introduction to cell and organelles Flashcards
What is a cell ?
The basic unit from which living organisms are made consisting of an aqueous solution of organic molecules enclosed by a membrane
What is the difference between eukaryotic cels and prokaryotic cells ?
Eukaryotic cells are organised and compartmentalised with membrane bound organelles
What can be found in a basic human cell
Nucleus
Endoplasmic reticulum
Golgi apparatus
Mitochondria
Plasma membrane
Peroxisomes and lysosomes
Cytoskeleton
What are organelles
Sub cellular compartments
Localise cell function
Usually membrane bound -> ribosomes exception
Specialised for unique functions
What is the nucleas ?
The largest organelle in the cell an contains genetic material of cell (dna) in form of chromosomes
What are chromosomes
Chromatin associated with histones
Each chromosome -> contains number of genes joined end to end with each gene coding for structure of single protein
The genetic blue print for all proteins (structural and enzymes) is contained where ?
The nucleas
What are the key features of the nucleas and label them
What is the function of nuclear membrane (nuclear envelope)
Double membrane layer that acts as a barrier that separates contents of nucleus from the cytoplasm
What is the structure of nuclear membrane
Inner and outer membrane
Phospholipid bilayers
Outer membrane is continuous with rough ER
Inner membrane contains nuclear lamina
What is the nuclear lamina
Structural mesh
Underneath nuclear membrane
Consists of intermediate filaments called lamins that link inner membrane proteins
Provide support
What is the nuclear pore and its function ?
Protein lined channel in the nuclear envelope.
Each nuclear pore complex consists of 30 proteins (nucleoporins)
Regulates transportation of molecules between nucleas and cytoplasm
What is the nucleolus ?
Spherical structure found in cells
Site of ribsomal rna synthesis
Production of ribosomes and ribosomal assembly
What are the main components of a plasma membrane ?
Phospholipid bilayer
Cholesterol
Carbs
Proteins
Lipid/ membrane rafts
What is the function of the plasma membrane ?
Form a barrier between each cell and its environment
Partitions cytoplasm of eukaryotes into compartment.
Ion gradients are maintained.
Explain the phospholipid bilayer ?
Thin polar membrane made up of two layers od phospholipid molecules
Explain phospholipid molecules
Amphiphilic
Consist of polar, hydrophilic head
Non polar hydrophobic tail
Form bilayer in aqueous solution
Hydrophilic heads directed outwards + hydrophobic forced together inwards
What do weak intermolecular forces of phospholipid allow it to do ?
Individual phospholipids can move freely between layers
What is the role of cholesterol in the bilayer
1:1 ratio with cholesterol
Amphiphillic
Prevent overpacking of phospholipid fatty acid tails
Stabilise an regulate fluidity of phospholipid bilayer
What is the importance of membrane proteins ?
Cell to cell adhesion
Cell-matrix adhesion and intercellular signalling
Membrane lipids and proteins can also conjugate with what ?
Polysaccharides to form glycoproteins or glycolipids
What does mitochondria have its own of ?
Genome -> always inherited from mother
Explain the outer membrane of the mitochondria
Relatively permeable
Allows free passage of small molecules
Explain the inner membrane
Thinner than outer
Has complex folds and tubules called Cristae-> provide large surface area
Explain the inter membrane space ?
Between the two membranes
Contains cytochrome c
Contains enzymes important in the etc chain
Explain the mitochondrial matrix
Site of mitochondrial DNA and ribosomes
And contain enzymes for TCA cycle
What are functions of mitochondria
ATP production and apoptosis
Explain apoptosis
Release of cytochrome c from mitochondria to cytosol
Initiates apoptosis
- occurs when cells detect significant DNA damage
What is the function of rough ER
Associated with ribosomes
Protein synthesis
Protein folding
Protein modifications
What is the function of smooth er
It is not dotted with ribosomes
Lipid synthesis
Calcium storage
Explain the structure of the Golgi apparatus
A stack of flattened membrane bound sacs called cisternae
With vesicles
Briefly describe function of Golgi apparatus
Proteins received from ER
Modified and stored for eventual destination in the cell
What is the function of lysosomes
Degrade unwanted molecules
Contain approx 50 degradative enzymes
Optimal ph 5 - therefore only work in acid environments
What are peroxisomes ?
Membrane bound organelles
Present in all cells but have different functions in different cell types
What is the function of peroxisomes
Perform enzymatic oxidation and contain a range of oxidative enzymes such as catalase
Break down of fatty acids in b oxidation
What is the cytoskeleton
A framework of filaments and tubules
What is the function of the cytoskeleton
To organise cell structure
To maintain correct shape of the cell -> organise internal structure
Supports fragile plasma membrane
Provide mechanical linkages that let tissue bear stress
Facilitate movement of organelles
Allows cell to adopt specific behaviours
What specific behaviours does the cytoskeleton allow
Growth, division, motility
What are the three types of cytoskeleton
Microtubles
Micro filaments
Intermediate filaments
What are classed as the dynamic type of cytoskeleton
Microtubles and microfilaments
What is classed as stable filaments ?
Intermediate filaments
Explain intermediate filaments ?
Play a structural role
Provide mechanical strength
Consist of filaments that self assemble into larger filaments and bind to intracellular structures to each other ad to plasma membrane proteins
What are the different intermediate filaments
Keratin family found in epithelial cells
Vimentin found in fibroblasts
Lamins found in nuclei of all eukaryotic cells
Where are intermediate filaments found in terms of the skin
What does the nuclear lamina provide ?
Nuclear organisation
Nuclear membrane support
Chromatin organisation
Explain the structure microtubules
Dynamic structures
Larger than microfilaments
Made up of globular protein subunits to form polymers of either a and b tubulin
What is the function of microtubules
Cell movement
Intracellular transport of organelles
Forms mitotic spindle
Where do microtubules originate from ?
Specialised microtubule organising centre -> the centriole found in centrosome
What are microtubules also associated with ?
Motor proteins called kinesics and dyneins
What do kinesics and dyneins do
Motor proteins That attach to membranous organelles and move them about within cytoplasm
Kinesins - move cargo away from the centrosome
Dyneins - move cargo towards centrosome
Microtubules also Orem what structure
Cilia and flagella
What is the cytoskeletal compound of cilia and flagella called
Axonemes
What do axonemes allow
Bending when microtubules slide through dynein allowing bending force
In cilia how are microtubules arranged
Nine pairs of microtubules form a cylindrical structure
What are microfilaments ?
Polymers of actin
What are the functions of microfilaments
Skelton of actin filaments are found in specialisations such as microvilli
Membrane extensions -> lamellipodia and filopedia
Cell contraction and shape change
Cytokinesis
Form supporting network
Cell movement such as phagocytosis
Actin associates with transmembrane and linking proteins to form what ?
Cell cortex - supporting mesh work
Why do cell rarely function on their own ?
Because they work together cooperatively to perform a given function
How is aggregation of cells and integration of function possible ?
Through cell junctions
What are cellular junctions ?
Transmembrane protein complexes
What is the function of cellular junctions ?
Connect plasma membrane to adjacent cells
Basement membrane, cytoskeleton and extra cellular matrix
Briefly describe the extra cellular matrix ?
Molecules outside of the cell
What are samples of cell to cell junctions
Adherens and desmosomes
What is the function of adherens ?
Tissue integrity, motility, contractibility
What is the cytoskeleton in an adherens junction
Actin
What is the function of desmosome
Strong adhesion
Resist mechanical stress
What is the cytoskeleton of desmosmes made up out of
Intermediate filaments
What examples of cell-ecm junctions
Focal adhesions
And hemidesmosomes
What is the function of focal adhesions
Cell anchorage
What is the cytoskeleton of focal adhesions
Actin
Where can desmosomes be found
Epidermis
Where are focal adhesion junction used
Cell migration
What is the function of hemidesmosomes
Cell anchorage
What is the cytoskeleton of hemidesmosomes
Intermediate filaments
Where can hemidesmosomes be found ?
Dermal - epidermal junction
What is the overall function of tight junction
Function as gates and fences
Allow selective permeability and cell polarity
What is the function of gate
Regulation of paracellular activity
Movement of substances in between cells
What is function of the fence
Allow formation of apical (top side) and basolateral (bottom) intramembrane diffusion barrier
Stopped apical components mixing with components at the bottom
Where is tight junction found
Epidermis - it is polarised
Has distinct top and bottom
What is the function of GAP junction
Allows chemical and electrical communication
Allow passage of small molecules
What is the structure of GAP junction
Cell to cell contact
Composed of hexameters of Connexins
