S1-L7: Cell Organelles-Structure and Function Flashcards
Define and describe the cytoplasm
- contains all cellular components between memebrane AND nucleus
- contains 2 components:
- ->cytosol- intracellular fluid
- ->organelles- specialised structures which co-operate to maintain homeostasis
Outline what the cytosol is and its function
- intracellular fluid- 55% of cell’s total volume- 75-90% water
- contains dissolved ions/ glucose/ amino acids/ ATP/ lipids AND waste products
- site of wide range of enzymatically controlled reactions
Briefly explain what the cytoskeleton is and it’s function
- consists of network of protein filaments extending throughout cytoplasm
- ->helps maintain cell shape AND internal organisation
- ->provides mechanical support- enables cell to carry out essential functions like division/ movement
State the 3 main protein filaments
- microfilaments
- intermediate filaments
- microtubules
Outline and describe the function of microfilaments (figure 1)
- help generate movement- contraction/locomotion & cell division
- provide mechanical support needed for cell strength & shape
- surround edge of cell
- actin & myosin proteins
- create microvilli- like in small intestine
What is the function of intermediate filaments-explain?
refer to figure 2
- help stabilise positions of organelles
- found in parts of cell subject to mechanical stress
- ->v. strong
- ->proteins like keratin/ vimentin & lamin
Describe microtubules and their function (figure 3)
- long unbranched hollow tubules made from tubulin
- ->form in centrosome & radiate outwards
- help strengthen cell/cell shape & organelle movement like vesicles and during division
- help provide structure to flagella- like spermatozoa
Outline the link between the centrosome & microtubules
- during prophase centrosome associated with nuclear membrane
- in mitosis nuclear membrane breaks down AND centrosome nucleated microtubule able to interact with chromosomes to build mitotic spindle
Outline what the flagellum is and it’s function
- whip-like structure which allows cell to move
- found in all 3 domains of living world- bacteria/ archaea & eukaryotes AKA protists/ animals & fungi
- all 3 flagella types used for locomotion BUT structurally differ
What are microfilaments composed of? (figure 4)
- made up of protein actin strands
- ->often interact with strands of other proteins
Describe the structure of intermediate filaments and their function (refer to figure 5)
- made up of tough fibrous proteins organised in to tough rope like assemblies
- ->stabilise cells structure AND help maintain it’s shape
Outline the structure of microtubules (figure 6)
- long hollow cylinders made up of many molecules of protein tubulin
- ->tubulin consists of 2 subunits: a-tubulin AND B-tubulin
How are the three different components of cytoskeleton linked?
-work in unison to provide support AND functionality
Summary of microfilaments/ intermediate filaments & microtubules
Microfilaments:
-thickest/ cell structure & cell motility (movement)/ tubulin
Intermediate Filaments:
-intermediate/ more permanent fixtures/ keratin
Microtubules:
-thinnest/internal movements/within cell/actin & myosin
What is the centrosome?
- serves as main microtubule organising centre AND regulator of cell cycle progression
- function- growth of mitotic spindle during cell division
- found near nucleus
Outline the two centrioles the centrosome consists of
- cylindrical structures composed of 9 clusters of microtubule triplets- both right angles to each other
- pericentriolar material surrounds centrioles AND consists of numerous tubulin rings
How does the division process of eukaryotic cells affect the presence and function of centrosome? (refer to figure 7)
- in dividing eukaryotic cell most microtubules spread out from centrosome
- when cell not undergoing division- single centrosome present
- ->BUT when cell begins to divide- centrosome replicates earlier on
- ->spindle apparatus then begins to form
What is the function of the chromosome in the process outlined previously?
-chromosome function is to maintain equal distribution of chromosomes in daughter cells
Outline what Cilia & Flagella are
- primarily made from microtubules
- ->are motile projections on cell surface
How are Cilia organised? (figure 8)
- numerous short hair type of projections
- each cilium anchored to basal body has core of microtubules enclosed in membrane
- ->9 pairs of microtubules encircle central pair
State the function of cilia
-transport of fluid along cells surface
Explain the effect of smoking on cilia
- destroys cilia-results in mucus/dust AND bacteria build up within lungs
- ->cough persistently to remove
How does smoking affect pregnancy?
- pass oocyte (egg) towards uterus
- ->but female smokers have increased risk of ectopic (abnormal position/not right place) pregnancy
What is the structure of flagella like?
Where are each of the following found?: (refer to figure 9)
1-Cilia
2-Flagella
3-Microvilli
1-found on ciliated epithelial cells like in lungs
–>wave rhythmically to move dirt + mucus
2-found on some bacteria AND allow them to swing
3-found in small intestine AND increases S. Area for nutrient absorption
Define what the endoplasmic reticulum (ER) is
-ER is network of membranes in form of flattened s\cs AND tubules extending from nuclear envelope in to cytoplasm
What are the two types of endoplasmic reticulum’s?
- rough ER
- smooth ER
Outline the structure & function of the rough ER (refer to figure 11)
- rough ER has ribosomes attached- site of protein synthesis
- proteins made by ribosomes enter ER space for processing AND sorting (“factory”)
- enzymes may attach carbohydrate groups/ proteins to phospholipid
- ->these molecules may be incorporated into membrane of organelles OR plasma membrane OR secreted via exocytosis
Describe the structure of ribosomes (figure 12)
- consists of large subunit AND small subunit synthesised separately in nucleolus
- are rich in ribosomal RNA (information) AND contain 50+ proteins each
Where may ribosomes be found?
- may be present free in cytoplasm
- ->within mitochondria OR attached to endoplasmic reticulum
State the function of ribosomes
-site of protein synthesis
Describe the smooth ER
- extends from rough ER
- contains no ribosomes BUT has greater enzyme range–>making its function more diverse
What is the function of the smooth ER?
- synthesises fatty acids & steroids like oestrogen plus testosterone
- in liver helps release glucose from fluc-6-p & detoxify lipid soluble drugs like alcohol AND pesticides
- sores Ca2+ ions in muscle
Explain the effect of repeatedly taking drugs on the ER
- individuals repeatedly taking drugs like sedative phenobarbital
- ->develop changes in smooth ER in liver cells
- ->cells produce more smooth ER to counteract poison- means person has to take more of drug to feel it’s effect
Outline the structure of the golgi complex (refer to figure 13)
- consists of 3-20 membranous cisternae (sac like structures) with bulging edges arranged in stack
- ->entry (or cis) face faces ER AND exit (trans) face faces plasma membrane
- ->in between sacs called medial cisternae
What is the link between the golgi complex and the ER?
-most proteins from rough ER transported to other regions of cell including golgi complex
What is Retrograde transport?
-refers to motion from periphery (outside boundary) of cell to centre
Outline the processing & packaging process steps by the golgi complex (refer to figure 14)
1-transport vesicles containing polypeptide bud off smooth ER
–>fuse with cis face of golgi apparatus
–>releasing polypeptide into lumen of golgi apparatus
2-processing through golgi complex occurs
3-polypeptide packaged in to vesicle released from trans side
–>secretory vesicle releases polypeptide via exocytosis
–>secretory vesicle may become lysosome
-membrane protein attached to a vesicle–> this vesicle inserted into plasma membrane
What is the function of lysosomes? (figure 15)
-digestion of substances entering cell/ worn out organelles (autography) AND entire cells (autolysis)
What is autography required for? (figure 16)
-for renewal/ cellular differentiation/ control of growth AND tissue modelling
Outline what Tay-Sachs disease is
- inherited condition affecting children- caused by lysosomal enzyme Hex A mutation
- ->normally breaks down glycolipid ganglioside GM2-especially in prevalent cells
Explain the effect of the enzymes absence that causes the Tay-Sachs disease (refer to figure 17)
- in enzyme absence glycolipid builds up–> destroying nerves cell function
- ->patient suffers from seizures/ muscle rigidity AND becomes blind
- ->death occurs before age 5
State and explain the function of peroxisomes
- involved with amino acids AND fatty acid metabolism
- oxidise toxic substances like alcohol- high copy number in liver
- also contain enzyme catalase to protect against toxic effect of hydrogen peroxide (made in oxidation reactions)
- contains oxidases/similar to lysosomes BUT smaller
What are peroxisomal disorders?
- form heterogeneous disease group with different degrees of severity
- ->are metabolic disease- these share dysfunction of peroxisomes
- ->all lead to brain disorders & respiratory infections
Outline how fatal each of the following peroxisomal disorders are:
1-Zellweger Syndrome (ZS)
2-Neontal adrenoleukodystrophy
3-Rhizomelic chondroysplasia punctata (RCDP)
1-usually fatal within first year of life
2-usually fatal within first 10 years
3-most sever form in first 2 years of life
When may metabolic disorders happen?
-can happen when abnormal chemical reactions in body alter normal metabolic process
Define what proteasomes are and their importance
- lysosomes which specifically degrade proteins (unneeded/damaged or faulty)
- contain protease enzymes
- important in negative feedback–>switch off pathway once response achieved
How many proteasomes does a typical cell contain?
-thousands of these structures but they have only bee recently discovered
What causes Alzheimer’s disease and is there any possible cure?
- caused by misfolded proteins (in brain) building up
- on-going research to look at why these proteins not degrades
- ->possible cause is proteasome dysfunction
Outline the function of the mitochondria
- aerobic respiration site–>converts glucose to produce energy (from ATP)
- ->3 main steps to process: glycolysis/ citric acid cycle AND Krebs cycle & ATP synthesis
- “power house of cell”
- cells have 100-1000’s depending on function
- other functions: signalling/ cell differentiation/ cell death
What is the structure of the mitochondria?
-2 membranes made of phospholipids double layer + proteins–>both have different properties
What are the 5 distinct compartments within mitochondrion?
- outer mitochondrial membrane
- intermembrane space–>space between outer AND inner membranes
- inner mitochondrial membrane
- cristae & matrix (space within inner membrane)
- ->cristae provide v. big S.A for respiration
- ->enzymes needed for respiration found in matrix on cristae
State how the following parts of the mitochondria are adapted for their function (refer to figure 18)
1-Intermemebrane space 2-Inner membrane space 3-Cristae 4-Matrix 5-Outer membrane
1-small space to quickly accumulate protons
2-contains ETC and ATP synthase for oxidative phosphorylation
3-highly folded to increase SA:V ratio
4-has appropriate enzymes AND suitable pH for Kreb’s cycle
5-contains transport proteins for shuttling pyruvate into mitochondrion
What may be the cause of mitochondrial disease?
- disorders caused by dysfunctional mitochondria
- sometimes caused by mutations in mitochondrial DNA- affect mitochondrial function
- mutations in genes of nuclear DNA-whose gene products imported into mitochondria (mitochondrial proteins) & acquired mitochondrial condition
Why do mitochondrial diseases take on unique characteristics?
- due to way disease often inherited
- also as mitochondria very critical to cell function
State some of the symptoms/problems experienced from mitochondrial disease
- poor growth
- muscle co-ordination loss
- visual problems
- hearing problems
- heart/liver disease
- respiratory disease
- dementia
Outline some of acquired conditions in which mitochondrial dysfunction has been involved
- diabetes
- Huntington’s disease
- cancer
- bipolar disorder
- anxiety disorders
- cardiovascular disease
What is the basic structure of the nucleus?
- spherical/oval shaped & most cells have one
- surrounded by double membrane (nuclear envelope)
How are the structures of the nucleus adapted for it’s functions?
- many nuclear pores extended throughout envelope
- ->channels for ions. A. transport for RNAs & proteins
- in centre spherical bodies called nuclei present
- clusters of proteins/DNA + RNA
- ->responsible for producing ribosomes
Define the term Chroatin and outline it’s function
- complex of DNA + protein found in eukaryotic cells
- ->primary function- packaging long DNA molecules into compact AND denser structures
What is transcription?
- process of constructing messenger RNA molecule using DNA molecules as template with resulting transfer of genetic info to messenger RNA (conveys message)
- happens in nucleus
Outline how the first process (transcription) occurs (figure 19)
- DNA separates into two complementary strands
- mRNA makes copy of DNA
What is translation?
- mRNA formed in transcription transcribed out of nucleus in to cytoplasm to ribosome (cell’s protein synthesis factory)
- ->here directs protein synthesis and this process occurs in rough ER/ cytoplasm
How does the second process of translation occur? (figure 19)
- mRNA bonds with ribosomes at start of codon
- ->tRNA brings amino acids to polypeptide
- ribosome reads codons AND assembles amino acids in order
- stop codon releases polypeptide AND ribosome
Outline how everything discussed in this lecture comes together
-observe figure 20 to understand the process
