Eukaryotic Organelles and Functions ✅ Flashcards
Draw and label a eukaryotic cell.
.
What are two types of organelles are there in eukaryotic cells?
non-membranous and membranous
What are the non-membranous cell organelles in the eukaryotic cell?
- Ribosomes
- Microtubules
- Microfilaments
- Chromosomes
What are the membranous cell organelles in the eukaryotic cell (one membrane)?
- Plasmolema
- Endoplasmic reticulum
- Golgi apparatus
- Lysosomes
- Vacoules
What are the membranous cell organelles in the eukaryotic cell (two membrane)?
- Mitochondria
- Plastids
- Nucleus
- Chloroplasts
What does the endomembrane system include?
- Nuclear envelope
- Endoplasmic Reticulum
- Golgi Apparatus
- Lysosomes
- Vesicles
- Plasma membrane
What does the ER enclose?
A series of intercommunicating channels called “CISTERNAE”.
What does ER stand for?
Endoplasmic Reticulum
What is the function of the ER?
ER is a major site for vital cellular activities:
- biosynthesis of proteins
- biosynthesis of lipids.
What are the two types of endoplasmic reticulums?
- rough ER
- smooth ER
What is the function of the rough ER?
The rough ER is the site for the synthesis of most membrane-bound proteins.
(production of membrane-associated proteins, proteins of many membranous organelles, and proteins to be secreted by exocytosis.)
What is the function of the smoth ER?
1) lipid biosynthesis,
2) detoxification of potentially harmful compounds,
3) sequestration (storing) and controlled release of Ca2+ ions.
How does the rough ER look like?
- saclike and parallel stacks of flattened cisternae,
- cisternae are limited by membranes that are continuous with the outer membrane of the nuclear envelope
What is a ribosome?
A ribosome is a complex structure, containing many different proteins and at least three ribosomal RNAs.
What is the function of ribosomes?
Ribosomes are a site of protein synthesis.
What do free ribosomes synthesize?
Free ribosomes synthesize PROTEINS for USE in the CYTOPLASM.
What do ribosomes bound to the ER synthesize?
Ribosomes bound to the endoplasmic reticulum membrane synthesize PROTEINS that are EXPORTED from the cell or INCORPORATED into the membrane.
What is the sedimentation coefficient?
The sedimentation coefficient (s) of a particle characterises its sedimentation during centrifugation.
What is “protein trafficing”?
The movement of newly synthesized proteins in a cell.
What is protein traffic characterised by?
Protein traffic is characterised by common principles that make up protein targetting molecular mechanism.
What is the role of the endomembrane system?
Modify, package, and transport lipids and proteins.
What is the effect of protein trafficing?
- Protein activity and stability are changing.
- Proteins are targeted to specific sites in the cell or secretion to the outside of the cell.
Why does the RER have a highly regulated system?
To PREVENT nonfunctional proteins being forwarded to the pathway for secretion or to other organelles.
What happens with proteins that cannot be folded or assembled properly by chaperones?
proteins undergo ER-associated degradation (ERAD), in which unsalvageable proteins are translocated back into the cytosol, conjugated to ubiquitin, and then degraded by proteasomes.
RER vs SER cisternea.
RER- flattened cisternea
SER- tubular cisternea
What happens during ER-associated degradation (ERAD)?
Unsalvageable proteins are translocated back into the cytosol, conjugated to ubiquitin, and then degraded by proteasomes.
What does ERAD stand for?
ER-associated degradation.
What are proteins controlled by (the regulated system)?
Chaperones.
What are the structures within the golgi apparatus?
- Cisternae
- Vesicles (in the end of cisternae)
- Dictyosomes (a group of parallel, flattened cisternae with flared ends)
What are the three major “regions” of the Golgi apparatus?
Cis face
- mannosidase I
- golgi-recieving region
Medial
- mannosidase II
- enzymatic modifications
Trans face
- galactosyltransferase sialyltransferase,
- distinguishing region
What is the function of the different golgi apparatus faces?
- Cis-face: golgi-receiving region
- Medial region: enzymatic modifications
- Trans-face: distinguishing region
What are the different enzymes at different cis, medial, and trans levels?
Cis face: mannosidase I
Medial: mannosidase II
Trans face: galactosyltransferase sialyltransferase.
What are the functions of the golgi apparatus?
- Modifying secretory products
- Sorting secretory products
- Forming transport vacuoles.
The golgi apparatus completes post-translational modifications of proteins produced in the RER and then packages and addresses the proteins to their proper destinations.
What is the golgi apparatus?
A dynamic organelle consisting of stacked membranous cisternae in which proteins made in RER are processed further and packaged for secretion or other roles.
How, and in what do proteins enter the recieving face of the Golgi?
Proteins in transport vesicles enter the cis or receiving face of the Golgi.
What happens with the proteins in transport vesicles once they already enter the Golgi through medical cisternea?
They move through medial cisternae of the Golgi network for enzymatic modifications, and are released in other vesicles at the trans face.
Where do modified proteins exit by?
Released in other vesicles at the trans face of the golgi apparatus.
Explain the movement of proteins through the golgi apparatus.
Proteins in transport vesicles enter the cis or receiving face of the Golgi, move through medial cisternae of the Golgi network for enzymatic modifications, and are released in other vesicles at the trans face.
What is the vesicle movement through the Golgi apparatus guided by?
specific coat proteins such as COPII and COPI.
What is COPII and COPI?
specific coat proteins that guide vesicle movement through the golgi apparatus.
What are important protein modifications that occur in the Golgi Apparatus?
- sulfation reactions
- glycosylation reactions
What happens to proteins once they exit the Golgi Apparatus?
Modified proteins leave the Golgi apparatus with COAT PROTEINS that DIRECT movement to lysosomes, the plasma membrane, or secretion by exocytosis.
What is the function of coat proteins?
direct movement of modified proteins to lysosomes, the plasma membrane, or secretion by exocytosis.
What is a polyribosome? polysome?
A cluster of ribosomes linked together by a molecule of messenger RNA and forming the site of protein synthesis.
Where are proteins broken down? longer-acting proteins? shorter lived proteins?
longer acting proteins- lysosomes
short living proteins- 26S proteasome
What is the max number of lysosomes that an animal cell can contain?
100 lysosomes
What is the max number of lysosomes that a phagocytic macrophage cell can contain?
up to 1000.
What are lysosomes composed of?
- peroxysomes
- mitochondria fragments
What are lysosomes?
Lysosomes are:
- spherical membrane-enclosed vesicles
- function as sites of intracellular digestion
- numerous in cells active after the various types of endocytosis.
What is the function of lysosomes?
Lysosomes are sites of intracellular digestion.
What is the pH of lysosomes? What is a lysosome surrounded by? Why is the pH so high?
- surrounded by membranes
- interior of lysosomes is more acidic than the rest of the cytoplasm
- lysosomes contain many hydrolytic enzymes (40), main enzyme - acid phosphatase
What do lysosomes contain? Why?
over 40 types of hydrolytic enzymes.
These enzymes hydrolytically degrade proteins, nucleic acids, carbohydrates and lipids.
What is the main enzyme of lysosomes?
acid phosphatase
How are cytosolic components protected from the enzymes on the lysosomes?
- protected by the membrane
- additionally as the enzymes have optimal activity at an acidic pH (~5.0), any leaked lysosomal enzymes are practically inactive at the pH of cytosol (~7.2) and harmless to the cell.
What is heterophagia?
The breakdown of a FOREIGN substances which are absorbed by endocytosis.
What is autophagy?
The breakdown of OWN materials.
e.g.
- storage nutrients
- macromolecules
- organelles
(that have lost their functional activity)
What is Autolysis?
The DIGESTION of cells due to PATHOLOGY or AGING (due to the breakdown of lysosomal membranes).
What three types of lysosomes are there?
primary lysosomes, secondary lysosomes, and residual bodies.
What is the function of primary lysosomes? Where do they emerge from? What do they contain (enzyme)?
- emerge from the Golgi apparatus,
- contain inactive acid hydrolases,
- degrade a wide variety of cellular macromolecules.
What is the function of secondary lysosomes? Where do they emerge from? What do they contain (enzyme)?
- Secondary lysosomes are more heterogeneous, having fused with vesicles PRODUCED BY ENDOCYTOSIS
- contain material to be digested by the hydrolytic enzymes.
What happens during autogaphy? What does it remove?
Lysosomes digest unneeded or nonfunctional organelles after these are surrounded by membrane that then fuses with a lysosome.
(autophagy removes residues of mitochondria, peroxisomes, other structures.)
What are residual bodies?
residual bodies - final condensed vesicles containing indigestible molecules
(products of digestion in secondary lysosomes are released to the cytoplasm for reuse)
What happens to products of digestion in secondary lysosomes?
Released to the cytoplasm for reuse.
What is autolysis?
The disruption of cell contents acting on lysosome-derived hydrolases.
What are the biological functions of lysosomes?
- DEGREDATION OF SUBSTANCES (released from the environment by endocytosis or phagocytosis).
- lysosomes perform the function of a “RECYCLING” system.
(in the circulation of the INTERNAL MATERIALS and STRUCTURES of the cell).
(eg. specialized liver Kupfer cells phagocytose old erythrocytes and disrupt them in lysosomes.) - cell-derived lysosomal ENZYMES perform specific functions and are important in EMBRYOGENESIS PROCESSES.
What are lysosomal diseases caused by?
genetic heredity
What is the pathomechanism of lysosomal diseases based on?
the pathomechanism of lysosomal diseases is based on the EXCESSIVE ACCUMULATION of MACROMOLECULES in cell lysosomes.
Why does the accumulation process of macromolecules occur in lysosomes?
The accumulation process occurs due to a SINGLE DEFICIENCY of lysosomal enzymes.
What does the accumulation of macromolecules cause?
an increase in lysosomes, resulting in destroyed cell function.
What do accumulated macromolecules damage?
the CNS: central nervous system
What is the old age pigment called? How does it connect to lysosomes?
LIPOFUSCIN,
- depicts the accumulation of undigested substances in the organism
(undigested materials can also accumulate in the liver and muscle cells).
How many lysosomal diseases have been discovered? Are they serious?
over 60 lysosomal diseases (can be fatal)
What are peroxisomes?
- small spherical, membranous organelles,
- contain enzymes that use O2 to remove hydrogen atoms from fatty acids, in a reaction that produces hydrogen peroxide (H2O2) that must be broken down to water and O2 by enzyme - catalase.
- 2H2O2–> 2H2O + O2
What is the average diameter of peroxisomes?
0.5 μm in diameter
What are peroxisomes surrounded by?
a membrane
What do peroxisomes contain? For what?
contain enzymes that can either produce H2O2 (oxidases) or break it down (catalases).
What are the main enzymes of peroxisomes?
catalases
How are proteins directed to peroxisomes?
By a unique signal sequence with the help of protein chaperones, PEROXINS.
What does the peroxisome membrane contain?
A number of peroxisome-specific proteins that are concerned with transport of substances into and out of the matrix of the peroxisome.
What is the peroxisome matrix composed of?
more than 40 enzymes,
- the enzymes can operate in concert with enzymes outside the peroxisome to catalyze a variety of anabolic and catabolic reactions (e.g, breakdown of lipids)
How do peroxisomes form?
by the budding of the endoplasmic reticulum, or by division.
What is the structure of the peroxisome?
- spherical or oval in shape,
- their size and appearance can vary - they do not have a clear structure.
What are oxidases?
enzymes oxidizing substrates by removing hydrogen atoms that are transferred to molecular oxygen (O2).
producing H2O2!!
What two major types of enzymes exist within the peroxisome?
Oxidases and Catalases
What are catalases?
- enzymes which immediately break down H2O2!!
(H2O2 is potentially damaging to the cell.) - catalases also inactivate various potentially toxic molecules, including some prescription drugs, (particularly in the large and abundant peroxisomes of liver and kidney cells).
Explain the structure of mitochondria.
- membrane enclosed organelle
- with arrays of enzymes (specialised for aerobic respiration and production of adenosine triphosphate (ATP), with high- energy phosphate bonds, which supplies energy for most cellular activities.)
- size 0,5μm-10μm.
- typical mitochondria are
elliptical in shape
STRUCTURE:
- 70S ribosomes,
- double stranded DNA (mtDNA),
- Outer membrane.
- Inner membrane (cristae).
- Intermembrane space.
- Matrix.
What do mitochondria have that not many other organelles have?
a double membrane!!
How much space of the entire cell do internal membranes of mitochondria take up?
Internal membranes of all mitochondria makes up 1/3 of the total cell membrane area.
What are some peculiarities of mitochondria?
- Move slowly, (changing their size and shape.)
- Size 0,5μm-10μm.
- The number per cell can range from 1-1000.
- The typical mitochondria are
ELLIPTICAL in shape ( The morphology of mitochondria can be very different in different tissues) - Mitochondria have their own DNA, ribosomes,
capable of synthesizing proteins.
What allows mitochondria to synthesize its own proteins?
Mitochondria have their own DNA and ribosomes.
What type of ribosomes do mitochondria have?
70S ribosomes
What does the number of cristae in mitochondria corresponds to?
the energy needs of the cell
What is the function of integral proteins in mitochondria?
Integral proteins include various transport proteins that make the inner membrane SELECTIVELY PERMEABLE to the small molecules required by enzymes in the matrix.
How do eukaryotic organisms create energy?
- organisms produce energy by OXIDATIVE PHOSPHORYLATION,
- convert the energy stored in the chemical bonds (eg. carbohydrates and fatty acids) into ATP molecules.
What is the received energy in the form of ATP used for by cells?
- movement,
- reproduction,
- synthesis of various compounds (heme, lipids, amino acids).
What are the major functions of mitochondria?
- form the energy-rich compound ATP (by oxidative phosphorylation)
- regulation of apoptosis (programmed cell death)
Explain the outer membranes of mitochondria.
- smooth,
- sieve-like
- consists of 50% lipids and 50 % protein,
- contain many transmembrane proteins called PORINS (that form channels through which small molecules such as pyruvate and other metabolites readily pass from the cytoplasm to the intermembrane space)
(transmits molecules with a molecular weight of up to 5,000–10,000 Da (because it contains a large number of integral protein porins that form pores)).
Explain the inner membranes of mitochondria.
- many long folds called CRISTEA
- less permeable
- cristae project into the matrix increasing the membrane’s surface area
- the lipid bilayer of the inner membrane contains unusual phospholipids = highly impermeable to ions.
- transport proteins (integral proteins) make the inner membrane selectively permeable to the small molecules required by enzymes in the matrix.
- the inner membrane contains inner membrane subunits (these are sites of mitochondrial ATP synthase activity) eg. ETC, ATP synthase.
What are the transmembrane proteins of mitochondria called?
porins
What does the different composition and structure of mitochondrial membranes lead to?
different conductivity to various compounds and ions.
What does the number of cristea in the mitochondria correspond to?
the energy needs of the cell
What do mitochondrial membranes create?
two membrane-limited spaces
What are the two membrane-limited spaces that mitochondrial membranes create?
- intermembrane space
- intercristal space (matrix space)
What is the intermembrane space of mitochondria?
- located between the inner and outer membranes
- is continuous with the intra-cristal space, which extends into the cristae.
What is the intercristal space of mitochondria? Different name?
- matrix space,
- enclosed by the inner membrane
- contains the mitochondrial matrix.
What is the mitochondrial matrix composed of?
- WATER,
- SOLUTES,
- large matrix GRANULES (play a role
in mitochondrial calcium ion concentration), - circular DNA ,
- mitochondrial RIBOSOMES (similar to ribosomes of bacteria) ,
- soluble ENZYMES (involved in specialized mitochondrial functions eg. citric acid (Krebs, tricarboxylic acid) cycle, lipid oxidation, and mitochondrial
protein and DNA synthesis).
Who determined the nucleotide sequence of human and mouse MtDNA? When?
Sanger in 1981
What is mtDNA? What does its size depend on?
- circular, double-stranded molecule,
- its size depends on the species
What are mitochondrial diseases? How many are there?
- diseases occur:
a) following inheritance
b) following spontaneous mutations (in mitochondrial or nuclear DNA that lead to altered functions of the mitochondrial proteins (or RNA)). - at least 40 diverse disorders (due to mitochondrial failure)
What do the symptoms of mitochondrial diseases depend on?
- the target cell,
- tissues affected,
Although there is evidence for tissue-specific isoforms of mitochondrial proteins, mutations in these proteins do not fully explain the highly variable patterns or targeted organ systems observed with mitochondrial diseases.
What are possible symptoms of mitochondrial diseases?
- altered motor control;
- altered muscle output;
- gastrointestinal dysfunction;
- altered growth;
- diabetes;
- seizures;
- visual/hearing problems;
- lactic acidosis;
- developmental delays;
- susceptibility to infection or cardiac, liver, and respiratory disease.
Do mutations fully explain the highly variable patterns/organ systems observed with mitochondrial diseases?
although there is evidence for tissue-specific isoforms of mitochondrial proteins, mutations in these proteins do not fully explain the highly variable patterns or targeted organ systems observed with mitochondrial diseases.
State examples of mitochondrial diseases.
- Degenerative diseases of the brain and muscles
- Diabetes,
- heart failure
- Alzheimer’s disease
- Parkinson’s disease
- Various motor disorders
- mtDNA mutations (somatic).
- mtDNA defects are inherited
What does mtDNA encode?
mtDNA encodes important components of oxidative phosphorylation and molecules required for their synthesis.
Explain the structure of the vacuole. What is the chemical composition of the ‘cell juice’? What is its pH?
- tonoplast takes up 90% of the cell
- pH 3-6
- 70-95 % water
- 5-30 % organic and mineral
substances
What is the tonoplast?
restricted portion of the cell filled with cell juice.
What are the functions of the vacuole?
- Storing substances
- Isolating materials that might be harmful or a threat to the cell
- Containing waste products
- Containing water in plant cells
(Maintaining internal hydrostatic pressure or turgor within the cell) - Allows plants to support structures such as leaves and flowers due to the pressure of the central vacuole
- Maintaining an acidic internal pH
- Containing small molecules
- Exporting unwanted substances from the cell
What are the three major types of plastids?
- Chromoplasts
- Leucoplasts
- Chloroplasts
Explain the structure of a chloroplast.
- double membrane Stroma
- thylacoids
- granum
- stromal thylacoids or lamellae
- DNA
- chlorophyll
- carotenoids (carotenes, xantophylls)
- enzymes
- lecithin (improve firmness, size, color and stability)
What are the functions of chloroplasts?
- photosynthesis
- synthesis of DNA, RNA, aminoacids and some proteins;
- synthesis of fatty acids , lipids, phytohormones, vitamins and secondary metabolites;
- main nutrient value of green grasses and vegetables
What are chromoplasts? What is their function? What is their structure?
- determinate red, orange and yellow colour of fruits, petals and root-crops.
- different in shape. (depending on the crystallization of pigments).
What are leukoplasts? What is their function? What is their structure?
- colorless,
- different in shape
- used for the storage of nutrients (carbohydrates, oils, proteins).
- no other structures in stroma except accumulation of nutrients.
- make plants decorative (eg. Chlorophytum)
What can plastids do?
All plastids have the ABILITY TO TRANSFORM into each other.
- (depends on the growing conditions of the plant).
