3.4- EUKARYOTIC CELL STRUCTURE Flashcards
1
Q
What is the name for when each cell type has an internal structure that suits it for its job?
A
ultrastructure
2
Q
What do eukaryotic cells have that prokaryotic cells do not?
(2)
A
distinct nucleus
possess membrane-bound organelles
3
Q
What can be used to see the structure of organelles within a cell?
A
electron microscope
4
Q
What is the most prominent feature of a eukaryotic cell?
A
nucleus
5
Q
What does the nucleus contain?
A
organism’s hereditary material
6
Q
What does the nucleus do?
A
controls the cell’s activities
7
Q
What shape is the nucleus usually?
A
spherical
8
Q
Usually what is the diameter of the nucleus?
A
between 10 and 20μm in diameter
9
Q
What is the nuclear envelope?
A
double membrane that surrounds the nucleus
10
Q
What does the outer membrane of the nuclear envelope continuous with?
A
endoplasmic reticulum of cell and often has ribosomes on its surface
11
Q
What does the nuclear envelope do? (2)
A
controls entry and exit of materials in and out of nucleus
contains reactions taking within in
12
Q
What do the nuclear pores do?
A
allow passage of large molecules
13
Q
Example of large molecules nuclear pores allow the passage of?
A
messenger RNA out of nucleus
14
Q
Typically how many nuclear pores are in each nucleus?
A
3000 pores
15
Q
What is the diameter of the nuclear pores like?
A
40-100 nm in diameter
16
Q
What is the nucleoplasm?
A
granular, jelly-like material that makes up bulk of nucleus
17
Q
What do chromosomes consist of?
A
protein-bound, linear DNA
18
Q
What is the nucleolus?
A
small spherical region within the nucleoplasm
19
Q
What does the nucleolus do? (2)
A
manufactures ribosomal RNA
assembles ribosomes
20
Q
Can there be more than one nucleolus in the nucleus?
A
yes
21
Q
Functions of the nucleus? (3)
A
act as control centre of cell through production of mRNA and tRNA and hence protein synthesis
retain genetic material of cell in form of DNA + chromosomes
manufacture ribosomal RNA and ribosomes
22
Q
What shape is the mitochondria usually?
A
rod-shaped
23
Q
What is usually the length of mitochondria?
A
1-10μm in length
24
Q
Is there a double membrane around mitochondria?
A
yes
25
What does the double membrane around mitochondria do?
controls entry + exit of material
26
What is done to the inner membrane of the double membrane of the mitochondria?
folded to from extensions known as cristae
27
What are cristae? (mitochondria)
extensions of the inner membrane
28
What does the cristae do in some species? (mitochondria)
extend across the whole width of the mitochondria
29
What do the cristae do?
| mitochondria
provide large SA for attachment of enzymes and other proteins involved in respiration
30
What does the matrix make up? (mitochondria)
makes up the remainder of the mitochondrion
31
What does the matrix contain? (mitochondria)
protein, lipids, ribosomes, and DNA
32
What does the substances the matrix contains allow the mitochondria to do?
allows mitochondria to control the production of some of their own proteins
33
What is also found in the matrix? (mitochondria)
enzymes involved in respiration
34
What is mitochondria the site of?
aerobic stages of respiration
35
As mitochondria is the site of the aerobic stages of respiration, what is it responsible for?
production of energy-carrier molecule, ATP, from respiratory substances such as glucose
36
As mitochondria is responsible for production of ATP what may vary about mitochondria in cells that have a high level of metabolic activity? (2)
number and size of mitochondria
number of their cristae
37
Examples of metabolically active cells? (2)
muscle cells
epithelial cells
38
Why do epithelial cells in the intestines require a lot of ATP?
in process of absorption of substances from intestines by active transport
39
What do chloroplasts carry out?
photosynthesis
40
What do chloroplasts vary in?
shape and size
41
Typically what shape are chloroplasts?
disc-shaped
42
Typically how long is a chloroplast?
2-10μm long
43
Typically what is the diameter of a chloroplast?
1μm in diameter
44
What is the chloroplast envelope?
double plasma membrane that surrounds the organelle
45
How selective is the chloroplast envelope?
highly selective
46
What is the chloroplast envelope highly selective in?
in what is allows to enter and leave the chloroplast
47
What is the grana? (chloroplast)
stacks of up to 100 disc-like structures called thylakoids
48
What is within the thylakoid? (chloroplast)
photosynthetic pigment called chlorophyll
49
What do some thylakoids have? (chloroplast)
tubular extensions that join up with thylakoids In adjacent grana
50
What happens at the grana? (chloroplast)
where the first stages of photosynthesis takes place
51
What is the first stage of photosynthesis? (chloroplast)
light absorption
52
What is the stroma? (chloroplast)
fluid-filled matrix
53
What happens at the stroma? (chloroplast)
where second stage of photosynthesis takes place
54
What is the second stage of photosynthesis?
synthesis of sugars
55
What is within the stroma? (chloroplast)
number of other structures, i.e. starch grains
56
How is chloroplast adapted to its function of harvesting sunlight and carrying out photosynthesis? (3)
granal membranes provide large SA for attachment of chlorophyll, electron carriers and enzymes that carry out first stages of photosynthesis. these chemicals attached to membrane in highly ordered fashion
fluid of stroma possesses all the enzymes needed to make sugars in second stage of photosynthesis
chloroplast contain both DNA and ribosomes so they can quickly + easily manufacture some of the proteins needed for photosynthesis
57
What is the endoplasmic reticulum?
elaborate, three-dimensional system of sheet-like membranes,, spreading the cytoplasm of the cells
58
What is the ER continuous with?
outer nuclear membrane
59
What do the membranes enclose? (ER)
network of tubules and flattened sacs called cisternae
60
What are the two types of ER?
rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER)
61
What does the RER have?
ribosomes present on the outer surfaces of the membranes
62
What are the functions of RER? (2)
provide large SA for synthesis of proteins and glycoproteins
provide pathway for transport of materials, especially proteins, throughout cell
63
What does the SER lack?
ribosomes on its surface
64
How does the appearance of the SER differ from the RER?
often more tubular in appearance
65
What are the functions of SER? (2)
synthesise, store and transport lipids
synthesise, store and transport carbohydrates
66
What cells have a very extensive ER?
cells that manufacture and store large quantities of carbohydrates, proteins and lipids
67
Examples of cells that have very extensive ER? (2)
liver cells
| secretory cells- e.g. epithelial cells that line the intestines
68
What is the structure of the Golgi apparatus similar to?
SER
69
How is the structure of the Golgi apparatus different to the SER?
Golgi is more compact
70
What does the Golgi apparatus consist of?
stack of membranes that make up flattened sacs, or cisternae, with small rounded hollow structures called vesicles
71
What are the proteins and lipids produced by the ER passed through?
passed through the Golgi apparatus
72
What does the Golgi do to the proteins made by the ER?
modifies proteins often adding non-protein components i.e. carbohydrates to them
'labels' them, allowing them to be accurately sorted + sent to correct destinations
73
What happens once the proteins and lipids are modified by the Golgi apparatus?
modified proteins and lipids transported in Golgi vesicles which are regularly pinched off from ends of Golgi cisternae
74
Where may the Golgi vesicles move to and what do they do?
move to the cell surface, where they fuse with the membrane + release contents to outside
75
Functions of Golgi apparatus (5)
add carbohydrates to proteins to form glycoproteins
produce secretory enzymes, i.e. those secreted by pancreas
secrete carbohydrates, i.e. those used in making cells walls in plants
transport, modify + store lipids
form lysosomes
76
In what cells is the Golgi apparatus well developed in?
secretory cells- e.g. epithelial cells that line intestines
77
How are lysosomes formed?
when vesicles produced by Golgi apparatus contain enzymes such as proteases and lipases
78
What else do the lysosomes contain?
contain lysozymes
79
What do lysozymes do?
hydrolyse cell walls of certain bacteria
80
Up to how many lysozymes can be in a single lysosome?
50
81
What is the diameter of lysosomes like?
1.0 μm
82
What does the lysosome do to the enzymes?
isolate enzymes from rest of the cell before releasing them
83
Where can the lysosome release the enzymes?
to the outside
OR
into a phagocytic vesicle within the cell
84
What are the functions of lysosomes? (4)
hydrolyse material ingested by phagocytic cells, i.e. white blood cells + bacteria
release enzymes to outside of cell (exocytosis) to destroy material around cell
digest worn out organelles so useful chemicals they're made of can be re-used
completely break down cells after they have died (autolysis)
85
What types of cells are lysosomes especially abundant in? (2)
secretory cells- i.e. epithelial cells
phagocytic cells
86
What are ribosomes?
small cytoplasmic granules found in all cells
87
How can ribosomes occur? (2)
in cytoplasm OR associated with RER
88
What does the types of ribosome depend on?
depends on cells in which they're found
89
What are the two types of cells?
80S and 70S
90
Where are all 80S ribosomes found?
in eukaryotic cells
91
What is the diameter of 80S ribosomes like?
around 25μm in diameter
92
Where are all 70S ribosomes found?
in prokaryotic cells, mitochondria and chloroplast
93
What is the size of 70S ribosomes like in comparison to 80S ribosomes?
70S ribosomes are smaller
94
How many subunits do ribosomes have?
two
95
What are the subunits of ribosomes like?
one large and one small
96
What do each subunit of the ribosome contain?
contains ribosomal RNA and protein
97
In what numbers do ribosomes occur in?
in vast numbers
98
As ribosomes occur in vast numbers what percent of dry mass of a cell do they account for?
25%
99
What is the ribosome the site of?
protein synthesis
100
What type of cell is cell walls a characteristic of?
plant cells
101
What do the cell walls of plant cells consist of?
microfibrils of the polysaccharide cellulose, embedded in a matrix
102
What characteristic do cellulose microfibrils have?
considerable strength
103
As cellulose microfibrils have considerable strength what do they contribute to?
to overall strength of cell wall
104
What features do cell walls have? (2)
consist of number of polysaccharides, i.e. cellulose
there's a thin layer, called middle lamella, which marks boundary between adjacent cell walls + cements adjacent cells together
105
What are the functions of the cellulose cell wall? (3)
provide mechanical strength to prevent cell bursting under pressure created by osmotic entry of water
give mechanical strength to plant as a whole
allow water to pass along it and so contribute to movement of water through plant
106
What are the cell walls of algae made up of?
either cellulose or glycoproteins, or a mixture of both
107
What are the cell walls of fungi made up of?
mixture of nitrogen-containing polysaccharide called chitin, a polysaccharide called glycan and glycoproteins
108
What may be termed as a vacuole?
fluid-filled sacs bounded by a single membrane
109
Within a mature plant cell what is the vacuole like?
one large central vacuole
110
What is the single membrane around a vacuole called?
tonoplast
111
What does a plant vacuole contain?
solution of mineral salts, sugars, amino acids, wastes and sometimes pigments
112
Example of pigment that may be in a vacuole?
anthocyanins
113
What are the functions of vacuoles? (3)
support herbaceous plants, + herbaceous parts of woody plant, by making cells turgid
sugars + amino acids may act as temporary food store
pigments may colour petals to attract pollinating insects
