E1 Introduction to cells Flashcards
what are some exceptions of cells that can replicate themselves?
- erythrocytes
- platelets
describe the nuclear structure of prokaryotes
no defined nuclear structure
describe the nuclear structure of eukaryotes
defined nuclear structure
what is the main principle of viruses?
need a host to live / replicate
what is the cytosol?
- represents the water containing inorganic ions and small organic molecules and accounts for 70-80% of the weight of a living cell
- macromolecules (proteins, polysaccharides, lipids and DNA/RNA) account for the remaining weight of the cell
what is cytoplasm?
a semi-solid / fluid that typically includes all contents: cytosol, various organelles of the cell outside the nucleus and within the cytoplasmic membrane
describe how form relates to function in a red blood cell
- discoid shape and lack of nucleus facilitates movement through blood vessels
- provides large SA for gas exchange and for sticking to each other to form blood clots
describe how form relates to function in an epithelial cell
- any cells in contact with the outside environment
- some have microvilli at one end giving the cell polarity and a larger surface area for the absorption of nutrients
describe the function of chondrocytes
- found in cartilage and embedded in a thick extracellular matrix of proteins
- hold water for cushioning / shock absorption eg. in knees
describe the nucleus structure and function
- contains DNA in chromosomes
- diploid (except gametes)
- surrounded by double membrane (outer and inner nuclear membrane)
- some cells have more than one
describe the nuclear membrane
- nuclear envelope is a lipid bilayer and is continuous with the ER
- hydrophobic and hydrophilic domains
- large structures can’t move through
- need transporters or pores
- nucleus has pores that allow newly formed ribosomes to move through
what is the nuclear lamina?
a dense network of protein fibres that help provide structural integrity
give an example of cells that have more than one nucleus
osteoclasts
muscle cells
describe the structure of the endoplasmic reticulum
- membrane bound
- network of cistern with a common, interconnected lumen
- in contact with the nuclear membrane
- receives ribosomes form the nuclear pores
- rough has ribosomes attached for translation
- smooth has no ribosomes attached
how is the destination of ribosomes decided?
based on what proteins they end up coding for and where these proteins go to
describe the functions of the ER
- rough ER has ribosomes for translation
- proteins are synthesised (translated) then modified within the ER before being passed to the Golgi or lysosomes for further modification
- stores calcium ions (especially in sarcomeres)
- synthesises lipids and steroids
- detoxifies drugs in liver cells
describe the structure and function of the Golgi
- similar to ER (derived from ER but no longer connected)
- stacks of flattened smooth membrane sacs and vesicles
- ribosomes from nucleus to ER then ER makes proteins which are delivered to Golgi
- undertakes post-translational modification of many proteins
describe the structure and function of the different Golgi membrane sacs
- cis (facing ER) receives proteins and lipids from ER
- stack (main body) processes proteins and lipids
- trans (facing cytoplasmic membrane) targets delivery of proteins etc.
describe the structure of the mitochondria
- double membrane structure
- enzymes of ETC embedded in the inner membrane
- enzymes involved in Krebs cycle and fatty acid oxidation in matrix
- has own DNA, RNA and ribosomes
- inherited maternally from egg cell, sperm only has nucleus in its head
describe the mitochondrial genome
- very small
- encodes for some RNAs and some ETC proteins
why does the number of mitochondria vary in certain cells?
- muscle cells have more for contraction
- other cells have less due to their functional adpatations
why are inherited diseases usually inherited from the mother?
- mitochondrial diseases
- mitochondria are only inherited from the mother
describe the structure and function of lysosomes
- pinch off Golgi so are derived from Golgi complex
- contained environment
- different pH to cell and allows for different chemistry
- contain various enzymes that work in acidic environment
describe the structure and function of phagosomes
- found in specialised cells eg. macrophages
- break down ‘foreign bodies’ eg. bacteria
- perform phagocytosis
- antigen-presenting cell afterwards for the immune system
what are peroxisomes?
organelles involved in redox reactions
what are endosomes?
- structures formed by pinching off part of the cytoplasmic membrane
- happens when material like lipoproteins or ‘foreign bodies’ are brought into the cell
are ribosomes classified as an organelle? explain
no, they are not membrane-bound
describe the structure and function of ribosomes
- site of protein synthesis
- 2 subunits
- decodes mRNA in translation and creates protein from genetic code
- complex of rRNA and ribosomal proteins
describe the structure of different types of ribosomes in detail
- there are large and small
- eukaryotic are 80S
- prokaryotic are 70S
- complexes of rRNA and ribosomal proteins
- rRNAs fold and interact to give the ribosome 3D structure
describe the structure of the cytoskeleton
- made of distinct filamentous proteins that provide an internal scaffold
- consist of microfilaments, intermediate filaments and microtubules
describe the structure and function of the microfilaments in a cell’s cytoskeleton
- eg. actin
- provide mechanical support
- actin binds many different proteins and contributes to many cell functions
describe the structure and function of the intermediate filaments in a cell’s cytoskeleton
- bigger than microfilaments
- eg. keratin, desmin
- mechanical strength
- resistance to shear stresses
- air through lungs detected by changes in cytoskeleton
describe the structure and function of the microtubules in a cell’s cytoskeleton
- bigger than microfilaments and intermediate filaments
- eg. tubular involved in movement / separation of chromosomes (‘mitotic spindle’)
- centrioles found in animal cells (and some plants)
- paired structures associated with mitosis - centrosome
- single structures associated with cilia or flagella
describe the structure and function of muscle cells in relation to the cytoskeleton
- contain specific protein fibres (actin and myosin)
- in skeletal and cardiac tissues, the contractile fibres are arranged into prominent structures called sarcomeres
- smooth muscles have less defined sarcomeres and they contract in a twisting manner
describe the structure and function of the cytoplasmic membrane
- all cells bound by a membrane
- interacts with environment and regulates movement across it with designated transporters
- phospholipid bilayer
- organelles’ membranes have similar properties for their membranes
describe the structure of a phospholipid bilayer
- 2 phospholipid layers / leaflets
- assemble to form closed bilayer due to amphipathic properties (hydrophobic and hydrophilic)
what do the interactions of the cytoplasmic membrane depend on?
interactions depend on properties of the membrane and the molecules embedded in or on the membrane
describe the structure of prokaryotes (bacteria mainly)
- DNA is free-floating in the cytoplasm
- smaller genome
- less complex
- haploid
- reproduce quickly
- transcription and translation are similar processes
- naked, extra-chromosomal DNA
- ribosomes are smaller
- good target for drugs due to subtle differences in structure and biochemistry
- rigid cell wall made of distinctive molecules
- lack membrane-bound organelles
describe the DNA in bacteria
- plasmids
- linked to pathogenicity
- resistant to antimicrobials
- insert genes into plasmids for DNA technology
what features of bacteria make them a good target for drugs?
- cell wall, animal cells don’t have one
- different structure and biochemistry
where can spore-forming prokaryotes be a problem and why?
- in hospitals
- they can survive many years and are resistant to many antimicrobials
- can be a major cause for infections
what are some recognisable conditions caused by viruses?
- measles
- hepatitis
- covid
- influenza
- HPV
- HIV
- colds
describe the genomes of viruses compared to eukaryotic cells
- simple but no less complex
- variation among viruses
describe how viruses can be classified
- naked or enveloped
- by the host or the tissue they infect eg. hepatitis is liver
describe the anatomy of a virus particle
- capsid protects genome
- assembly of viral proteins protect genomic material
- capsid encapsulates a small number of enzymes / other proteins
- capsomers bind receptors on host cells to help facilitate invasion of them
what is tissue tropism in viruses?
- viruses recognise receptors on our cells which is why certain viruses affect certain organs / tissues and cause certain diseases
- this is why certain viruses cause specific symptoms / diseases
describe naked classified viruses
- capsid only
- eg. papilloma virus, Polio, Hepatitis A
describe enveloped classified viruses
- capsid surrounded by lipid bilayer or ‘envelope’ (lipid is derived from the host cell which it pinched off from)
- envelope also contains viral proteins for targeting / infecting specific cell types
- eg. HIV, influenza A, influenza B, Coronaviruses
