Chapter 6: A Tour of the Cell
A muscle tear injury would probably involve the rupture of which type of cell junction?
Anchoring junction
Describe two different ways in which cilia can function in organisms.
Cilia may propel a cell through its environment or sweep a fluid environment past the cell
The structures of these two organelles are easily recognizable. They both have two membranes, and the inside of the chloroplast also has stacks of membrane disks that are individually called thylakoids and collectively called grana. The functions of these two organelles are fundamental opposites: 1. The chloroplast builds glucose in order to store energy for the cell. It uses carbon dioxide and water and releases oxygen during this process of photosynthesis. 2. The mitochondrion breaks glucose down in order to get the energy out to make ATP. ATP is what the cells use directly for energy for any cell processes. The process uses glucose and oxygen and releases carbon dioxide and water during cellular respiration.
Compare the structures and functions of chloroplasts and mitochondria.
What is the difference between immunofluorescence microscopy and molecular cytochemistry?
In the former, fluorescently labeled antibodies show the lacations of specific molecules. In the latter, the molecules themselves are labeled, and their behavior within a living cell can be tracked.
How is lysosome like a recycling center?
It breaks down damaged organelles and recycles their molecules.
• shape and support the cell and • act as tracks along which organelles equipped with motor proteins move.
Microtubules [made of tubulin (a protein)]
Which membrane in a chloroplast appears to be the most extensive? Why might this be so?
The thylakoid membranes contain chlorophyll for photosynthesis.
• the production of enzymes important in the synthesis of lipids, oils, phospholipids, and steroids, • the production of enzymes that detoxify drugs, alcohol, and other substances • storage of calcium ions
What are the metabolic processes that smooth ER is involved in?
• additional membrane for itself, • secreted proteins (peptide hormones), • Integral membrane proteins (channels and transporters, e.g.), and • Proteins destined for incorporation into other organelles (digestive enzymes targeted to lysosome, e.g.).
What does Rough ER make?
a protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protsists; protects the cell and helps maintain its shape.
cell wall
A system within a cell that includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and the plasma membrane.
endomembrane system
the largest component of the endomembrane system; an extensive network of flattened sacs and tubules; (Latin meaning: "within the cytoplasm;" "little net.")
endoplasmic reticulum
A theory that states mitochondria and chloroplasts were formerly small prokaryotes that began living within larger cells. These prokaryotes may have gained entry to the larger cell as undigested prey or parasites.
endosymbiont theory
A type of cell that has a membrane-enclosed nucleus and membrane-enclosed organelles. All organisms except bacteria and archaea are placed in the domain Eukarya.
eukaryotic cells
also called actin filaments, are solid rods composed mainly of globular proteins, arranged i a twisted double chain; form a three-dimensional network just inside the plasma membrane that helps support the cell's shape.
microfilaments
the thickest of the three main kinds of fibers making up the cytoskeleton of a eukaryotic cell; a hollow tube made of globular proteins called tubulins; found in cilia and flagella
microtubules
1. The intermembrane space is the narrow region between the inner and outer membranes. 2. The mitochondrial matrix
mitochondria
organelles that carry out cellular respiration in nearly all eukaryotic cells, converting the chemical energy of foods such as sugars to the chemical energy of the molecule called ATP (adenosine triphosphate).
mitochondria
An endoplasmic reticulum that lacks attached ribosomes;
smooth endoplasmic reticulum (ER)
Which component of the cytoskeleton is most important in (a) holding the nucleus in place within the cell; (b) guiding transport vesicles from the Golgi to the plasma membrane; (c) contracting muscle cells?
(a) intermediate filaments; (b) microtubules; (c) microfilaments
Which type of microscope would you use to study (a) the changes in shape of a living human white blood cell; (b) the finest details of surface texture of a human hair; (c) the detailed structure of an oraganelle in a liver cell?
(a) light microscope; (b) scanning electron microscope; (c) transmission electron microscope
What is cellular respiration?
A process that converts the chemical energy of sugars and other food molecules to the chemical energy of ATP.
list three features that are common to prokaryotic and eukaryotic cells. list three features that differ.
Both types of cells have plasma membranes, chromosomes containing DNA, and ribosomes. Prokaryotic cells are smaller, do not have a nucleus that houses their DNA or other membrane-enclosed organelles, and have smaller, somewhat different ribosomes.
1. Spindle fibers: important for separating chromosomes during mitosis 2. Flagella: important for motility (flagella of bacteria or sperm, e.g.) 3. Cilia: motility (Paramecium) and movement of mucus in respiratory tract
Centrioles synthesize:
Identify the structures in the plant cell that are not present in the animal cell.
Chloroplasts, central vacuole, cell wall, and plasmodesmata
What four cellular components are shared by prokaryotic and eukaryotic cells?
DNA as genetic material, ribosomes, plasma membrane, and cytosol
Describe the processes that occur in the nucleus.
DNA is copied and passed on to daughter cells in cell division; rRNA is made and ribosome sub units assembled; protein-making instructions in DNA are transcribed into mRNA.
1.) Genetic Control- Nucleus and Ribosomes. 2.) Manufacturing, Distribution, and Breakdown- Rough ER, Smooth ER, Golgi Apparatus, Lysosomes, Vacuoles, Peroxisome 3.) Energy Processing- Mitochondria, Chloroplasts 4.) Structural Support, Movement, and Communication Between Cells- Cytoskeleton, Extracellular matrix, Cell junctions, Cell walls
Describe the four functional categories of organelles in eukaryotic cells.
Which structure includes all others in the list: rough ER, smooth ER, endomembrane system, nuclear envelope?
Endomembrane system
a cell with a membrane bound nucleus and organelles
Eukaryotic cells
How do mitochondria, smooth ER, and the cytoskeleton all contribute to the contraction of a muscle cell?
Mitochontdria supply energy in the form of ATP. The smooth ER helps regulate contraction by the uptake and release of calcium ions. Microfilaments function in the actual contractile apparatus.
double membrane of the nucleus, separating its content from the cytoplasm
Nuclear envelope
a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope
Nuclear lamina
Cell's control center; membrane-bound organelle that contains most of the cell's genetic material and synthesizes messenger RNA (mRNA) according to instructions provided by DNA
Nucleus
are eukaryotic organisms that are not animal, plant, or fungus. Paramecium and algae are examples
Protist
all living things are composed of cells that all cells come from other cells.
cell theory
An open channel in a plant cell wall through which strands of cytoplasm connect from adjacent cells. Water and other small molecules can readily pass from cell to cell.
Relate the structures of plant cell walls and plasmodesmata to their functions.
What role do ribosomes play in carrying out the genetic instructions of a cell?
Ribosomes synthesize proteins according to the instructions of messenger RNA, which was transcribed from DNA in the nucleus.
The cells of an ant and an elephant are, on average, the same small size; an elephant just has more of them. What is the main advantage of small cell size? (Explain your reasoning)
Small cells can better take up sufficient nutrients and oxygen to service their cell volume (small cells have a greater ratio of surface area to volume.)
break down fatty acids to be used as cellular fuel.
Some peroxisomes
What is the relationship of the Golgi apparatus to the ER protein-secreting cell?
The Golgi receives transport vesicles budded from the ERt hat contain proteins synthesized by bound ribosomes. The Golgi finishes processing the proteins and dispatches transport vesicles to the plasma membrane, where proteins are secreted.
All eukaryotes have mitochondrria, but not all have chloroplasts. What is the evolutionary explanation?
The first endosymboiosis would have given rise to eukaryotic cells containing mitochondria. A second endosymbiotic event gave rise to cells containing chloroplasts as well as mitochondria.
Referring to figure 4.19, describe the structures that provide support to the plasma membrane.
The membrane is attached through membrane proteins *integrins) to microfilaments in the cytoskeleton and collagen fibers of the ECM.
Primary ciliary dyskinesia (PCD), also known as immotile cilia syndrome, is a fairly rare disease in which cilia and flagella are lacking motor proteins. PCD is characterized by recurrent respiatory tract infections and immotile sperm. How would you explain these seemingly unrelated symptoms?
Without motor proteins, microtubules cannot bend. Thus cilia cannot cleanse the respiratory tract, and sperm cannot swim.
is a food vacuole part of the endomembrane system? Explain.
Yes; it forms by pinching in from the plasma membrane, which is part of the endomembrane system.
Which animal cell junction is analogous to plasmodesma?
a gap junction
are attached to the outside of the endoplasmic reticulum (forming the rough endoplasmic reticulum or RER) or nuclear envelope.
bound ribosomes
all the chemical activities of a cell
cellular metabolism
in a plant cell, a large membranous sac with diverse roles in growth and the storage of chemical and wastes
central vacuole
In animal cells, microtubules grow out from this region near the nucleus
centrosome
photosynthesizing organelles of plants and algae
chloroplasts
The complex of DNA and prteins that makes up eukaryotic chromosomes; often used to refer to the diffuse, very extended form taken by chromosomes when a cell is not dividing.
chromatin
carry genes made of DNA
chromosones
short, numerous appendages that propel protists such as Paramecium
cilia
an infolding of the inner mitochondrial membrane.
cristae
the region between the nucleus and the plasma membrane in a eukaryotic cell
cytoplasm
Network of protein fibers extend throughout a cell; fibers play a major role in organizing the structures and activities of the cell.
cytoskeleton
a microscope which focuses a beam of electrons through a specimen or onto its surface
electron microscope (EM)
This elaborate layers helps hold cells together in tissues and protects and supports the plasma membrane; the main components are the glycoproteins, proteins bonded with carbohydrates.
extracellular matrix
a surface projection that propels a prokaryotic cell through its liquid environment.
flagella
are suspended in the cytosol
free ribosomes
short chains of sugars are often linked to the polypeptide
glycoprotein
serves as a molecular warehouse and processing station for products manufactured by the ER
golgi apparatus
The sacs in a thylakoid are often stacked like poker chips
granum
The ETC may attach to the cell through other glycoproteins that then bind to these membrane proteins
integrins
found in the cells of most animals and made of various fibrous proteins that supercoil into cabels; reinforce cell shape and anchor some organelles.
intermediate filaments
To convince yourself that a small cell has a greater surface area relative to volume than a large cell, compare the surface-to-volume ratios of the large cube and one of the small cubes in Figure 4.2A.
large cube: 54/27 = 2; small cube: 6/1 = 6 (surface area is 1 x 1 x 6 sides = 6 units ^ 2; volume is 1 x 1 x 1 unit^3.
a microscope in which visible light is passed through a specimen, such as a microorganism or a thin slice of animal or plant tissue, and then through glass lenses.
light microscope (LM)
a membrane-enclosed sac of digestive enzymes
lysosome
contains mitochondrial DNA and ribosomes, as well as enzymes that catalyze some of the reacttions of cellular respiration. The inner membrane is highly folded and contains many embedded protein molecules that function in ATP syntehsis
mitochondrial matrix
• the mitochondrial DNA, • ribosomes, and • many enzymes that catalyze some of the reactions of cellular respiration.
mitochondrial matrix
In what cell would you find the most mitochondria?
muscle cell in the thigh of a long-distance runner
a double membrane that encloses the nucleus; it has pores that allow you to move things in and out like mRNA and sub units of ribsomes
nuclear envelope
a region that DNA is coiled into
nucleoid
a prominent structure in the nucleus is the site where a special type of RNA called ribosomal RNA (rRNA) is synthesized according to instructions in the DNA
nucleolus
the organelle of a eukaryotic cell that contains the genetic material in the form of chromosomes, made of chromatin.
nucleus
membrane enclosed structures within eukaryotic cells
organelle
"little organs"; preforms specific functions in the cell.
organelles
In what cell would you find the most smooth ER?
ovarian cell that produces estrogen (a steroid hormone)
In what cell would you find the most rough ER?
pancreatic cell that secretes digestive enzymes
metabolic compartments that do not originate from the endomembrane system; an organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen, producing and then degrading hydrogen peroxide
peroxisomes
Which of the following is one of the major components of the plasma membrane of a plant cell? phospholipids; cellulose fibers; collagen fibers; pectins
phospholipids
cells structure that forms a flexible boundary between the living cell and its surroundings
plasma membrane
an open channel in a plant cell wall that connects the cytoplasm of adjacent cells
plasmodesmata
A type of cell lacking a membrane-enclosed nucleus and other membrane-enclosed organelles; found only in the domains Bacteria and Archaea.
prokaryotic cells
tiny structures that make proteins according to instructions from the genes; some are free and some bound
ribosomes
an endoplasmic reticule that has bound ribosomes that stud the outer surface of the membrane; works with Golgi to get proteins made and shipped to where they belong
rough endoplasmic reticulum
a microscope used to study the detailed architecture of cell surfaces; This uses an electron beam to scan the surface of a cell or other sample, which is usually coated with a thin film of gold.
scanning electron microscope (SEM)
The compartment inside the inner membrane holds a thick fluid which contains chloroplast DNA and ribosomes as well as many enzymes
stroma
Explain why we say that the endoplasmic reticulum is a biosynthetic workshop.
the ER produces a huge variety of molecules, including phospholipids for cell membranes, steroid hormones, and proteins (synthesized by bound ribosomes) for membranes, other organelles, and secretion by the cell.
A network of interconnected sacs that are suspended in the stroma
thylakoids
The ultastructure of a chloroplast is best studied using a:
transmission electron
a microscope which is used to study the details of internal cell structure; aims a beam of light through a specimen that is stained with atoms of heavy metals.
transmission electron microscope (TEM)
a small membranous sac in a eukaryotic cell's cytoplasm carrying molecules produced by the cell. the vesicle buds from the endoplasmic reticulum or Golgi and eventually fuses with another organelle or the plasma membrane, releasing its contents
transport vesicle
How do transport vesicleshelp tie together the membrane system?
transport vesicles mover membranes and the substances they enclose between components of the endomembrane system.
large vesicles that have a variety of functions
vacuoles
a sac made of membrane in the cytoplasm of a eukaryotic cell
vesicles
Which of the following clues would tell you whether a cell is prokarayotic or eukaryotic?: the presence or absence of a rigid cell wall; the presence or absence of ribosomes; whether or not the cell is partitioned by internal membranes
whether or not the cell is partitioned by internal membranes
In what cell would you find the most lysosomes?
white blood cell that engulfs bacteria