Biology Chapter 4

List the four basic functional groupings of eukaryotic organelles and structures and give an example within each group

(1) The nucleus and ribosomes carry out the genetic control of the cell. (2) Organelles involved in the manufacture, distribution, and breakdown of molecules include the endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and peroxisomes. (3) Mitochondria in all cells and chloroplasts in plant cells function in energy processing. (4) Structural support, movement, and communication between cells are the functions of the cytoskeleton, plasma membrane, and plant cell wall.

Which component of the cytoskeleton is most important in a) holding the nucleus in place within an animal cell; b) guiding transport vesicles from the Golgi to the plasma membrane c) contracting muscle cells?

(a) Intermediate filaments; (b) microtubules; (c) microfilaments

Synthesis and packaging of a secretory protein by the rough ER

1)As the polypeptide is synthesized by a bound ribosome following the instructions of an mRNA, it isthreaded into the cavity of the rough ER. As it enters, the new protein folds into its three-dimensional shape. 2)Short chains of sugars are often linked to the polypeptide, making the molecule a glycoprotein 3)When the molecule is ready for export from the ER, it is packaged in a transport vesicle, a vesicle that moves from one part of the cell to another. 4)This vesicle buds off from the ER membrane.

The Golgi apparatus receiving, processing, and shipping products

1)One side of a Golgi stack serves as a receiving dock for transport vesicles produced by the ER. 2)A vesicle fuses with a Golgi sac, adding its membrane and contents to the "receiving" side. 3)Products of the ER are modified as they progress through the stack. 4)The "shipping" side of the Golgi functions as a depot, dispatching its products in vesicles that bud off and travel to other sites.

Intermediate filaments

A component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments. Are found in the cells of most animals. They are made of various fibrous proteins that supercoil into cables. Intermediate filaments reinforce cell shape and anchor some organelles. For example, the nucleus typically sits in a cage made of intermediate filaments. Whereas microtubules may be disassembled and reassembled elsewhere, intermediate filaments are often more permanent fixtures in the cell. The outer layer of your skin consists of dead skin cells packed full of intermediate filaments.

Lyosome

A digestive organelle in eukaryotic cells; contains hydrolytic enzymes that digest engulfed food or damaged organelles. a lysosome provides an acidic environment for its enzymes, while safely isolating them from the rest of the cell.

Flagella

A long, whip-like filament that helps in cell motility. Many bacteria are flagellated, and sperm are flagellated. propels the cell by an undulating whiplike motion. In contrast, cilia work more like the coordinated oars of a rowing team.

Vacuoles

A membrane-enclosed sac that is part of the endomembrane system of a eukaryotic cell and has diverse functions in different kinds of cells.

endomembrane system

A network of membranes inside and surrounding a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles.

cytoskeleton

A network of protein fibers in the cytoplasm of a eukaryotic cell; includes microfilaments, intermediate filaments, and microtubules.

What is cellular respiration?

A process that converts the chemical energy of food molecules to the chemical energy of ATP

cell wall

A protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists; protects the cell and helps maintain its shape.

motor proteins

A protein that interacts with the cytoskeleton and other cell components, producing movement of the whole cell or parts of the cell.

transport vesicles

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

Centrosome

A structure found in animal cells from which microtubules originate and that is important during cell division. A centrosome has two centrioles.

Nucleolus

A structure within the nucleus where ribosomal RNA is made and assembled with proteins imported from the cytoplasm to make ribosomal subunits.

Which of the following is one of the major components of the plasma membrane of a plant cell? A. phospholipids B. cellulose fibers C. collagen fibers D. pectins

A. phospholipids

In which cell would you find the most rough ER? A.pancreatic cell that secretes digestive enzymes B.ovarian cell that produces estrogen (a steroid hormone) C.muscle cell in the thigh of a long-distance runner D.white blood cell that engulfs bacteria

A.pancreatic cell that secretes digestive enzymes

smooth endoplasmic reticulum

An endomembrane system where lipids are synthesized, calcium levels are regulated, and toxic substances are broken down. That portion of the endoplasmic reticulum that lacks ribosomes

Endoplasmic Reticulum (ER)

An extensive membranous network in a eukaryotic cell, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.

electron microscope (EM)

An instrument that focuses an electron beam through, or onto the surface of, a specimen. An electron microscope achieves a hundredfold greater resolution than a light microscope.

Describe the pathway of the protein hormone insulin from its gene to its export from a cell of your pancreas

An mRNA molecule is transcribed from the gene for insulin and moves into the cytosol. There it joins with a ribosome that becomes attached to the outside of the rough ER (a bound ribosome). The ribosome produces a polypeptide that is threaded into the ER compartment. The polypeptide folds up and may be modified within the ER. It is then packaged into a transport vesicle. The vesicle joins with a Golgi sac, and the protein may be further modified during its journey through the Golgi apparatus. A transport vesicle pinches off from the "shipping" face of the Golgi and fuses with the plasma membrane, secreting insulin from the cell.

light microscope (LM)

An optical instrument with lenses that refract (bend) visible light to magnify images of specimens.

Golgi apparatus

An organelle in eukaryotic cells consisting of stacks of membranous sacs that modify, store, and ship products of the endoplasmic reticulum.

A muscle tear injury would probably involve the rupture of which type of cell junction?

Anchoring junction

Which of the following is the correct sequence of structures for a mitochondrion, from outside to inside? a. Cristae b. Outer membrane c. Intermembrane space d. Matrix

B. Outer membrane C. Intermembrane space D. Matrix A. Cristae

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.) A. small cell has a larger plasma membrane surface area than does a large cell. B.Small cells can better take up sufficient nutrients and oxygen to service their cell volume. C.It takes less energy to make an organism out of small cells. D.Small cells require less oxygen than do large cells.

B.Small cells can better take up sufficient nutrients and oxygen to service their cell volume.

In which cell would you find the most smooth ER? A.pancreatic cell that secretes digestive enzymes B.ovarian cell that produces estrogen (a steroid hormone) C.muscle cell in the thigh of a long-distance runner D.white blood cell that engulfs bacteria

B.ovarian cell that produces estrogen (a steroid hormone)

Which of the following clues would tell you whether a cell is prokaryotic or eukaryotic? A.the presence or absence of a rigid cell wall B.whether or not the cell is partitioned by internal membranes C.the presence or absence of ribosomes D. Both b and c are important clues.

B.whether or not the cell is partitioned by internal membranes

Which of the following associations is incorrect? a. Light microscope; live bacterial cell b. TEM; internal cellular structures c. SEM; detailed structure of a nucleus d. All of the above are correct.

C. surface details of a cell or other specimen

In which cell would you find the most mitochondria? A.pancreatic cell that secretes digestive enzymes B.ovarian cell that produces estrogen (a steroid hormone) C.muscle cell in the thigh of a long-distance runner D.white blood cell that engulfs bacteria

C.muscle cell in the thigh of a long-distance runner

The organelle responsible for performing photosynthesis

Chloroplast: An organelle found in plants and algae that absorbs sunlight and uses it to drive the synthesis of organic compounds (sugars) from carbon dioxide and water.

Identify the structures in the plant cell that are not present in the animal cell

Chloroplasts, central vacuole, cell wall, and plasmodesmata

DNA and its associated proteins are referred to as ____________.

Chromatin; the complex of DNA and proteins that makes up eukaryotic chromosomes; often used to refer to the diffuse, very extended form taken by chromosomes when a cell is not dividing.

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.

Peroxisomes

Contain oxidase enzymes that detoxify alcohol, hydrogen peroxide, and other harmful chemicals An organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen, producing and then degrading hydrogen peroxide.

Which of the following cellular components is not part of the endomembrane system? a. Vacuoles b. Golgi apparatus c. Endoplasmic reticulum d. Mitochondria

D. Mitochondria

The nuclear envelope has passages for substances moving into and out of the nucleus. These passages are called nuclear pores and they are made by proteins that are inserted into the plasma membrane that makes up the nuclear envelope. These proteins are assembled by which of the following? a. Free ribosomes b. The nucleus c. Bound ribosomes d. Nuclear pores

D. Nuclear Pores

In which cell would you find the most lysosomes? A.pancreatic cell that secretes digestive enzymes B.ovarian cell that produces estrogen (a steroid hormone) C.muscle cell in the thigh of a long-distance runner D.white blood cell that engulfs bacteria

D.white blood cell that engulfs bacteria

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 ribosomal subunits assembled; protein-making instructions in DNA are transcribed into mRNA.

In what ways do the internal membranes of a eukaryotic cell contribute to the functioning of the cell?

Different conditions and conflicting processes can occur simultaneously within separate, membrane-enclosed compartments. AlsO, there is increased area for membrane-attached enzymes that carry out metabolic processes.

nuclear envelope

Double membrane perforated with pores that control the flow of materials in and out of the nucleus.

Which structure includes all others in the list: ER, vesicle, endomembrane system, nuclear envelope?

Endomembrane system

True or false: Gap junctions prevent substances from leaking through cell layers. If false, make it a correct statement.

False: Tight junctions

Cilia

Hairlike projections that extend from the plasma membrane and are used for locomotion These cilia sweep mucus containing trapped debris out of your lungs. (This cleaning function is impaired by cigarette smoke, which paralyzes the cilia.) Most animals and some plants have flagellated sperm

central vacuole

In a plant cell, a large membranous sac with diverse roles in growth and the storage of chemicals and wastes.

._______________are a distinguishing characteristic of eukaryotic cells.

Internal Membranes

How is a lysosome like a recycling center?

It breaks down damaged organelles and recycles their molecules.

A(n)_________ uses a beam of light to illuminate the specimen.

Light Microscope

Beginning students usually confuse magnification and resolution. Briefly compare magnification with resolution.

Magnification is the increase in an object's image size compared with its actual size. Resolution is the ability to distinguish two nearby objects as separate. For example, what you see as a single star in the sky may be resolved as twin stars with a telescope

tight junctions

Membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid

___________are responsible for converting the energy within food to molecules of ATP.

Mitochondria

How do mitochondria, smooth ER, and the cytoskeleton all contribute to the contraction of a muscle cell?

Mitochondria 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.

Is this statement true or false? "Animal cells have mitochondria; plant cells have chloroplasts." Explain your answer, and describe the functions of these organelles.

Part true, part false. All animal and plant cells have mitochondria; plant cells do have chloroplasts, but animal cells do not. Both organelles process energy. A mitochondrion converts chemical energy (such as in sugar molecules) to another form of chemical energy (ATP). This process provides eukaryotic cells with ATP needed for cellular work. A chloroplast converts light energy to chemical energy (sugar molecules). These sugar molecules may then provide a plant cell's mitochondria with a source of energy. Or they may be stored in the plant body and passed to animals that eat plants or each other.

_____________are organelles involved in the metabolism of fatty acids

Peroxisomes

Mitochondria

Powerhouse of the cell, An organelle in eukaryotic cells where cellular respiration occurs. Enclosed by two membranes, it is where most of the cell's ATP is made.

Smooth endoplasmic reticulum (SER) lacks ____________, which gives it a "smooth" appearance.

Ribosomes

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.

Compare plant and animal cells

Similarities - nucleus, cell membrane, cytoplasm, mitochondria, ribosomes Differences - only plant cells have chloroplasts, vacuole, cell wall

Vesicle

Small membrane-bound sac that functions in moving products into, out of, and within a cell. A sac made of membrane in the cytoplasm of a eukaryotic cell.

Some vesicles devlop into...

Some vesicles develop into lysosomes or vacuoles. Others travel to and fuse with the plasma membrane, secreting their contents and adding their membrane to the plasma membrane.

Enzymes of the smooth ER are important because

Synthesis of lipids, including oils, phospholipids, and steroids. In vertebrates, for example, cells of the ovaries and testes synthesize the steroid sex hormones. These cells are rich in smooth ER, a structural feature that fits their function by providing ample machinery for steroid synthesis.

Rough Endoplasmic Reticulum

That portion of the endoplasmic reticulum with ribosomes attached that make membrane proteins and secretory proteins.

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.

What is the relationship of the Golgi apparatus to the ER in a protein-secreting cell?

The Golgi receives transport vesicles budded from the ER that contain proteins synthesized by bound ribosomes. The Golgi finishes processing the proteins and dispatches transport vesicles to the plasma membrane, where the proteins are secreted.

mitochondrial matrix

The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle.

All eukaryotes have mitochondria, but not all have chloroplasts. What is the evolutionary explanation?

The first endosymbiosis would have given rise to eukaryotic cells containing mitochondria. A second endosymbiotic event gave rise to cells containing chloroplasts as well as mitochondria.

The mitochondrion has two internal compartments

The first is the intermembrane space, the narrow region between the inner and outer membranes. The inner membrane encloses the second compartment, the mitochondrial matrix, which contains mitochondrial DNA and ribosomes, as well as enzymes that catalyze some of the reactions of cellular respiration. The inner membrane is highly folded and contains many embedded protein molecules that function in ATP synthesis. The folds, called cristae, increase the membrane's surface area, enhancing the mitochondrion's ability to produce ATP.

A cell's plasma membrane acts as both a boundary and barrier for the cell. Briefly explain the plasma membrane.

The membrane at the boundary of every cell that acts as a selective barrier to the passage of ions and molecules into and out of the cell; consists of a phospholipid bilayer with embedded proteins.

describe the structures that provide support to the plasma membrane.

The membrane is attached through membrane proteins to microfilaments of the cytoskeleton and to connecting glycoproteins and collagen fibers of the ECM.

extracellular matrix (ECM)

The meshwork surrounding animal cells; consists of glycoproteins and polysaccharides synthesized and secreted by cells. This elaborate layer helps hold cells together in tissues and protects and supports the plasma membrane.

Describe the structure of the plasma membrane of an animal cell. What would be found directly inside and outside the membrane?

The plasma membrane is a phospholipid bilayer with the hydrophilic heads facing the aqueous environment on both sides and the hydrophobic fatty acid tails mingling in the center of the membrane. Proteins are embedded in and attached to this membrane. Microfilaments form a three-dimensional network just inside the plasma membrane. The extracellular matrix outside the membrane is composed largely of glycoproteins, which may be attached to membrane proteins called integrins. Integrins can transmit information from the ECM to microfilaments on the other side of the membrane.

cystol

The semifluid portion of the cytoplasm.

endosymbiont theory

The theory that mitochondria and chloroplasts originated as prokaryotic cells engulfed by an ancestral eukaryotic cell. The engulfed cell and its host cell then evolved into a single organism.

Microtubules

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 shape and support the cell and also act as tracks along which organelles equipped with motor proteins move. For example, a lysosome might use its motor protein "feet" to "walk" along a microtubule to reach a food vacuole. Microtubules also guide the movement of chromosomes when cells divide, and they are the main components of cilia and flagella.

Microfilaments

The thinnest of the three main kinds of protein fibers making up the cytoskeleton of a eukaryotic cell; a solid, helical rod composed of the globular protein actin. Microfilaments form a three-dimensional network just inside the plasma membrane that helps support the cell's shape. This is especially important for animal cells, which lack cell walls. Microfilaments are also involved in cell movements.

Which membrane in a chloroplast appears to be the most extensive? Why might this be so?

The thylakoids are the most extensive. The chlorophyll molecules that trap solar energy are embedded in them.

How do transport vesicles help tie together the endomembrane system?

Transport vesicles move membranes and the substances they enclose between components of the endomembrane system.

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.

Similarties to Flagella and Cilia

a common structure and mechanism of movement Both are composed of microtubules wrapped in an extension of the plasma membrane. In nearly all eukaryotic cilia and flagella, a ring of nine microtubule doublets surrounds a central pair of microtubules. This arrangement is called the "9 + 2" pattern. The microtubule assembly is anchored in the cell by a basal body (not shown in the figure), which is structurally very similar to a centriole. In fact, in humans and many other animals, the basal body of the fertilizing sperm's flagellum enters the egg and becomes a centriole.

Scanning Electron Microscope (SEM)

a microscope which excites electrons on the surface of the cell, and shows the specimen's topography

gap junctions

also called communicating junctions, are channels that allow small molecules to flow through protein-lined pores between cells. The flow of ions through gap junctions in the cells of heart muscle coordinates their contraction. Gap junctions are common in embryos, where communication between cells is essential for development.

The ultrastructure of a chloroplast is best studied using a a.light microscope b.scanning electron microscope. c.transmission electron microscope. d. light microscope and fluorescent dyes.

b. scanning electron microscope.

Rigid structure that helps maintain bacterial cell shape

cell wall

Carry genes

chromosomes

The ___________ refers to a collection of protein fibers that provides structural support to the cell in addition to movement.

cytoskelton

Thick fluid inside cells

cytosol

Anchoring junctions

fasten cells together into sheets

Used for movement by certain cells

flagella

a stack of interconnected sacs

granum: A stack of membrane-bounded thylakoids in a chloroplast. Grana are the sites where light energy is trapped by chlorophyll and converted to chemical energy during the light reactions of photosynthesis.

Three main kinds of fibers make up the cytoskeleton

microtubules: the thickest fiber microfilaments: the thinnest intermediate filaments: in between in thickness.

Region where bacterial DNA resides

nucleoid

____________are connections between plant cells that allow for the passage of water and nutrients.

plasmodesmata

glycoprotein

protein with one or more short chains of sugars attached to it.

Structures within cells that assemble proteins

ribosomes

Thick fluid found within the inner membrane

stroma: The dense fluid within the chloroplast that surrounds the thylakoid membrane. Sugars are made in the stroma by the enzymes of the Calvin cycle. which contains chloroplast DNA and ribosomes as well as many enzymes.

The compartment inside the thylakoids is called

the thylakoid space.

Contain chlorophyll molecules embedded into a membrane

thylakoid : is suspended in the stroma A flattened membranous sac inside a chloroplast. Thylakoid membranes contain chlorophyll and the molecular complexes of the light reactions of photosynthesis. A stack of thylakoids is called a granum.