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Biology > Chapter 1: Cell Structure > Flashcards

Chapter 1: Cell Structure Flashcards

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1
Q

What is cell theory?

A

Cell theory states that the basic unit of function and structure of all living organisms is the cell.

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2
Q

What structures do plant and animal cells have in common?

A
  1. Cell surface membrane
  2. Nucleus
  3. Cytoplasm
  4. Mitochondria
  5. Golgi complex
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3
Q

What is a cell?

A

It is the smallest unit of life.

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4
Q

What is magnification?

A

Magnification is the number of times greater an image is compared to the actual size of the object.

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5
Q

Describe the two scales present in the light microscope and how they work.

A

The eyepiece graticule is a transparent disc that commonly has 100 divisions. It is placed in the eyepiece so that it can be viewed at the same time as the specimen to be measured. To calibrate the eyepiece graticule, a transparent scale known as the stage micrometer is placed on the microscope stage and has subdivisions of 0.1 and 0.01 mm. The images of the two scales can then be superimposed.

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6
Q

Give an example of a temporary stain used for staining plant cells

A

Iodine in potassium iodide solution. It stains starch blue-black and will also colour the nuclei and cell walls a pale yellow.

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7
Q

Give an example of stain used to prepare animal cells.

A

A dilute solution of methylene blue.

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8
Q

How does a light microscope work?

A

Once the microscope is switched on, the light bulb comes on. The rays of light travel upwards and illuminate the stage. The light is focused onto the stage using the condenser lens and the amount of light is controlled by the condenser iris diaphragm. The image is picked up by the objective lens which magnifies the image (4, 10, 40, 100) to be seen when viewing it through the eyepiece.

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9
Q

In which two ways can a specimen be prevented from drying out?

A

A cover slip can be placed over the specimen to protect eh microscope lens and to help prevent the specimen from drying out. A drop of glycerine mixed with the temporary stain added can also prevent drying out.

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10
Q

What are the disadvantages of using electron microscopes?

A

The electron beam and therefore the fluorescent screen as well as the specimen must be placed in a vacuum. This is because if electrons were to collide with air molecules, they would scatter, making it impossible to produce a sharp image. Furthermore, water boils at room temperature in a vacuum. this means that only deal material can be examined as the specimen would have to be dehydrated before being placed in a vacuum.

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11
Q

What are the two types of microscope?

A

Light and electron microscope

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12
Q

What is a TEM and how does it work?

A

In the transmission electron microscope, a beam of electrons is passed through the specimen before being viewed and only those electrons which pass through are viewed enabling thin sections of the specimen to be seen.

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13
Q

What is an SEM and how does it work?

A

In the scanning electron microscope, the beam of electrons is used to scan the surfaces of structures and only the reflected beam is observed.

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14
Q

What is resolution?

A

Resolution is the ability to distinguish between two objects very close together. The higher the resolution, the greater the detail that can be seen.

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15
Q

What is the disadvantage of the SEM compared to the TEM?

A

The SEM cannot achieve the same resolution as the TEM. With an SEM, a resolution between 3nm and 20 nm is possible.

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16
Q

What is the electromagnetic spectrum?

A

The whole range of different wavelengths is known as the electromagnetic spectrum.

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17
Q

What is the general rule regarding wavelength and resolution?

A

The general rule states that the limit of resolution is one half the wavelength of the radiation used to view the specimen.

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18
Q

What is the wavelength of radiation using a light microscope?

A

400-700nm

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19
Q

When calculating total magnification, what is multiplied together?

A

eyepiece lens magnification and the objective lens magnification

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20
Q

Why are electrons suitable for microscopy?

A

Free electrons behave like electromagnetic radiation and have a very short wavelength due to having a greater amount of energy. The greater the energy, the shorter the wavelength. Also, due to the negative charge of electrons, they can be focused easily using an electromagnet.

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21
Q

With which two factors does the wavelength change?

A

The higher the frequency, the shorter the wavelength. Wavelength changes with energy: The greater the energy, the shorter the wavelength.

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22
Q

Define ultrastructure.

A

Ultrastructure is the fine detailed structure of a specimen as revealed by the electron microscope.

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23
Q

Describe the images obtained using an electron and light microscope.

A

Coloured photomicrograph.

Black and white electron micrograph.

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24
Q

Describe the structure of a nucleus.

A

The nucleus is the largest cell organelle present in a cell and is surrounded by a double membrane made up of a double phospholipid bilayer. The nuclear envelope contains many small gaps and the outer membrane is continuous with the rough endoplasmic reticulum. Within the nucleus, chromosomes can be seen in a loosely coiled state with 1-5 nucleoli.

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25
Describe the structure of the nuclear envelope.
The nuclear envelope is made up of two membranes. Each membrane is made up of a phospholipid bilayer, hence making the nuclear envelope a double phospholipid bilayer. The outer membrane of the nuclear envelope is continuous with the endoplasmic reticulum. The nuclear envelope contains many gaps within its walls.
26
How are the images viewed in the light and electron microscope?
Light: eyepiece electron: fluorescent screen
27
What are nuclear pores and its function?
Nuclear pores are gaps in the nuclear envelope that allow and control the exchange between the nucleus and cytoplasm.
28
What are some differences between animal and plant cells? 3:2
Animal: Centrioles, microvilli Plants: Cell wall, Vacuoles, chloroplasts
29
What are some features that animal and plant cells have in common? (5)
Cell surface membrane, nucleus, mitochondria, golgi bodies, cytoplasm.
30
What are the lens used in the light and electron microscope?
Light: glass Electron: Electromagnet
31
What do the stains used in electron microscopy contain?
heavy metal atoms
32
What is an organelle?
An organelle is a functionally and structurally distinct part of a cell, usually membrane bound.
33
What is compartmentalisation?
Organelles are often surrounded by membrane(s) which keep its processes separate from the surrounding cytoplasm. This is known as compartmentalisation.
34
What is the division of labour?
Since each type of organelle has its own specific function, the cell is said to show division of labour, which is the sharing of work between different specialised organelles.
35
What is the function of the cell surface membrane?
It is a partially permeable barrier that controls the exchange of molecules and ions between the cell and its environment.
36
What is the maximum resolution possible with a light microscope?
200nm
37
What is the maximum resolution possible with an electron microscope?
0.1-0.5nm
38
What is the structure of the cell membrane?
The cell surface membrane is extremely thin and has a trilaminar appearance consisting of two dark lines on either side of a pale narrow interior. This appearance is due to the phospholipid bilayer with hydrophilic phosphate heads facing outwards and hydrophobic tails facing inwards.
39
What is the usual measurement of a cell surface membrane?
7nm
40
What is the usual measurement of a nucleus?
10 um
41
What is the wavelength of radiation using an electron microscope?
+-0.005nm
42
Describe the structure of the rough endoplasmic reticulum.
The outer membrane of the nuclear envelope is continuous with the rough endoplasmic reticulum. The RER is so called as it is covered with many tiny black dots known as ribosomes giving it a rough appearance.
43
Describe the structure of the smooth endoplasmic reticulum.
It is a meshwork of tubular membrane vesicles with fluid filled sacs that have no ribosomes on its surface.
44
Explain how compartmentalisation applies in the endoplasmic reticulum.
Processes can take place within the membrane-bound flattened sacs, separated from the surrounding cytoplasm.
45
Name the substances entering the nucleus through the nuclear pores. (4)
Proteins for ribosome synthesis, nucleotides, ATP, some hormones such as thyroid hormone T3.
46
Name the substances leaving the nucleus through the nuclear pores. (2)
mRNA and ribosomes for protein synthesis.
47
Specify which type of ribosome is found where.
80S ribosome: on the rough endoplasmic reticulum and free in the cytoplasm 70S ribosome: in chloroplasts and in mitochondria
48
What are ribosomes made of?
RNA and protein
49
What are the types of endoplasmic reticulum?
Smooth and rough
50
What divides first when a cell is about to divide?
The nucleus divides first so that each new cell has its own nucleus.
51
What do chromosomes contain?
Chromosomes contain the hereditary material DNA that is organised into functional units known as genes which controls the activities of the cell and inheritance.
52
What happens to the proteins produced by the ribosomes on the RER?
They enter the sacs and move through them. The proteins are often modified on their journey.
53
What is a nucleolus made up of?
It is made up of loops of DNA from several chromosomes and RNA.
54
What is chromatin?
Within the nucleus, chromosomes are in a loosely coiled state known as chromatin.
55
What is the endoplasmic reticulum?
The ER is an extensive system of membrane-bound flattened sacs running through the cytoplasm.
56
What is the function of a nucleolus?
It is the site for ribosome production using information in its own DNA.
57
What is the function of a ribosome?
It is the site for protein synthesis.
58
What is the function of the RER?
The RER provides a pathway for the transport of materials through the cell and are sites for protein synthesis.
59
What is the usual measurement of a nucleolus?
0.2-0.5um
60
What is the usual measurement of a ribosome?
25nm in diameter
61
What is the usual range of the number of nucleoli found in mammals?
1-5
62
Describe the structure of mitochondria
Mitochondria are surrounded by two membranes separated by intermembrane space. The inner membrane is folded to form finger-like 'cristae' which project into the interior solution known as the matrix.
63
How are golgi bodies formed?
Small vesicles bud off from the ER and join together to form the Golgi body.
64
How do golgi bodies move material out of the cell?
In the process of secretion/exocytosis, the Golgi vesicles fuse with the cell membrane to release the material.
65
How does energy get released from an ATP molecule?
ATP gets broken down to ADP in the process of hydrolysis. The release of energy during this hydrolysis reaction is used as a fuel for that particular part of the cell that requires it.
66
How is the Golgi body constantly being formed and broken down?
The stack of flattened sacs is constantly being formed at one end from vesicles budding off from the ER and being broken down at the other end to form Golgi vesicles.
67
In which cells would there be a high quantity of mitochondria?
Cells that have a high demand for energy such as the live and muscle cells.
68
What are some of the contents of the matrix of mitochondria?
70S ribosomes, circular DNA, enzymes
69
What are the functions of mitochondria?
Mitochondria carry out respiration as well as the synthesis of lipids.
70
What are the functions of the Golgi body?
It collects, processes, modifies and sorts molecules ready for transport to other parts of the cell or out of the cell. They also make lysosomes, glycoproteins and functioning proteins.
71
What biological molecule does the outer membrane of mitochondria contain?
It contains a transport protein called Porin.
72
What is ATP?
Adenosine triphosphate
73
What is the cristae of mitochondria?
It is the folding of the inner membrane which project into the interior solution of the matrix.
74
What is the function of an ATP molecule?
It is an energy carrying molecule which spreads to parts of the cell where energy is needed. It is small and soluble.
75
What is the function of the inner membrane of mitochondria?
It is a selective barrier controlling the entrance of molecules and ions into the matrix.
76
What is the function of the outer membrane of mitochondria with reference to the biological molecule in contains?
The transport protein 'Porin' forms wide, aqueous channels allowing water soluble molecules from the cytoplasm to the intermembrane space.
77
What is the function of the smooth endoplasmic reticulum?
It produced lipids, steroids such as cholestrol as well as the reproductive hormones oestrogen and testosterone.
78
What is the most numerous organelle as seen with a light microscope?
Mitochondria
79
What is the usual measurement of a mitochondrion?
1um
80
Where is ATP produced?
Chloroplasts and mitochondria
81
Describe the structure and components of a microtubule.
A dimer molecule made up of one a and b- tubulin joins from end to end with other dimer molecules to form long 'protofilaments' in the process of polymerisation. Thirteen protofilaments then line up alongside each other in a ring to form a cylinder with a hollow centre. This cylinder is known as the microtubule.
82
How are lysosomes formed?
They are formed from Golgi vesicles containing hydrolytic enzymes.
83
What are microvilli and where are they typically found?
Microvilli are finger-like extensions of the cell membrane, typical of certain epithelial cells.
84
What are MTOCs?
Microtubule organising centres are special locations in cells where microtubules are formed and broken according to need.
85
What are the functions of a lysosome? (3)
They are responsible for the breakdown of old organelles or even whole cells in the process of autophagy. They also digest bacteria in the process of phagocytosis. They are also present in the heads of sperm with the function of digesting a path to the egg.
86
What are the functions of microtubules?
They make up the cytoskeleton why determines the cell shape as well as acting as an intracellular transport system by moving along secretory vesicles, organelles and cell components. Membrane bound organelles are held in place by the cytoskeleton.
87
What do lysosomes contain and why?
Lysosomes contain digestive/hydrolytic enzymes which must be kept separate from the surrounding cytoplasm to prevent damage.
88
What do microtubules look like?
They are long, rigid hollow tubes.
89
What happens to the ADP produced?
The ADP produced can then be recycles back to mitochondria for conversion back to ATP during aerobic respiration.
90
What is the biological molecule that makes up the microtubule?
Tubulin is a protein molecule that has two forms, namely a-tubulin and b-tubulin.
91
What is the endosymbiont theory?
The theory states that both mitochondria and chloroplasts are ancient bacteria that now live in a mutually beneficial relationship with another organism and hence have circular DNA to produce their own proteins with the ribosomes present in their matrix.
92
What is the function of microvilli?
They increase the surface area of the cell surface membrane.
93
What is the relationship between the folding of the cristae and efficiency?
The folding of the cristae increases the surface area, hence increasing the efficiency.
94
What is the structure of a lysosome?
They are spherical sacs surrounded by a single membrane and having no internal structure.
95
What is the usual diameter of tubulin?
5 nm
96
What is the usual measurement of lysosome?
0.1-0.5um
97
What is the usual measurement of a microtubule?
25nm in diameter.
98
Where are microtubules found?
In the cytoplasm
99
Where in mitochondria does aerobic respiration take place?
In the matrix and cristae of the inner membrane.
100
Describe the membrane system of a chloroplast.
The membrane system consists of fluid-filled sacs called thylakoids that stack up like piles of coins forming structures called grana. Grana are linked together by lamella.
101
How and what does a chloroplast do to receive maximum amount of light?
Both the membranes and the whole chloroplasts can change their orientation within the cell to receive the maximum amount of light.
102
How many centrioles can be seen under a light and electron microscope?
1 under the light microscope, 2 under the electron microscope.
103
In which cells are centrioles found?
Animal cells
104
What are basal bodies and what do they do?
Centrioles that are found at the bases of cilia and flagella are known as basal bodies act as MTOCs. The microtubules that extend from the basal bodies into the cilia and flagella are essential for the beating movements of these organelles.
105
What are the usual measurements of a centriole?
Each centriole is around 200nm in diameter and 500nm long.
106
What biological molecules do cell walls contain?
They contain cellulose and lignin for extra strength.
107
What can be seen as black spheres in the stroma of a chloroplast in e-micrographs and what do they do?
They are lipid droplets that are reserves of lipids for making membranes or from the breakdown of membranes in the chloroplast.
108
What do both mitochondria and chloroplasts do during cell division?
Both replicate themselves independently of cell division by dividing into two.
109
What do mitochondria and chloroplasts have in common?
They are both endosymbiotic bacteria, they have double membranes, produce ATP, have circular DNA, have 70S ribosomes.
110
What do thylakoids contain?
They contain a photosynthetic pigment known as chlorophyll.
111
What does a stroma contain? (4)
It contains starch grains, lipid droplets, circular DNA, 70S ribosomes.
112
What is a centriole made up of and describe its structure?
A centriole is a hollow cylinder formed from a ring of nine triplets of short microtubules.
113
What is a centrosome and what does it do?
It is a pair of centrioles at right angles that is involved in nuclear division and act as MTOCs.
114
What is the function of a cell wall?
It is a freely permeable membrane that gives the cell a definite shape and prevents the cell from bursting when water enters by osmosis.
115
What is the main function of a chloroplast?
To carry out photosynthesis.
116
What is the matrix of a chloroplast known as?
Stroma
117
What is the usual measurement of a cell wall?
10 nm
118
What is the usual measurement of a chloroplast?
3-10um
119
What kind of shape does a chloroplast have?
An elongated shape.
120
Compare organelles of eukaryotes with prokaryotes.
Prokaryote: Very few organelles(not membrane bound, unless formed by the infolding of the cell surface membrane) Eukaryotes: Many types of organelles (can be single, double or have no membrane)
121
Compare the cell walls of eukaryotes with prokaryotes
Prokaryote: Wall contains murein, a peptidoglycan (a polysaccharide combined with amino acids) Eukaryotes: Cellulose and lignin in plants; Chitin (nitrogen containing polysaccharide) in fungi
122
Compare the diameter of cells of eukaryotes with prokaryotes
Prokaryotes: 0.5-5um Eukaryotes: 40um (commonly 1000-10000 times the volume of prokaryotic cells)
123
Compare the DNA of eukaryotes with prokaryotes
Prokaryotes: have naked, circular DNA that lies free in the cytoplasm. Eukaryotes: have linear DNA present in the nucleus and is associated with protein, histone forming chromosomes.
124
Compare the endoplasmic reticulum of eukaryotes with prokaryotes
Prokaryotes: Absent Eukaryotes: Present (ribosomes may be attached)
125
Compare the ribosomes of eukaryotes with prokaryotes
Prokaryotes: have 70S ribosomes (20nm) Eukaryotes: have 80S ribosomes (25nm)
126
Describe the structure of a plant vacuole.
The large, central, permanent vacuole is surrounded by a partially permeable membrane known as the tonoplast, which controls the exchange between the vacuole and the cytoplasm.
127
Describe the structure of a virus.
A virus has non-cellular structures. It has a symmetrical shape with a self-replicating molecule of DNA/RNA which acts as its genetic code. The genetic code is surrounded by a protein coat called a capsid which is made up of protein molecules called capsomeres.
128
Describe the vacuole found in animal cells.
It is a small, temporary structure, normally a phagocytic vacuole.
129
How are viruses parasitic?
They reproduce by infecting and taking over the protein synthesising machinery of the host cell, which then helps to make new virus proteins to make capsids.
130
What are some examples of contents present in a plant vacuole? (7)
It is a solution of enzymes, pigments, sugars and other organic compounds(including some waste products), mineral salts, oxygen and carbon dioxide.
131
What are some functions of a vacuole?
Apart from storing material, they help to regulate the osmotic properties of cells.
132
What are some organelles that are bounded by a double membrane?
Nucleus, mitochondria, chloroplast.
133
What are some organelles that are bounded by a single membrane?
Lysosomes, golgi body, vacuoles
134
What do viruses not have?
They do not have a membrane, cell structures or cytoplasm.
135
What is a eukaryote?
Organisms that have a nucleus and have membrane bound organelles.
136
What is a prokaryote?
Organisms that lack a nucleus and have a simpler structure. e.g. bacteria
137
What is plasmodesmata?
They are fine strands of cytoplasm passing through the pore like structures in the cell walls, linking one plant cell to the next.
138
What is the measurement range of a virus?
20-300nm
139
What are some organelles that have no membrane?
Ribosomes, centrioles and microtubules.

Biology (19 decks)

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