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Cell structures Flashcards

1
Q

Features of the nucleus

A

nuclear envelope surrounds
nuclear pores perforate envelope
contains DNA organised into chromosomes
nucleolus - complex of rRNA and proteins - ribosoomes

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2
Q

Features of the nuclear envelope

A

Surrounds nucleus
Double membrane – each a lipid bilayer with proteins
Each membrane separated by a narrow space (20-40 nm)
Perforated by pore structures
Pore structures lined by pore complex which controls the entry and exit of proteins, RNA and macromolecules

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3
Q

What is the nucleolus made from?

A

rRNA (ribosomal RNA) and proteins
a region rather than bound
proteins come from the cytosol

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4
Q

Does every cell have a nucleolus?

A

only visible in non dividing cells (disappears during mitosis)
Sometimes there are two or more nucleoli - the number depends on the species and the stage of the cells cell’s reproductive cycle

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5
Q

what is the function of the nucleolus

A

synthesises ribosomal RNA from instructions in the DNA
Proteins imported from the cytosol are assembled with rRNA into the small and large units of the ribosomes
Ribosome subunits exit through nuclear pores to cytoplasm where they join to form a ribosome

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6
Q

Where are ribosomes made?

A

Ribosomes are synthesised in the nucleolus
In the nucleolus proteins and rRNA are assembled into large and small subunits of the ribosomes
Subunits are then exported through nuclear pores to the cytoplasm

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7
Q

Are ribosomes organelles?

A

Ribosomes are not membrane bound and so are not considered to be organelles

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8
Q

What is the nuclear lamina

A

The nuclear lamina is a netlike array of proteins filaments found on the nuclear side of the nuclear envelope
Maintain the shape of the nucleus
May help organise genetic material

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9
Q

what is the nuclear matrix

A

The nuclear matrix is a framework of protein fibres extending throughout the nuclear interior

May help organise genetic material

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10
Q

what is the function of ribosomes

A

protein synthesis

rRNAs carry out peptidyl transferase activity - protein synthesis

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11
Q

What is the structure of ribosomes

A

large and small units

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12
Q

Are ribosomes present in all cells

A

Eukaryotic cells have ribosomes
Prokaryotes have some ribosomes but they are smaller
cells that have high rates of protein synthesis have more ribosomes as well as prominent nucleoli e.g. pancreatic cells which need to produce a lot of insulin and other digestive enzymes

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13
Q

what is the difference between free and bound ribosomes

A

Free ribosomes are found floating in the cytosol

Bound ribosomes are attached to the ER or the nuclear envelope

Proteins made in free ribosomes function in the cytosol e.g. enzymes

Proteins made in bound ribosomes – used in membranes / lysosomes or exit the cell e.g. digestive enzymes

Bound and free ribosomes are structurally identical and can play either role at different times

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14
Q

What role do ribosomes play in carrying out genetic instructions?

A

Ribosomes translate the genetic message carried from the DNA in the nucleus by mRNA into a polypeptide chain

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15
Q

What cellular structures make up the endomembrane system?

A 
Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vesicles and vacculoles
Plasma membrane
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16
Q

where are bound ribosomes located

A

bound ribosomes are attached to the outside of the endoplasmic reticulum or the nuclear envelope

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17
Q

where are free ribosomes located

A

free ribosomes are located in the cytosol

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18
Q

What happens to proteins made in free ribosomes?

A

free ribosomes are suspended in the cytosol and most of the proteins they make are used within the cytosol for example enzymes that catalyse the first steps of sugar breakdown

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19
Q

what happens to proteins made in bound ribosomes

A

bound ribosomes (attached to ER and nuclear envelope) are inserted into membranes/ for packaging into certain organelles like the lysosomes or for export out of the cell

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20
Q

what is the structure of the ER

A

Network of membranous tubules and sacs called cisternae
The ER membrane separates the internal compartment of the ER – called the ER lumen (cavity) or cisternal space from the cytosol
The Er membrane is continuous with the nuclear envelope

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21
Q

what are cisternae?

A

Sacs in the ER

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22
Q

What is the ER lumen?

A

internal compartment of the ER
cisternal space
separated from cytosol
because the ER membrane is continuous with the nuclear envelope, the space between the two membranes of the envelope is continuous with the lumen of the ER

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23
Q

how are the nuclear envelope and the ER connected

A

the ER membrane is continuous with the nuclear envelope

the space between the two membranes of the nuclear envelope is continuous with the ER lumen

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24
Q

what are the two regions of the ER

A

smooth Er and rough ER

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25
how are the smooth ER and rough ER different?
smooth ER lacks ribosomes | rough ER studded with ribosomes on the outer surface of the membrane
26
where are ribosomes found in the cell
ribosomes attach to the outer surface of the rough ER and also to the cytoplasmic side of the nuclear envelope Free ribosomes also found in cytosol
27
what are the functions of the smooth ER
synthesis of lipids metabolism of carbohydrates detoxification of drugs and poisons storage of calcium ions
28
what types of lipids are produced in the smooth ER
oils steroids e.g. sex hormones new membrane phospholipids
29
what are the functions of the rough ER?
aids in the synthesis of secretory and other proteins on bound ribosomes adds carbohydrates to proteins to make glycoproteins produces new membrane
30
how does the rough ER function in making secretory proteins
polypeptide chain forms from ribosome enters the lumen and folds to functional shape in the lumen carbohydrates are attached to form glycoproteins (enzymes built into the ER membrane) ER membrane keeps new proteins separate from cytosol ER makes vesicles
31
what are transport vesicles
Vesicles that transit from one part of the cell to another transport vesicles bud off from a region of the rough ER called the transitional ER after leaving the ER many transport vesicles travel to the golgi apparatus
32
what is the function of the golgi apparatus
``` modifies products of ER stores products sends products to other destinations receives and dispatches transport vesicles manufactures some macromolecules ```
33
what is the structure of the golgi apparatus?
group of associated flattened membranous sacs - cisternae (unlike ER these sacs are not connected) membrane separates internal space from cytosol
34
what are the two sides of the golgi?
cis face - located near the ER / receiving vesicles containing ER products trans face - shipping department - dispatches vesicles that pinch off and travel to other sites
35
How does the golgi function to modify products
products are modified as they move from the cis to the trans region glycoproteins formed in the ER have their carbohydrates modified (glycosolation) membrane phospholipids also altered
36
what macromolecules are made in the golgi apparatus?
many polysaccarides secreted by cells are made in the golgi e.g. pectins
37
how does the golgi sort products before dispatch
the golgi sorts products and targets them for various parts of the cell attach molecular identification tags like phosphate groups transport vesicles may have external molecules that recognise docking sites on the surface of organelles or on the plasma membrane
38
what is the structure of cell membranes
cell membranes consist of a double layer of phospholipids hydrophillic parts are in contact with the aqueous solutions inside and outside the cell hydrophobic parts are inside and not in contact with liquids embedded within and attached to the surface are diverse proteins
39
How does the plasma membrane contribute to cellular metabolism
many enzymes built into membranes
40
what is the structure of a lysosome?
membranous sac filled with hydrolytic enzymes
41
how is a lysosome made
hydrolytic enzymes and lysosome membranes form in the rough ER transferred to golgi for further processing lysosomes bud from the trans face of the golgi
42
what is phagocytosis?
lysosomes digest (hydrolyse) materials taken into the cell vacuole taken into the cell fuses with a lysosome whose enzymes digest the food e.g. amoeba and other unicellular eukaryotes eat by engulfing smaller organisms - make vacuoles some human cells carry out phagocytosis e.g. white blood cells destroy bacteria
43
what is autophagy?
lysosomes recycle intracellular materials / cell's organic material a damaged organelle or small amount of cytosol becomes surrounded by double membrane and the lysosome fuses with it
44
what is a vacuole?
large vesicle derived from the endoplasmic reticulum and golgi apparatus part of the cell's endomembrane system compartment that has different conditions to cytosol
45
what are contractile vacuoles
unicellular eukaryotes living in fresh water pump excess water out of the cell maintain concentration of ions and molecules inside the cell
46
do plant and fungi cells have lysosomes?
No - enzymatic hydrolysis is carried out in vacuoles
47
what are the functions of vacuoles?
``` food particles - digestion contractile vacuoles act like lysosomes in plants - break down wastes in plants may store compounds - storage cell growth and protection ```
48
what is the central vacuole
found in plant cells largest compartment in plant cells contains cell sap (store of inorganic ions) enlarge as the plant absorbs water
49
what are the distinctions between the rough and smooth ER?
presence of ribosomes on rough ER both types of ER make phospholipids membrane proteins and secretory proteins are produced on the ribosomes of the rough ER the smooth ER functions in detoxification, carbohydrate metabolism and storage of calcium ions
50
how are mitochondria and chloroplasts similar
both convert energy to forms that cells can use for work mitochondria - cellular respiration chloroplasts - photosynthesis
51
what is evidence for the endosymbiont theory
both mitochondria and chloroplasts are bound by two membranes (in contrast to other organelles bound by single membrane) both contain ribosomes both contain circular DNA both are autonomous organelles that grow and reproduce within the cell
52
what cells contain mitochondria
mitochondria are found in nearly all eukaryotic cells | some cells have one but more often a cell has hundreds
53
How many mitochondria in a cell
some cells have only one but most have hundreds or even thousands how many a cell has depends on its level of metabolic activity
54
describe the membranes of the mitochondria
two membranes each membrane is a phospholipid bilayer outer membrane is smooth inner membrane folded called cristae intermembrane space is the space between the inner and outer membrane mitochondrial matrix - the compartment enclosed by the inner membrane
55
what is cristae
infoldings of the mitochondria
56
what is the inner membrane space
the space between the inner and outer membranes of the mitochondria
57
what is the mitochondrial matrix
enclosed by the inner membrane of the mitochondria contains different enzymes contains mitochondrial DNA and ribosomes enzymes that function in cellular respiration embedded into the inner membrane
58
why is the cristae folded?
gives a larger surface area for cellular respiration
59
what does a chloroplast contain?
a chloroplast contains chlorophyll (green pigment) along with enzymes and other molecules that function in photosynthesis
60
where are chloroplasts located
in leaves and other green parts of plants and algae
61
describe the structure of a chloroplast
two membranes separated by a narrow intermembrane space inner membranes divide the chloroplast into 3 compartments - intermembrane space thylakoids (stacks called granum) fluid outside the thylakoids called stroma - contains chloroplast DNA and ribosomoes
62
what is a plastid?
plant organelle | chloroplast is one kind of plastid
63
describe two characteristics shared by chloroplasts and mitochondria
both involved in energy production both have multiple membranes that separate their interiors into compartments both have inner membranes that give large surface area - cristae in mitochondria and thylakoids in chloroplasts both have embedded enzymes
64
Do plant cells have mitochondria?
Yes | plant cells are able to make their own sugar by photosynthesis but mitochondria are needed to make ATP
65
are mitochondria and chloroplasts part of the endomembrane system
No different structure to membranes - double membrane for mitochondria and chloroplasts / single for others not derived from ER
66
what is a peroxisome
bound by s single membrane contain enzymes for metabolism different functions cooperate with mitochondria and chloroplasts
67
what is the function of peroxisomes
remove hydrogen atoms from various substrates and transfer them to oxygen producing hydrogen peroxide peroxisoomes contain enzymes that convert hydrogen peroxide to water
68
what structures make up the cytoskeleton?
microtubules microfilaments and intermediate filament
69
what are the functions of the cytoskeleton?
structural support maintain shape provides anchorage for organelles in some cells facilitates motility - changes in cell location and movement of cell parts
70
what is the structure of microtubules
globular proteins called tubulins | microtubules are hollow rods made of tubulin protein subunits
71
describe tubulin
hollow tubes | a dimer made from alpha tubulin and beta tubulin
72
what is a dimer
a molecule made up of two components
73
what is the function of microtubules
shape cell support cell tracks along which motor proteins can move - guide vesicles from the ER to Golgi and from golgi to plasma membrane microtubules are also involved in the separation of chromosomes during cell division cilia and flagella
74
what is a centrosome?
microtubules grow out of the centrosome | located near the nucleus
75
what is a centriole
found within the centrosome (where microtubules grow) | nine sets of three microtubules arranged in a ring
76
what is a primary cilium?
in vertebrate animals almost all cells have a primary cilium | signal receiving antenna
77
how are cilia and flagella different
usually large numbers of cilia (except primary cilium) usually only one or a few flagella flagella are longer different beating pattern
78
what is the structure of cilia and flagella
group of microtubules sheathed in an extension of the plasma membrane 9 doublets of microtubules in a ring with 2 in centre (9+2) anchored by a basal body dyneins (motor proteins) involved in movement
79
what are microfilaments made from
actin (also called actin filaments)
80
what is the role of microfilaments
support cell shape (network inside the plasma membrane) | cell motility - allow cell to contract e.g. amoeboid crawling / cytoplasmic streaming in plants
81
what are pseudopodia
``` some cells (amoeba and white blood cells) move along by crawling movement. The cell crawls along a surface by extending cellular extensions called pseudopodia and moving towards them made possible by microfilaments and myosin ```
82
what is cytoplasmic streaming?
in plant cells circular flow of cytoplasm made possible by microfilaments speeds up the movement of organelles and the distribution of materials within the cell
83
what cells have intermediate filaments
only the cells of some animals including vertebrates | microtubules and microfilaments found in all eukaryotes
84
what is the role of intermediate filaments
play an important role in reinforcing cell shape and fixing the position of organelles (permanent framework for the cell) sturdy and more permanents than microtubules and microfilaments
85
what brings about cell movement
interaction between actin filaments (microfilaments ) and myosin e.g. muscle cells amoeba movement (pseudopodia) cytoplasmic streaming
86
what cells have cell walls
this is one feature that distinguishes plant and animal cells prokaryotes fungi and some unicellular eukaryotes (protists)
87
functions of the cell wall
protects the plant cell maintains its shape prevents excessive uptake of water hold the plant upright
88
what are cell walls made from
cellulose fibres embedded in other polysaccharides and proteins in fungi - chitin
89
what is the structure of the cell wall
young plant cell secretes a thin and flexible cell wall (around one cell) called the primary cell wall the primary cell walls of adjacent cells is glued together by the middle lamella (pectins) when the plant stops growing it strengthens its cell wall by secreting hardening substances
90
what is the middle lamella
a layer of sticky polysaccharides (pectins) that glue the cell walls of plant cells together
91
what is the extracellular matrix
like the cell wall of animal cells
92
what is the extracellular matrix made of
glycoproteins - collagen proteoglycans proteins and sugars
93
what are integrins
cell surface receptor proteins built into the plasma membrane attach to microfilaments of the cytoskeleton transmit signals between the extracellular matrix and cytoskeleton - can result in changes in cell behaviour
94
what is fibronectin
glycoproteins that attach cells to the extracellular matrix bind to integrins helps ECM to communicate with cell - mechanical signalling
95
what are plasmodesma
perforate cell walls channels that connect plant cells cytosol can pass through plasmodesma to other cells water and some solutes can pass freely from cell to cell
96
what types of cell junctions exist in animal cells
tight junctions desmosomes gap junctions
97
what are tight junctions
plasma membranes of neighbouring cells are bound together by proteins continuous seal prevents leakage of extracellular fluid e.g. skin cells are watertight
98
what are desmosomes
like rivets fasten cells together (hinges) | attach muscle cells to each other
99
what are gap junctions
found in animal cells also called communicating junctions provide cytoplasmic channels from one cell to an adjacent cell (similar to plasmodesma in plants) allows ions, sugars, amino acids and other small molecules to pass pores surrounded by membrane proteins necessary for communication between cells in many types of tissues - heart/muscle/ animal embryos
100
what are membrane proteins and what are their function
proteins embedded in the plasma membrane or other cellular membranes transport substances across membranes conduct signals e.g. proton pump / calcium channel / aquaporin
101
Which cells have ribosomes
all living organisms have ribosomes Eukaryotic ribosomes are called 80s ribosomes Prokaryotic (bacteria/archaea) ribosomes are 70s - smaller Mitochondria in cells also have ribosomes - these are smaller than those in the cytoplasm and are made separately to them s - relates to centrifugiing
102
what are cell wall's made of?
primary cell wall - cellulose in a gel like matrix | secondary cell wall - cellulose and polysaccharides
103
which organisms have mitochondria
all eukaryotic cells | not in prokaryotes - they don't have membrane bound organelles
104
what do mitochondria , chloroplasts and nuclei have in common
all have functional DNA

Bio1MGC (11 decks)

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