Chapter 3 (Raven) Flashcards
Cells are
the structural and functional units of life.
Cell theory has 3 components. list them.
- all organisms are composed of cells
- cells are the smallest units of life.
a. cells are fundamental units of structure, function, and organization in living organisms.
b. nothing smaller than a cell can be alive. - new cells can only arise from preexisting cells
Who are the two scientists that are credited with formulation of the cell theory?
Schwann and Schleiden
How do prokaryotic cells differ from eukaryotic cells?
they lack a nucleus (nucleoid instead) most only have one chromosome lack organelles (membrane-bound structures that perform specific functions) lacks a cytoskeleton no nuclear envelop
What are the four basic parts of the cell wall?
middle lamella
primary wall
secondary wall
plasmodesmata
What are the two regions within the protoplast?
nucleus
cytoplasm
What are the four major structures of the nucleus?
nuclear envelope
nucleoplasm
chromatin
nucleolus
What are the eight structures located in the cytoplasm?
plasma membrane cytosol organelles surround be two membranes organelles surrounded by one membrane endomembrane system cytoskeleton robosomes oil bodies
What organelles in the cytoplasm are surrounded by two membranes?
Plastids and mitochondria
What organelles in the cytoplasm are surrounded by one membrane?
Peroxisomes
vacuoles (tonoplast)
What are the major components of the endomembrane system?
Endoplasmic reticulum
Golgi bodies
vesicles
What are the two components of the cytoskeleton?
microtubules and actin filaments
What are the four important functions of the plasma membrane?
- it separates the protoplast from the external environment
- it mediates the transport of substances into and out of the protoplast
- coordinates the synthesis and assembly of cell wall microfibrils (cellulose)
- detects and facilitates responses to hormonal and environmental signals involved in the control of cell growth and differentiation.
What structure inside the cell do plants cells have that animal cells lack?
the vacuole and its surrounding tonoplast.
What is cytoplasmic streaming (cyclosis)?
movement of suspended substances in the cytosol, being swept along in an orderly fashion in moving currents. It facilitates the transport of materials within the cell and between the cell and its environment.
What are the two important functions of the nucleus?
- controls the ongoing activities of the cell by determining which protein molecules are produced by the cell and when they are produced
- stores genetic information, passing it on to the daughter cells in the course of cell division.
What is the nuclear genome?
total amount of genetic information stored in the nucleus.
What does the nuclear envelope contain that allows direct passage for the exchange of materials between the nucleus and the cytoplasm?
pores, 30-100 nanometers in diameter.
True or False. The outer membrane of the nuclear envelope is sometimes aligned with the endoplasmic reticulum.
True.
chromatin resides in the…
nuclear matrix.
What is chromatin?
it is made up of DNA and histone proteins. During nuclear division, these coil to form chromosomes.
True or False. the content of DNA per cell is higher in bacteria than in eukaryotic cells.
False. eukaryotic cells have more DNA per cell.
What are haploid cells?
in gametes or sex cells, haploid cells represent half of the number of chromosomes (not in pairs) of the organism and is designated as n.
What are diploid cells?
in gametes or sex cells, diploid cells are the pairs of chromosomes of the organism and is designated as 2n.
What is usually the most visible section of the nucleus?
the nucleoli.
What is the nucleolus responsible for producing?
it is the site of formation of ribosomal subunits which are then transferred (by pores) to the cytosol, where they are assembled to form ribosomes.
RNA constitutes what percentage of the mass of a ribosome?
60%
How large are ribosomes?
17-23 nanometers
where are ribosomes found in metabolically active cells?
freely in the cytosol
attached to the endoplasmic reticulum.
True or false. Plastids and mitochondria contain their own ribosomes.
true.
Ribosomes can chain to form complex proteins. What are these chains called?
polysomes.
True or false. ribosomes will vary in structure by the protein they produce.
False. Ribosomes are structurally and functionally identical, and they only differ in the type of proteins they are making at a given time.
What two processes are plastids concerned with?
photosynthesis and storage
What are the three principal types of plastids?
chloroplasts, chromoplasts, and leucoplasts.
Plastids are surrounded by an envelope consisting of two membranes whereas internally…
They form a membrane system consisting of flattened sacs called thylakoids and a homogenous matrix called the stroma.
Chloroplasts contain what two pigments?
chlorophylls (green) and carotenoids (yellow and orange)
Describe chloroplasts in plants (not algae).
disk-shaped and measure 4-6 micrometers in diameter.
True or False. Chloroplasts can reorient themselves depending on the amount of light.
True. they orient in bright light into perpendicular structures to avoid too much light absorption and photodamage.
True or False. The thylakoids in the chloroplasts are believed to constitute a single, interconnected system.
True.
Chloroplasts are generally characterized by the presence of …
grana, (granum) or stacks of disklike thylakoids that resemble a stack of coins.
True or False. Grana thylakoids are interconnected with stroma thylakoids.
True.
True or False. Chlorophylls and carotenoids are found embedded everywhere except inside the thylakoid membranes.
False. They are inside the thylakoid membranes.
What are starch grains?
temporary storage products that accumulate only when the algae or plant is actively photosynthesizing.
True or false. Chloroplasts are completely autonomous, meaning they contain all the components necessary for the synthesis of all of their own polypeptides.
False. they are semiautonomous, meaning they contain some of the components necessary for the synthesis of their own polypeptides.
How do chloroplasts resemble bacteria?
chloroplast DNA occurs in nucleoids
DNA is also not associated with histones.
their ribosomes are 2/3 of the size of those found in the eukaryotic cell.
both replicate by binary fission
How are chloroplasts different from bacteria?
bacteria have only a single DNA molecules, whereas chloroplasts have multiple DNA copies.
True or False. the formation of chloroplasts only involves the NDA from plastids.
False. both nuclear and plastid DNA are necessary for the formation of chloroplasts.
Why are chloroplasts important?
- ultimate source of all our food supplies and fuel
- use light energy and carbon dioxide to form carbs, but also involved in synthesis of amino acids, fatty acids, and a number of secondary metabolites.
- provide space for starch storage
How are chromoplasts different from chloroplasts?
they lack chlorophyll
can engulf a mass of carotenoids as occurs during the ripening of fruit
functions are not well known, but do serve as attractant for insects, so they are important in cross-fertilization.
How are leucoplasts different from chromoplasts and chloroplasts?
they lack any pigment, are less differentiated, lack an elaborate system of inner membranes.
What is the function of leucoplasts?
for amyloplasts (a type of leucoplast) the function is the synthesis of starch. for other types, they are thought to be capable of forming a variety of substances like oils and proteins.
What are proplastids?
small, colorless or green, undifferentiated plastids that occur in meristematic cells of roots and shoots; precursors to other plastid types.
what is an etioplast?
a plastid containing prolamellar bodies, which develop in leaf cells of plants grown in the dark. They become chloroplasts when exposed to light.
True or False. Plastids can change type.
True.
True or False. Proplastids in embryos of seeds develop first into etioplasts, then into chloroplasts upon light exposure.
True.
How do plastids reproduce?
by fission. in meristematic cells, the division keeps pace with cell division, but in mature cells, most plastids are derived from the division of mature plastids.
What is the purpose of cristae in mitochondria?
they increase surface area available to proteins and reactions associated with them. (folds or tubules)
True or False. both mitochondria and plastids have 2 membranes and are the same size.
False. While they both have two membranes, mitochondria are smaller, measuring about half a micrometer in diameter, and exhibit great variation in length and shape.
Mitochondria are the site of…
respiration
What is respiration?
the process involving the release of energy from organic molecules and its conversion to ATP (adenosine triphosphate), the chief immediate source of energy for all eukaryotic cells.
True or false. the number of mitochondria in cells is related to the cell’s demand for ATP.
True.
Other than respiration, what processes are mitochondria involved in?
biosynthesis of amino acids, vitamin cofactors, and fatty acids
play a role in programmed cell death
What is programmed cell death?
genetically determined process that leads to the death of the cell.
What is cytochrome c?
it is released by mitochondrial swelling prior to programmed cell death. It normally involved in electron transport. It’s release is critical for the activation of proteases and nucleases (enzymes) that bring about degradation of the protoplast.
True or false. Mitochondria are semiautonomous organelles.
True.
In plant cells, genetic information is found in these three different compartments:
- nucleus
- plastids
- mitochondria
True or false. mitochondria and chloroplasts evolved from engulfed bacteria in independent symbiotic events.
true.
as a consequence of the symbiosis of mitochondria and chloroplasts, (which received protection) eukaryotic cells were able…
invade the land and acidic waters where the prokaryotic cyanobacteria are absent but the eukaryotic green algae abound.
What is another name for Peroxisomes?
microbodies
What are peroxisomes?
spherical organelles that have a single bounding membrane and range in diameter from 0.5-1.5 micrometers, a granular interior composed of protein, lack internal membranes, and are closely associated with one or two segments of endoplasmic reticulum. self-replicating, but have no DNA, so must import materials required for replication as well as all their proteins. Undergo movement within the cell.
What are the two purposes of peroxisomes?
- play in important role in photorespiration
2. glyoxysomes contain enzymes necessary for the conversion of stored fats to sucrose during germination in many seeds.
What is photorespiration?
a process that consumes oxygen and releases carbon dioxide.
True or false. the two types of peroxisomes are not interconvertible.
False. they are.
what three structures distinguish plant cells from animal cells?
the vacuole, plastids, and cell wall.
Vacuoles can originate directly from the endoplasmic reticulum, but most tonoplasts and vacuolar proteins…
originate in the Golgi bodies.
Vacuoles are filled with a liquid called…
cell sap.
though the cell sap can vary based on type of plant, organ, cell, and developmental and physiological state, the main ingredient in cell sap is…
water.
What inorganic ions are contained in cell sap?
calcium 2 ions, potassium ions, chloride ions, sodium ions, and hydrogen phosphate.
Other than inorganic compounds, cell sap commonly contains…
sugars, organic acids, and amino acids. crystals can form, calcium oxalate being most common.
True or false. vacuoles synthesize the molecules they accumulate.
False. they (mostly) cannot synthesize, they merely receive them from other parts of the cytoplasm.
What are the functions of vacuoles?
storage
removal of toxic secondary metabolites
pigment deposition (anthocyanins)
breakdown of macromolecules and their recycling inside of the cell
What is the ER (endoplasmic reticulum)?
a complex, three dimensional membrane system that permeates the entire cytosol.
What does ER appear as in sectional view?
two parallel membranes with a narrow lumen.
While rough endoplasmic reticulum is involved in protein storage, smooth ER…
secretes lipids.
Rough ER forms cisternae, while smoother ER…
is more tubular.
True or False. Cells can only have one type of ER, not both.
False both types (Rough and smooth) exist in the same cell.
What is another term for the peripheral cytoplasm?
cortical cytoplasm.
What is the function of cortical ER?
regulation of calcium ions in the cytosol
anchors the cytoskeleton of the cell
indication of metabolic/developmental status (quiescent cells have less, active have more)
communication and material transport system
through plasmodesmata, communicates with other neighboring cells
production of oil bodies
True or false. Oil bodies are considered to be an organelle.
False. they are not organelles, as they have no membrane.
dictyosomes are also known as…
Golgi bodies
Golgi bodies consist of 5-8…
cisternae (disk-shaped sacs) that are branched into a series of tubules at their margins.
Unlike mammalian Golgi bodies, plant cells consist of many separate….
stacks that remain active during mitosis and cytokinesis.
What are the two poles of a Golgi body called?
cis (forming) and trans (maturing)
What is the trans-Golgi network?
a route running from the maturing face of a Golgi body to the plasma membrane.
Golgi bodies are involved in….
secretion.
In plants, Golgi bodies are mostly involved in…
the synthesis and secretion of noncellulosic polysaccharides (hemicelluloses and pectins) destined for incorporation into the cell wall.
What, besides their primary function, do Golgi bodies secrete?
glycoproteins transferred from the ER in transition vesicles.
What are shuttle vessicles?
they are located in the Golgi body and move the vesicle through the layers of the maturing face.
True or false. Golgi bodies can process polysaccharides and glycoproteins simultaneously.
True.
coated vessicles contain which protein?
clathrin.
those vessicles destined for the cell wall are…
not coated, and their movement depends on the presence of actin filaments.
Vesicles are fused into the cell wall by a process called…
exocytosis.
Cells return to the Golgi bodies from the cell wall by a process called…
endocytosis.
Which membranes comprise the endomembrane system?
plasma membrane, nuclear envelope, ER, Golgi bodies, tonoplast and various kinds of vesicles.
What is a cytoskeleton?
a three-dimensional network of protein filaments extended through the cytosol and has many functions.
What processes is the cytoskeleton involved with?
cell division, growth, differentiation, as well as the movement of organelles from one location to another within the cell.
what two types of protein filaments exist in plant cells?
microtubules and actin filaments
True or false. both plant and animal cells may contain a third filament referred to as the intermediate filament, about which little is known.
True.
microtubules are cylindrical structures around 24 nanometers in diameter, varying length, and made up of subunits of which protein?
tubulin
microtubules are comprised of how many helix-shaped protofilaments
13
Microtubules have two ends, the growing end labeled the _____ and the receding end labeled as the _____.
plus end; slow growing end
True or false. Once microtubules are formed, they are never changed.
False. they are dynamic and undergo sequences of breakdown, re-formation, and rearrangement coinciding with specific times in the cell cycle and during differentiation, a behavior called dynamic instability.
The assembly of microtubules takes place at specific nucleating sites called…
microtubule organizing centers.
What two places have been identified as microtubule organizing centers?
the surface of the nucleus and portions of the cortical cytoplasm.
What are the functions of microtubules?
- orderly growth of the cell wall
- direction of wall growth aligns with the cellulose microfibrils in the wall.
- direct Golgi vesicles with noncellulosic substances toward the developing wall.
- make up spindle fibers, important in cell division. \
- components of flagella and cilia and are involved with those structures’ movements.
True or false. actin filaments, unlike microtubules, are not polarized.
False. they are.
what activities are actin filaments involved with?
- cell wall deposition
- tip growth of pollen tubes
- organelle movement
- movement of nucleus before and after cell division
- vesicle-mediated secretion
- organization of the ER
- cytoplasmic streaming
Where are flagella found in plants?
only in gametes that have motile sperm (mosses, liverworts, ferns, cycads, and maidenhair tree (Gingko Biloba).
explain the 9 plus 2 organization in flagella (in all eukaryotes.)
an outer ring of 9 pairs of microtubules, surrounding two additional microtubules.
how does a flagellum produce movement?
the microtubules of one side will move, creating a bend in the structure.
how are flagella produced?
the arise from basal bodies, cylindrical structures located in the cytoplasm.
what are the functions of the cell wall?
- constrains expansion of the protoplast and prevents rupture of the plasma membrane when the protoplast enlarges (due to uptake of water).
- determines the size and shpae of the cell and the texutre of the tissue, and contributes to the final shape of the plant organ.
- cell types are identified by the structure of their walls.
True or False. cell walls lack enzymes.
False. they contain a variety of enzymes.
True or False. cell walls play important roles in the absorption, transport, and secretion of substances in cells.
True.
How do cell walls play a role in defense against pathogens?
by receiving and transmitting information from the pathogen’s surface to the plasma membrane.
What is the principal component of the cell wall?
cellulose
cellulose is made of…
repeating monomers of glucose attached end to end
cellulose has crystalline properties due to…
the orderly arrangement of molecules in the micelles.
True or false. cellulose microfibrils are stronger than the equivalent amount of steel.
True.
how do hemicelluloses play a role in regulating cell enlargement?
they are hydrogen-bonded to the cellulose microfibrils, and tether adjacent microfibrils.
How do pectins create the plastic or pliable properties of the cell wall?
they are hydrophilic, and this water they attract create that property.
growing primary walls are…
65% water and are low in clacium.
what is callose?
spirally wound chains of glucose residues which are a widely distributed cell wall polysaccharide.
Callose is most known for its association with the walls of ___________ (food conducting cells) of angiosperm phloem (food conducting tissue.)
sieve elements
What is the purpose of callose?
- it is deposited rapidly upon mechanical wounding or pathogenic stress, closing plasmodesmata between contiguous cells.
- development in pollen tubes
- associated with cell plates of dividing cells.
extensins are a type of…
glycoprotein.
what does lignin add to the cell wall?
compressive strength and bending stiffness. commonly found in walls of plant cells that have supporting or mechanical functions.
What three fatty substances are found in the outer protective tissues of the plant body that reduce water loss?
cutin, suberin, and waxes.
cutin is found in the walls of the_____________ and suberin is found in _________________________.
epidermis; secondary protective tissue (cork).
The cellulose layers formed first make up the ______ cell wall. The region of union of the primary walls of adjacent cells is the middle ________. Additional wall layers in some cells can make up the ________ cell wall.
primary; lamella; secondary
The secondary wall is laid down by the _______ on the inner surface of the primary wall.
protoplast
What is the role of the middle lamella?
it joins adjacent cells
the primary wall is deposited while…
the cell is increasing in size.
actively dividing cells commonly have…
only primary cell walls.
cells with only primary cell walls include:
actively dividing cells, mature cells involved in photosynthesis, respiration, and secretion, principal cells involved in wound healing and regeneration.
primary walls have pit fields, which creates an uneven thickness through which ____________ are commonly aggregated.
plasmodesmata.
True or False. Primary and secondary walls for at the same time.
false. secondary walls develop after primary walls stop growing.
secondary walls are important in specialized cells that…
have a strengthening function and those involved in the conduction of water.
The lack of pectin in secondary cell walls means that…
they are rigid and not readily stretched.
the matrix of the secondary wall is composed of…
hemicellulose, structural proteins, and enzymes.
the secondary wall has how many layers?
three: S1, S2, and S3.
Why are the three secondary walls considered distinct?
because they differ from one another in the orientation of their cellulose microfibrils.
True or false. the cellulose microfibrils of secondary walls are laid down in a denser pattern than in the primary wall.
true.
Secondary walls are not laid down over _______ and thus create ______ in the secondary wall.
pit fields; pits
the plasma membrane, secretory vesicles and microtubules create interactions to promote ______ of the cell wall.
growth
true or false. the protoplast biochemically controls extension of the cell wall.
True.
How does a primary wall become loosened to allow for growth?
by hormones and expansins (class of wall proteins.)
cellulose microfibrils involved in primary wall growth are synthesized by _________________ complexes that occur in the plasma membrane.
cellulose synthase
in seed plants, cellulose synthase complexes appear as six hexagonally arranged particles that span the membrane called …
rosettes.
explain the process by which cellulose microfibrils are connected to the existing primary cell wall to allow growth.
Rosettes extrude the microfibrils
movement is guided by the underlying cortical microtubules
the rosettes are inserted into the plasma membrane by secretory vesicles from the trans-Golgi network.
Plasmodesmata are cytoplasmic strands….
that connect the protoplasts of adjacent cells.
what is the primary function of plasmodesmata?
they provide a pathway for the exchange of certain nutrients.
