Anatomy of Cell Flashcards
Describe the composition of each of the following components based on average, %range, and comment: water, protein, lipid, carbohydrate, and inorganic.
Water: 80%, 75-85%, 90% free/ 5% bound.
Protein: 15%, 10-20%
Lipid: 2.5%, 2-3%
Carbohydrate: 1.5%, ~1%
Inorganic: 1.0%, 1%
Describe the features common to all eukaryotic cells.
Outer membrane, inner cytosol (solution of proteins, carbohydrates, and electrolytes. It has both fluid and gel-like properties), cytoskeleton - determines the shape and fluidity of cell (made from thin and intermediate filaments and microtubules), membrane bound organelles within cytosol, other structures which may or may not be bound by a membrane - inclusions.
What is a plasma membrane?
Bimolecular layer of amphipathic phospholipid molecules with their hydrophilic heads at the outer and inner surfaces and their hydrophobic fatty acid chains facing towards the middle of the 2 layers.
What does the plasma membrane contain?
Integral proteins which the cell inserts into the membrane. These include receptors, channels, transporters, enzymes, and cell attachment proteins.
What ability does the cell have?
Exocytose and endocytose material through the cell membrane.
In what way do membrane proteins diffuse?
Laterally, but many are anchored, so it’s important to realise that many proteins are not distributed equally within the cell membrane.
What is the cell membrane permeable and impermeable to?
Highly permeable to: water, oxygen, and small hydrophobic molecules.
Virtually impermeable to charged ions (eg Na+).
On what basis can structures in the cytoplasm be identified under the microscope?
Size, shape, and staining reactions.
What are organelles?
Small, intracellular ‘organs’ with a specific function and structural organisation.
List examples of organelles.
Mitochondria, rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi apparatus, lysosomes, and the nucleus.
What are inclusions?
They are dispensable and may be present only as transients.
What do inclusions represent?
Components that have been synthesised by the cell itself (pigment, glycogen stores, lipid droplets, presecretion product) or taken up from the extracellular environment (endocytotic vesicle).
What are the 3 main classes of filaments?
Microfilaments (7nm in diameter) - composed of the protein actin, intermediate filaments (>10nm in diameter) - composed of 6 main proteins, which vary in different cell types, microtubules (25nm in diameter) - composed of 2 tubulin proteins.
What can actin molecules do?
Assemble into filaments and later dissociate, making them very dynamic cytoskeletal elements.
What is the function of intermediate filaments?
Bind intracellular elements together and to plasma membrane.
List the type of intermediate filament and its location/cell type.
Neurofilaments - nerve cells, glial fibrillary acidic protein - glial cells of nervous system, desmin, muscle cells, cytokeratins - epithelial cells, vimentin - mesenchymal cells, filesin - lens of the eye, lamin - nuclei of all cells.
What do intermediate filaments form?
A network throughout the cytoplasm.
What are microtubules?
Hollow tubule composed of 2 types of tubulin subunits, α & β in an alternating array. It can be assembled and disassembled.
Where do microtubules originate?
From a special organising centre called the centrosome. Include stabilizing proteins: microtubule-associated proteins (MAPS).
What is the microtubules important in?
Cilia, flagella, and the mitotic spindle.
What do microtubules serve as?
The ‘motorway’ network of the cell.
What are the two proteins that attach to the microtubules and move along them?
Dynein and kinesin.
What is the function of dynein and kinesin?
Kinesin is an ATPase that moves toward the cell periphery and dynein is an ATPase that moves toward the cell centre. These proteins are very important in the movement of components in cells with long processes, eg the very long axonal process of many neurons.
Describe the structure of the nucleus.
It is enclosed by a nuclear envelope, composed of an inner and an outer nuclear membrane with nuclear pores providing continuity with the cytoplasm. The outer nuclear membrane is studded with ribosomes and is continuous with the cytoplasmic rough endoplasmic reticulum.
