What does electron microscopy of a cell fraction indicate?
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It can show the presence of a large number of mitochondria.
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What does electron microscopy of a cell fraction indicate?
It can show the presence of a large number of mitochondria.
What defines the boundary of a eukaryotic cell?
The cell surface membrane.
What is cell fractionation?
A technique to separate major organelles from each other to study their structures and functions.
What is the primary purpose of cell fractionation?
To isolate specific cell components in bulk to identify the functions of organelles.
What conclusion can biologists draw from the presence of mitochondria in a cell fraction?
That mitochondria are the sites of cellular respiration.
What does the cytoplasm consist of?
Cytosol and organelles.
What methods can enhance contrast in microscopy?
Staining or chemical-labeling of cell components.
What is the role of membranes in organelles?
They allow compartmentalization, maintaining optimum conditions for specific functions.
What types of protein filaments are found in the cytoskeleton?
Microtubules, microfilaments, and intermediate filaments.
What are the two types of centrifugation techniques?
Differential centrifugation and density gradient centrifugation.
How do new daughter cells arise?
From cell division of a parental cell.
What is a key characteristic of the cytoplasm in bacteria?
It lacks membrane-bound organelles found in eukaryotes.
What is a key structural difference between prokaryotes and eukaryotes?
Prokaryotes lack a nucleus, while eukaryotes have a defined nucleus.
What types of storage granules can be found in the cytoplasm of bacteria?
Glycogen and lipid droplets.
What type of organisms are eukaryotes?
Plants, animals, fungi, and protists.
Who were the key figures in the development of the Cell Theory?
Matthias Schleiden and Theodor Schwann.
What is the function of the nucleus in a eukaryotic cell?
It contains hereditary material, DNA, that directs cellular activities.
What is the function of polyribosomes in bacteria?
They allow the simultaneous synthesis of many polypeptide chains from a single mRNA.
What role does the Golgi apparatus (GA) play in plant cells after nuclear division?
It is involved in the formation of the new cell wall.
What are lysosomes?
Small spherical vesicles (0.2-0.5 μm) formed by vesicles from the Golgi apparatus found in animal cells.
Do eukaryotic cells have a complex cytoskeleton?
Yes, eukaryotic cells have a complex cytoskeleton.
What are the three most common shapes of bacteria?
Spheres (cocci), rods (bacilli), and spirals.
What role do centrioles play in animal cells?
They are involved in nuclear division.
In which type of cells are lysosomes found?
Only in animal cells.
What tools do biologists use to study cells?
Microscopes and other tools of biochemistry.
How are bacteria classified based on their cell wall structure?
Into Gram positive or Gram negative bacteria.
What is the endomembrane system?
A system of intracellular membranes in eukaryotic cells that compartmentalizes organelles.
What triggers autolysis in a cell?
Lysosomes releasing their contents within the cell, usually after damage or death.
Where is most of the DNA located in a prokaryotic cell?
In a region called the nucleoid, which is not membrane-bound.
What is the size range of chloroplasts?
Diameter: 0.5-2 μm; Length: 5-10 μm.
What types of organelles do eukaryotic cells have?
Double-membrane (e.g., nucleus, chloroplast, mitochondria), single-membrane (e.g., endoplasmic reticulum, Golgi apparatus, lysosomes), and non-membrane bound (e.g., ribosomes, centrioles).
Are free and bound ribosomes structurally different?
No, free and bound ribosomes are structurally identical and can alternate between roles.
What is contrast in microscopy?
The visible differences between various parts of the sample.
What is magnification in microscopy?
The ratio of an object's image size to its real size.
What type of organisms are bacteria classified as?
Prokaryotes.
Do prokaryotes have membrane-bound organelles?
No, prokaryotes do not have membrane-bound organelles.
What is the resolution capability of modern electron microscopes?
About 2 nm.
What are nuclear pores?
Channels on the nuclear envelope for the movement of molecules between the nucleus and cytoplasm.
What are some characteristics that define a living organism?
What do bacterial cell surface membranes consist of?
A phospholipid bilayer and proteins.
What is the role of lysosomes in white blood cells like macrophages?
They engulf bacteria for defense.
What type of cell did an early ancestor of eukaryotic cells engulf?
An oxygen-using non-photosynthetic prokaryotic cell.
What is an endosymbiont?
A cell living within another cell.
What adaptations do larger eukaryotic cells have for transport?
Organelles and structural adaptations.
What does the nucleus store that is essential for genetic continuity?
Hereditary material (DNA).
What are the two main types of microscopes mentioned?
Light microscopes and electron microscopes.
How do prokaryotic and eukaryotic cells differ in size?
Prokaryotic cells are generally smaller than eukaryotic cells.
What is homogenisation?
The process of breaking open cells to release cellular contents.
What is the cytoskeleton?
A framework of protein filaments that gives eukaryotic cells their shape and serves other functions.
What are the two main components of the peptidoglycan structure?
N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
What happens to the surface area-to-volume ratio as a cell increases in size?
It decreases.
What are histones?
Proteins around which DNA is coiled to form chromatin.
What is a mesosome in bacteria?
An in-folding of the membrane for attachment of the bacterial chromosome during binary fission.
What is the glycocalyx and its forms?
A coating on the outer surface of the cell wall that can be a slime layer or a structured capsule.
What advantages does the glycocalyx provide to bacteria?
Helps adhere to surfaces, protects from viral attack and toxic substances, conserves water, and aids mobility.
What do the large arrows in the endosymbiotic theory diagram represent?
Change over evolutionary time.
How does the nucleus control cell activities?
By regulating gene expression and protein synthesis.
What happens to proteins synthesized in the rER?
They are either inserted into membranes, secreted, or packaged into lysosomes.
What is the structure of centrioles?
Centrioles exist as a pair of rod-like structures with a diameter of 200 nm and a length of 500 nm, positioned at right angles to each other.
What is the appearance of the cytoplasm in an electron micrograph?
It often appears more darkly stained outside of the nucleoid region.
What are the three important parameters in microscopy?
Magnification, resolution, and contrast.
Why are most organelles within eukaryotic cells difficult to resolve using standard light microscopy?
Because they are too small.
How can cells be broken apart during homogenisation?
By cutting, grinding, chemicals, enzymes, sound waves, or forcing through small spaces at high pressure.
What is centrifugation?
The separation and isolation of organelles of different sizes using centrifugal force.
What is the smallest and most basic unit of life?
The cell.
What is the genetic material structure in prokaryotes?
Circular DNA.
What is the purpose of a transmission electron microscope (TEM)?
To study the internal structure of cells.
Where is most of a cell's DNA located?
In the nucleus.
How do the proportions of proteins and lipids in bacterial membranes compare to eukaryotic membranes?
Bacterial membranes usually have a higher proportion of proteins.
Do fungi and plant cells have centrioles?
No, they do not have centrioles in their centrosomes.
What process do lysosomes use to degrade worn-out organelles?
Autophagy.
What are some components of the endomembrane system?
Nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and cell surface membrane.
What are plasmids?
Small, double-stranded, circular, extra-chromosomal DNA found throughout the cytoplasm.
What do the small arrows inside the cells in the endosymbiotic theory diagram indicate?
The process of the endosymbiont becoming an organelle.
What distinguishes proteins made on free ribosomes from those made on rough ER?
Proteins made on free ribosomes generally function within the cell, while those made on rough ER are destined for membranes, organelles, or export from the cell.
What is the endomembrane system?
A complex internal membrane system in eukaryotes involved in the synthesis, transport, and modification of proteins and lipids.
What types of reactions occur in the chloroplast during photosynthesis?
Light-dependent reactions occur on the thylakoid membrane, while light-independent reactions (Calvin cycle) occur in the stroma.
How does a light microscope work?
It passes visible light through the specimen and glass lenses to magnify the image.
What are organelles?
Discrete subcellular structures with specific functions.
What is the shape and size of the nucleus?
Spherical or ovoid shape with a diameter of 10-20 μm.
What encloses the nucleus?
A double membrane called the nuclear envelope.
What is the resolution limit of a light microscope?
About 0.2 μm, regardless of magnification.
What is the primary component of the bacterial cell wall?
Peptidoglycan.
What does differential centrifugation involve?
A series of centrifugation at successively higher speeds to spin down organelles of increasingly smaller sizes.
What fills the nucleus?
A semi-fluid matrix called nucleoplasm.
What do lysosomes fuse with to digest materials?
Vesicles formed by endocytosis, such as food vacuoles.
What does the endosymbiotic theory explain?
The evolution of eukaryotic cells.
What are the two types of cells based on size?
Prokaryotic cells (0.5-10 μm) and eukaryotic cells (10-100 μm).
What does the term 'eukaryotic' mean?
'True nucleus' (from Greek 'eu' meaning true and 'karyon' meaning kernel).
What are the functions of organelles in eukaryotic cells?
Organelles perform various functions essential for the cell's survival and operation, such as energy production, protein synthesis, and waste processing.
What type of DNA is found in mitochondria and chloroplasts?
Circular DNA.
What is the diameter of a eukaryotic ribosome?
About 20 nm.
What is a major difference between prokaryotic and eukaryotic cells regarding organelles?
Prokaryotes lack membrane-bound organelles, while eukaryotes have many.
What is the distinct structural polarity of the Golgi apparatus?
The membranes of the cisternae on opposite sides differ in molecular composition.
Do prokaryotic cells have internal membranes?
Most do not, but some have infoldings of the cell surface membrane associated with respiration or photosynthesis.
What types of genetic material are found in the stroma of chloroplasts?
Circular DNA and 70S ribosomes.
What is one of the roles of calcium ions stored in the sER?
They are required for signal transduction during cell signaling or muscle contraction.
What separates the outer and inner membranes of the mitochondrion?
The intermembrane space.
What are clusters of ribosomes in bacteria called?
Polyribosomes or polysomes.
What are the two phases of cell fractionation?
Homogenisation and centrifugation.
What is the effective magnification limit of light microscopes?
About 1,000 times the actual size of the specimen.
What is resolution in microscopy?
A measure of the clarity of the image, defined as the minimum distance that allows two points to be distinguished as separate.
What is the purpose of a scanning electron microscope (SEM)?
To study the detailed surface of a specimen.
What are bacilli?
Rod-like prokaryotes that are mostly solitary but can form chains.
What are the two main types of cells?
Prokaryotic and eukaryotic.
What is the structure of a typical bacterial cell?
Small and unicellular, with a peptidoglycan cell wall, circular DNA, 70S ribosomes, and lack of membrane-bound organelles.
What are the two forms of chromatin in a non-dividing cell?
Heterochromatin (more condensed) and euchromatin (less condensed).
What is the significance of microscopy in cell theory development?
Microscopy allowed scientists to observe cells, leading to the formulation and expansion of the Cell Theory.
What membranes are not included in the endomembrane system?
Mitochondrial or chloroplast envelopes.
What is the primary function of ribosomes?
They are the site of protein synthesis, where amino acids are joined to form polypeptide chains via peptide bonds.
What is the gel-like matrix inside chloroplasts called?
Stroma.
What is glycosylation in the context of the Golgi apparatus?
It is the addition of short chains of sugar molecules to proteins for proper function and routing.
What are the two types of endoplasmic reticulum?
Rough endoplasmic reticulum (rER) and smooth endoplasmic reticulum (sER).
Are the membranes of the rough and smooth ER connected?
Yes, the membranes are connected and their internal spaces are continuous.
What is the primary function of mitochondria?
They are the site of cellular respiration, producing ATP.
What are examples of eukaryotic cells?
Animal and plant cells.
What can biochemical tests on a cell fraction reveal?
They can show the presence of enzymes for cellular respiration.
What type of ribosomes are found in the cytoplasm of bacteria?
70S ribosomes, consisting of a small subunit (30S) and a large subunit (50S).
What is cytosol?
The fluid portion of the cytoplasm that contains ions and organic compounds.
What is the largest organelle in a eukaryotic cell?
The nucleus.
What type of microscope is required to see organelles in detail?
An electron microscope (EM).
What does an electron microscope use instead of light?
A beam of electrons.
What do lysosomes contain?
Hydrolytic enzymes (e.g., lipases, proteases, nucleases) surrounded by a single membrane.
What is the pH level of the contents inside lysosomes?
The contents are acidic, and the enzymes have a low optimum pH.
What is the primary function of lysosomes in animal cells?
They serve as a digestive component and organelle-recycling facility.
What do centrioles function as in the cell?
Microtubule organizing centers (MTOC) for spindle fiber assembly.
What is the distinct and most visible structure within the nucleus?
The nucleolus.
What are the two types of spiral prokaryotes?
Spirilla and spirochetes.
Why can prokaryotic cells efficiently transport materials?
Their small size allows for quick diffusion of ions and organic molecules.
Where is most of the DNA located in a eukaryotic cell?
In the nucleus, enclosed by a nuclear envelope.
What may have happened after the formation of the mitochondrion?
The eukaryotic cell may have engulfed a photosynthetic prokaryote, leading to chloroplasts.
What are polyribosomes?
Clusters of ribosomes that allow simultaneous synthesis of many polypeptide chains from a single mRNA.
What role do ribosomes play in the rER?
They synthesize proteins attached to the rER.
What happens to modified proteins in the Golgi apparatus?
They are sorted and packaged into secretory vesicles that bud off from the trans face.
What distinguishes rough endoplasmic reticulum (rER) from smooth endoplasmic reticulum (sER)?
rER has ribosomes attached, giving it a studded appearance, while sER does not.
How is the rER connected to the nuclear envelope?
It is continuous with the outer membrane of the nuclear envelope.
What type of organisms are prokaryotes?
Bacteria and archaea.
How do Golgi vesicles contribute to the formation of the new cell wall in plant cells?
They move between the two daughter nuclei, forming the new cell membrane and contributing to the new cell wall.
What are the three principles of cell theory?
What is the typical size range of bacteria?
0.1-10 μm in length, with an average diameter of 1 μm.
What are cocci?
Spherical prokaryotes that can be found singly, in pairs, in chains, or in clusters.
What did Robert Hooke contribute to cell biology?
He discovered cells in 1665 using one of the first microscopes.
What allows the passage of water, ions, and small molecules in the bacterial cell wall?
Tiny pores in the cell wall.
What happens to the products of digestion in lysosomes?
They may be absorbed into the cytoplasm or released from the cell.
What is the primary function of the nucleolus?
Site of transcription of rRNA and assembly of ribosomal subunits.
Is the nucleolus a membrane-bound organelle?
No, it is not enclosed by a membrane.
What are ribosomes composed of?
Proteins and ribosomal RNA (rRNA).
What is the primary function of the rough endoplasmic reticulum (rER)?
Protein synthesis and transport.
Where can ribosomes be found in a cell?
Attached to the rough endoplasmic reticulum (rER) or free in the cytosol.
What are grana in chloroplasts?
Stacks of thylakoids.
What are the main functions of the Golgi apparatus?
To chemically modify, sort, and package proteins or lipids made in the rER and sER.
What are microtubules made of?
Microtubules are long hollow tubes made up of tubulin proteins.
What can happen to vesicles from the Golgi apparatus?
They can fuse with each other to form lysosomes.
What is the function of the inner membrane's cristae?
They project into the matrix and increase surface area for biochemical reactions.
What does the semi-fluid matrix of the mitochondrion contain?
Circular DNA and 70S ribosomes.
What are the main characteristics of prokaryotes?
They are simple, unicellular microorganisms that lack nuclei or membrane-bound organelles.
What is the outer membrane of the nucleus continuous with?
The endoplasmic reticulum.
What is the Cell Theory?
The Cell Theory states that cells are the smallest unit of life, all cells come from pre-existing cells, and living organisms are composed of cells.
What is the genetic material structure in eukaryotes?
Linear DNA organized into chromosomes.
How does the bacterial cell wall prevent cell lysis?
It prevents bacteria from bursting when they absorb water.
What happens to centrioles before a cell divides?
They replicate.
What does the nucleolus contain that is essential for ribosome production?
Genes coding for ribosomal ribonucleic acid (rRNA).
What did the engulfed prokaryotic cell eventually become?
A mitochondrion within the host eukaryotic cell.
Why is the cell surface membrane considered part of the endomembrane system?
Because it interacts with other organelles of the endomembrane system.
What are plasmids?
Smaller circular DNA molecules found throughout the cytoplasm of prokaryotic cells.
What is the structure of the Golgi apparatus (GA)?
It consists of a stack of flattened membrane-bound sacs known as cisternae, which are not physically connected.
What is the function of the thylakoid membrane in chloroplasts?
It forms a network of thylakoids, which are involved in photosynthesis.
What occurs at the cis face of the Golgi apparatus?
Transport vesicles from the rough endoplasmic reticulum (rER) fuse, bringing proteins to the GA.
What is the role of transport vesicles in the rER?
They package proteins and move them to other parts of the cell, like the Golgi apparatus.
What is density gradient centrifugation?
Involves setting up a sucrose gradient where organelles migrate to form a band at the position where their density equals that of the sucrose solution.
How do digestive processes in plant cells differ from those in animal cells?
In plant cells, digestive processes involve the vacuole, while in animal cells, they involve lysosomes.
What happens to chromatin during nuclear division?
It condenses into chromosomes.
What type of DNA do all bacteria have?
A single, double-stranded, circular DNA called bacterial chromosome.
Where is the bacterial chromosome located?
In a region of the cytoplasm known as the nucleoid, which is not membrane-bound.
What role does DNA within the nucleus play in protein synthesis?
It serves as templates for protein synthesis.
What are the sedimentation coefficients of eukaryotic ribosomes?
80S, consisting of a small subunit (40S) and a large subunit (60S).
Where are proteins folded into their specific shapes?
In the ER lumen.
What is the shape and function of the trans face of the Golgi apparatus?
The trans face is concave and is where budding of secretory vesicles occurs.
What is the function of the smooth endoplasmic reticulum (sER)?
Lipid synthesis, detoxification of drugs, and storage of calcium ions.
What type of membrane structure does a mitochondrion have?
It is bound by a double membrane.
What is the significance of the 70S ribosomes in mitochondria?
They allow for protein synthesis within the mitochondrion.
What type of genes do plasmids contain?
Genes that are not essential for survival but beneficial in stressful conditions, such as antibiotic resistance.
What surrounds each chloroplast?
A double membrane called the chloroplast envelope.
Where are centrioles located in animal cells?
Next to the nucleus in a region called the centrosome.
Why is the rER abundant in liver cells?
Because it synthesizes and modifies proteins that will be secreted from the cell.
What is the typical shape of a mitochondrion?
Cylindrical or rod-shaped.
What theory explains the presence of circular DNA and 70S ribosomes in mitochondria?
The endosymbiotic theory.
What type of proteins are most secretory proteins?
Glycoproteins.
How are proteins modified as they move through the Golgi apparatus?
Proteins are transported from one cisterna to the next via vesicles and modified through a series of reactions.
What are the dimensions of a mitochondrion?
Width ranges from 0.5-1.5μm and length ranges from 3-10μm.
What is the internal compartment of the ER called?
ER lumen.
What is the arrangement of microtubules in centrioles?
Centrioles have 9 triplets of microtubules arranged in a ring, with each triplet attached by fibrils.
What separates the internal compartment of the ER from the cytosol?
The ER membrane.
How many mitochondria can a metabolically-active cell have?
More than 1000 mitochondria.
What substances are found in the stroma of chloroplasts?
Starch grains and oil droplets.
What is the structure of the endoplasmic reticulum (ER)?
A series of interconnected membranous sacs and tubules called cisternae.
