Cell Structure Flashcards
features of absorbative cell
microvilli
many cell junctions
What is a Cytoskeleton?
A dynamic (changes rapidly) system of protein filaments in the cytoplasm of a eukaryote that gives the cell shape and the capacity for movement of substances
What is diapedesis?
The crawling of cells along a surface
allows the passage of white blood cells through capillary walls into the tissues.
What are the functions of the cytoskeleton?
Responsible for:
Large-scale cellular movements such as diapedesis and cytokinesis and muscle cell contraction
Changes in cell shape and fluidity that accompany embryonic development
Also provides machinery for intracellular movements e.g movement of organelles/vesicles and anaphase
What are the 3 intracellular movements that involve the Cytoskeleton?
Transport of organelles from one place to another
Segregation of chromosomes into 2 daughter cells during anaphase of mitosis
cytokinesis
What are the three types of protein filaments within the cytoskeleton?
Microtubules
Intermediate Filaments
Actin Filaments
What are the characteristics of Microtubules?
They are…
long stiff, cylindrical intracellular structures
20nm diameter
composed of tubulin protein
grow out of the centrosome and create a system of tracks for transport vesicles, organelles and other cells components
Utilize motor proteins for movement
What are motor proteins?
proteins that bind to organelles within a cell and move them along microtubules (and sometimes actin filaments)
What are the characteristics of Intermediate Filaments?
Intermediate in size
10nm in diameter
Stable rope-like polymers
Made of fibrous proteins which give mechanical strength
STRONGEST OF THE 3 CYTOSKELETON PROTEINS!
Also found in the nucleus under the nuclear envelope (forming the nuclear lamina)
attach organelles to each other or organelles to the cell membrane
Which type of protein filament is rope-like and forms a nuclear lamina under the nuclear envelope of a cell - therefore strengthening the envelope?
Intermediate filaments
True or False
Protein filaments participate in cell junctions
True
What are the characteristics of Actin Filaments (microfilaments) ?
Small
made of filamentous protein
formed from a chain of globular actin molecules
Found in cross-linked bundles and networks (stronger)
Forming contractile skeleton in cell
used in muscle contraction
involved in regulating cell shape
What are integrins?
Cell surface receptors that attach cells to the extracellular matrix and mediate mechanical and chemical signals
Which protein filament type forms the cell cortex?
Actin Filaments in a network of cross-linked bundles
What are Cell Inclusions?
various nutrients or pigments that can be found within the cell, but do not have activity like other organelles. Examples of cell inclusions are glycogen, lipids, and pigments such as melanin
can be cell products or ingested material
What are the 4 types of cell inclusions?
Glycogen
Lipids
Pigment Granules
Secretory Granules
What is glycogen?
a large branched polysaccharide found in the cytoplasm of several cell types including liver and muscle
What are lipids?
non-membrane bound droplets in the cytoplasm that vary in size
Require special stain to see with LM
What are the 2 types of lipid cell inclusions?
Neutral
Metabolic
Give an example of Neutral Lipid Cell Inclusions and where they are found in the body
Triglycerides
stored in adipose tissue
Give an example of metabolic lipid cell inclusions and where they are found in the body
Steroids as a substrate for estrogen or cortisol
What are pigment granules?
Melanin (to block UV damage)
heme (oxygen transport)
What are secretory granules?
membrane bound vesicles that contain inactive enzymes, proteins and neurotransmitters
What is the nuclear envelope?
The envelope surrounding the nucleus which consists of 2 lipid bilayer membranes and is perforated by nuclear pores
the membranes are continuous with the ER (although structurally different)
What is the nuclear lamina?
a network of protein filaments that support the nuclear envelope
What do the nuclear pores on the nuclear envelope do?
- Actively transport selected molecules to and from the cytoplasm
- Critical role in regulating gene expression
- ringed by many proteins
What is the Nucleolus?
non-membrane bound
the region of the nucleus where different chromosomes carrying genes for ribosomal RNA cluster (1 per nucleus) are found
site of production of rRNA
Contains both granular and fibrous material
role in cell cycle regulation / sensor for DNA damage
features of secretory cells
cell membrane structure / function
phospholipid bilayer that is formed spontaneously
hydrophobic tails face inwards and are shielded by hydrophilic groups which face outwards on either side
fluid allowing lateral diffusion of membrane proteins and cell mobility
highly permeable to water oxygen and small hydrophobic molecules e.g ethanol
impermeable to large and/or charged ions
cell-cell and cell-ECM adhesions (interactions)
components of cell membrane
50% phospholipids
cholesterol reduces fluidity and improves stability
define pinocytosis
when cells take up fluid and small molecules to form small vesicles by budding
define potocytosis
type of receptor-mediated endocytosis
define endocytosis
general process
when cells ingest large molecules to form endosomes (membrane bound vesicle)
define phagocytosis
type of endocytosis
when cells ingest large solid particles to form a phagosome
exocytosis
opposite of endocytosis
fusion of vesivles with membrane to discharge its contents
buds if cell membrane may also pinch off to form extracellular vesicles that acts as transport vesicles
mitochondria functions and structure
site of energy production via oxidative phosphorylation and ATP production
metabolism of amino acids and lipids
biosynthesis of haem and Fe-S clusters
act as a sensor for health of cell and trigger apoptosis
Outer (double) membrane smooth
Inner (double) membrane folded to form cristae
Two compartments: Outer compartment & Inner matrix
difference between cilia/flagellae and microvilli
- Cilia (and flagellae): extensions of the microtubule cytoskeleton that actively move
- Microvili : extensions of the actin microfilament cytoskeleton, no active movement. they act to increase surface area
structure of cilia
microtubule core
Each cilium contains nine pairs of microtubules forming the outside of a ring, and two central microtubules
known as 9 + 2 arrangement
microtubules joined by nexin
Between the nine outer pairs are motor proteins called dynein which allow the movement
coated in plasma membrane
structure of centrioles
Centrioles are cylindrical structures, found in animal cells
groupings of microtubules arranged in a 9 (triplets) + 0 pattern
help to organize the assembly of microtubules during cell division
difference between cell cortex and cytoskeleton
cell cortex provides support to the plasma membrane whereas the cytoskeleton maintains the overall shape of the cell
tight junctions
•act as barriers, preventing the passage of substances between adjacent cells
- Help maintain position of membrane proteins (called polarity)
- found near top of cells
adherens junctions
attach cells to each other and to the cytoskeleton
e.g •zonula adherens (actin extension)
and desmosomes (intermediate fillaments extension)
Hemidesmosomes
•type of anchoring junction
- they attach epithelia to the basement membrane and hence to the tissues beneath e.g. skin
•Made of integrins, laminin, collagen (all ECM proteins)
gap junctions
allow direct communication between adjacent cells
permits coordinated cell activity e.g cardiac cycle
consist of connexins which together form connexons
junctional complexes
how are the different junction types arranged within a cell?
tight junction , adherens junctions/gap junction , anchoring junctions
top of cell bottom of cell
RER and SER
ER = series of flatenned membranous channels and vesicles
RER is covered by ribosomes that produce proteins for export
involved in synthesis, folding, modification, and transport of proteins.
SER involved in lipid synthesis and export of large molecules
golgi apparatus
series of flattened membrane sacs
processes and packages and sorts proteins received from ER into membrane bound vesicles
lysosome
vesicle containing digestive enzymes which are kept separated by membrane.
Destroys material from outside & within cell
Produced from ER and Golgi Apparatus
Acid pH inside
peroxisome and proteosome
special type of lysosomes containing catalase, converts hydrogen peroxide (toxic) to water (harmless)
proteosome - degrades ubiquitinated (degraded) proteins
Differences between eukaryotic and prokaryotic cells
Prokaryotic cells Eukaryotic cells
(bacteria, mycoplasmas, (other algae, fungi, protozoa,
blue-green algae) multicellular plants and animals)
- Size 0.1-5.0 µm - allows ions and organic molecules that enter them to quickly spread to other parts of the cell
- Size ranging from 10–100 µm – requires more complex organelles and cytoskeleton
- No nuclear envelope
- Prominent nuclear envelope
- No nucleoli
- Nucleoli present
- No histones
- DNA complexed with histones
- Few intracellular membranes
- Many membrane-bound organelles
- 60-70s ribosomes
- 70-80s ribosomes
