts?
- Coloured plastids, containing non-photosynthetic pigments.
66
What are ribosomes?
- Site of protein synthesis.
67
How is the size of a ribosome calculated?
- Recorded in **Svedberg** units. - Measure of rate of **sedimentation** during **centrifugation** under standardised conditions. - Eukaryotic have sedimentation rate of 80S.
68
What are ribosomes made up of?
- Two sub-units + don't have membranes. - Consists of protein + Nucleic acid (RNA).
69
Where are ribosomes found in cells?
- Found free in cytoplasm + also bound to ER to form rough ER.
70
What is endoplasmic reticulum?
- Consists of networks of folded single membranes forming interconnected sheets, tubes or sacs.
71
What is the rough endoplasmic reticulum and where is it found in eukaryotic cells?
- Continuous outer membrane surrounding nucleus. - Develops tertiary + quaternary structures of proteins. - Links AAs to form polypeptide chains.
72
What is the definition of a vesicle?
- Small, spherical organelle bounded by a single membrane - used to store + transport substances around cell.
73
What is the smooth endoplasmic reticulum and where is it found in eukaryotic cells?
- Not near nucleus + no ribosomes. - Synthesises lipids, phospholipids + steroids.
74
What happens in the smooth ER in the cytoplasm of voluntary muscle fibres?
- Special type of smooth ER, stores calcium ions - essential in contraction of muscle fibres.
75
What is the Golgi apparatus?
- Stack of membranous disks called cisternae. - One side is formed by fusion of vesicles from rough ER. - Other side, vesicles are formed + pinched off.
76
What cells are Golgi apparatus most common in?
- Metabolically active - sort, modify + package polymers for secretion or use within cell.
77
What are lysosomes?
- Small spherical vesicles bound by single membrane. - contain mix of 50 hydrolytic enzymes produced by RER + modified by GA.
78
What is the function of lysosomes?
- Breakdown of imported food vacuoles, old organelles + harmful bacteria.
79
How are centrioles formed?
- Microtubules of globular proteins called tubulin form network of hollow cylinders. - These form centrioles.
80
How do centrioles occur?
- Occur in pairs. - Normally lie at right angles right outside nucleus. - Each is made of 9 bundles of microtubules. - During cell division centrioles move apart creating spindle.
81
What are plant cell walls made of?
- Long, straight fibres of cellulose held together by hydrogen bonds.
82
How do plant cell walls protect the cell?
- Cellulose bundles at diff directions prevent stretching. - Prevents bursting in dilute solutions.
83
What is the apoplast pathway in plant cell walls?
- Spaces between bundles of cellulose - allow movement of water from cell wall to cell wall.
84
What is the middle lamella?
- First boundary between cells during cell division - gel-like layer of calcium pectate. - ER from parent cell gets trapped when cellulose is laid down forming plasmodesmata.
85
What is the definition of plasmodesmata?
- Cytoplasmic connections between plant cells through gaps in cell walls. - Part of symplast pathway.
86
What is a permanent vacuole in plant cells?
- Fluid-filled + takes up bulk of cell. - Presses cytoplasm + cell membrane against cell wall. - Surrounded by tonoplast.
87
What is the tonoplast?
- Membrane surrounding vacuole. - Barrier between fluid contents of vacuole + cytoplasm.
88
What are the different parts of a compound light microscope called?
- Eyepiece lens. - Nosepiece. - Objective lens. - Stage. - Condenser. - Coarse focus. - Fine focus. - Built-in light source.
89
What is the purpose of the nosepiece on a compound light microscope?
- It is turned and clicks into different objective lenses.
90
What are the powers of the objective lenses on a compound light microscope?
- 4x (low). - 10x (medium). - 100x (high).
91
What is temporary preparation of a sample for viewing in a compound light microscope?
- Placing tissue on glass slide, cover w water-based liquid to stop it from drying out + put thin coverslip over.
92
What is permanent preparation of a sample for viewing in a compound light microscope?
- Water removed from tissue + replaced by firmer substance. Coverslip held in place by resin.
93
Why is it important to stain cells when viewing them under a compound light microscope?
- Cells translucent ∴ must use chemicals to react + see cell components.
94
What is digital microscopy?
- Attach microscope coupler or eyepiece adaptor to appropriate camera. - Can be viewed on VDU monitor or can be printed.
95
What is the definition of magnification?
- Extent to which an object has been enlarged by a microscope in a drawing or photograph.
96
What is the magnification equation?
- M=I/A.
97
What is the definition of resolution?
- Ability to distinguish between 2 points that are very close together.
98
What is the resolution in a light microscope and an electron microscope?
- Light --> 2μm (2000nm). - Electron --> 5nm.
99
How does a transmission electron microscope work?
- Electron beam passed through extremely thin section of material. - Structures stain w heavy metal ions, making them electron opaque. - These then look dark on image.
100
What can be seen on a transmission electron micrograph that cannot be seen through a light microscope?
- Cell ultrastructure.
101
What does Eukaryotic mean?
- True nucleus.
102
What does prokaryotic mean?
- Before the nucleus.