Anatomy of the Cell Flashcards
What are the common features of all eukaryotic cells?
- outer membrane
- inner cytosol (cytoplasm)
- cytoskeleton
- membrane bound organelles
- inclusions
What is cytosol (cytoplasm) made up of?
Solution of proteins, electrolytes and carbohydrates
What is the function of the cytoskeleton?
Determines the shape and fluidity of the cell
What is the function of the plasma membrane?
Separates the cytoplasm from the outside environment
Describe the composition of the plasma membrane.
Bimolecular layer of amphipathic phospholipid molecules
Describe the orientation of the phospholipid molecules of the plasma membrane.
Hydrophilic heads pointing to the outer and inner surfaces.
Hydrophobic fatty acid chains facing towards middle of the 2 layers
List all the integral proteins which lie within the cell membrane.
- receptors
- channels
- transporters
- enzymes
- cell attachment proteins
True or false: A cell has the ability to exo and endocytose material through the cell membrane.
True
Describe what is meant by “the cell membrane is fluid”.
it can change its shape easily
not fixed in one rigid position
Are all proteins that lie in the cell membrane distributed equally?
No
Some of the membrane proteins can diffuse laterally along the cell membrane but most of the proteins are anchored.
What is the cell membrane permeable to?
- water
- oxygen
- small hydrophobic molecules
What is the cell membrane impermeable to?
charged ions (Na+)
Define organelle
Small, intracellular organs with specific functions and structural organisation
Are organelles essential to life
Yes
Where are organelles found in cells?
In the cytoplasm
List the organelles found in the cytoplasm.
- mitochondria
- rough endoplasmic reticulum
- smooth endoplasmic reticulum
- golgi apparatus
- lysosomes
- nucleus
What organelles contain DNA?
- nucleus
- mitochondria
Function of mitochondria
energy production
Function of rough endoplasmic reticulum
protein synthesis
Function of smooth endoplasmic reticulum
synthesis and detoxification of cholesterol and lipid
Function of golgi apparatus
modification and packaging of secretions
Function of lysosomes
produce hydrolytic enzymes for intracellular digestion
Function of nucleus
contains genetic code
Define cellular inclusions
Non living substances found within the cytoplasm that are not bound by a membrane
List some examples of cellular inclusions
- pigmentation
- lipids
- proteins
What are the 3 main classes of filament found in the cytoskeleton?
- microfilaments
- intermediate filaments
- microtubules
How do the cytoskeletal proteins create the cytoskeleton?
filamentous proteins become attached to cell membrane and each other by anchoring and joining proteins to form internal scaffolding
Features of microfilaments
- 7 nm in diameter
- composed of actin
What makes microfilament dynamic cytoskeletal elements?
actin molecules can assemble and later dissociate making them dynamic
Describe the features of intermediate filaments
- ~10 nm
- composed of 6 main proteins
- proteins vary in different cell types
What are the classes of intermediate filaments?
neurofilaments –> nerve cells
glial fibrillary acidic protein –> nervous glial cells
desmin –> muscle cells
cytokeratins –> epithelial cells
vimentin –> mesenchymal cells
filesin –> lens of the eye
lamin –> nuclei of all cells
Describe microtubules
- 25 nm in diameter
- composed of 2 proteins (alpha/beta)
- originate from centrosome
- can be assembled and disassembled
- contain MAPS (stabilising proteins)
What microstructures are microtubules important in?
- cilia
- flagella
- mitotic spindle
Define kinesin
ATPase that moves toward cell periphery
Define dynein
ATPase that moves toward the cell centre
What is the role of dynein and kinesin
important in movement of components in cells with long processes
attach to microtubules and move along them
Describe the nuclear envelope
- composed of inner and outer nuclear membrane
- nuclear pores provide continuity with cytoplasm
Describe the outer nuclear membrane
- studded with ribosomes
- continuous with cytoplasmic RER
What is the function of the nucleus?
- contains chromosomes
- location of RNA synthesis
- transcription of tRNA and mRNA
What does the nucleus contain?
- euchromatin
- heterochromatin
- nucleolus
Define euchromatin.
DNA that is more dispersed and actively undergoing transcription
Describe heterochromatin.
DNA that is highly condensed and not undergoing transcription
What is the function of the nucleolus?
transcription of rRNA
Describe the features of ribosomes.
- formed in the nucleolus
- instrumental in protein synthesis
Describe the structure of ribosomes
- small, RNA binding subunit
- large subunit that catalyses the formation of peptide bonds
Describe the structure of the endoplasmic reticulum
network of interconnecting membrane bound compartments in a cell
Describe the structure of the RER
studded with ribosomes
What is the role of the RER?
- synthesis of proteins destined for insertion into membranes or secretion
- associated with initiation of glycoprotein formation
What is the function of SER
- continues processing of proteins produced in the RER
- vital role as the site of lipid synthesis
Describe the structure of the golgi apparatus.
- group of flattened membrane bound cisternae
- arranged in sub-compartments
What is the function of the golgi apparatus?
- transport vesicles arrive at golgi from SER/RER
- cisterns function in modification and packaging of macromolecules that were synthesised in the ER
- adds sugars
- cleaves some proteins
Describe the structure of a mitochondria
- oblong/cylindrical
- inner and outer membrane
- inner membrane extensively folded to increase surface area
What is the function of the mitochondria?
- function in the generation of ATP via oxidative phosphorylation
- synthesis of certain lipids and proteins
- contains own DNA and system for protein production
Define intercellular junctions
specialised membrane structures which link individual cells together into a functional unit
Where are intercellular junctions most prominent?
in epithelia
What are the 3 types of junction?
- Occluding
- Anchoring
- Communicating
Define occluding junctions
- link cells to form a diffusion barrier
- appear as a focal region of close apposition between adjacent cell membranes
Define anchoring junctions.
- provide mechanical strength
- link sub-membrane actin bundles of adjacent cells via transmembrane cadherin molecules in the extracellular space
Describe desmosomes
- anchoring junction
- common in skin
- link sub-membrane intermediate filaments of adjacent cells
Define communicating junctions.
- allow selective diffusion of molecules between adjacent cells
- circular patch with pores produced by connexon proteins
What is a junctional complex?
close association of several types of junctions found in certain epithelial tissues
