Ch 1 Cell Structure and Function Flashcards
1
Q
histology
A
the study of normal cells and tissues, mainly using microscopes
2
Q
cell
A
the functional unit of all living organisms
3
Q
eukaryote
A
organisms whose cells consist of cytoplasm and a defined nucleus bounded by a nuclear membrane
4
Q
prokaryote
A
cells who do not have a membrane-bound nucleus
5
Q
differentiation
A
process by which cells adopt a specialised structure and function
6
Q
plasma membrane
A
an external lipid membrane that binds cells and which serves as a dynamic interface with the external environment
7
Q
plasma membrane functions
A
transfer of nutrients and metabolites
attachment of the cell to adjacent cells and extracellular matrix
communication with the external environment
8
Q
nucleus
A
the largest organelle, its substance is bounded by a membrane system called the nuclear envelope or membrane and contains the genetic material of the cell (DNA)
9
Q
nuclear membrane/envelope
A
the membrane system that encloses the nucleus and consists of two lipid bilayers with the intermembranous or perinuclear space between.
10
Q
endoplasmic reticulum
A
an extensive system of flattened membrane-bound tubules, saccules, and flattened cisterns (sacs)
11
Q
Golgi apparatus
A
AKA Golgi complex or sack
a discrete system of membrane-bound saccules that is typically located close to the nucleus
12
Q
mitochondria
A
large, elongated organelles which have a smooth outer membrane and a convoluted inner membrane system that degrades pyruvic acid in the presence of oxygen to carbon dioxide and water; this process yields a large quantity of ATP
13
Q
cytosol
A
the gel-like medium in which the cytoplasmic organelles are suspended
14
Q
cytoskeleton
A
a network of minute tubules and filaments within the cytosol which provides structural support for the cell and its organelles, as well as providing a mechanism for the transfer of materials within the cell and movement of the cell itself
15
Q
phospholipid
A
molecule that makes up the lipid bilayers and are amphoteric
16
Q
amphoteric
A
consist of a polar head and a non-polar tail
17
Q
sphingomyelin
A
an important and plentiful phospholipid in cell membranes
18
Q
the lipid structure of membranes
A
not homogeneous
certain lipids, glycolipids and proteins may be transiently enriched to form a membrane or lipid ‘raft’ which is involved in various membrane functions, including the formation of caveolac
19
Q
cholesterol
A
molecules present in the bilayer in an almost 1 : 1 ratio with phospholipids; amphiphilic
20
Q
cholesterol function
A
Cholesterol has a kinked conformation, thus preventing overly dense packing of the phospholipid tails and also filling the gaps between the ‘kinks’ of the unsaturated fatty acid tails.
This helps cholesterol molecules stabilize and regulate the fluidity of the phospholipid bilayer.
21
Q
intrinsic proteins
A
Also called integral proteins, these protein molecules are embedded within the lipid bilayer
22
Q
transmembrane proteins
A
these proteins span the entire thickness of the membrane to be exposed to each surface,
23
Q
peripheral membrane proteins
A
proteins attached to the inner or outer membrane leaflet by weak non-covalent bonds to other proteins or lipids
24
Q
membrane proteins functions
A
cell-cell adhesion
cell-matrix adhesion
intercellular signaling
the formation of transmembrane channels for the transport of materials into and out of the cell
[Them MP’s didn’t do nothing for us common folk govnur, they just SAT (signaling, adhesion,transportation) on their rears, they did]
25
aquaporin
transmembrane protein which transports water molecules across the cell membrane
26
glycolipids
membrane lipids conjugated with short chains of polysaccharide
27
glycoproteins
membrane proteins conjugated with short chains of polysaccharide
E.g. surface mucins
28
glycocalyx
an outer coating of glycoproteins (surface mucins) and glycolipids which project from the surface of the bilayer, varying in thickness in different cell types
29
glycocalyx function
cell recognition phenomena
the formation of intercellular adhesions
the adsorption of molecules to the cell surface
provides mechanical and chemical protection for the plasma membrane
["Coats" protect, are recognizable, adheres to your body, and adsorbs rain]
30
chromosome
contains a number of genes joined end to end, with each gene encoding the structure of a single protein according to the sequence of nucleotides along the length of the gene
31
nucleoplasm
the substance of the nucleus
32
nucleoprotein
two major types:
low molecular weight, positively charged histone proteins, & non-histone proteins
found in the nucleus after being synthesized in the cytoplasm
33
histone proteins
form a protein core around which the chromosome is coiled to form nucleosomes and control the uncoiling and expression of the genes encoded by the DNA strand.
34
nucelosomes
the coiled unit of chromosomes around a histone core
35
non-histone proteins
a type of nucleoprotein and includes all the enzymes for the synthesis of DNA and RNA and other regulatory proteins
36
heterochromatin
tightly coiled, inactive chromatin found in irregular clumps, often around the periphery of the nucleus
37
Barr body
the inactivated X-chromosome in females which may form a small discrete mass within the nucleus
38
euchromatin
the part of the DNA that is active in RNA synthesis; uncoiled heterochromatin
39
chromosome territories
particular areas of the nucleus where individual chromosomes tend to clump
40
intermembranous/perinuclear space
the area between the two lipid bilayers of the nuclear envelope, and is continuous with the lumen of the ER
41
outer lipid bilayer of the nuclear envelope
continuous with the endoplasmic reticulum ER and has ribosomes R on its cytoplasmic face
42
nuclear lamina
an electron-dense layer of intermediate filaments (lamins) found on the inner aspect of the inner nuclear membrane which link inner membrane proteins and heterochromatin
43
lamins
intermediate filaments that make up the nuclear lamina and link inner membrane proteins and heterochromatin
44
nuclear pores
areas in the nuclear envelope and at the pores' margins, the inner and outer membranes become continuous
45
nuclear pore complex
an elaborate cylindrical structure consisting of approximately 30 proteins (nucleoporins) forming a central pore approximately 125 nm in diameter
46
nucleoporins
proteins that comprise the cylindrical structure of nuclear pore complexes, creating a pore approximately 125 nm in diameter
47
nuclear pores functions
permit and regulate the exchange of metabolites, macromolecules, and ribosomal subunits between the nucleus and cytoplasm
ions and small molecules diffuse freely through, but larger molecules (e.g. mRNA moving nucleus -> cytoplasm, histones moving cytoplasm -> nucleus) have to dock to the nuclear pore complex via a targeting sequence and are transported by an energy-dependent process
may also hold together the two lipid bilayers of the nuclear envelope
48
nucleolus
dense structure within the nucleus which is the site of ribosomal RNA (rRNA) synthesis and ribosome assembly.
Also processes transfer RNA (tRNA)
49
nucleolar organiser regions (NORs)
where the ribosomal genes are found across five specific chromosomes
50
nucleoli appearance commonalities
most contain dense fibrillar components (sites of rRNA synthesis) and paler fibrillar centers surrounded by the granular component (ribosome assembly site)
[nuclei = plural of nucleus; nucle"ol"i = plural of nucle"ol"us]
51
ribosome
protein factory of the cell
52
pre-messenger RNA
pre-mRNA
a complementary copy of the DNA template (the gene) of a particular protein
53
transcription
the process of copying the DNA template (the gene) of a particular protein to form a complementary pre-messenger RNA ( pre-mRNA ) copy
54
introns
non-coding regions of the mRNA strand which is excised during the post-transcriptional processing of the mRNA
55
small nuclear RNAs
snRNA
controls the post-transcriptional step of intron excision, and forms the spliceosome with various other proteins
56
spliceosome
a complex of various proteins including snRNA which excises introns from mRNA during post-transcriptional processing
57
messenger RNA
mRNA
the post-transcriptional processing result of pre-mRNA after intron excision
passes from the nucleus to the cytoplasm through a nuclear pore complex and then binds to ribosomes
58
ribosomes
organelles that synthesise proteins using the mRNA strand as a template to determine the specific amino acid sequence of the protein
59
translation
the act of using the mRNA strand as a template to synthesize the specific amino acid sequence of the protein
60
ribosomal RNA
rRNA
molecules that make up a strand of RNA which in turn makes up one the two ribosomal subunits
61
transfer RNA
tRNA
molecules which add amino acids sequentially to a growing peptide chain by reading the mRNA found in a ribosome
62
ribozymes
RNA molecules found in ribosomes that catalyze peptide bond formation between amino acids
63
polyribosomes/polysomes
small circular aggregations that are formed by a single strand of mRNA with ribosomes attached along its length.
64
rough endoplasmic reticulum
rER
the portions of the endoplasmic reticulum which are studded with ribosomes
65
Functions of the rough endoplasmic reticulum
Synthesize proteins destined for export, integral membrane proteins, and lysosomal proteins
[either going outside the cell wall, inside the cell wall, or within a new cell wall (as lysosomes are essentially vesicles with digestive enzymes)]
helps fold many proteins into the tertiary structure, forming intrachain disulfide bonds and performing the first steps of glycosylation
66
free ribosomes functions
synthesizing proteins destined for the cytoplasm, nucleus, and mitochondria
[within the cell membrane, within the nuclear membrane, or within the mitochondrial membrane]
folding and other post-translational modifications also take place there
67
ubiquitin
protein which binds to (some) proteins that are damaged or no longer required by the cell as the first step in the process of degrading the damaged proteins into short peptides
68
proteasomes
non–membrane bound arrays of proteolytic enzymes which respond to a signal of ubiquitin binding to damaged or no longer required proteins for degradation into short peptides
69
smooth endoplasmic reticulum
sER
continuous with and similar to rER except that it lacks ribosomes
70
smooth endoplasmic reticulum functions in most cells
lipid biosynthesis (cholesterol), and membrane synthesis and repair (phospholipids synthesis)
In most cells, involved in the storage and release of Ca 2+ ions (an important mechanism of cell signaling)
71
smooth endoplasmic reticulum functions in muscle cells
in muscle cells, the sER is called the sarcoplasmic reticulum. The release and reuptake of Ca 2+ ions by the sER activates the contractile mechanism of the muscles
72
smooth endoplasmic reticulum functions in liver cells
in liver cells, sER is rich in cytochrome P450 and plays a major role in the metabolism of glycogen and detoxification of various noxious metabolic by-products, drugs, and alcohol
73
lysosomes
membrane-bound organelles which contain degradative enzymes which can digest proteins not degraded by proteasomes
74
passive diffusion
type of transport that is dependent on the presence of a concentration gradient across the membrane and also on the size and polarity of the molecule
(e.g. lipids/lipid-soluble molecules and gases like O2, N, and CO2 passively diffuse freely)
75
facilitated diffusion
type of transport that involves the movement of polar/charged/hydrophilic molecules (e.g. water, ions, glucose, amino acids, etc.) passively down an electrochemical gradient with the use of protein carrier molecules
76
two types of intermembrane protein carrier molecules
pore/channel - forms a water-filled channel across the membrane through which selected molecules/ions can pass depending on concentration, size, and electrical charge. Can be gated (i.e. the pore is open or closed depending on different physiological conditions)
transporter/carrier - binds a particular molecule/ion and then undergoes a change in conformation, moving the substrate to the other side of the membrane
77
active transport
type of transport that is independent of electrochemical gradients, and often operates against extreme electrochemical gradients
E.g. Na+-K+ ATPase
78
bulk transport
transport of large molecules or small particles into, out of, or between compartments within the cell that is mediated by subcellular, transient membrane-bound vesicles
E.g. endocytosis, exocytosis, and intracellular transport vesicles
79
transport vesicles
formed by the assembly of a protein ‘coat,’ leading to the budding of a section of the membrane which is pinched off to form a vesicle
at their destination, the reverse process takes place when the transport vesicle fuses with the target membrane, incorporating into it and releasing its contents
80
Golgi apparatus functions
an important site of protein and lipid glycosylation
the site of synthesis of many glycosaminoglycans that form the extracellular matrix
81
cisternae
4 to 6 saucer-shaped membrane-bound sacs with make up the Golgi apparatus
82
cis and trans Golgi network
CGN and TGN, respectively
a network of tubules comprised of the Golgi apparatus' outermost cisternae
83
coated vesicles
the transport method of proteins synthesized in the rER to the Golgi apparatus; created by the coat protein complex II
84
coat protein complex II
COP II
the proteins responsible for the formation of vesicles from the endoplasmic reticulum (coated vesicles) which transport proteins to the Golgi apparatus
85
coat protein complex I
COP I
the coated vesicles which pass proteins (not very large ones) from cisterna to cisterna through the Golgi apparatus
86
secretory granules
secretory vesicles of the Golgi apparatus which became increasingly condensed as they migrated through the cytoplasm into these matured granules
expelled through exocytosis
87
SNAREs
a group of membrane proteins that regulate docking and the fusion of coated vesicles to their target membrane
[these proteins enSNARE vesicles into the membrane]
88
constitutive secretion
secretory vesicles are delivered to the cell membrane after they are formed, and the protein product is IMMEDIATELY released; continuous exocytosis which is not regulated, it just goes from Golgi to wall without guidance
happens in all cells, required to maintain the cell membrane
89
regulated secretion
signal-dependent exocytosis
occurs in specialized secretory cells (e.g. digestive enzymes into the duodenum)
90
porosome
a transient opening that occurs after the secretory granules dock with the plasma membrane and through which the secretory product is discharged
91
endocytosis
the collective name for the variety of processes by which cells take up particulate matter and large macromolecules
92
phagocytosis
a form of endocytosis that is used by specialized phagocytic cells to ingest particulate matter (e.g. bacteria, fungi, apoptotic cells), usually larger than 0.5 µm
93
pinocytosis
a form of endocytosis that is used by all cells to take up fluid and solutes
94
clathrin-mediated endocytosis
takes place continuously, with clathrin-coated pits constantly forming and pinching off to form coated vesicles to take in extracellular fluid and molecules, or specific molecules which bind to certain cell surface receptors
[clathrin-mediated is constantly-making vesicles]
95
clathrin-coated pits
areas of the plasma membrane which constantly form and pinch off to form coated vesicles
96
clathrin
binds to specialized areas of the plasma membrane and shapes them into vesicles, thus the cell takes up extracellular fluid and molecules
97
sorting endosomes
dynamic tubulovesicular structures, usually found close to the plasma membrane, with which clathrin-coated vesicles fuse
98
recycling endosomes
receive most of the membrane and its intrinsic receptors after dissociation of receptors and ligands taken in by endocytosis, and then shuttle the contents back to the cell surface
99
multivesicular body
sorting endosome that is moved towards the Golgi apparatus where it becomes a late endosome and fuses with a lysosome
100
late endosome
what multivesicular bodies become after they are moved towards the Golgi apparatus, after which they fuse with lysosomes for degredation
[late = death of contents]
101
endolysosomes
the degradative enzymes within the lysosomes
102
transcytosis
the process when vesicles leave the sorting endosome and migrate to another part of the cell membrane, such as the basal membrane of an epithelial cell. There, the vesicle fuses with the plasma membrane, releasing its contents to the extracellular space
used in the GI tract for absorption of nutrients from food
103
neutrophil
specialized phagocytic cell
104
macrophage
specialized phagocytic cell
105
pseudopodia
the initial step of phagocytosis wherein extensions of the cell surface that form when bacterium binds to cell surface receptors, extending around the organism until they fuse
106
phagosome
when pseudopodia have fused around a bacterium and the bacterium is engulfed in a membrane-bound pocket within the cytoplasm during phagocytosis
107
phagolysosome
the membrane-bound pocket that occurs when a phagosome fuses with a lysosome
subjects the bacterium to the toxic activities of the lysosomal enzymes, which also break down the components of the dead bacteria, which may be released into the cytoplasm, exocytosed from the cell, or remain in the cytoplasm as a residual body
108
residual body
the components of the dead bacteria that remain in the cytoplasm after bacterium is degraded within a phagolysosome
109
autophagy
the degradation of cellular organelles by lysosomes
110
lipofuscin granules
with advancing age, residual bodies accumulate in the cells of some tissues from phagocytosis and appear as these brown granules
111
microfilaments
extremely fine strands (5 to 9 nm in diameter) of the protein actin
112
actin
makes up microfilaments and each actin filament (F-actin) consists of two protofilaments twisted together to form a helix
113
protofilaments
consist of multiple G-actin (globular actin) monomers joined together head to tail and associated with ATP molecules to provide energy for contraction
114
cell cortex
a robust supporting meshwork beneath the plasma membrane, formed by actin in association with various transmembrane and linking proteins, which protects against deformation and yet can be rearranged to accommodate changes in cell morphology
115
actin functions
comprises microfilaments and the skeleton of certain membrane specializations, such as microvilli
plays a central role in cell movement, pinocytosis, and phagocytosis
may also bind to intrinsic plasma membrane proteins to anchor them in position
116
intermediate filaments
proteins which have a purely structural function and consist of filaments that self-assemble into larger filaments and bind intracellular structures to each other and to plasma membrane proteins [they intermediate btw structures and PMP's]
they are intermediate in size between microfilaments and microtubules (approximately 10 nm in diameter)
117
keratin/cytokeratin
an intermediate filament family that is characteristic of epithelial cells, where they form a supporting network within the cytoplasm and are anchored to the plasma membrane at intercellular junctions
118
vimentin
intermediate filament found in cells of mesodermal origin
119
desmin
intermediated filament found in muscle cells (skeletal, smooth, and cardiac)
associated with desmosomes in the heart
120
neurofilament proteins
intermediate filament found in nerve cells and glial fibrillary acidic protein in glial cells
121
lamin
intermediate filaments that form a structural layer on the inner side of the nuclear membrane
122
microtubules
comprised of globular protein subunits which can readily be assembled and disassembled to provide for alterations in cell shape and position of organelles
much larger than microfilaments (25 nm in diameter)
123
the two types of microtubule subunits
α- and β-tubulin, which polymerise to form a hollow tubule; when seen in cross-section, thirteen tubulin molecules make up a circle
124
centriole
specialized microtubule organizing center from where microtubules originate, and it is found in the centrosome
125
how may microtubule movement be effected
by the addition or subtraction of tubulin subunits from the microtubules, making them longer or shorter
126
microtubule-associated proteins (MAPs) function
stabilise the tubular structure of microtubules and include capping proteins
127
capping proteins
a part of microtubule-associated proteins (MAPs) that stabilise the growing ends of the tubules
128
dynein
motor protein which moves along microtubules towards the cell center
129
kinesin
motor protein which moves along microtubules away from the cell center
130
centrosomes
consisting of a pair of centrioles, each of nine triplets of microtubules, and the centrosome matrix or pericentriolar material, which organizes the microtubules of the cell spindle during cell division
131
microtubules in cilia
nine pairs of microtubules form a cylindrical structure and movement occurs by rearrangement of chemical bonds between adjacent microtubule pairs
132
diplosome
a pair of centrioles
133
aster
the star-like arrangement created when microtubules radiate outwards from the centrioles during cell division
134
cellular respiration
the process during which the sequential breakdown of organic molecules creates a continuous supply of energy for cells; results in energy stored in the form of ATP molecules
135
glycolysis
cellular respiration of glucose that begins in the cytosol, where glucose is partially degraded to form pyruvic acid, yielding a small amount of ATP
136
anaerobic respiration
glycolysis that occurs in the absence of oxygen
137
aerobic respiration
dependent on a continuous supply of oxygen and takes place within the matrix and on the inner membrane, a process enhanced by the large surface area provided by the cristae
138
adipose cells
fat cells where triglycerides are stored
139
outer membrane of the mitochondria
this layer relatively permeable due to the protein porin, which allows free passage of small molecules
also contains enzymes that convert certain lipid substrates into forms that can be metabolised within the mitochondrion
140
inner membrane of the mitochondria
thinner than the outer membrane, this layer is thrown into complex folds and tubules called cristae that project into the inner cavity
in some cell types, mitochondria typically have tubular cristae
141
inner cavity of the mitochondria
filled by the mitochondrial matrix
142
mitochondrial matrix
fills the inner cavity of the mitochondria and is the site of the mitochondrial DNA and ribosomes
contains most of the enzymes involved in oxidation of fatty acids and the Krebs cycle
also contains a number of dense matrix granules, the function of which is unknown
143
intermembranous space of mitochondria
the space between the outer and inner membranes which contains a variety of enzymes
144
porin
a pore-forming protein that which allows free passage of small molecules through the outer membrane of mitochondria
145
cytochromes
the carrier molecules of the electron transport chain, and the enzymes involved in ATP production found in the inner membrane of mitochondria
146
unusual features of mitochondria
Unique DNA - the mitochondrial matrix contains one or more circular strands of DNA resembling the chromosomes of bacteria
Unique ribosomes - contains ribosomes with a similar structure to bacterial ribosomes
Self-Protein synthesis - mitochondria synthesize 13 of their own constituent proteins, others being synthesised by the usual protein synthetic mechanisms of the cell and imported into the mitochondrion
Self-Replication - mitochondria undergo self-replication in a manner similar to bacterial cell division
147
hepatocytes
liver cells
148
β particles
irregular single granules that form when plentiful glycogen granules are present
149
glycogen rosettes
also called α particles, appear as aggregations that form when plentiful glycogen granules are present
150
peroxisomes/microbodies
present in all cells but have different functions in different cell types and in the same cell type in different species
broadly speaking, peroxisomes perform enzymatic oxidation and contain a range of oxidative enzymes
151
peroxisomes/microbodies functions
β-oxidation of certain long chain fatty acids
some steps in the synthesis of plasmalogens (lipids found in the myelin sheath of nerve axons) and some steps in the synthesis of bile acids (in the liver)
creates hydrogen peroxide as a by-product during some reactions and then use catalase to utilize the hydrogen peroxide to detoxify other substances, such as phenols and alcohol by peroxidation
152
lipofuscin
an intracellular pigment which probably represents an insoluble degradation product of organelle turnover
with increasing age, it accumulates as brown, granular material in the cytoplasm
153
melanin
an intracellular
