Anatomy of the Cell Flashcards
What are common to all eukaryotic cells?
Outer membrane
Inner cytosol - solution of proteins, carbohydrates and electrolytes that has fluid and gel-like properties.
Cytoskeleton - determines shape and fluidity of cell and consists of microfilaments, intermediate filaments and microtubules.
Membrane-bound Organelles
Inclusions (non-living components of cell that are not necessary for life, that may be bound by a membrane, and are either produced by the cell or taken up from the ECF.
Describe the plasmalemma’s structure and function.
Biomolecular layer of AMPHIPATHIC (hydrophilic and hydrophobic properties) phospholipid molecules. Function is to separate the cytoplasm form the ECF.
The membrane contains integral proteins (inserted into the membrane) like receptors, channels, transporters, cell attachment proteins, enzymes. The membrane also contains cholesterol and peripheral proteins.
Describe the selective permeability of the plasmalemma.
The membrane is also SELECTIVELY PERMEABLE and is highly permeable to water, small HYDROPHOBIC molecules and is virtually impermeable to charged ions.
Give examples of eukaryotic organelles and their functions
Mitochondria - site of aerobic respiration and ATP production
RER - synthesis of proteins for export
SER - cholesterol and lipid synthesis, and detoxification
Golgi - modification and packagins of secretions, lysosomes, etc
Lysosomes - contain hydrolytic enzymes for digestion
Nucleus (contains genetic material)
Describe microfilaments
Composed of actin molecules and 7nm in diameter
Describe intermediate filaments
10-15nm in diameter and composed of 6 main proteins. They bind intracellular elements together and to the plasmalemma.
More than 50 types that are divided into classes; used in pathology to identify tumour origin
Describe microtubules and their function in moving organelles
Hollow tubules composed of α and β tubulin in an alternating array. They include stabilising proteins, like MAPS (microtubule associated proteins).
They originate from the centrosome (microtubules originate from centre of cell and radiate out, making them polar) and can be assembled/disassembled.
Dynein and kinesin (both protein ATPases) move along microtubules and associate with organelles/vesicles and “drag” the along.
Dynein moves to cell centre and kinesin move to cell periphery
Describe the structure of the nucleus
Enclosed by a nuclear membrane (innner and outer membrane that have nuclear pores)
Between the two is the perinuclear cistern, which is continuous with the ER cistern
Outer membrane - studded with ibosomes and is continuous with ER
Briefly describe nucleus contents
Site of RNA synthesis Contains chromosomes Two types of DNA: Euchromatin (DNA undergoing transcription) Heterchromatin (condensed DNA)
Describe ribosomes (origins, function, structure)
Formed in nucleolus, with the export depending on nuclear pore complex
Site of protein synthesis
Each consists of a small sub-unit (binds RNA) and a large sun-unit (catalyses formation of peptide bonds)
Describe the structure and function of RER
Studded with ribosomes for synthesis of proteins inserted into membrane or exported from cell
Also associated with initiation of glycoprotein formation
Amount of RER related to how active cell is
Describe protein synthesis at the RER
Free ribsome attaches to mRNA
If ER signal present, growing peptide inserted into an ER pore
Growing peptide forms in the ER (signal sequence removed)
Ribomsome detached (most proteins then enter SER)
Describe SER and function
Continues processing proteins from RER
Site of lipid synthesis
Some cells contain little SER, other, e.g: steroid hormone producing cells, contain a lot
Describe Golgi structure and function
A complex composed of flattened, membrane-bound cisternae (arranged in sub-compartments)
Vesicles arrive from SER and golgi cisterns modifies (may add sugars, cleave proteins) and package (sort macromolecules) contents from the ER.
Describe mitochondria structure and function
Inner (folded to from cristae- increase SA) and outer membrane
Generate ATP, via oxidative phosphorylation
Synthesis of certain lipids and proteins
What are lipid droplets?
Inclusions that are not surrounded by a membrane
In adipose cells (store triglycerides), there is 90% lipid
What are intercellular junctions and what cells are they particularly abundant in?
Specialised membrane structures linking individual cells into functional units (particularly prominent in epithelia)
What are the types of intercellular junctions?
Occluding junction (tight junctions or zona occludeus)
Anchoring junctions - adherent junctions (zonula adherens), desmosomes and hemidesmosomes
Communicating junctions
Junctional complex
Describe occluding junctions
Cells linked to from barrier that prevents diffusion. Appear as a focal regions of cells close to one another.
Describe adherent junctions
Link submembrane actin bundles of adjacent cells. Transemembrane cadherin molecule bind to each other in extracellular space and link to actin of cytoskeleton
Describe desmosomes, common sites and function
Link submembrane intermediate filaments of adjacent cells. Common in skin where they provide mechanical stability
Describe hemidesmosomes
Link submembrane intermediate filaments of a cell to EC matrix, through transmembrane proteins
Describe junctional complexes and sites
Close association of several types of junctions found in certain EPITHELIAL tissues
Describe communicating junctions
AKA gap junctions, allow selective molecular diffusion between adjacent cells.
Circular patch with several hundred pores, produced by CONNEXON proteins
Found in epithelia, some smooth muscle, and in cardiac muscles (critical for excitation spread)
How do material move into and out of the cell?
Diffusion Transport protein (pumps of channels) Vesicular transport (by incorporation into vesicles )
Describe endo and exocytosis?
Endocytosis - material from EC space incorporated in cell. Process is often receptor mediated.
Cell membrane invaginates, fuses and forms an endocytotic vesicle (ENDOSOME) that buds into the cell
Exocytosis - opposite of endo, material is discharged
Describe phagosytosis
Bacteria/larger particulate material from EC space incorporated into cell
Bacterium binds to cell surface receptors
Triggers extensions of cell to engulf it forming a phagosome
Phagosome binds with lysosome to form phagolysosome
