Eukaryotes And Prokaryotes Flashcards
Where is DNA located in eukaryotes?
In membrane-bound organelles.
Where is DNA located in prokaryotes?
In a non-enclosed nucleoid.
What shape are chromosomes in prokaryotes?
Circular.
What shape are chromosomes in eukaryotes?
Linear.
Where is extra-chromosomal DNA found in prokaryotes?
In plasmids.
Where is extra-chromosomal DNA found in eukaryotes?
In plasmids only in yeast.
How does cell division take place in prokaryotes?
By binary fission.
How does cell division take place in eukaryotes?
By mitosis/cytokinesis.
How does recombination of genetic material occur in prokaryotes?
Through conjugation, transduction and transformation.
How does recombination of genetic material occur in eukaryotes?
Through sexual reproduction - Meiosis produces haploid gametes.
Do prokaryotes have membrane-bound organelles?
No.
Do eukaryotes have membrane-bound organelles?
Yes.
What does the cell membrane of prokaryotes contain?
Hopanoids.
What does the cell membrane of eukaryotes contain?
Sterols.
What is the structure of a flagella in prokaryotes?
There are diverse structures, however there is only one protein known as flagellin.
What is the structure of a flagella in eukaryotes?
9 double and 2 single microtubules.
What is the size of a ribosome in prokaryotes?
70S (50S + 30S).
What is the size of a ribosome in eukaryotes?
80S (60S + 40S).
What is the cell wall composed of in prokaryotes?
Eubacteria = Peptidoglycan Archaea = Other polymers.
What is the cell wall composed of in eukaryotes?
Plants = Cellulose Fungi = Chitin
Where does respiration occur in prokaryotes?
Across the cell membrane.
Where does respiration occur in eukaryotes?
In the mitochondria.
Where does photosynthesis occur in prokaryotes?
In association with membranes and vesicles.
Where does photosynthesis occur in eukaryotes?
In chloroplasts.
Describe the structure of the nucleus.
- Composed of chromatin and nucleoplasm.
- Nucleolus is a dense region.
- Nuclear envelope is a double membrane which is lined by lamina and perforated by pores for exchange.
- The envelope is continuous with endoplasmic reticulum; both have ribosomes.
What two organelles does the nucleus interact with?
- Cytoskeleton.
2. Endomembrane system.
State five functions of the nucleus.
- Compartmentalisation.
- Stores genetic information in a loose and condensed form.
- It uncoils loose DNA for replication and mRNA production.
- It organises chromosomes into a condensed form before mitosis.
- Ribosome production.
Describe five features of the structure of the nuclear envelope.
- It has a double membrane and the outer membrane links to RER.
- There is perinuclear space in between.
- Ribosomes are on outer membrane.
- Pores span the envelope.
- Membrane proteins link to cytoskeleton.
State two functions of the nuclear envelope.
- It separates the nucleoplasm from the cytoplasm which is known as compartmentalisation.
- The nuclear lamina of protein filaments maintain the shape.
Pores contain a large protein complex that regulates what two things?
- Importation of proteins e.g. histones.
2. Export of mRNA and ribosome subunits.
Describe the structure of a nucleolus.
It has more than one dark region in the nucleus and is not membrane bound.
What three things does the nucleolus contain?
- Hundreds of copies of ribosomal genes which code for rRNA.
- rRNA transcripts.
- r-proteins from cytoplasm.
What is the function of the nucleolus?
Ribosome synthesis.
How does the nucleolus carry out ribosome synthesis?
rRNA + r-proteins = ribosome subunit. The subunits are then exported to the cytoplasm.
Describe the structure of a ribosome.
It is a complex of catalytic rRNA and structural protein. It may exist as a polysome.
What are the two subunits of a ribosome?
Large sub-unint (LSU) and small sub-unit (SSU).
What is a small sub-unit composed of?
One strand of rRNA and more than twenty proteins.
What is a large sub-unit composed of?
Two strands of rRNA and more than thirty proteins.
What is the purpose of a sub-unit?
They only join to translate mRNA to amino acids.
What is the function of free ribosomes?
They make proteins that function in cytosol.
What is the function of membrane-bound ribosomes?
They make proteins for exportation.
Briefly state four stages in how a ribosome translates the genetic code on mRNA into protein.
- mRNA and tRNA molecules bind to the ribosome.
- tRNA brings an amino acid to the ribosome in order dictated by mRNA.
- The small sub-unit compares sequences on mRNA and tRNA.
- The large sub-unit forms peptide bonds between amino acids.
What four organelles are related through the endomembrane system?
- Nuclear envelope.
- Endoplasmic reticulum.
- Golgi apparatus.
- Cell membrane.
Define endoplasmic reticulum.
An extensive network of membranous tubules/sacs (cisternae).
What is the inside of the endoplasmic reticulum known as?
Cisternal space.
State four functions of smooth endoplasmic reticulum (SER).
- Lipid synthesis - Steroid hormones, cholesterol and phospholipids.
- Carbohydrate metabolism - It removes the phosphoryl group to produce glucose.
- Detoxify drugs - It adds a hydroxyl group to make them more soluble.
- Stores calcium ions - It transports it across the membrane to cytosol which triggers muscle contraction.
What two things does rough endoplasmic reticulum (RER) synthesise?
- Polypeptides for secretion/membranes.
2. Phospholipids for membranes.
How is a polypeptide for secretion synthesised by a rough endoplasmic reticulum?
The polypeptide is made by a bound ribosome which moves into the RER lumen and consequently has a oligosaccharide (glycoprotein) added. This then folds into an active protein and buds off in a vesicle at transitional endoplasmic reticulum and then moves along microtubule tracks.
What are the five functions of the Golgi apparatus?
- The vesicles fuse with cis face.
- Enzymes modify molecules e.g. oligosaccharide on glycoprotein.
- Molecules in vesicles bud off at trans face.
- Lysosomes also bud off.
5, Marcomolecules are synthesised e.g. pectin.
State three features of a vesicle.
- They are sacs of membrane found in cytosol.
- They are composed of one phospholipid bilayer and proteins.
- They include lysosomes, peroxisomes and vacuoles.
Define lysosome.
A digestive compartment that contain hydrolytic enzymes.
Where are lysosomes formed?
In the endoplasmic reticulum.
Where are lysosomes modified?
In the Golgi apparatus.
How do lysosomes increase their size?
By fusing with other vesicles.
How does a lysosome maintain its PH?
Its membrane pumps H+ ions in to maintain enzyme function.
Lysosomes use hydrolases to digest macromolecules. In what three ways does the lysosome carry this out?
- They fuse with food vacuoles formed by phagocytosis and digest contents.
- They digest invading bacteria and viruses in phagosomes.
- They recycle cell components which is known as autophagy.
Define autophagy.
Organelles are enclosed by endoplasmic reticulum which forms autophagosomes.
Define phagocytosis.
Large particles are taken up into phagosomes.
Define phagolysosomes.
A combination of autophagy and phagocytosis that digest the contents of a lysosome.
Define peroxisome.
They incorporate lipids from endoplasmic reticulum and proteins from cytosolic ribosomes.
What is the core enzyme of peroxisomes?
Peroxidases.
What is the purpose of oxidative enzymes in peroxisomes?
They break down molecules by transfer of H+ to O^2, producing H^2O^2.
Where is 2H^2O^2 —> 2H^2O + O^2 catalysed?
In a peroxisome.
Peroxisome enzymes transfer H+ to O2. State four functions of peroxisome enzymes.
- They break down long-chain fatty acids for cellular respiration.
- They convert fatty acids o sugar in plant seed glyoxysomes.
- They degrade toxins e.g. ethanol in liver cells.
- They are involved in cholesterol synthesis.
Define glyoxysomes.
They are pre-photosynthesis energy.
Plants cells have a LCV. What is a LCV?
Large central vacuole.
Define tonoplast.
Membrane surrounding the large central vacuole.
State three functions of vacuoles.
- They absorb H2O to allow rapid increase in cell size.
- They contain petal pigments and toxins to harm herbivores.
- Storage - Inorganic ions, carbon compounds and waste products.
What forms food vacuoles?
Phagocytosis.
What is the purpose of contractile vacuoles?
They pump H2O out of cells.
Mitochondria is enclosed in a double membrane. Describe what the outer membrane is like.
It is smooth and has porins which allow free diffusion of small molecules.
Mitochondria is enclosed in a double membrane. Describe what the inner membrane is like.
Cristea are infoldings, it is protein rich and impermeable to most ions.
mt genes are transferred to what type of DNA?
nDNA.
mtDNA allows control of what?
Cellular respiration.
Define cytoskeleton.
A network of fibres that organises cell structures and activities and extends throughout the cytoplasm.
What are the three main structural elements of the cytoskeleton?
- Microtubules.
- Intermediate filaments.
- Actin filaments.
State four features explaining the structure of microfilaments.
- Actin is globular.
- There are two intertwined filaments.
- It has thin cytoskeleton elements.
- It forms 3D branching networks.
State two features of microfilaments.
- It can rapidly dis/reassemble which is known as reversible polymerisation.
- They are polar.
State six functions of microfilaments.
- Bear tension (pulling) forces.
- They line the cell membrane so are the cell cortex.
- Muscle contraction.
- Pseudopodia.
- They form a cleavage furrow.
- Cytoplasmic streaming.
What molecule connects the extracellular matrix with actin filaments?
Integrin.
Describe the structure of intermediate filaments.
They have more than seventy fibrous proteins including keratins. They are cell-specific proteins e.g. neurofilaments. They are supercoiled into thicker “cables”.
State two features of intermediate filaments.
- They persist after cell death.
2. They are dynamic.
State four features of intermediate filaments.
- Reinforces cell shape.
- They bear tension forces.
- Support microtubules.
- Anchor the nucleus and organelles.
What is the purpose of nuclear lamina?
They have a supportive role and regulate transcription.
Describe the structure of microtubules.
- Globular tubin.
- Dimers are one alpha and one beta tubulin polypeptides.
- Dimers form thirteen protofilaments around a hollow core.
- Polar structures.
State two features of microtubules.
- They are organised by a centrosome.
2. They continually dis/reassemble.
What two functions does microtubules have?
- Shape maintenance as they resist compression.
2. They form mitotic spindles.
What four movements does microtubules allow?
- Chromatids on spindle.
- Cell locomotion e.g. flagella.
- Cilia beating.
- Intracellular organelle movement.
What two proteins allow movement of microtubules?
Kinesin and dynein.
How do bacteria grow?
Through binary fission.
What three factors limit bacterial growth?
Nutrients, waste products and environment.
What are the limitations of total cell count?
- Dead and live cells are counted.
- Small cells are difficult to see.
- Precision is difficult.
- Phase contrast needed if unstained cells.
- Not suitable for low density cells.
State three features of using ATP assay as a form of indirect measurements.
- It’s used by environmental health inspectors.
- Swap surfaces and measure light production.
- Quick and sensitive.
State three features of using impedance measurements as a form of indirect measurements.
- Measures changes in electrical properties of material due to microbial growth.
- Can be monitored in real time.
- Good in the food industry.
What are four advantages of using indirect measurements?
- Rapid.
- Often automatable.
- Some methods can be connected to a computer system and monitored in real time.
- May perform many tests at once with some methods.
What are three limitations of using indirect measurements?
- No indication of actual numbers of organisms.
- No indication of nature of organisms.
- Subculture needed to asses nature of microbial growth.
What happens as bacteria begin to run out of nutrients?
- Adaptation.
- Synthesis of storage compounds.
- Cell wall becomes stronger.
- Increased resistance to stresses.
What are the two basic types of bacteriophages?
Lytic and lysogenic.
State the six stages of the bacteriophage lytic cycle.
- Phage infects bacterial cell.
- Phage replicates genome bacterial DNA fragments.
- Synthesis of phage components.
- Packaging of DNA into phage heads.
- Phage assembly.
- Cell lysis and release of progeny virus.
What are obligate intercellular parasites?
Viruses.
What are the purposes of a capsule?
- Virulence factors.
- Prevent phagocytosis by macrophages.
- Adherence.
- Composed of colonic acid and/or polypeptides.
- Helps prevent dessication.
- Antigenic.
