Anatomy of the Cell (1) Flashcards
Describe composition of membranes, and their role in enclosing the cell and in establishing compartments within the cell Describe the basic morphology and function of the nucleus and cell organelles 3. Describe the cytoskeleton helps to maintain cell shape and integrity and leads to cell locomotion and contraction 4. Describe intercellular junctions in providing tissue integrity and in cell- to-cell communication
Describe the Composition of a Cell
in terms of water, protein, lipids, carbohydrates + inorganics.
Water 80%
Protein 15%
Lipid 2.5%
Carbohydrates 1.5%
Inorganic 1.0%
List 5 features common to all eukaryotic cells
an outer membrane.
an inner cytosol
a cytoskeleton
membrane bound organelles
inclusions
What is the cytosol?
a solution of proteins, electrolytes & carbohydrates. It has both fluid and gel-like properties
What is the cytoskeleton?
The cytoskeleton determines the shape and fluidity of the cell.
It is made from:
* thin filaments
* intermediate filaments
* microtubules
What are inclusions?
Other structures within the cytoplasm
may or may not be bound by a membrane
synthesised by the cell itself e.g.:
* pigment
* glycogen stores
* lipid droplets
from extracellular environment (endocytotic vesicle)
Describe amphipatic phospholipid position
in the plasma membrane
-Hydrophilic heads (choline and phosphate) at the outer and inner surfaces.
-Hydrophobic fatty acid chains facing towards the middle of the 2 layers.
List 5 examples of integral proteins
(proteins which the cell inserts into the membrane)
-receptors
-channels
-transporters
-enzymes
-cell attachment proteins
What is meant by the term selectively permeable?
The cell membrane is selectively permeable
Highly permeable to: water, oxygen, small hydrophobic molecules.
Virtually impermeable to charged ions (e.g. Na+)
Controls exocytosis and endocytosis of material through the cell membrane
Give a brief description of the function of the main organelles
Mitochondria, RER, SER, Golgi apparatus, Lysosomes, Nucleus
Mitochondria - (energy production)
Rough endoplasmic reticulum - (protein synthesis)
Smooth endoplasmic reticulum - (cholesterol & lipid synthesis/detoxification)
Golgi apparatus - (modification & packaging of secretions)
Lysosomes – (hydrolytic enzymes for intracellular digestion)
Nucleus – (contains genetic code/ DNA)
What are the 3 main classes of filements?
Microfilaments:
Intermediate filaments
Microtubules
Describe Microfilaments
Microfilaments:
-(7 nanometres in diameter)
-composed of the protein actin
-Globular (G) actin polymerizes to form filamentous (F) actin
-(F) actin can dissociate making them very dynamic cytoskeletal elements
Describe Intermediate Filaments
Intermediate filaments:
-(>10 nanometres in diameter)
-composed of 6 main proteins (vary in different cell types)
-identify tumour origins
Describe Microtubules
size + composition
Microtubules:
-(25 nanometres in diameter)
-Hollow tubule composed of two types of tubulin subunits, α & β in an alternating array.
-Can be assembled and disassembled
-Originate from a special organising centre called the centrosome.
-Include stabilizing proteins: microtubule-associated proteins (MAPS)
-Polar
-Serve as the ‘motorway’ network (dynein and kinesin attach and move along them)
Breif description of Kinesin + Dynein (actins)
Kinesin- ATPase that moves toward the cell periphery.
Dynein- ATPase that moves toward the cell centre.
What is the nuclear envelope?
+ pores
Nuclear envelope:
- Encloses nucleus
- Inner and outer nuclear membrane with the perinuclear cistern in the middle
- Outer nuclear membrane is studded with ribosomes
- Nuclear pore to allow the transport of molecules across the nuclear envelope
What is the role of the Nucleus?
+ nucleolus
The nucleus contains chromosomes and is the location of RNA synthesis.
Both mRNA and tRNA are transcribed in the nucleus, and rRNA (ribosomes) is transcribed in the nucleolus, a 1-3µm diameter dense area within the nucleus
Describe the 2 types of chromosomes in the Nucleus
- Euchromatin: DNA is more dispersed and undergoing transcription
- Heterochromatin: DNA highly condensed and not undergoing transcription
Is this image the RER or the SER?
RER
Is this image the RER or the SER?
SER
What is the function of the Golgi Aparatus?
Golgi apparatus:
- Composed of a group of flattened, membrane bound cisternae
- Transport vesicles arrive at Golgi from SER; Golgi modifies (PTM) and packages them by:
- Adds sugars
-Cleaves some proteins
-Sorts macromolecules into vesicles.
Describe the Mitochondria
functions + composition
Function:
-Power generators of the cell (generation of ATP via oxidative phosphorylation)
-Synthesis of certain lipids and proteins
Composition:
-Outer and an inner membrane
-The inner membrane is extensively folded to form cristae (increase the available surface area)
-Contain their own DNA and system for protein production
What are the 3 Intercellular Junctions
Occluding
Anchoring
Communicating
What is an Occluding Junction?
-Tight Junctions
-Zonula occludens (ZO).
-Prevent diffusion.
-Appear as a focal region of close apposition between adjacent cell membranes.
What is a Communicating Junction?
-Gap junctions
- Allow movement of molecules between cells
- Each junction is a circular patch studded with pores
What is an Anchoring Junction?
-provide mechanical strength
-3 types (Adherent junctions, Desmosomes, Hemidesmosomes)
