2.4 Eukaryotic cell structure Flashcards
(120 cards)
1
Q
Microscopes not only make cells visible, what also do they do?
A
they also enable us to look deep inside individual cells
2
Q
The basic unit of all living things is the cell. What are the two fundamental types of cell?
A
prokaryotic and eukarytoic
3
Q
What are prokaryotes?
A
single-celled organisms with a simple structure of just a single undivided internal area called the cytoplasm
4
Q
Development of microscopes has allowed biologists to discover increasing amounts of detail of cell ultrastructure.
A
The increased knowledge of structure has led to a better understanding of cell structure
5
Q
What is the cytoplasm composed of
A
cytosol, which is made of water, salts ad organic molecules
6
Q
What do eukaryotic cells make up?
A
multicellular organisms like animals, plants and fungi
7
Q
Eukaryotic cells have a much more complicated internal structure, containing what?
A
a membrane bound nucleus (nucleoplasm) and cytoplasm, which contains many membrane-bound cellular components
8
Q
Chemical reactions are the fundamental processes of life, in cells what do they require?
A
both enzymes and specific reaction conditions
9
Q
What does metabolism both involve?
A
1) the synthesis and the breaking down of molecules
10
Q
What is synthesis?
A
building up
11
Q
Different sets of reactions take place in…
A
different regions of the ultrastructure of the cell
12
Q
Where do reactions take place?
A
in the cytplasm
13
Q
what is the cell cytoplasm separated from?
A
the external environmnt by a cell-surface membrane
14
Q
In eukaryotic cells, the cytoplasm is divided into many different what?
A
membrane-bound compartments, known as organelles
15
Q
What do organelles provide
A
distinct environments and therefore conditions for the different cellular reactions
16
Q
Membranes are _______ ________ and control the ______ of substances into and out of the ____ and ________
A
i) selectively permeable
ii) movement
iii) cell
iv) organelles
17
Q
Membranes are effective what?
A
barriers in controlling which substances enter and exit cells
18
Q
What is a drawback of membranes?
A
fragile
19
Q
The nucleus contains what?
A
coded genetic information in the form of DNA molecules
20
Q
What does DNA do?
A
direct the synthesis of all proteins required by the cell (although this protein synthesis occurs outside of the nucleus at ribosomes)
21
Q
DNA can direct the synthesis of all proteins required by the cell. What does this mean DNA can do and why?
A
i) DNA controls the metabolic activities of the cell
ii) as many of these proteins are the enzymes necessary for metabolism to take place
22
Q
What is often the biggest single organelle in the cell?
A
nucleus
23
Q
Where is DNA contained and why?
A
within a double membrane called a nuclear envelope to protect it from damage in the cytoplasm
24
Q
What does the nuclear envelope (double membrane) contain?
A
nuclear pores that allow molecules to move into and out of the nucleus
25
Why can't DNA itself leave the nucleus to the site of protein synthesis in the cell cytoplasm?
it is too large
26
DNA is too large to leave the nucleus to the site of protein synthesis in the cell cytoplasm?
transcribed into smaller RNA molecules, which are exported via the nuclear pores
27
What do DNA associates with and what does it form?
i) proteins called histones
| ii) a complex called chromatin
28
What does chromatin do?
coils and condenses to form structures known as chromosomes
29
When do chromosomes only become visible?
when cells are preparing to divide
30
What is the nucleolus?
an area within the nucleus, responsible for producing RIBOSOMES
31
What is the nucleolus composed of?
proteins and RNA
32
What is RNA used for?
to produce ribosomal RNA (rRNA) which is then combined with proteins to form the ribosomes necessary for protein synthesis
33
What is the singular for mitochondria?
mitochondrion
34
What are mitochondria?
the site of the final stages of cellular respiration, where the energy stored in the bonds of complex, organic molecules is made available for the cell to use by the production of the molecule ATP
35
The number of mitochondria in a cell is generally a reflection of what?
the amount of energy it uses, so very active cells usually have a lot of mitochondria
36
Mitochondria have a _______ ________
double membrane
37
describe the inner membrane of the mitochondria
highly folded to form structures called cristae and the fluid interior is called the matrix
38
What does the membrane forming the cristae in mitochondria contain?
the enzymes used in aerobic respiration
39
Mitochondira also contain a small amount of ___, called _________ __
DNA, mitochondrial (mt) DNA
40
What can the mitochondria produce and how?
can produce their own enzymes and reproduce themselves
41
What are vesicles?
membranous sacs that have storage and transport roles
42
What do vesicles consist of?
simply of a single membrane with fluid inside
43
What are vesicles used for?
to transport materials inside the cell
44
What are lysosomes?
specialised forms of vesicles that contain hydrolytic enzymes
45
What are lysosomes responsible for
breaking down waste material in cells, including old organelles
46
What system do lysosomes play an important part in and why?
immune system as they are responsible for breaking down pathogens ingested by phagocytic cells
47
What do lysosomes also play an important role in other than the immune system?
programmed cell death or apoptosis
48
Where is the cytoskeleton present?
throughout the cytoplasm of all eukaryotic cells
49
What is the cytoskeleton?
a network of fibres necessary for the shape and stability of the cell
50
How are organelles held in place?
by the cytoskeleton
51
What does the cytoskeleton control?
cell movement and the movement of organelles within cells
52
What three components to the cytoskeleton have?
1) microfilaments
2) microtubules
3) intermediate fibres
53
What are microfilaments
contractile fibres formed from the protein actin
54
What are microfilaments responible for?
cel movement and also cell contraction during cytokinesis
55
what is the process cytokinesis?
the cytoplasm of a single eukaryotic cell is divided to form two daughter cells
56
What are microtubules?
globular tubulin proteins polymerise to form tubes that are used to form a scaffold-like structure that determines the shape of a cell
57
What do microtubules act as?
tracks for the movement of organelles, including vesicles, around the cell
58
What are spindle fibres composed of?
microtubles
59
What role do spindle fibres have?
a role in the physical segregation of chromosomes in cell division
60
What do intermediate fibres do?
give mechanical strength to cells and help maintain their integrity
61
What is integrity
the state of being whole and undivided.
62
what is segregation?
the separation of pairs of alleles at meiosis and their independent transmission via separate gametes.
63
The movement of cells like phagocytes depends on the activity of what?
actin filaments in the cytoskeleton
64
what are phagocytes
cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells
65
When do the actin filament lengths in the cytoskeleton change?
with the addition and removal of monomer subunits
66
The rate at which these monomer subunits is added are what to each end of a filament for the filament lengths to change?
the rate at which these subunits are added is different at each end of a filament
67
Describe the subunits for the filament lengths to change?
not symmetrical and can be only added if they are in the correct orinetation
68
What do the subunits have to do befor they are added to one end (the minus end) of the filament but not the other end (the plus end)
they have to change shape
69
What does the subunits having to change shape befire they are added to one end of the filament for cell movement mean?
the subunits are added at a faster rate at the plus end
70
What dothe subunits being being added to the plus side faster therefore result in?
an increase in length at a faster rate in one particular direction
71
What are the subunits being added or removed at either end is determined by what?
the concentration of subunits in the cytoplasm
72
Due to the different rates of addition of subunits of filaments at either end, at certain concentrations...
what is this called
i) subunits will be added at one end and removed at the other
ii) treadmilling
73
What does the increasing length of the filaments at one edge of a cell, the leading edge, leads to?
cells such as phagocytes in a particular direction
74
What are centriules?
a component of the cytoskeleton present in most eukaryotic cells with the exception of flowering plants and most fungi
75
What are centrioles composed of?
microtubles
76
What do two associated centrioles form?
the centrosome
77
What is the form of the centrosome involved in?
two centrioles form the centrosome, which is invlolved in the assembly and organisation of the spindle fibres during cell division
78
In organisms with flagella cilia, what do centriules play a role in?
the positioning of the flagella and cilia
79
What is a similarity between flagella (whip-like) and cilia (hair-like)
they both are extensions that produce from some cell types
80
Flagella are ____ than cilia but cilia are usually present in much _____ numbers
i) longer
| ii) greater
81
What are flagella primarily used for
to enable cells motility
82
what is motility?
the ability of organisms and fluid to move or get around
83
In some cells, what can flagella be used for?
used as a sensory orgonelle detecting chemical changes in the cells environement
84
Cilia can be ____ or statiionary
mobile
85
Stationary cilia are present where?
on the surface of many cells and have important function in sensory such as the nose
86
How do mobile cilia beat?
in a rhythmic manner, creating a current, abd cause fluids or objects adjacent to the cell to move
87
Give two examples of mobile cilia
1) they are present in the trachea to move mucus away from the lungs (helping tokeep the air passages clean)
2) fallopian tubes to move egg cells from the ovary to the uterus
88
What does each cillium contain?
two central microtubles (black circles) surrounded by nine pairs of microtubles arranged like a "wheel"
89
What are the nine pairs of microtubles arranged like a whell known as?
the 9+2 arrangement
90
What causes the mobile cilia to movie in a beating motion?
pairs of parallel microbules slide over each other
91
A key function of a cell is to synthesise proteins (including enzymes). What for?
internal use and for secretion (transport out of the cell)
92
A significant portion of what is required for secretion?
internal structure of the cell
93
What internal structures are closely linked and coordinate the production of proteins and their preparation for different roles within the cell
i) the ribosomes
ii) the endoplasmic reticulum
iii) golgi apparatus
94
The cytoskeleton plays a key role in coordinating what?
coordinating protein synthesis
95
What is the endoplasmic reticulym (ER)?
a network of membranes enclosing flattened sacs called cisternae
96
What is cisternae
flattened sacs
97
What is cisternae connected to ?
the outer membrane of the nucleus
98
What are the two types of endoplasmic reticulum
i) smooth endoplasmic reticulum
| ii) rough endoplasmic reticulum
99
what is the smooth endoplasmic reticulum responsible for?
lipid and carbohydrate synthesis, and storage
100
what is the rough endoplasmic reticulum responsible for?
has ribosomes bound to the surface and is responsible for the synthesis and transport of proteins
101
What sort of cells have more rough endoplasmic reticulum than cells that do not release proteins?
secretory cells
102
Where are the ribosomes located?
it can be free-floating in the cytoplasm or attached to endoplasmic reticulum. forming rough endoplasmic reticulum
103
What are ribosomes not surrounded by?
a membrane
104
What are ribosomes constructed with and where?
RNA molecules made in the nucleolus of the cell
105
What are the site of protein synthesis
ribosomes
106
What also contains ribosomes other than being free floating inthe cytoplasm or attached to endoplasmic reticulum
mitochondria and chloroplasts, as do prokaryotic cells
107
What is the Golgi apparatus similar in strucutre to?
the smooth endoplasmic reticulum
108
What sort of structure of the Golgi appartus?
a compact structure formed of cisternae and does not contain ribosomes
109
What is the Golgi apparatus
an organelle in most eukaryotic cells formed from an interconnected network of flattened, membrane-enclosed sacs or cisternae
110
What does the Golgi apparatus play a role in?
modifying and packaging proteins into vesicles
111
What sort of vesicles could the Golgi appartus package?
secretory vesicles, if the proteins are destined to leave the cell, or lysosomes, which stay in the cell
112
Proteins are synthesised on what ribosomes?
on the ribosomes bound to the endoplasmic reticulum
113
After the proteins are synthesised on the ribosomes, what happens?
they are pass into a cisternae and are packaged into transport vesicles
114
Vesicles containing the newly synthesised proteins move towards the what and how?`
the Golgi apparatus via the transport function of the cytoskeleton
115
What do the vesicles fuse with while the proteins enter?
the vesicles fuse with the cis face of the Golgi apparatus
116
Describe the proteins before leaving the Golgi aparatus in vesicles from its trans face
structurally modified
117
Secretory vesicles carry proteins that are..
to be released from the cell
118
The secretory vesicles move towards and fuse with the what after they carriend the proteins that are ? and releasing what and how in the process?
with the cell surface membrane, releasing their contents by exocytosis
119
Some vesicles form what which contain enzymes for use in the cell?
lysosomes
120
Some vesicles form lysosomes. What do these contain?
enzymes for use in the cell
