Chapter 2 Flashcards
What is the cell theory?
Cell Theory
- All organisms are composed of one or more cells.
● Prokaryotes - one cell (unicellular- carry out activities necessary for life)
● Eukaryotes - one or more cells (uni or multicellular- the activities of life are divided among numerous types of specialized cells)
- The cell is the basic structural and functional unit of all living organisms. (cannot separate mitochondria or other individual parts)
- Cells arise only from the division of preexisting cells (do not occur spontaneously)
What two types of microscopes are used to see cells and the structures within them?
Light microscopes use light to illuminate the specimen
Electron microscopes use electrons to illuminate the specimen
How big are cells?
Most cells are too small to be seen by the unaided eye—ranging from about 0.5 μm (bacteria) to a few hundred micrometres (plant cells)
Largest known cell called Valonia Ventricosa (algae)
What is the plasma membrane and what are its main functions?
All cells are surrounded by the plasma membrane, a bilayer made of lipids with embedded protein molecules
- Plasma membrane - bilayer made of lipids w/ embedded protein molecules
- Plasma membrane consists of phospholipid bilayer - hydrophobic barrier to water-soluble
substances
● Selected water-soluble substances can penetrate cell membranes through the transport of protein
channels
● Selective transport of ions + water-soluble molecules maintain specialized internal
environments required for cellular life
● Amphipathic - hydrophobic tail, hydrophilic head
What are the differences between prokaryotic cells and eukaryotes?
Prokaryotic cell (characteristic of domains Bacteria and Archaea)
□ The nucleoid region has no boundary membrane (no nucleus)
□ Many Bacteria and Archaea species contain few if any internal membranes
Eukaryotes (domain, or sub-domain?, Eukarya)
□ Have a membrane-bound compartment called the nucleus
□ Cytoplasm typically contains extensive membrane systems that form organelles
What type of cell is single-cellular but still eukaryotic?
Protists
What are the characteristics of Eukaryotic cells?
The eukaryotes include animals, plants, fungi and protists
Eukaryotic cells have a membrane-bound compartment called the nucleus
► ”eu” = “true” or “well”; “karyon” = “kernel” or “nucleus”
► “pro” = “before”
The eukaryotic cytoplasm contains a system of membranous organelles, specialized to carry out functions of energy metabolism and molecular synthesis, storage, and transport
The cytosol participates in energy metabolism and molecular synthesis and functions in support and motility
Photosynthesis occurs in the chloroplasts
What are the characteristics of prokaryotic cells?
Three shapes are common among bacterial prokaryotes: spherical, rodlike, and spiral
Information from DNA has copied into messenger RNA (mRNA) molecules and carried to ribosomes in the cytoplasm, which assemble amino acids into proteins
The plasma membrane is typically surrounded by a more rigid bilayer external cell wall coated with polysaccharides (glycocalyx)- assume they all have a cell wall, it is a slime layer; when it is firmly attached, it is a capsule
The plasma membrane contains molecular systems that metabolize food molecules (or light energy) into the chemical energy of ATP (cellular respiration occurs in prokaryotes)
Many bacteria and archaeans move using long flagella—the bacterial flagellum rotates in a socket and pushes the cell through a liquid medium
How do the plasma membrane and cell wall relate?
The eukaryotic plasma membrane is responsible for many functions involving multiple types of integral membrane proteins:
► Channel proteins transport substances in and out of cells
► Receptors recognize and bind specific signal molecules in the cellular environment and trigger internal responses
► Immune system proteins label cells as “self”
► Membranes and membrane proteins covered
A supportive cell wall surrounds the plasma membrane of fungal, plant, and many protist cells
What are Eukaryotic Ribosomes?
consist of large and small subunits
□ Designated as “80S” ribosomes (prokaryotic, mitochondrial and chloroplast ribosomes are referred to as “70S”)
Some ribosomes are freely suspended in the cytosol; others are attached to the membrane of the endoplasmic reticulum
Proteins made on free ribosomes may remain in the cytosol, pass into the nucleus, or become parts of mitochondria, chloroplasts, cytoskeleton, or other cytoplasmic structures
Proteins made on ribosomes attached to the endoplasmic reticulum (ER) follow a special path to other organelles in the cell
What is magnification?
The ratio of the object as viewed to its real size (e.g., 1200X, 400:1)
What is resolution?
The minimum distance that two points in the specimen can be separated and still be seen as two points
Depends primarily on the wavelength of light or electrons used to illuminate the specimen
Why are cells so small?
Cell size is limited by the surface area-to-volume ratio
The volume of a cell determines the amount of chemical activity that can take place within the cell.
Surface area determines the number of substances that can be exchanged between a cell and the outside environment
When a cell gets bigger, does its surface area-to-volume ratio go up or down? Explain
● Bigger cell = more capacity to undertake biochem rxns
- Surface area determines the number of substances that can be exchanged b/w cell and outside environment
● Bigger SA = more space to move things in/out
- Doubling diameter of cell = increase SA by 4x = incrase volume by 8x
- Increase size of cell = V + SA don’t increase at same rate = ratio so unproportionate that SA won’t be able to support the biochem means that V can manage
What is the difference between the word prokaryote and prokaryotic cell?
- Prokaryote - describes a unique group of evolutionarily related organisms
- Prokaryotic cell - refers to a particular cell architecture
● Lacks nucleus & not to single group of organisms
In what way is scanning electron microscopy different from transmission electron microscopy?
Scanning e- microscopy - a beam of e- scanned across a whole cell or organism
● e- excited on the specimen surface is converted to a 3D appearing image
Transmission e- microscopy - a beam of e- focused on a thin section of specimen in a vacuum
● e- that pass through from the image
● Structures that scatter e- appear dark
● Used primarily to examine structures w/in cells
● Staining + fixing methods used to highlight structures of interest
What is featured in the internal organization of the cell?
Central region
Genes
Cytoplasm
Cytoskelton
Cytosol
What is the central region?
Contains DNA molecules, which store hereditary information (genes)
Genes?
segments of DNA that code for individual proteins
Cytoplasm?
Between the plasma membrane and the central region, contains the cytosol and cytoskeleton
Cytosol?
Aqueous solution containing ions, various organic molecules, and organelles
Cytoskeleton?
Maintains cell shape and plays key roles in cell division, chromosome segregation, and transportation within the cell
What is the nucleus?
Separated from the cytoplasm by the nuclear envelope, which consists of two membranes
One membrane is layered just inside the other and separated by a narrow aqueous space (2 phospholipid bilayers)
Nuclear pore complexes embedded in the nuclear envelope regulate the transport of proteins and RNA molecules between the nucleus and cytoplasm (messenger RNA)
A channel through the nuclear pore complex, a nuclear pore, is the path for the assisted exchange of large molecules with the cytoplasm
What is the space inside the nucleus is mostly occupied by?
chromatin (a substance that is produced after combining), a combination of DNA and proteins
Chromatin can be more or less condensed at different times, giving chromosomes a different appearance
In eukaryotes, each DNA molecule is linear, and associates with proteins into chromosomes?
True
Does a eukaryotic nucleus contain one or more nucleoli, formed around the genes coding for rRNA molecules (transcription) of ribosomes (several different rRNA that go into forming ribosomes)?
True
How are ribosomal subunits formed and where do they exit?
Ribosomal subunits are formed in nucleoli and exit the nucleus through nuclear pore complexes. In the cytoplasm, they combine with other rRNA molecules and proteins to form ribosomes
What are ribosomes are the site of? What occurs?
Ribosomes are the site of translation, where mRNA is converted into proteins. Expression of genes is carefully controlled, according with the function of each cell
More protein = more ribosomes = nucleoli will be larger?
True
3 most common shapes of prokaryotes?
Spherical, rodlike, spiral
Eukayotic cells have an …. system that divides the cell into functional and structural compartments
Endomembrane
collection of interrelated internal membranous sacs that divide a cell into
functional and structural compartments
What are the compnent of the endomembrane system?
The membranes may be connected directly (physically) or indirectly by vesicles, small membrane-bound sacs that transfer substances between parts of the system
ER
Nuclear envelope
Golgi
Lysosomes
Vacuoles
Plasma membrane
What is the ER?
Endoplasmic reticulum (ER)
→ Extensive interconnected network (reticulum) of membranous channels and
cisternae
→ Each cisterna is formed by a single membrane that surrounds an enclosed space (ER lumen)
ER occurs in two forms: rough ER and smooth ER
What is the difference between the rough ER and the Smooth ER
Rough ER has many ribosomes attached to its outer surface
Proteins that are made on ribosomes attached to the ER enter the ER lumen or become integrated into the ER membrane
Rough ER contains ribosomes, proteins, lumen, carbohydrates
Proteins are then delivered to other regions of the cell (Golgi complex) using small vesicles that form from the ER
Smooth ER membranes have no ribosomes attached to their surfaces (no porteins being made)
synthesizes lipids that become part of cell membranes, stores Ca2+ ions and cell signaling
In the liver, smooth ER converts drugs, poisons, and toxic by-products into substances that can be tolerated or more easily and removed from the bod
What is the golgi complex?
The Golgi complex consists of a stack of flattened, membranous sacs (cisternae)
Responsible for final modification, sorting, + distribution of proteins + lipids
Proteins enter cis face through vesicles and modified porteins exit by trans face to plasma membrane (from which they leave out of cell by exocytosis)
Add carbs, lipids + functional groups (can cut but NOT add amino acids)
Exocytosis?
A secretory vesicle fuses with the okasma membrance, releasing the vesicle contets to the cell exterior. The vesicle membrane becomes a part of the plasma mebrane
Can be used to deliver plasma membrane proteins to the plasma membrane.
What is the relationship between the golgi complex and exocytosis?
The Golgi complex “sorts” proteins to ensure they are delivered to their final destination. (some proteins are taken back).
Proteins to be secreted from the cell are transported to the plasma membrane in secretory vesicles, which release their contents to the exterior by exocytosis
The membrane of the vesicle fuses with the plasma membrane and becomes part of the plasma membrane
Endocyosis?
Materials from the cell exterior are enclosed in a segment of plasma membrane that pockets inward and pinches off as an endocytic vesicle
Vesicles also form by the reverse process, endocytosis, which brings molecules into the cell from the exterior
The plasma membrane forms a pocket, which bulges inward and pinches off into the cytoplasm as an endocytic vesicle
Endocytic vesicles carry materials to the Golgi complex or other destinations such as lysosomes
What are lysosomes?
Lysosomes are small, membrane-bound compartments containing hydrolytic enzymes that digest complex molecules
► Cells recycle the constituents of these molecules
Found in animals + plants (eukaryotes)
Formed by budding from golgi complex
pH in lysosome is acidic (5) < pH of cytosol (7.2)
- Lysosomes do not digest endocytic vesicles
● Secretory vesicles carry materials out
● Endocytic vesicles carry materials in
In lysosomal storage diseases, one of the hydrolytic enzymes normally found in the lysosome is absent (cannot break down and recycle things).
Vesicle traffic and the endomembrane system porcess
- Proteins made by ER
ribosomes enter ek membranes
or the space inside ER cisternae.
Chemical modification of some
proteins begins. Membrane lipids
are also made in the ER. - Vesicles bud from
the ER membrane and
then transport unfinished
proteins and lipids to the
Golgi complex. - Protein and lipid
modification is completed
in the Golgi complex, and
products are sorted into
vesicles that bud from
the complex. - Secretory vesicles budding
from the Golgi membranes
transport finished products to the
plasma membrane. The products
are released by exocytosis. Other
vesicles remain in storage in
the cytoplasm. - Lysosomes budding from the
Golgi membranes contain
hydrolytic enzymes that digest
damaged organelles or the
contents of endocytic vesicles that
fuse with them. Endocytic vesicles
form at the plasma membrane
and move into the cytoplasm.
What is a nucleoid?
Nucleoid - central region of a prokaryotic cell with no boundary membrane separating it from the
cytoplasm (containing cytosol + cytoskeleton), where DNA replication and RNA transcription occur
Genetic material of archaea and bacteria in nucleoid
Some bacteria and archaeans have internal membranes. How are these internal membranes formed?
Endomembrane system - a collection of internal membranes that divide cell into structural +
functional regions
● Include golgi complex, ER, + nuclear envelope
- Internal membranes formed infolding of plasma membrane
● Most often the sites of photosynthetic + respiratory e- transport chains
Basic structure of prokaryotic cell
Plasma membrane surrounded by cell wall
- Cell wall - provides rigidity to prokaryotic cells
- Cell wall coated w/ glycocalyx - a carbohydrate coat covering the cell surface
● Glycocalyx diffused + loosely associated w/ cells = slime layer
● Glycocalyx gelatinous + more firmly attached to cells = capsule
● Helps prokaryotic cells from physical damage + desiccation
● can enable cell to attach to surfaces s/a other prokaryotic cells (forming a colony),
eukaryotic cells (streptococcus attaching to lung cells), or non-living substrate (rock)
Where in a eukaryotic cell is DNA found? How is that DNA organized?
DNA found in nucleus
- Space inside nucleus mostly occupied by chromatin (combo of DNA + proteins)
- DNA molecule is linear and organized as chromosome
● DNA → histones → nucleosome (made of 8 histones) → chromatin (4 nucleosomes) → chromosome
What is the nucleolus and what is its function?
Nucleolus (plural - nucleoli) - nuclear sites of rRNA transcription, processing + ribosome assembly
in eukaryotes
- Function
● Info in rRNA genes copied into rRNA molecules, combine w/ proteins to form ribosomal subunits
● Ribosomal subunits leave nucleoli + exit nucleus through nuclear pore complexes to enter cytoplasm = join onto mRNA to form complete ribosome
- Ribosomal subunits made of one large + one small subunit
What is the nuclear envelop?
In eukaryotes, membrane separating nucleus from cytoplasm
Vacuoles?
Large vesicles identified as distinct organelles of plant cells
Tonoplast (surrounds central vacuole) contains transport proteins moving substances in/out of central vacuole
Store salts, organic acids, sugars, storage proteins, waste products, pigments
Plasma Membrane?
Outer limit of cytoplasm responsible for regulation of substances moving in/out of cells
Bilayer made of lipids w/ embedded protein molecules
Nuclear proteins NOT an integral protein in plasma membranes
What is the structure and function of a mitochondrion?
Mitochondrion (plural - mitochondria) - membrane-bound organelle responsible for synthesis ofmost of ATP in eukaryotic cells (where cellular respiration occurs)
● 2 membranes surrounding mitochondrial matrix (innermost compartment/liquid of
mitochondrion) - outer (covers organelle) & inner (expanded by cristae)
● ATP synthesis in matrix + cristae
● Folds = more SA for cellular respiration
● Inner membrane SA > outer membrane SA
What is the mitochondria?
Membrane-bound organelles in which cellular respiration occurs
Cellular respiration is the process by which energy-rich food molecules are broken down to water and carbon dioxide by mitochondrial reactions, and energy is converted to ATP
Require oxygen for cellular respiration
→ In animals, breathing provides the oxygen to keep the process going
Two membranes surrounding the inner soluble compartment (the mitochondrial matrix)
The outer mitochondrial membrane covers the organelle; the inner mitochondrial membrane is expanded by folds called cristae
Where does ATP-generating reactions occur in?
The cristae and matrix
What is the structure and function of the cytoskeleton?
An interconnected system of protein fibers and tubes that extends throughout the cytoplasm
The cytoskeleton maintains a cell’s characteristic shape and internal organization, and functions in movement
The cytoskeleton of animal cells is comprised of microtubules, intermediate filaments, and microfilaments
What are the functions of the microtubules?
Assembled from dimers of alpha (+ end) and beta (- end) tubulin proteins
- 25 nm outer diameter (15 nm inner diameter)
- DO NOT hold CELLS in place
- Provide tracks for vesicles by moving along microtubules through push/pull mvmts
(ex. Motor proteins s/a kinesin & diesin), vesicles move between the cell interior and the plasma membrane
- Have polarity (+ and - ends)
- Dynamic = change lengths by addition/removal of tubulin dimers
- Tubulin → microtubules → centrioles (9 triplets of microtub) → centrosome (comprised of two short, barrel-shaped structures- centrioles) → MTOC (microtubule organizing centre - holds organelles in place)
- Organizes microtubule arrays that are involved in various processes
» mitosis, holding organelles in position, and others
What are the functions if intermediate filaments?
cytoskeletal filament providing mechanical strength + structural support to cells in tissues
Intermediate in size between microtubules and microfilaments (8-12 nm)
Assembled from a large and varied group of intermediate filament proteins
Occur singly, in parallel bundles, and in interlinked networks
Provides structural support in many cells and tissues, and are tissue-specific in their protein composition
Stable, form + stay the way they established
Microfilaments < intermediate filaments < microtubules
What are the functions of micofilaments?
thin protein fibres assembled from actin subunits
5-7 nm diameter
Polarity (+ and - ends)
Involved in cytoplasmic streaming - intracellular movmentt of cytoplasm
Can transport nutrients, proteins + organelles in plant/animal cells → responsible for amoeboid movment
Structural + locomotor functions (contractile elements in muscle fibres, divide cytoplasm when animal cells divide)
What are specilizaed structure of plant cells?
· Several structures are found in plant cells but not in animal cells:
► Chloroplasts
► A large central vacuole
► Plant cell walls
Chloroplasts also occur in algal protists, and cell walls in algal protists and fungi
What are flagella and Cilia and what are theit functions?
Elongated, motile structures that extend from the cell surface
Cilia are shorter than flagella and occur in greater numbers
Movements of a flagellum propel a cell through a watery medium, and cilia move fluids over the cell surface
Cilia and flagella are found in protozoa and algae
Many types of animal cells have flagella—the tail of a sperm cell is a flagellum—as do the
reproductive cells of some plants
Cilia covers the surface of cells lining cavities or tubs in some parts of the body. (cilia on cells lining the ventricles (cavities) of the brain circulate fluid through the brain, and cilia in the oviducts conduct eggs from the ovaries to the uterus.
genes that encode the components of the flagellar apparatus of cells of Bacteria, Archaea, and Eukarya are different in each case.
Flagella and Ciliary beating patterns?
Flagella beat in
smooth, S-shaped
waves that travel
from base to tip.
Cilia beat in an
oarlike power stroke
(dark orange) followed
by a recovery stroke
(light orange).
Plants are a?
Photoautotroph (produces its own energy using light)
In plant cell, function of plastids?
Chloroplasts yellow-green plastids—the sites of photosynthesis in plant cells
Others colorless and store starch (or other molecules), others are brightly colored with pigments such as carotenoids or lycopene
Contain DNA genomes + molecular machinery for gene expression and synthesis of porteins and ribosomes
- Some of the proteins within plastids are encoded by their genomes; but most are encoded by nuclear genes and are imported into the organelles from the cytosol
What is choloplasts in a plant cell?
● Surrounded by inner + outer membrane (inside the inner membrane = stroma)
● Inside stroma = thylakoids (flattened, closed sacs) which contain chlorophyll (green pigment
converted into chem energy in photosynthesis)
- Thylakoids stacked = grana
- Thylakoid membrane encloses thylakoid lumen - soluble compartment
- Thylakoid membranes contain chlorophyll, a green pigment that absorbs light energy that is ultimately converted into chemical energy in photosynthesis
In plant cells, what is the function of the vacuole?
Vacuoles - large vesicles identified as distinct organelles of plant cells
90% or more of the cell’s volume may be occupied by one or more large central vacuoles
- Tonoplast (surrounds central vacuole) contains transport proteins moving substances in/out of
central vacuole - Store salts, organic acids, sugars, storage proteins, waste products, pigments
● Contain enzymes breaking down biological molecules
● Provide chem defences against pathogenic organisms
●Supports the cell structure
●Pigments produce colors of many flowers and fruits (e.g. red-blue anthocyanin pigments used by flowers)
What are the functions of the cell walls?
- Plant cell walls
● Support individual cells, support + protect against invading bacteria
● Cell walls made of cellulose (long polymers of glucose - most abundant molecule), Aggregate into bundles called microfibrils, Embedded in a network of other polysaccharides
● Walls of adjacent cells held together by middle lamela (layer of polysaccharides - pectin)
●Contribute to the turgor pressure produced in the central vacuole
What role do plasmodesmata serve in the plant cell wall?
cell walls perforated by cytosol-filled channels lined by plasma membrane
Primary and secondary cell walls are perforated by plasmodesmata
1000 to 100 000 plasmodesmata in typical plant cell wall
Allow ions + small molecules to move directly from one cell to another through connecting
cytosol w/o having to penetrate plasma membrane or cell walls
Proteins + nucleic acids move through some plasmodesmata using energy dependent
processes
What occurs in The Animal Cell Surface?
Cell adhesion molecules organize animal cells into tissues and organs
Animal cells have specialized structures that organize cells at three levels:
1. Individual cell adhesion molecules bind cells together
2. Cell junctions seal the spaces between cells and provide direct communication between cells
3. Extracellular matrix (ECM) supports and protects cells and provides mechanical linkages between tissues
What do cell adhesion molecules do?
Glycoproteins (proteins with carbohydrates, made in the ER) in the plasma membrane that bind to specific molecules on other cells ●
Organize animal cells into tissues and organs
Cancer cells typically lose these adhesions, allowing them to break loose and migrate to new locations (which allow cancer cells to move around the body)
Cell junctions reinforce cell adhesions and provide avenues of communication
What are the 3 cell junctions in animal cells?
Anchoring, tight and gap
Define and describe functions of anchoding junctions.
Form buttonlike spots, or belts, that run entirely around cells, “welding” adjacent cells together
Desmosomes- anchoring junctions with intermediate filaments that anchor the junction in underlying cytoplasm
Adheres- anchoring junctions with microfilaments as the anchoring cytoskeletal component
● Wield adjacent cells together
● Most common in tissues subject to stretching, shear
● Have strings poking out
● Ex. heart muscle, skin
Define and describe functions of tight junctions.
Regions of tight connections between membranes of adjacent cells
Seal spaces between cells in cell layers that cover internal organs, outer surface of the body, or layers that line internal cavities and ducts
Formed by direct fusion of proteins on the outer surfaces of plasma membranes of adjacent
Connection so tight it can keep particles as small as ions from moving b/w cells in layers
Look like stitch work
● Ex. tight junctions b/w stomach, intestine, bladder
Define and describe functions of gap junctions.
Open direct channels that allow ions and small molecules to pass directly from one cell to another
Hollow protein cylinders embedded in plasma membranes of adjacent cells connects the cytoplasm of one cell with the cytoplasm of the next
Gap junctions communicate between cells within a tissue, such as heart muscle tissue
Occur b/w cells w/in almost all body tissues but not b/w cells of diff tissues
● Ex. heart muscle tissues, smooth muscle tissues forming uterus
What is the structure and function of the ECM?
Extracellular Matrix (ECM) - molecular system supporting and protecting cells + providing mechanical linkages
Many animal cells are embedded in an ECM that consists of proteins and polysaccharides secreted by the cells themselves
ECM provides protection and support, also affects cell division, adhesion, motility, and embryonic development, and takes part in reactions to wounds and disease
- Structure + support
- Forms mass of skin, bones, tendons, highly specialized extracellular structures
- Glycoproteins main component of ECM
- Consistency of ECM (from soft/jellylike to hard/elastic) depends on network of proteoglycans that surround collagen fibres
● Tendons = almost pure collagen = tough + elastic - In cartilage, which contains a high proportion of interlinked glycoproteins, the ECM is relatively soft
- In bone, the network is impregnated with mineral crystals, producing an ECM that is dense and hard, yet elastic
All organisms are composed of more than once cell.
- False (single-cell organisms exist)
- 1 cell in prokaryotes
1 or more cells in eukaryotes
- 1 cell in prokaryotes
The cell is the basic structural and functional unit of life.
True
Cells can spontaneously develop
False
Why are cells so small?
Area-to-volume ratio (volume of cell determines how much chemical reaction, must be proportional)
All cells are surrounded by a plasma membrane which is hydrophilic
False (hydrophobic- doesn’t like water)
The lipid bilayer contains
Phospholipid molecules ( hydrophilic tails and hydrophobic heads)
The order of components in the phospholipid bilayer
Head, tail, tail, head
A gene is a segment of DNA that codes for multiple proteins
False (a gene codes for a protein)
What is not contained in cytosol?
Cytoplasm ( cytoplasm contains cytosol and cytoskeleton)
Which is not one of the three common shapes among bacterial prokaryotes?
Circular
Prokaryotes contain:
Nucleoid (nucleolus in the nucleus)
The plasma membrane is usually surrounded by a cell wall coated with polysaccharides in prokaryotes:
True
The polysaccharide coating is also known as:
Glycocalyx, capsule, slime layer (slime is hard it is like a pill which Is capsule)
Cell walls are only found In prokaryotes:
False (some eukaryotes have cell walls like plants)
Which is not a type of integral; protein in eukaryotic plasma membranes?
Nuclear (recognition so your body knows which cells are cells)
Chromatin is a combination of DNA and proteins
True
Ribosomal subunits are formed in the nucleoli prokaryotic cells
False (prokaryotic cells do not have nucellus and nucleoli, true for eukaryotes)
Eukaryotic ribosomes have one large subunit and two small subunits
False (one large unit, one small unit)
Which is not part one the endomembrane system:
DNA
Rough ER does not contain
Vacuoles
Smooth ER membranes have no ribosomes attached to their surfaces
True (in the rough ER no smooth ER)
What is a function of the smooth ER?
Synthesise lipids (not synthesize proteins because rough ER is where proteins are made because it has ribosomes)
Proteins are delivered from the rough ER to the Golgi complex using small vesicles
True (rough ER to the Golgi to the vesicles)
Proteins from the ER enter the Golgi on the trans face of the complex
False (enter on the cis face)
What is not a function of the Golgi complex?
Add amino acids (ribosomes are on rough ER which add amino acids)
Secretory vesicles carry materials to the Golgi complex and lysosomes
False (secretory vesicles carry out materials, endocytic bring materials in)
Which is not something that lysosomal enzymes digest?
Endocytic vesicles (morphs with vesicle)
The intramitochondrial membrane is expanded by folds called cristae
True
Atp-generating reactions occur in the cristae and matrix
True (inside mitochondria is called matrix)
What is the smallest component of the cytoskeleton?
Microfilaments
Microtubes are assembled from dimers of A-tubulin and B-tubulin proteins
True
What do microtubules not do?
Hold cells in place (providing tracks for vesicles- kinesin and disoin are molecules that move along the microtubes which provide tracks)
What do microtubules not do?
Hold cells in place (providing tracks for vesicles- kinesin and disoin are molecules that move along the microtubes which provide tracks)
Motor proteins such as myosin push or pull against microtubules to generate filaments
False (kinesin and disoin not myosin)
What is true about intermediate filaments
provides structural support (Microtubules are 25 cm and provide tracks for vesicles.)
What isn’t true about microfilaments?
they have polarity( different charges on different ends), they have acting subunits, involved in cytoplasmic streaming (all true), microtubules have polarity
What is not specialized structure of plant cells?
Cytoskeleton (eukaryotic and prokaryotic cells have cytoskeletons)
