Cell Structure Flashcards
(84 cards)
1
Q
Light Microscope: Medium, Dimensions, Max Magnification, Max Resolution
A
Medium: Light Beam
Dimensions: 2D
Max Magnification: X 1500
Max Resolution: 200nm
2
Q
SEM: Medium, Dimensions, Max Magnification, Max Resolution
A
Medium: Electron Beam
Dimensions: 3D
Max Magnification: X 200 000
Max Resolution: 20nm
3
Q
TEM: Medium, Dimensions, Max Magnification, Max Resolution
A
Medium: Electron Beam
Dimensions: 2D
Max Magnification: X 2 000 000
Max Resolution: 0.1nm
4
Q
Magnification Equation
A
Magnification = (size of image)/(size of object)
5
Q
Magnification meaning
A
Magnification is how much bigger the image is compared to the original object viewed with the naked eye
6
Q
Resolution Meaning
A
Resolution is how well a microscope distinguishes between two points that are close together.
7
Q
To prepare slides for light microscopy, the specimen must be:
A
Dehydrated
Embedded in wax and sectioned
Stained
Mounted
8
Q
Staining
A
Staining is used to increase contrast in a specimen, in order to observe transparent and colourless structures. Stains work by binding to different types of molecules or cell structures. This allows different components of cells to be identified, and is known as differential staining
9
Q
Eukaryotes include
A
Eukaryotes include animal, plant & fungal cells.
10
Q
Plant cells
A
Plant cells: cell wall with plasmodesmata, vacuole, chloroplasts
11
Q
Plasma cell surface membrane
A
Plasma cell surface membrane: animal cell surface, inside cell wall of plant cells and prokaryotic cells, made of lipids and proteins. Regulates substance movement in and out of the cell. Contains receptor molecules.
12
Q
Cell Wall
A
Cell Wall: rigid structure. Provides support.
13
Q
Nucleus
A
Nucleus: large. Surrounded by a nuclear envelope (double membrane containing pores). Contains chromatin (made from DNA and proteins). Contains Nucleolus. Nucleus controls transcription of DNA. DNA contains instructions to create proteins. Nucleolus makes ribosomes. Pores allows substances to move between cytoplasm and nucleus.
14
Q
Lysosomes
A
surrounded by membrane. No clear internal structure. Contains digestive enzymes selected from cytoplasm. Digest invading cells. Break down worn out cell components
15
Q
Ribosomes
A
very small organelle. Floats free in cytoplasm or attached to RER. Made of proteins and RNA. No membrane. Site where proteins are synthesised
16
Q
RER
A
Systems of membranes enclosing fluid-filled space. Folds and processes proteins made at the ribosomes
17
Q
SER
A
synthesises and processes lipids
18
Q
Vesicle
A
fluid-filled sac surrounded by membrane. Transports substances between cells and between organelles. Formed by golgi or ER or at cell surface.
19
Q
Golgi
A
group of fluid-filled, membrane-bound, flattened sacs. Processes and packages new lipids and proteins and makes lysosomes.
20
Q
Mitochondrion
A
oval shaped. Double membrane. Inner membrane folds to form cristae. Inside is matrix (contains enzymes involved in respiration)
21
Q
Chloroplast
A
small, flattened structure surrounded by double membrane. Contains thylakoids membranes. Membranes stack to form grana. Linked together by lamellar - thin, flat pieces of thylakoids membrane. Stroma is thick fluid. Photosynthesis occurs in stroma and grana
22
Q
Centriole
A
small, hollow cylinders made of microtubules (tiny protein cylinders). In animals cells and few plant cells. Involved with chromosome separation
23
Q
Cilia
A
small, hair-like structures on surface membranes. Outer membrane and ring of protein microtubules in 9 plus 2 formation microtubules allow cilia movement.
24
Q
Flagellum
A
longer than cilia on eukaryotic cells. Surrounded by plasma membrane. 9 plus two formation. Microtubules contract to make flagellum move. Used as propellor.
25
Organelles in protein production
Proteins made at ribosomes
Free ribosome proteins stay in cytoplasm, RER proteins excreted or attached to membrane
Proteins produced at RER folded and processed (eg. Sugar chains added) in RER
Transported from ER to golgi in vesicle
At golgi, further processing may occur (eg. Sugar chains added or trimmed)
Proteins enter vesicles -> transported around cells (eg mucus glycoproteins move to cell surface membrane)
26
Functions of cytoplasm
Microtubules and microfilaments support the cell’s organelles -> keeps positions
Help strengthen cell + maintain shape
Responsible for material movement within cell (eg. Contraction of microtubules on the spindle)
Proteins of cytoskeleton cause cell movement. Eg. Flagellum
27
Prokaryotes
Prokaryotes: extremely small (>8micrometres), circular DNA, DNA free/no nucleus, polysaccharide cell wall (not chitin or cellulose), few organelles (non membrane-bound ), flagella made of protein flagellin (arranged in a helix), small ribosomes, eg. E.coli bacterium
28
Eukaryotes
Eukaryotes: Larger cells (10-100micrometer diameter), linear DNA, nucleus present, cell wall (animals=not present, plants = cellulose, fungi=chitin), many organelles (mitochondria and other membrane-bound organelles), flagella (made of microtubule proteins arranged in a 9+2 formation), larger ribosomes, eg. Human liver cell
29
Bacterial cells are prokaryotic
Bacterial cells are prokaryotic: prokaryotes roughly 1/10th size of eukaryotic cells. Normal microscopes not powerful enough to look at internal structure
30
Magnification
Magnification = how much larger an image is compared to specimen
31
Resolution
Resolution = how well a microscope distinguishes between two points
32
Laser scanning confocal microscope (type of light microscope)
Laser scanning confocal microscope (type of light microscope): Laser beam, specimen tagged with fluorescent dye, last causes de to fluoresce, light focused through pinhole (meaning out of focuses light blocked ∴ clearer image) onto detector (Hooked onto computer), 3D image generated, used to show different depths on thick specimens
33
TEM
TEM: use electromagnets, focuses beam of electrons, transmitted through specimen, Denser parts absorb more ∴ look darker, high resolution images, (see range of organelles), only thin specimens.
34
SEM
SEM: scan beam of electrons across specimen, knocks off electron from specimen, gathered in a cathode ray tube to form image, show surface and can be 3D, lower resolution than TEM.
35
Staining for light microscopes
Staining for light microscopes: dye, eg. Methylene blue and eosin, stains taken up more by some parts than others, different stains show different things eg. Eosin stains cytoplasm and methylene blue stains DNA, more than one stain can be used at once
36
Staining samples for electron microscopes
Staining samples for electron microscopes: objects dipped in solution of heavy metals (eg. Lead), metal ions scatter electrons creating contrast (some parts of object show up darker)
37
How to prepare a microscope slide: Dry Mount
Dry mount: Use thin slice of specimen, use tweezers to pick up specimen, place in centre of clean slide, place coverslip on top
38
Wet Mount
Wet mount: pipette small drop of water on slide, use tweezers place on water drop, stand cover slip upright on slide then carefully tilt and lower (no bubbles), add stain once in position, put paper towel next to opposite edge to draw stain across specimen
39
How to use light microscope
How to use light microscope:
1) clip slide onto stage
2) select lowest power objective lens
3) use coarse adjustment knob to just above slide
4) look down eyepiece and adjust focus with the fine adjustment knob until you get a clear image
5) swap to higher power objective lens and refocus
40
Outline how a student could prepare a temporary mount of tissue for a light microscope.
1. Obtain thin section of tissue e.g. using ultratome or by maceration.
2. Place plant tissue in a drop of water.
3. Stain tissue on a slide to make structures visible.
4. Add coverslip using mounted needle at 45° to
avoid trapping air bubbles.
41
Describe how light microscopes work.
1. Lenses focus rays of light and magnify the view of a thin slice of specimen.
2. Different structures absorb different amounts and wavelengths of light.
3. Reflected light is transmitted to the observer via the objective lens and eyepiece.
42
Describe how a transmission electron microscope (TEM) works.
1. Pass a high energy beam of electrons through a thin slice of specimen.
2. More dense structures appear darker since they absorb more electrons.
3. Focus image onto fluorescent screen or
photographic plate using magnetic lenses
43
Describe how a scanning electron microscope (SEM) works
1. Focus a beam of electrons onto a specimen’s surface using electromagnetic lenses.
2. Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate.
44
Describe how a laser scanning confocal microscope works.
1. Focus a laser beam onto a small area on a sample’s surface using objective lenses.
2. Fluorophores in the sample emit photons.
3. Photomultiplier tube amplifies the signal onto a
detector. An image is produced pixel by pixel in
the correct order
45
How should the field of view in microscopy be recorded?
Draw a diagram with a sharp pencil. Do not use sketchy lines or shading.
Include a scale bar.
Annotate visible structures.
IMAGE 1
46
State an equation to calculate the actual size of a structure from microscopy.
Actual size = Image size / Magnification
47
Define magnification and resolution
Magnification: factor by which the image is larger than the actual specimen.
Resolution: smallest separation distance at which 2 separate structures can be distinguished from one another.
48
Why do samples need to be stained for light microscopes?
Coloured dye binds to the structures.
Facilitates absorption of wavelengths of light to produce image. Differential staining: contrast between heavily & lightly stained areas distinguishes structures.
49
State the magnification and resolution of a compound optical microscope
magnification: x 2000 resolution: 200 nm
50
State the magnification and resolution of a TEM.
magnification: x 500 000 resolution: 0.5 nm
51
State the magnification and resolution of an SEM.
magnification: x 500 000 resolution: 3 - 10 nm
52
Explain how to use an eyepiece graticule and stage micrometer to measure the size of a structure
1. Place micrometer on stage to calibrate eyepiece graticule.
2. Line up scales on graticule and micrometer. Count how
many graticule divisions are in 100μm on the micrometer.
3. Length of 1 eyepiece division = 100μm / number of
divisions.
4. Use calibrated values to calculate actual length of
structures.
53
Describe the structure of the nucleus.
● Surrounded by a nuclear envelope, a semipermeable double membrane.
● Nuclear pores allow substances to enter/exit.
● Dense nucleolus made of RNA & proteins
assembles ribosomes.
54
Describe the function of the nucleus
● Contains DNA coiled around chromatin into chromosomes.
● Controls cellular processes: gene expression determines specialisation & site of mRNA transcription, mitosis, semiconservative replication.
55
Describe the structure and function of the endoplasmic reticulum (ER).
Cisternae: network of tubules & flattened sacs extends from cell membrane & connects to nuclear envelope:
● Rough ER: many ribosomes attached for protein synthesis & transport.
● Smooth ER: lipid synthesis.
56
Describe the structure and function of the Golgi apparatus.
Planar stack of membrane-bound, flattened sacs, cis face aligns with rER. Molecules are processed in cisternae. Vesicles bud off trans face via exocytosis
● Modifies & packages proteins for export.
● Synthesises glycoproteins.
57
Describe the structure and function of ribosomes.
Formed of protein & rRNA.
| Have large subunit which joins amino acids & small subunit with mRNA binding site.
58
Explain how to use an eyepiece graticule and stage micrometer to measure the size of a structure
1. Place micrometer on stage to calibrate eyepiece graticule.
2. Line up scales on graticule and micrometer. Count how
many graticule divisions are in 100μm on the micrometer.
3. Length of 1 eyepiece division = 100μm / number of
divisions.
4. Use calibrated values to calculate actual length of
structures.
59
Describe the structure of the nucleus.
● Surrounded by a nuclear envelope, a semipermeable double membrane.
● Nuclear pores allow substances to enter/exit.
● Dense nucleolus made of RNA & proteins
assembles ribosomes.
60
Describe the function of the nucleus
● Contains DNA coiled around chromatin into chromosomes.
● Controls cellular processes: gene expression determines specialisation & site of mRNA transcription, mitosis, semiconservative replication.
61
Describe the structure and function of the endoplasmic reticulum (ER).
Cisternae: network of tubules & flattened sacs extends from cell membrane & connects to nuclear envelope:
● Rough ER: many ribosomes attached for protein synthesis & transport.
● Smooth ER: lipid synthesis.
62
Describe the structure and function of the Golgi apparatus.
Planar stack of membrane-bound, flattened sacs, cis face aligns with rER. Molecules are processed in cisternae. Vesicles bud off trans face via exocytosis
● Modifies & packages proteins for export.
● Synthesises glycoproteins.
63
Describe the structure and function of ribosomes.
Formed of protein & rRNA.
| Have large subunit which joins amino acids & small subunit with mRNA binding site.
64
Explain how to use an eyepiece graticule and stage micrometer to measure the size of a structure.
1. Place micrometer on stage to calibrate eyepiece graticule.
2. Line up scales on graticule and micrometer. Count how
many graticule divisions are in 100μm on the micrometer.
3. Length of 1 eyepiece division = 100μm / number of
divisions.
4. Use calibrated values to calculate actual length of
structures.
65
Describe the structure of the nucleus.
● Surrounded by a nuclear envelope, a semipermeable double membrane.
● Nuclear pores allow substances to enter/exit. ● Dense nucleolus made of RNA & proteins
assembles ribosomes.
66
Describe the function of the nucleus.
● Contains DNA coiled around chromatin into chromosomes.
● Controls cellular processes: gene expression determines specialisation & site of mRNA transcription, mitosis, semiconservative replication.
67
Describe the structure and function of the endoplasmic reticulum (ER).
Cisternae: network of tubules & flattened sacs extends from cell membrane & connects to nuclear envelope:
● Rough ER: many ribosomes attached for protein synthesis & transport.
● Smooth ER: lipid synthesis.
68
Describe the structure and function of the Golgi apparatus.
Planar stack of membrane-bound, flattened sacs, cis face aligns with rER. Molecules are processed in cisternae. Vesicles bud off trans face via exocytosis
● Modifies & packages proteins for export.
● Synthesises glycoproteins.
69
Describe the structure and function of ribosomes.
Formed of protein & rRNA.
| Have large subunit which joins amino acids & small subunit with mRNA binding site.
70
Describe the relationship between the organelles involved in the production and secretion of proteins.
The ribosomes that synthesise proteins are attached to the rER. The Golgi apparatus, which modifies proteins for secretion, aligns with the rER.
71
Describe the structure of a mitochondrion.
● Surrounded by double membrane.
● Folded inner membrane forms cristae: site
of electron transport chain.
● Fluid matrix: contains mitochondrial DNA,
respiratory enzymes, lipids, proteins.
72
Describe the structure of a chloroplast.
● Vesicular plastid with double membrane.
● Thylakoids: flattened discs stack to form
grana; contain photosystems with chlorophyll.
● Intergranal lamellae: tubes attach thylakoids in
adjacent grana.
● Stroma: fluid-filled matrix.
73
State the function of mitochondria and chloroplasts.
● Mitochondria: site of aerobic respiration to produce ATP.
| ● Chloroplasts: site of photosynthesis to convert solar energy to chemical energy.
74
Describe the structure and function of a lysosome.
Sac surrounded by single membrane embedded H+ pump maintains acidic conditions contains digestive hydrolase enzymes. Glycoprotein coat protects cell interior:
● digests contents of phagosome
● exocytosis of digestive enzymes
75
Describe the structure and function of a plant cell wall.
● Made of cellulose microfibrils for mechanical support.
● Plasmodesmata form part of apoplast pathway to allow molecules to pass between cells.
● Middle lamella separates adjacent cell walls.
76
What are bacterial and fungal cell walls made of?
bacteria: peptidoglycan (murein) fungi: chitin
77
Describe the structure and function of centrioles.
● Spherical group of 9 microtubules arranged in triples.
● Located in centrosomes.
● Migrate to opposite poles of cell during
prophase & spindle fibres form between them.
78
Describe the structure and function of the cell-surface plasma membrane.
‘Fluid mosaic’ phospholipid bilayer with extrinsic & intrinsic proteins embedded.
● Isolates cytoplasm from extracellular environment.
● Selectively permeable to regulate transport of
substances.
● Involved in cell signalling / cell recognition.
79
Explain the role of cholesterol, glycoproteins & glycolipids in the cell- surface membrane.
● Cholesterol: steroid molecule connects phospholipids & reduces fluidity.
● Glycoproteins: cell signalling, cell recognition (antigens) & binding cells together.
● Glycolipids: cell signalling & cell recognition.
80
Describe the structure and function of flagella.
● Hollow helical tube made of the protein flagellin.
| ● Rotates to propel (usually unicellular) organism.
81
Describe the structure and function of cilia.
● Hairlike protrusions on eukaryotic cells.
● Move back and forth rhythmically to
sweep foreign substances e.g. dust or pathogens away / to enable the cell to move.
82
Why is the cytoskeleton important?
● Provides mechanical strength. ● Aids transport within cells.
● Enables cell movement.
83
Compare eukaryotic and prokaryotic cells.
Both have:
● cell membrane ● cytoplasm
● ribosomes
84
Contrast eukaryotic and prokaryotic cells
IMAGE 2
