basic components of living systems Flashcards
explain how the development of electrons microscopes has improved our understanding of cell structure
-they have a higher resolution (around 0.1nm) compared to light microscope (around 200nm) for allowing the visualisation of smaller structures such as organlles
- they provide higfher magtnification to see detailed structures like cirstae in mitochondria and the membrane bound compartments
state the difference between magnification and resolution
magnification is tthe process of enlarging the image of a specimen
resolution is the ability to distinguish two seperate points that are close, as separate entities
outline the structural differences between prokaryotic and eukaryotic cells
-prokarytoic cells lack a nucleus while eukaryotic cells have a membrane bound nucleus
- prokarytoic cells do not have any membrane bound organelles
describe the structure and function of the mitochondrion
- double membrane
- inner membrane folded into cristae increasing surface area for aerobic respiration
- fluid filled interior called matrix which contains enzynes for krebs cycle
- mitochondria produces ATP, providing energy for cellular processes
explain the roles of lysosomes in the immune response
- lysosomes contain hydrolytic enzymes
- they break down pathogens engulfed by phagocytic cells
this process destroys the pathogen and prevents the spread of infection
describe the structure and function of the rough endoplasmic reticulum
- the RER consists of flattened sacs (cisternae) with ribosomes attached to its surface
- its repsonsible for the syntehsis and transport of proteins
- proteins are packaged into transport vesicles and sent to golgi apparatus
outline the sequence of events in the production and secretion of proteins in eukaryotic cells
- ribsosmes on the RER synthesise proteins
- the proteins enter the cisternae of the RER
- they are packaged into transport vesicles
- vesicles move along cytoskeleton to golgi apparatus
- golgi moddifies the proteins and packages them into secretory vesicles
- the secretory vesicles fuse with cell membrane, releasing proteins by exocytosis
explain the role of the cytoskeleton in the movement of organelles
- the cytoskeleton contains microtubules which forms tracks along which organelles (e.g vesicles) move
- motor proteins use ATP to move organelles along tracks
- microfilaments contract to move the cell membrane during cytokenesis
- the cytoskeleton also positions the centrioles during cell division
describe the process of treadmilling in the cytoskeleton
- treadmilling occurs in the microfilaments
- actin monomers are added at the plus end and removed at the minus end
- this creates a dynamic lengthening and shortening effect, driving cell movement
explain how the structures of cell membranes enables permeability
- cell membranes consist of a phospholipid bilayer with hydrophobic tails facing inward and hydrophillic heads facing outward
- this structure creates a barrier to polar molecules and ions
- protein channels and carriers allow specific substances to pass through
- cholesterol in the bilayer provides stability and controlls fluidity
explain why cells with a high energy demand contain mitochondria
mitochondria are the site of aerobic repsiration, where ATP is produced
- cells with higher energy demands (e.g muscle cells) require more ATP and therefore contain more mitochodnria
compare the structure and fucntion of the smooth endoplasmic reticulum and the rough endoplasmic reticulum
- the SER lacks ribosomes, while the RER has ribosomes attatched
- the SER is involved in lipid and carbohyderate synthesis and storage
- the RER is responsible for protein synthesis and trasnport
- both ar composed of cisternae
explain the structural differences between flagella and cilia and how their functions differ
- flagella are logner and typically and typically fewer in number, while cilia are shorter and more numerous
- flagella are used for cell mobility (e.g sperm cells)
- cilia can be mobile or stationary. mobile cilia sway rhymically to move substances (e.g mucus in the trachea)
- both contain a 9+2 arrangement of microtubules
A scientist observes a eukaryotic cell with a large number of mitochondria and extensive RER.
suggest the likely function of this cell and explain your reasoning
- the many mitochondria suggests high energy demand, as mitochondria prodice ATP
- extensive RER indicating significant protein synthesis
-the cell is likely a secretory cell (e.g pancreatic or glandular cells)
it requirres large amounts of atp and proteins for secretion
describe the structure and function of the nucleus in the eukaryotes
- the nucleus is surrounded by a double membrane called the nuclear envelope
- the nuclear envelope contains nuclear pores that allow molecules (e.g RNA) to move in an dout
- inside the nucleus, dna associates with histone proteins to form chromatin which coils and condenses into chromosomes during cell division
the nucleus controls gene expression and the synthesis of RNA for protein production
what is the function of the nucleolus
- the nucleolus is repsonsible for producing ribosomes
- it synthesises ribosomal RNA (rRNA) and combines it with proteins to form ribsosomal subunits
explain the difference between vesicles and lysosomes in terms of their structure and function
- both are membrane bound sacs with fluid inside
- vesicles are involoved in transport and storage within the cell
- lysosomes contain hydrolytic enzymes and are resposnible for breaking down waste, old organelles and pathogens
describe the role of lysosomes in apoptosis
- lysosomes release hyrolytic enzymes into the cell during apoptosis
- this causes controlled breakdown of cellular components which leads to programmed cell death
explain the role of centrioles in cell division
- centrioles are composed of microtubules and form the centrosome
- during cell diviison, centrioles organise the spindle fibres
- spindle fibres attatch to chromosomes and separate them during mitosis and meiosis
explain how actin filaments enable cell movement
- actin filaments polymerise and depolymerise, changing length
- the addition of monomers at the plus end and removal at the minus end causing treadmilling
- this drives the leadiong edge of the cell forward, enables movement (e.g in phagocytes)
describe the 9+2 arrangement of microtubules in cilia and flagella
- both cilia and flagella contain two central microtubules surrounded by 9 pairs of microtubules
- This 9+2 structures allows them to bend and move by microtubule sliding
explain the role of enzymes in cellular metabolism and how they are affected by cellular conditions
- enzymes catalyse metabolic reactions by lowering actiavtion energy
- in anabolic reactions, they build larger molecules, while in catabolic reactions they break down substances
- enzyme activityt is affected by temp, pH and substrate concentration
- chnages in these conditions can lead to denaturisation or reduces enzyme efficiency
explain how the cytoskeleton and golgi apparartus are involved in protein transport
- proteins are synthesised on ribosomes attached to the RER
- they are packaged into vesicles which move along the cytoskeleton
- the microtubules act as tracks for vesicle trasnport
- the vesicles fuse with the cis face of the golgi apparatus, where the proteins are modified and packaged into secretory vesicles
explain the roles of spindle fibres during mitosis and how they relate to the cytoskelton
- spindle fibres are composed of microtubules, part of the cytoskelton
- they attatch to chromosomes at the centromere
- during mitosis, the spindle fibres contract, serparating sister chromatids and pulling them to opposite poles
explain why eukaryotic cells are compartmentalised and how this benefits cellular processes
- eukarytoic cells have membrane bound organelles that compartmentalise reactions
- this allows for different conditions in different organelles
- compartmentalisation improves efficiency by separating incomptatible reactions
- also enables the concentration of enzymes and substrates in specific area
describe the three structures that are unique to plant cells
- cellulose cell wall: provides structural support, rigidity and protections against pathogens
- large permanent vacuole: maintains turgor pressure and supports the plant structure
- chloroplasts: organelles responsible for photosynthesis, containing chlorophyll pigments
explain the role and structure of the cell wall in plant cells
- made of cellulose, a complex carbohyderate
- freely permeable, allowing substances to pass in and out
- provides mechanical strength, preventing the cell from bursting when water enters
- acts as a defense barrier against invading pathogens
explain how the vacuole and tonoplast contribute to plant cell stability
- the vacuole contains cell sap (water, enzymes and ions) which maintain turgor pressure
- the tonoplast (the membrane surrounding the vacuole) is selectively permeable, controlling the movement of molecules in and out
- turgor pressure pushes the cyoplasm against the cell wall
describe the structure and functions of chloroplasts
- double membrane structure, similar to mitochondria
- stroma: the fluid filled interior where light independant reactions occur
- thylakoids: flattened sacs containing chlorophyll for light absorbtions
- grana: stacks of thylakoids, connected by lamellae, where light dependent reactions occur
explain how the internal membrane structure of chloroplasts is adapted for photosynthesis
- the grana provides a large surface area for light dependent reactions
- enzymes, proteins and pigments necessary for photosynthesis are embedded into the thylakoid membranes
- the stroma containsb enzymes needed for the calvin cycle (light independent reactions)
identify two structural differences between plant and animal cells
- plant cells have cellulose cell walls, while animal cells do not
- plant cells contain chloroplast for photosynthesis, animal cells do not
describe three similarities and differences between plant root cells and human cells
similarities:
- both eukarytoic cells with membrane bound organelles
- both have nuclei containing genetic information
- both contain ribosomes for protein synthesis
differences:
- plant root cells have cell wall, human cells dont
- root cells have large vacuole for water storage, whereas animal cells have small, temporary vacuoles
- root cells lack chloroplasts (as theyre underground) but human cells dont have it al all
describe the main structural features of prokarytotic cells
- no membrane bound organelles (e.g no nucleus or mitochondria)
- circular DNA in the nucleoid region, not enclosed by a membrane
- 70S ribosomes, smaller than eukaryotic ribosomes
- cell walls made of peptidoglycan (murein) providing structural support
explain two differences between prokaryotes and eukaryotes
- prokaryotic cells have naked circular DNA, while eukaryotic cells have linear DNA associates with histones
- prokarytotic cells have 70S ribosomes , while eukarytoic cells have 80S ribosomes
explain how the flagella of prokaryotic cells differ from those in prokaryotic cells
- prokaryotic flagells are thinner and lack 9+2 arrangement of microtubules
- they rotate using energy from chemiosmosis rather than ATP
- the basal body and molecular motor rotate the filament, propelling the cell forward
what is the function of the peptidogylcan in prokaryotic cell wall
- provides structural strength, preventing the cell from bursting due to osmotic pressure
- acts as a protective barrier against environmental stress
explain the endosymbiotic theory and describe one piece of evidence supporting it
- the endosymbiatic theory suggest suggests that mitochondria and chloroplast were once free living prokaryotic cells
- they were engulfed by a larger cell in a symbiotic relationship
- overtime they became permanent organelles
- evidence: mitochondria and chloroplast have their own circular DNA and 70S ribosomes, similar to prokaryotic cells
- thee dna can self replicate, indicating a degree of independance from the host cell
explain how the structuire of cellulose is related to its function
- cellulose is made of beta glucose monomers linked by a 1’4 glycosidic bond
- the chains form straight unbranched fibres that form microfibrils
- the microfibrils provide strenght and rigidity to the plant cell wall
explain how the vacuole and cell wall work together to maintain plant cell stability
- the vacuole maintains turgor pressure by storing water and solutes
- the cell contents press against the cell wall, keeping the cell firm
- this prevents wilting and maintains the plants structural integrity
