The structure of Eukaryotic cells (lectures 3 and 4) Flashcards
Describe the key features of a eukaryotic cell.
- membrane-bound organelles
- have linear DNA molecules packaged as chromosomes enclosed in a nucleus
What are the functions of the plasma membrane?
- regulation of transport
- nutrients into the cell, waste materials out
- maintains balance of chemical conditions i.e. homeostasis
- provides a site for chemical reactions not likely to occur in an aqueous environment
- interacts with other cells or the extracellular matrix
What are the key features of the nucleus?
- contains genetic material
- electron microscopy reveals 2 membranes
- contents are in contact with cytoplasm via nuclear pores which pass through both membranes
- nucleolus: rich in protein and RNA which is involved in synthesis of ribosomal RNA and ribosomes
What are the 2 membranes of the nucleus and their functions?
- inner membrane is in contact with the nuclear contents
- outer membrane appears to be continuous with endoplasmic reticulum
functions of the rough endoplasmic reticulum?
-ribosomes attached to the surface
- plays a role in synthesising membrane-bound and secreted proteins
- extensive in cells synthesising these proteins
functions of the smooth endoplasmic reticulum?
- carries no ribosomes
- plays a role in producing lipids eg membrne lipids and steroid hormones
what are the key features of the endoplasmic reticulum?
responsible for
- lipid synthesis
- most membrane protein synthesis
- Ca2+ ion storage detoxification
key structure and functions of ribosomes?
- multisubunit structures comprised of roughly 50% protein and 50% ribosomal RNA
- rRNA are key to the structure and function of ribosomes
- involved in the synthesis of proteins
structure and function of mitochondria?
typically 0.5-10 micrometres in size
- contains DNA and ribosomes which are smaller than normal eukaryotic type
- self replicating: binary fission
sites of ATP production via aerobic metabolism
-play important role in apoptosis
describe the key features of mitochondrial DNA
- mitochondria contain multiple mtDNA molecules
- genes in mtDNA exhibit cytoplasmic inheritance and encode rRNAs, tRNAs and some mitochondrial proteins
- mutations in mtDNA cause several genetic diseases in humans eg leigh syndrome, leber hereditary optic neuropathy
explain the key structures and functions of the golgi apparatus
- stack of flattened membranous sacs which vary in number
- ensures that vesicles budding off outer face can fuse with plasma membrane
- packages lysosomal proteins and proteins to be secreted from cell
what are the key features of the golgi complex
- series of flattened compartments and vesicles
- composed of 3 regions: cis (entry), medial and trans (exit)
what is the function of lysosomes?
-single membrane-bound organelles containing hydrolytic enzymes
- hydrolytic enzymes degrade materials taken up by endocytosis and cell debris
- degrade damaged newly synthesised proteins
what are peroxisomes
-single membrane-bound organelles
- contain catalase and urate oxidase
- breaks down very long chain fatty acids via beta oxidation
-oxidation of toxins inc alcohol
3 key features of the cytosol of the cytoplasm?
- cytoskeleton
- polyribosomes
- metabolic enzymes
function of the cytoskeleton?
involved in:
- cell movement
- cell division
- cell shape
- intracellular trafficking of organelles
- coordinated movement of tissues
what are the 3 major components of the cytoskeleton
- microfilaments
- microtubules
- intermediate filaments
functions of microfilaments?
F-actin filaments are double helices of polymerised G-actin subunits
- fibres expand and contract by further polymerisation and depolymerisation
- ATP dependent
microfilaments interact with other filaments and motors to create movement: contraction can cause shape change
what do actin and myosin do?
- actin microfilaments work with myosin in muscle fibres
- myosin filaments walk along the tethered actin, hence pulling the filaments towards the centre to cause muscle contraction
how do microtubules grow
-grow by polymerisation from specific microtubule organising centres
role of microtubules?
fundamental role in partitioning of chromatids in cell division
role of vacuoles?
- store water, ions, nutrients and degrade macromolecules
- inflow of water by osmosis causes vacuole expansion and maintenance of turgor pressure
- expansion of vacuoles involved in cell elongation
role of chloroplasts?
-contain chlorophyll and other pigments that absorb light and generate NADPH and ATP during photosynthesis which is used to produce organic molecules
structure of chloroplasts?
- double membrane bound
- contain their own DNA
- thylakoid membranes, fused into stacks called grana
-capture light to produce ATP during photosynthesis
role of plasmodesmata?
directly connect the cytosol of adjacent cells in higher plants
