Cells and Organelles Flashcards
What is the role of the plasma membrane?
The plasma membrane encloses the cell contents and provides a barrier between the inside of the cell and the extracellular environment
What makes the phospholipid bilayer an effective barrier?
The amphipathic nature of the phospholipids
What is the role of carbohydrates and where are they found on the cell membrane?
Carbohydrates are found on the extracellular surface and allow cells to be recognised
What is the role of proteins and what are the 2 different types?
Proteins provide a passage and allow molecules to pass through.
Integral: allow transfer of molecules across the membrane (pump, carrier, channels)
Receptor: Ligands such as EGF bind to receptor
What is glycocalyx?
A coating of carbohydrates on the cell surface
What are lipid rafts and what is their role?
Lipid rafts are regions enriched in particular phospholipids and cholesterol.
They act as signalling platforms to direct proteins to receptors
What is the role of cholesterol in cell membrane?
It regulates fluidity of the cell membrane
Describe the nuclear membrane
It is a double membrane
What is nuclear lamina made of and what is its role?
It is made up of intermediate filaments
It provides mechanical support to the membrane and helps to position nuclear pores
What is the role of nuclear pores?
They let molecules pass through
Name and describe the four components of mitochondria
Outer membrane: selectively permeable to let pyruvate come in for Krebs’ cycle
Inner membrane: folded into multiple cristae, involved in ETC
Matrix: contains enzymes for the CaC
Intermembrane space: creates a gradient for the ETC
What are the 2 function of the mitochondria?
● The site of energy production in cells.
● Triggers cell apoptosis – When irreparable DNA damage occurs, Cytochrome C which resides in mitochondria and participates in the ETC is released into the cytoplasm to trigger a proteolytic (breaking down proteins) caspase cascade to achieve apoptosis.
What is the endoplasmic reticulum?
Flattened membrane which is continuous with the nuclear membrane
Name and describe the role of the 2 types of ER?
Rough ER: site of protein synthesis as it is covered in ribosomes
Smooth ER: Involved in lipid synthesis and calcium storage
Give an example of where rough and smooth ER can be found
Hepatocytes (liver cells) have smooth ER for lipid synthesis
Fibroblasts have ROUGH ER to produce the protein, collagen.
What is the role of the Golgi apparatus? What process occurs there?
It sorts proteins.
Proteins arrive from the ER in vesicles, they pass through the golgi stack and undergo ENZYMATIC MODIFICATION which labes them for a specific location.
Name the 3 vesicles found in the cell cytoplasm
Lysosomes
Endosomes
Peroxisomes
Describe lysosomes
They are vesicles containing hydrolytic enzymes, they degrade unwanted particles.
Describe endosomes
They are vesicles transporting molecules from the plasma membrane to lysosomes
Describe peroxisomes
vesicles containing enzymes involved in oxidative
reactions e.g. biosynthesis of bile acids, detoxification, fatty acids metabolism
Describe the role of cytoskeleton
Allows movement of cell components
Provides structure and support to cell
Provides mechanical linkages which allow tissue to bear stress
Allows cell to adopt different behaviours e.g. migration, division, growth
What are the 3 types of cytoskeletal filaments
Microtubules
Intermediate filaments
Microfilaments
Describe microtubules and the 3 roles they’re involved in
Microtubules are cylindrical tubes of tubulin.
Involved in:
● chromosomal movement - motor proteins dynein (moves cargo towards centrosomes) and kinesins (move cargo away from centrosomes)
● motility of cilia and flagella
● vesicle and organelle movement
Describe the 4 different intermediate filaments and where they’re found. What are the roles of Intermediate filaments?
Keratin (in keratinocytes)
Vimentin (in fibroblasts of the dermis)
Lamin (in nuclear lamin)
Desmin (in cardiac muscle)
Involved in nuclear membrane support, chromatin and nuclear organisation
What are 4 of the roles of Microfilaments?
● Cell projections e.g. stereocilia, microvilli
● Cytoplasm e.g. cell contraction, shape change
● Contractile ring e.g. cytokinesis
● Membrane extensions e.g. lamellopodia, filopodia
What cytoskeletal component do cilia and flagella contain? What does this allow them to do and what is it primarily composed of?
They contain axoneme.
This allows them to bend and it is primarily composed of microtubules.
Describe Tay Sach’s disease
Lysosomal storage disorder where lysosomes don’t break down lipids. This causes a build-up of lipids which destroy neurons; therefore causes progressive damage to the nervous system.
Describe Kartageners syndrome
Defects in cilia and flagella due to mutations in dynein microtubule. Causes recurring respiratory infections as mucus not cleared efficiently and male infertility due to immotile sperm.
What is Vohvinel syndrome?
Defective GAP junctions due to a recessive mutation in connexin protein. This causes thick, honeycomb-like calluses
Describe Epidermolysis Bullosa Simplex
Defective intermediate filaments in hemidesmosomes causes lack of integrity at the dermo-epidermal junction.
This causes blistering.
