Ch 1: Cells & Microscopy Flashcards
1
Q
What is a cell
A
The basic structural and functional unit of an organism
2
Q
What is the role of the cell membrane
A
To control the substances that enter or leave the cell
3
Q
What are the two key types of microscopes
A
- light microscope
- electron microscope (more advanced)
4
Q
What are the parts of a microscope (8)
A
- Eyepieces (ocular lens)
- Trinocular (camera) port
- Objective lens
- Stage
- Condenser
- Light bulb
- Coarse focusing
- Fine focusing
5
Q
Function of eyepieces
A
Key definition: Focuses image from the objective to the eye.
Look through as an observer to see what you want to observe in the microscope (always 10x magnification), both eyes should be open for an accurate observation
6
Q
Function of objective lens
A
Key definition: collects light passing through the specimen and produces a magnified image.
Magnifies an image, either by 10x, 40x and 100x magnification
7
Q
Function of the stage
A
Where you put the slide (containing specimen)
8
Q
Function of condenser lens
A
Key definition: focuses the light onto the specimen held between the cover slop and slide.
Concentrates light onto the slide so it flows through and illuminates the specimen
9
Q
Fine/Coarse focusing
A
Changes and adjusts the resolution of the image
10
Q
what is magnification
A
magnification is the number of times by which an image is bigger than the actual object
11
Q
what is resolution
A
the ability to distinguish between two objects which are very close together. A higher resolution means more detail can be seen
12
Q
Formula for magnification
A
Magnification = Image size/actual size
13
Q
How big is a micrometer
A
10^-6 of a meter (mm is 10^-3of a meter)
14
Q
How big is a nanometer
A
10^-9 of a meter (mm is 10^-3 of a meter)
15
Q
how to observe cellular material in more detail
A
- specimens can be prepared for viewing under a light microscope
- Samples need to be thin enough to allow light to pass through
16
Q
Biological drawings rules
A
- The drawing must have a title
- The magnification under which the observations shown by the drawing are made must be recorded
- A sharp HB pencil should be used (and a good eraser!)
- Drawings should be on plain white paper
- Lines should be clear, single lines (no thick shading)
- No shading
- The drawing should take up as much of the space on the page as possible
- Well-defined structures should be drawn
- The drawing should be made with proper proportions
- Label lines should not cross or have arrowheads and should connect directly to the part of the drawing being labelled
- Label lines should be kept to one side of the drawing (in parallel to the top of the page) and drawn with a ruler
17
Q
What is an eyepiece graticule
A
- it is used to measure the size of the object when viewed under a microscope
- it is a disc placed in the eyepiece with 100 divisions, this has no scale
18
Q
What is a stage micrometer
A
- used to measure the size of the object when viewed under a microscope
- a slide with a very accurate scale in micrometres (µm), it is usually in 10 µm divisions, so 1 mm divided into 100 divisions
19
Q
How to calibrate a microscope
A
To know what the divisions equal at each magnification the eyepiece graticule is calibrated to the stage micrometer at each magnification
20
Q
How to find the length of a graticule division
A
1 graticule division = number of micrometres ÷ number of graticule division
21
Q
How to calculate total magnification
A
eyepiece lens magnification x objective lens magnification
= total magnification
22
Q
How is resolution and magnification affected by wavelength of light
A
- The resolution of a light microscope is limited by the wavelength of light
- As light passes through the specimen, it will be diffracted
- The longer the wavelength of light, the more it is diffracted and the more that this diffraction will overlap as the points get closer together
23
Q
Why do electron microscopes have a much higher resolution and magnification than a light microscope
A
- Electron microscopes have a much higher resolution and magnification than a light microscope as electrons have a much smaller wavelength than visible light
- This means that they can be much closer before the diffracted beams overlap
24
Q
What is a photomicrograph
A
images obtained from a light microscope, these are used for specimens above 200 nm (a bacteria cell is about 1000 nm)
25
What is the cell membrane (purpose and characteristics)
- All cells are surrounded by a cell surface membrane which controls the exchange of materials between the internal cell environment and the external environment
- The membrane is described as being ‘partially permeable’
- The cell membrane is formed from a phospholipid bilayer of phospholipids spanning a diameter of around 10 nm
26
What is the cell wall (purpose and characteristics)
- Cell walls are formed outside of the cell membrane and offer structural support to cell
- Structural support is provided by the polysaccharide cellulose in plants, and peptidoglycan in most bacterial cells
- Narrow threads of cytoplasm (surrounded by a cell membrane) called plasmodesmata connect the cytoplasm of neighboring plant cells
27
what are the characteristics of the nucleus
- relatively large
- separated from the cytoplasm by a double membrane called the nuclear envelope which has many pores (for travel of mRNA, ribosomes, enzymes and signaling molecules
- contains chromatin
- at least one more darkly stained regions can be observed (nucleolus, site of ribosome production)
28
What are the characteristics of chloroplasts
- Larger than mitochondria, also surrounded by a double-membrane
- Membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called grana
- Grana are joined together by lamellae (thin and flat thylakoid membranes)
- Also contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis
29
Purpose of chloroplasts
Chloroplasts are the site of photosynthesis:
- The light-dependent stage takes place in the thylakoids
- The light-independent stage (Calvin Cycle) takes place in the stroma
30
properties of large permanent vacuole
- sac in plant cells surrounded by the tonoplast, a selectively permeable membrane
- vacuoles in animal cells are not permanent and small
31
purpose and characteristics of vesicles
membrane bound sac for transport and storage
32
purpose and characteristics of microvilli
cell membrane projections that increase the surface area for absorption
33
purpose and characteristics of flagella
- similar in structure to cilia, made of longer microtubules
| - contract to provide cell movement for example in sperm cells
34
where do all new cells come from
all new cells arise from already existing cells
35
what is a cell
a cell is the basic structural and functional unit of an organism
36
what does the cytoplasm contain
- cytosol (semi fluid)
| - organelles (suspended in cytosol)
37
what is an organelle
an organised structure within a cell in which specialised functions are carried out
38
what is the protoplasm
the living part of the cell, the nucleus+cytoplasm
39
what is a protoplast
a plant/fungal cell with its cell wall removed
40
what is the structure of a nucleus
- largest organelle
- may have mutiple nucleoli
- 10 micrometer
- spherical in a drawing (3D)
- round in a micrograph
- enclosed by 2 membranes
- outer membrane connected/continuous to rough endoplasmic reticulum
41
what is the nuclear envelope
- made up of double membrane (outer and inner)
- encloses nucleus
- they join to form the nuclear pore
42
what is the nuclear pore
- enclosed by nuclear proteins
- where the double membrane meets
- controls entry and exit of material through the nucleus
43
what are nucleoli (singular nucleolus
- irregular shape
- may have multiples in nucleus
- synthesizes ribosomes and rRNA
44
What are the characteristics and properties of lysosomes?
- specialist forms of vesicles which containhydrolytic enzymes (enzymes that break biological molecules down)
- break down waste materials such as worn out organelles, used extensively by cells of the immune system and in apoptosis (programmed cell death)
45
What are the key features ofan animal cell electron micrograph
- Golgi apparatus
- rough endoplasmic reticulum
- nucleus
- mitochondria
Picture: https://cdn.savemyexams.co.uk/wp-content/uploads/2020/10/Animal-Cell-micrograph-2.png
46
What are the key features of a plant cell electron micrograph?
- -Mitochondria
- Chloroplast
- Vacuole
- cell wall
- Nucleus
- nucleolus
- image:https://cdn.savemyexams.co.uk/wp-content/uploads/2020/10/Plant-Cell-Micrograph-2.png
47
What structures do animal cells have?
- centrosome with two centrioles close to the nucleus and at right angles to each other
-Lysosome
- mitochondrion
- rough endoplasmic reticulum
-Nucleus(with nucleolus,chromatin,nuclear
pore, nuclear envelope 2x membrane
-smooth endoplasmic reticulum
-Cytoplasm
- cell surface membrane
-Ribosomes
-microtubules radiating from centrosome
-Golgi body
-Golgi vesicle
-microvilli
48
What structures do plant cells have?
- Plasmodesma
- vacuole (with cell sap and tonoplast)
- cell surface membrane(pressed against cell wall)
- smooth endoplasmic reticulum
- nucleus (with nuclear pore,nucleolus, chromatin, nuclear envelope)
- rough endoplasmic reticulum
- microtubule
- Ribosomes
- chloroplast (with envelope and grana
- Mitochondrion
- Cytoplasm
- Golgi body
- golgi vesicle
- Chloroplast
- middle lamella
49
Why do organisms require a constant supply of energy?
All organisms require a constant supply of energy to maintain their cells and stay alive
50
Why is energy required for anabolic reactions in cells?
For building larger molecules from smaller molecules
51
Why is energy required for movement of substances?
To move substances across the cell (active transport) or to move substances within the cell
52
What is energy required for in animals?
- For muscle contraction, to coordinate movement at the whole organism level
- in the conduction of nerve impulses, as well as many other cellular processes
53
What are nucleotides?
Complex chemicals made up of an organic base, a sugar and a phosphate. They are the basic units from nucleic acids DNA and RNA are made
54
What is the general cellular structure of prokaryotes?
- their genetic material is not packaged within a membrane-bound nucleus and is usually circular (eukaryotic genetic material is packaged as linear chromosomes)
-Prokaryotes lack membrane-bound organelles
- they are many (100s/1000s)of times smaller than eukaryotic cells
- their ribosomes are structurally smaller (70S)in comparison to those found in
Eukaryotic cells (80S)
55
Which structures are always found in prokaryote cells
- Cell wall (containing peptidoglycan)
- cell surface membrane
- Cytoplasm
- Circular DNA
- Ribosomes
56
Which structures are sometimes found in prokaryote cells
- flagellum (for motion)
- capsule (for protection)
- Infolding of cell membrane to carry out photosynthesis or nitrogen fixation
- Plasmid (small circle of DNA)
- Pili (for attachment to other cells or surfaces; involved in sexual reproduction)
57
What sizes are prokaryotes?
1.5-10 micrometer
58
What size are eukaryotes?
10-100 micrometer (red blood cells are the exception with a size of 7 micrometers)
59
What genome do prokaryotes have?
DNA circular with no proteins, in the cytoplasm
60
Which genome do eukaryotes have?
DNA is associated with histones (proteins) formed into chromosomes
61
How does cell division happen in prokaryotes
Occurs by binary fission, no spindle involved
62
How does cell division happen in eukaryotes
Occurs by mitosis or meiosis and involves a spindle to separate chromosomes
63
what size ribosomes do prokaryotes have?
70S ribosomes
64
what size ribosomes do eukaryotes have
80S ribosomes
65
What kind of organelles do prokaryotes have?
-Very few membrane-bound organelles
66
What type of organelles do eukaryotes have?
Numerous types of organelles:
- Membrane-bound single membranes
- lysosomes
- Golgi complex
- Vacuoles
- double membranes
- Nucleus
- mitochondria
- Chloroplast no membrane
- Centrioles
- Ribosomes
- Microtubules
67
What are prokaryotes cell walls made of?
Made of peptidoglycan (polysaccharide and amino acids) and murein
68
What type of cell walls do eukaryotes have?
Present in plants (made of cellulose or lignin)and fungi (made of chitins similar to cellulose but contains nitrogen)
69
What are viruses?
Viruses are non-cellular infectious particles that straddle the boundary between 'living'and 'non-living'
70
What is the structure of viruses?
-They are relatively simple in structure, much smaller than prokaryotic cells (with diameters between 20 and 300 nm)
- they have a nucleic acid core (their genomes are either DNA or RNA and can be single or double-stranded)
- a protein coat called a capsid
- an envelope (a membrane-like outer layer),
Made up of phospholipids may be present in some viruses
71
What is a virus envelope
- outer layer formed usually from the membrane
| - made of phospholipids
72
How do viruses reproduce?
- it is parasitic
- infecting living cells and using their ribosomes with DNA and RNA inside to produce new viral particles
- the virus converts the host cell into a 'viral production factory '
73
Why/how are light microscopes and electron microscopes different?
Electron microscopes differ from light microscopes because they produce the image of a specimen using a beam of electrons. Visible light is used in the light microscopes to magnify images of tiny areas of materials or biological specimen. Electrons have a much shorter wavelength than light and this allows electron microscopes to produce higher resolution images
74
How big are viruses?
most viruses are 20-300 nanometers
75
what is the structure of the smooth endoplasmic reticulum?
- no ribosomes
| - tubular cisternae
76
what is the function of the rough endoplasmic reticulum
to synthesize proteins to be transported outwards towards the cell surface membrane/away from the nucleus
77
where do materials travel through in the endoplasmic reticulum
the cisternae transport the materials in the liquid space inside
78
what is the function of the smooth endoplasmic reticulum
to synthesize lipid and steroids to be transported outwards towards the cell membrane/away from the nucleus
79
what is a ribosome
structure made up of rRNA + protein synthesized in the nucleus
80
what is the structure of ribosomes
- made up of 2 subunits; big subunit and small subunit
- it is the smallest organelle
- there are two sizes: 80S and 70S
- found attached to rough endoplasmic reticulum (80S), or in mitochondria+chloroplasts (70S) or free in the cytosol
81
what is the function of ribosomes
- to synthesize proteins
- if the ribosomes are free in the cytosol, the proteins are used in the cytosol
- if the ribosome is attached to the RER the proteins are to be transported to organelles outside the cytosol (cell membrane, nucleus, cell wall, other organelles)
82
what is the structure of the Golgi apparatus/body/complex
- made up of cisternae and Golgi vesicles
- from top view appears to be disk shaped structures stacked ontop of each other
- from side view apears to be long u shapes
- top cisterna (called the inner maturing face) is concave
- bottom cisterna (called outerforming face) is convex
83
how are the Golgi apparatus cisternae formed
- pinched off/budding off from the ends of the endoplasmic reticulum cisternae
- move towards the cell membrane
- then transport vesicles fuse together to form the long cisternae of the Golgi apparatus
84
what is the function of the Golgi apparatus
it is the center of collection, modification, transportation and distribution
-it may also secrete mucus/wax/gum
85
what does th Golgi apparatus modify
the golgi apparatus changes glycoproteins to glycolipids through glycosylation
86
how does the golgi apparatus transport and distribute
after modification, the golgi vesicle pinches off from the edge of the cisterna of the outer formingface for transportation and distribution and fuse with the cell surface membrane to be released/become part of the membrane or to be used inside the cell
- the golgi vesicle (secretory vesicle) may also secrete mucus/wax/gum
87
what is a lysosome
lysosomes are golgi vesicles that are not secretory vesicles
88
what is the structure of a lysosome
- 0.5 micrometers in length
| - a fluid-filled sac
89
what are the characteristics/properties of lysosomes
- they contain many strong hydrolytic enzymes used for the breakdown of carbohydrates, proteins, lipids and nucleic acid
- they can work under acidic conditions
- only found in animal cells, not plant cells
90
how are lysosomes formed
they are formed by pinching/budding off the Golgi apparatus
91
what is the function of lysosomes
- digests materials taken in by endocytosis
- digest specific material outside the cell
- autophagy
- autolysis
92
what is endocytosis
a process where the cell takes in foreign substances
93
what is the process of endocytosis
- substance taken in
- surrounded by phagocytic vacuole
- lysosome fuses with vacuole
- substance is hydrolysed (digested)
- digested substance assimilated
- undigested remains exit the cell through exocytosis
94
what specific materials do lysosomes digest outside the cell?
bone cartilage
- to be replaced with new bone or to be remodeled after bone injury
- the enzyme used is lysosyme
digestion of protective coat layer of female egg cell by sperm cell
- for fertilization
- the lysosome here is called an acrosome
95
what is autophagy
the digestion of old, unwanted organelles from the cell itself
96
what is the process of autophagy
- unwanted organelle surrounded by phagocytic vacuole
- lysosome fuses with vacuole to form phagolysosome
- organelle is hydrolysed (digested)
- digested substance assimilated
- undigested remains exit the cell through exocytosis
97
what is autolysis
autolysis is a process in which a cell will self destroy/breakdown its whole self
98
why does autolysis happen
autolysis hapens when a cell is uneeded and needs to be recycled
99
in which cells can autolysis occur
autolysis only happens in a few cells such as
- tadpole tail cells
- extra uterus wall after pregnancy
- muscle degeneration
100
where is mitochondria thought to originate from
endosymbiotic aerobic bacteria
101
where do mitochondria now come from
mitochondria come fromalready existing mitochondria inside the cell
102
what is the structure of mitochondria
- double membrane (outer and inner)
- width is around 1 micrometer and diameter is 1.5-10 micrometer
- the shape can be from spherical to highly elongated
- inside is made up of the matrix and cristae, phosphate granules and 70S ribosomes
- nail like structures (stalked particle) along the surface of the inner membrane for ATP synthesis
103
what is the matrix (mitochondria)
- fluid filled space (ground substance)
| - where other material is suspended in, in the mitochondria
104
what are cristae
(singular- crista)
| -finger like projection (not villi/microvilli)
105
what is the function of the mitochondria
- the mitochondrion is the powerhouse of the cell
| - synthesizes ATP through aerobic respiration to do the cell's work
106
how/where does the mitochondria synthesize ATP
- the stalked particle contains the enzyme that catalyses the synthesis of ATP from a biochemical reaction (ADP + Pi -> ATP)
- the site of ATP synthesis is the inner membrane in the mitochondria
107
how do mitochondria appear in micrographs
sausage like structures with finger like projections/shadowed in the inside
108
what is ATP
- it is a universal (all cells in all organisms use it) energy carrier/source of energy that carries energy currency from Energy yielding reactions to Energy requiring reactions
- it is a small, soluble, intermediate (made from reaction to react further) molecule
- it is the energy currency of the cell, cell trades/donates ATP to energy required reactions to do work
109
how does ATP release energy
ATP releases energy through hydrolysis (ATP -(hydrolysis)> energy + ADP + Pi)
110
what is the role of ATP in cells
- anabolic reactions
- active transport
- movement/locomotion
111
what are anabolic reactions
the building up/synthesis process of complex compounds from simple compounds
112
what are examples of anabolic reactions
- photosynthesis
- DNA synthesis (nucleotides joining up to form DNA)
- activation of glucose in respiration
- protein synthesis (amino acids joining up to form polypeptides
- glycogenesis (synthesis of glycogen)
- starch synthesis (glucose joins up to form starch
- lipid synthesis (glucose joins up to form triglyceride
113
what is an example of active transport
sodium potassium pump
114
what is an example of movement/locomotion that requires ATP
- muscle contraction
- movement/beating of cilia/flagella
- endocytosis/exocytosis
- movementof vesicles on microtubules
115
what is the structure of a microtubule
- long rigid hollow tube
- 25 nanometer in diameter
- made up of protein subunits (tubulin)forming rings of protofilaments
- 1 ring = 13 protofilaments
116
what are tubulin dimers made up of
alpha tubulin +beta tubulin = tubulin dimer
117
what are protofilaments made up of
tubulin dimers join ends to form protofilaments
118
where can microtubules be found
in the cytoplasm of the cell
119
where are microtubules synthesized
they are synthesized in the MTOC (MicroTubule Organizing Center)
120
what is the function of microtubules
- to form the cytoskeleton of the cell
- for anchorage
- monorail
- building block of centriole, cilia and flagella
121
what is the cytoskeleton
- a complex network of interlinking microtubules, intermediate filaments and microfilaments
- gives shape and support to cell
- continuosly being dissembled, reassembled and rearranged (e.g. during exocytosis,endocytosis, mitosis and cell movement like amoebic movement of white blood cells
122
what is the purpose of microtubule anchorage
anchor organelles to fixed locations in the cell
123
what isthe purpose of the microtubule monorail
direct intracellular movement of organelles and vesicles
124
what is the structure/characteristics and properties of centrioles
- small hollow cylindrical structures made from microtubles found in centrosome (area near nucleus)
- always occur in a pair perpendicular to each other
- formed from 9 triplets of microtubules
- length of 500 nanometers
- width of 200 nanometers
125
what is the function of the centrioles
- form pores during mitosis and meiosis
| - form bases of cilia and flagella
126
what is a centrosome
centrosome is an organelle in plant and animal cells situated near the nucleus
127
what are the functions of a centrosome
- synthesizes microtubules
- assembles microtubules for the formation of other structures made of microtubules (e.g. centriole, spindle fibres, cilia, flagella, cytoskeleton microtubules)
- the centrosome acts as the MTOC (MicroTubule Organizing Center)
128
what is the singular word name for cilia cells
cilium
129
what is the structure of the cilia
- whiplike structure projecting outwards from the surface of some animal cells and the cells of many unicellular organisms
- the base of the cilia is a centriole (basal body) for anchorage by microtubules
- the axonemeis the cylindrical structure inside the cell surface membrane of the cilia made of microtubules
130
what is the arrangement of microtubules in the cilia
- the microtubules have a 9+2 arrangement
- the A and B microtubules join to form 9 microtuble doublets with 2 singlet microtubules in the center (this forms the outer ring of the cilia)
- the A microtubule has an outer arm and an inner arm made up of dynein protein arm
- the B microtubule is an incomplete ring as it attaches to the A microtubule
- A microtubule has 13 protofilaments but the B microtubule is an incomplete ring with only 10 protofilaments only
131
what is the comparison in length between cilia and flagella
- cilia is shorter
| - flagella is longer
132
what is the difference in the number of organelle per cell between cilia and flagella
- there are many cilia per cell
| - there are only one or two flagella per cell
133
how do cilia and flagella move/"beat"
beating is due to dynein (protein) arms contact and move along neighbouring B microtubules
134
what is the comparison in movement between cilia and flagella
- cilia have a beating/rowing motion in one direction
| - flagell have a wavelike motion from the base outward
135
what is the difference in function between cilia and flagella
- the purpose of cilia are to move the cell/fluid around the cell
- the purpose of flagella are to move the cell through locomotion
136
what is the singular name for microvilli
microvillus
137
what is the structure of microvilli
- thin fingerlike folding of the cell surface membrane/brush border of the cell
- encloses the cytoplasm and (actin) microfilaments (thinner than microtubules)
138
what is the function of microvilli
to increase surface area to volume ration for the absorption of H2O and digested food in the intestine
139
what are villi (singular villus)
- finger-like structure prohecting into the lumen from the lining of the small intestine
- not the same as microvilli
- villi are lined with many cells that have microvilli
140
what is the thickness comparison between cilia and microvilli
- cilia are longer and thinner
| - microvilli are shorter and thicker
141
what is the difference in ends between cilia and microvilli
- cilia have tapering (sharp) ends
| - microvilli have blunt ends
142
what is the difference in motility between cilia and microvilli
- cilia are motile(move to create current) for mucus/move cell
- microvilli are non-motile, they do not move and only absorb substances
143
what is the difference in microtubule/microfilament arrangement between cilia and microvili
- cilia have a 9+2 microtubule arrangement
| - made up of actin microfilaments
144
what is the difference in locations between cilia and microvilli
- cilia cells line airways
| - microvilli line the intestines and oviduct
145
where are chloroplasts thought to originate from?
endosymbiotic bacteria, anaerobic photosynthetic bacterium, lost some of their genes to host chromosomes
146
what is the structure of chloroplasts
- double membrane form chloroplast envelope
- thylakoid membranes stack up to form stack of thylakoid called 'granum' (plural: grana)
- the granum are connected by elongated thylakoids called intergranal lamella
- chloroplasts also have circular DNA, starch grains, lipid droplets and 70S ribosomes and stroma
147
what is the function of chloroplasts
- to carry out photosynthesis
- light dependent reactions occur in the thykaloid membranes
- light independent reactions occur in the stroma
148
what are intergranal lamella
thin plate-like structures that connect grana in the chloroplast
149
why do light dependent reactionsoccur in the thylakoid membranes in the chloroplasts
-to trap light energy by chlorophyll pigments in the thylakoid membranes to convert light energy to ATP
150
how/what light independent reactions occur in the stroma
chloroplasts use the ATP to convert CO2 (inorganic molecule) to sugar (C6H12O6, organic molecule)
151
what is the structure/location of the cell wall
- non living rigid structures formed outside the cell surface membrane
- also found outside fungal (chitin) and bacterial (peptidoglycan) cell surface membrane
- the plant cell wall consists of 3 possible layers (middle lamella, primary wall and secondary wall) + plasmodesma
152
what is the middle lamella
the layer between two adjoining plant cell walls,made up mainly of pectin that acts like a slime/gel
153
what is the primary wall layer in a cell wall
- first wall formed by cell
- thin and rigid
- made up of parallel cellulose fibres running through gel-like matrix of complex polysaccharides (hemicellulose + pectin)
- cellulose fibres are not elastic and have high tensile strength
- thin single line in micrograph
154
what is the secondary wall layer in the cell wall
- called 'lignified wall'
- produced when the cell differentiates
- extra layers of cellulose added between cell surface membrane and primary wall
- each layer is made up of parallel cellulose fibres+ hemicellulose+sometimes lignin/cutin/suberin
- thick double line appearing wall in micrograph
- the fibres in different directions like cross ply to make the structure stronger
155
what are the layers of root tip
- zoneof cell division
- zone of cell elongation
- cell differentiates and specialises in structure and function
156
what is the plasmodesma
a cytoplasmic strand (no cell wall) running across plant cellwalls, connecting cytoplam of adjacent cells
157
difference between primary and secondary cell walls in formation
- primary wall formed by newly formed cells
| - secondary wall formed from elongating and differentiating cells
158
difference between primary cell wall and secondary cell wall in location
- the primary wall is located between the middle lamella and the cell surface membrane/secondary wall
- the secondary wall is located between the primary wall and the cell surface membrane
159
what is the difference between primary cell wall and secondary cell wall in the types of cells they are found in
- the primary cell wall is found in all cells
| - the secondary cell wall is found in the xylem element, schlerenchyma, epidermal cells and endodermal cells
160
what is the difference between primary cell wall and secondary cell wall in terms of number of layers
- the primary cell wall has 1 layer
| - the secondary cell wall has 3 or more layers
161
what is the difference between primary and secondary cell walls in terms of composition
- the primary wall is composed of cellulose, hemicellulose and pectin
- the secondary cell wall is composed of cellulose, hemicellulose, lignin, cutin, suberin
162
what is the difference between primary and secondary cell walls in terms of cellulose content
- the primary wall has a low cellulose content
| - the secondary wall has a high cellulose content
163
is the primary wall pitted
no
164
is the secondary cell wall pitted
sometimes
165
difference between primary and secondary cell walls in terms of nature
- the primarywall is elastic and can expand
| - the secondary wall is rigid and cannot expand
166
what is the function of the cell wall
- mechanical support for individual cell and the plant by means of lignified wall and turgor support
- protects cells from bursting due to excessive water utake by osmosis
- provides shape to cell by different orientations of cellulose fibers layers
- controls movement of materials in and out of the cell (in exam must specify,,see next card)
167
how does the cell wall control the movement of materials in and out of the cell
- apoplast pathway (cel wall to cell wall) for transport of H20 and mineral ions
- symplast pathway (cytoplasm to cytoplasm)transport materials through plasmodesmata
- suberin (inside cell wall of root endodermal cells) is waterproof which force water and mineral ions to pass through the membrane and controls movement of material
- waxy cutin layer forms cutice that is waterproof to reduce water loss by evaporation from the epidermal cell wall surfaces (on leaves and stem surfaces)
168
what is the structure of vacuole/s
- in eukaryotic cells(plant, protozo, animal) usually made up of a large membrane bound sac in the cytoplasm
- plant cells have a permanent central vacuole surrounded by tonoplast(membrane)
- animal cell vacuoles are relatively smaller and temporary
169
what do vacuoles contain
vacuoles may contain solutionsof pigments, enzymes, sugars, mineral salts, oxygen CO2 and ther organic compounds
170
what are the types of animal cell vacuoles
- phagocytic vacuoles
- food vacuoles
- autophagic vacuoles
171
what is the function of plant cell vacuoles
- support (turgor support by osmosis)
- lysosomal activity (when containing hydrolases)
- secondary metabolites
- food reserves
- waste products e.g. calcium oxalate crystals
- growth insize (osmotic uptake)
172
what are metabolites stored in the plant cells
- anthocyanin pigments in onion, flower and fruit
- latex=a milky fluid found in rubber trees and poppy trees. Opium poppy contains morphine from which opium and heroine are obtained (anesthetics)
173
what is the size of red blood cells
7micrometers
174
how big are cell surface membranes
7nanometers
175
how big are nuclei
10micrometers
176
how big are most bacteria
1-5 micrometers
177
what is the minimum size the naked eye can see
0.1mm/100 micrometers
178
what is the max resolution of a light microscope
200nm (max resolution=minimum distance to be seen as 2 seperate objects)
179
what is the max resolution of an electron microscope
0.5 nanometers (max resolution=minimum distance to be seen as 2 seperate objects)
180
what is the max magnifictation on a light microscope
1,500
181
what is the max magnification of an electron microscope
250,000
182
What chemicals are secreted from the secretory vesicles
* Digestive enzymes
* antibodies
* mucus
* hormones
* wax and guns
183
What are the structures formed when a lysosome fuses with a phagocytic vacuole
- phagolysosome
| - secondary lysosome
184
Which cells contain cilia
paramecium and ciliated epithelial cells
185
what is the structure of rough endoplasmic reticulum
- circular structurs on the outer surface (ribosomes) to synthesize proteins
- flattened cisternae
186
what is the endoplasmic reticulum
- a system of highly branched and rejoined network of cisternae interconnected with one another
- it is made up of the smooth and rough endoplasmic reticulum which are connected to each other
187
what is cisterna/cisternae?
membrane bound sacs
188
where is euchromatin found
euchromatin (seen as tiny dots in a micrograph) are found around the center of the nucleus
189
where is heterochromatin found?
-its arranged at the sides of the nucleus (seen as dark shadows in micrographs) attached to the inside of the nuclear envelope
190
what re the characteristics of heterochromatin?
- not functional/not well expressed
- not used to make polypeptide
- more dense and coiled
191
what are the characeristics of euchromatin
- well expressed (its genes are often convertd into polypeptides)
- less dense and uncoiled
192
What are the two forms of chromatin
- euchromatin
| - heterochromatin
193
what is chromatin?
exists in the form of DNA wrapped around histone proteins which condense to form chromosomes during mitosis
194
What is DNA?
stores all our genetic codes in the form of genes (codes for polypeptides)
