Chapter 6: A Tour of the Cell

Who first observed cells under a microscope and who crafted the optical aid?

Robert Hooke first observed the dead cells of an oak tree under lenses that Anton van Leeuwenhoek crafted.

What is the difference between magnification and resolving power?

They both limit what we can say. Magnification is how many times larger the image is than he object. Where as resolution is the clarity, the smallest amount of distance between objects possible that can still be seen and identified as two separate objects

What is a major disadvantage to an electron microscope?

methods used to prepare specimens kills the cells.

What are the two different types of electron micrographs?

scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

What is scanning electron microscopy (SEM)? What type of image can be observed?

used to observe the surface of a specimen, electrons beams scan surface and excite electrons on the surface that can be detected. black and white three dimensional structure of the surface of a specimen.

What is transmission electron microscopy (TEM)? What type of image can be observed?

used to study internal structures of an organism. electrons are passed through, in denser areas less electrons pass through duh, image is recorded based on this. can see a thin section of a specimen, cross sections. black and what as well.

What are the different levels of cell fractionation?

the faster it is spun, the smaller components that result. first debris is nucleus then mitochondria, then peices of the membrane, then ribosomes

What is the smallest organelle isolated by cell fractionation?

Ribosomes

What two domains consist of prokaryotic cells?

Bacteria and Archaea

What is a major difference between prokaryotic cells and eukaryotic cells?

The location of their DNA, eukaryotes have nucleus's with a double membrane, prokaryotes have nucleoid that is unbound.

What is the function of the cytoplasm in bacteria?

It suspends the ribosomes needed for protein transcription.

Why are cells so small?

the smaller the cell, the larger the surface area to volume ratio is. This is ideal because a large surface area means many locations for molecules to enter, and a small volume means a small distance for molecules to travel to reach destination in cell.

Describe how many neurons and intestinal cells have greatly increased surface area?

nerve ells are narrow and have an elongated shape. intestinal cells have thin surface projections call microvilli that add surface area but very little/negligible amount of volume

Describe the nuclear envelope.

The nuclear envelope is two layers , each of a lipid bilayer. the layers are connected by nuclear pores by which materials can pass through

What is the nuclear lamina? Nuclear matrix?

Nuclear lamina lines the nuclear side of the envelope, it is a netlike array of protein filaments that maintains its shape. The nuclear matrix is the framework of protein fibers

What are the two components of chromatin?

protein and DNA

When do chromatin fibers become chromosomes?

They condense into chromosomes when the cell is preparing to divide. each species have a specific number of chromosomes, ex humans have 23 chromosomes in sex cells and 46 in body cells

When are the nucleoli visible, what is made here?

under a microscope, during reproduction? ribosmal RNA is synthesized here. and the subunits of ribosomes are assembled then they exit through the pores and become full ribosomes. basically ribosomes are made in the nucleoli.

What is the function of ribosomes? what are their two components?

they function to synthesize proteins based on mRNA. they are complexes of ribosomal RNA and proteins.

Where are free ribosomes found and what does their product generally do?

free ribosomes are suspended in cytosol (the cytoplasm) of a cell. their products serve a function within the cytosol such as enzymes. function inside of cell

Where are bound ribosomes found and what does their product generally do?

they are found attached to the outside of the ER or nuclear envelope. their proteins are prepared for export (secretion), such as digestive enzymes. these proteins serve a function elsewhere in the body, not within the cell

What are all the structures of the endomembrane system?

the nuclear envelope, the endoplasmic reticulum, the golgi apparatus, lysosomes, vesicles/vacuoles, and the plasma membrane.

What is the difference between the smooth ER and rough ER?

smooth ER has no ribosomes, rough ER has ribosomes

What are three functions of the smooth ER?

synthesis of lipids such as oils, phospholipids, and steroids (sex hormones). metabolize drugs/toxins. store calcium for muscle contractions

Why does alcohol abuse increase tolerance to other drugs such as barbiturates?

they are metabolized by the same broad spectrum detox enzymes. they induce proliferation of smooth ER which increases detox rate. this causes tolerance because the body metabolizes it more quickly, requiring higher dose to produce the same effect. if one

What does the ER do with secretory proteins?

secretory are packaged in transport vesicles that are produced in transitional ER, these vesicles take the protein where they need to go likely to the GOLGI!

Besides packaging secretory proteins into transport vesicles, what is another major function of rough ER? *

the rough ER is the "membrane factory for the cell"/ it adds membrane proteins and phospholipids to itself. the membrane expands and portions of it are packaged into vesicles and sent elsewhere.

What are the two faces of the golgi apparatus?

the cis face is the receiving face, the trans face is the shipping face.

Describe what happens to a transport vesicle when it arrives at the Golgi.

the vesicle adds its membrane and contents to the cis face, it is enveloped by the golgi. the golgi then modifies the product as needed. Then a new vesicle is formed from the trans face and the vesicle leaves the golgi.

What is another function of the golgi?

it can produce macromolecules such as polysaccharides

What is a lysosome? What do they contain? what is their pH?

a lysosome is a membranous sac of hydrolytic enzymes. it digests macromolecules. they contain enzymes that function in the acidic environment of the cell.

What protects cells from spilt hydrolytic enzymes?

the enzymes in lysosomes function at an acidic pH. when a small amount spills into the neutral cytosol, it does not digest everything. however large amounts can be bad for cells.

What are two functions of a lysosome?

digest food, but also damaged organelles through autophagy.

What is phagocytosis?

form of endocytosis, food molecules are enveloped in psudo something something then a lysosome fuses with the vesicle to break it down

What is a human cell that uses phagocytosis?

macrophages, white blood cells, do this. they engulf and destroy bacteria and foreign invaders.

What is a food vacuole?

Formed by phagocytosis, digestive function

What are contractile vacuoles?

pump excess water out of cells to maintain correct ion and molecule concentration. common in freshwater protists

What are central vacuoles?

present in plant cells. contains cell sap. inorganic ions are stored like potassium and chloride. enlarge as water is absorbed. they play a major role in growth, takes up space that cytosol does not, increasing surface area vs volume ratio

A second function of lysosomes is to recycle cellular components in a process called autophagy. Describe this process.

damaged organelle or small amount of cytosol becomes surrounded by double membrane, lysosome fuses with membrane, lysosome enzymes dismantle the organelle and the organic monomers are returned to cytosol to be reused.

What happens in tay- sachs disease? explain role of lysosomes

lysosome is missing or has inactive lipid digesting enzyme, hexosaminidase. lipids accumulate in brain causing deficits

How do the elements of the endomembrane system function together to secrete a protein.

Proteins are created in the ribosomes of the rough ER, then leave the ER packaged in a vacuole. The vacuole reaches and enters the golgi apparatus where the protein is modified if needed, then packaged in a vacuole labeled for its destination. The vacuole

Endosymbiont theory ?

early ancestor of eukaryotic cells engulfed an oxygen using nonphotosynthetic prokaryotic cell. merged into single organism, a eukaryotic cell with a mitochondria.

What is the function of the mitochondria?

use oxygen to generate ATP from sugars, fats, and other fuels. chemical energy conversion

What is the function of the chloroplasts?

sites of photosynthesis, absorb sunlight and use it to create sugars from carbon dioxide and water.

Why is the inner membrane of the mitochondria highly folded? what role do all the individual thylakoid membranes serve?

these folds create a higher surface are, increasing cell respiration

Explain the role of peroxisomes

contains enzymes that transfer hydrogen to water producing hydrogen eproxide. use oxygen to break fatty acids into smaller molecules to be used as fuel for cellular respiration. also, in the liver detoxify alcohol and other harmful compounds

What is the cytoskeleton?

a network of fibers extending through the cytoplasm

What are the three roles of the cytoskeleton?

organize structures and activities of cell, motility, mechanical support, maintain shape of cell

What are the three main types of fibers that make up the cytoskeleton.

Microtubules=thickest, microfilaments(Actin)=thinnest, and intermediate filaments

What is the composition of a microtubule?

hollow rods made of tubulin, a globular protein. each tubulin protein is a dimer made of two subunits.

What are four functions of microtubules?

shape/support cell, tracks for movement, guide secreting vesicles, separation of chromosomes during cell division

Animals have a centrosome that contains a pair of centrioles, what is this role ? *

microtubule organizing center" they replicate before the cell divides.

Describe the organization of microtubules in a centriole.

Nine sets of triplet microtubules arranged a round a ring

What are two examples of things composed of microtubules?

cillia and flagella.

What is the structure of microtubules in cilia and flagella?

Compare and contrast cilia and flagella.

Cilia can occur in large numbers, they are 2-20 micrometers in length, use rowing motion, can be signal receiving. Flagella occur alone usually. they are much longer, usually 10-200 micrometers in length. use undulation motion. Both are composed of microt

How do motor proteins called dyneins cause movement of cilia?

The two "feet" of the dyenin alternate between gripping and releasing causing movement. ATP is needed for the grip and release.

What are four functions of microfilaments? What are the motor proteins that move microfilaments?

support cell shape, increase surface area, cell motility. muscle contraction. motor protein=myosin

What are two functions of intermediate filaments?

Reinforce cell shape and position of organelles, support, strength, keep nerve cells strong. ex. keratin. they are more permanent fixtures than the other types of filaments

What are three functions of the cell wall?

maintain shape, prevent excessive uptake of water, hold plant upright against gravity.

What is the composition of the cell wall?

Cellulose in a matrix of polysaccharides and proteins (varies between cells)

What is the relatively thin and flexible wall secreted first by a plant cell?

The primary cell wall.

What is the middle lamella?

between primary walls of adjacent cells, a thin layer of sticky polysaccharides called pectins. glues adjacent cells together

Explain the deposition of a secondary cell wall. **wut

Several laminated layers, offer protection and support

What are the intercellular junctions between plant cells?

Plasmodesmata, cytoplasm is connected. cytosol, water, and small solutes pass freely. sometimes proteins and mRNA move through

What are the three types of intercellular junctions that occur in animal cells?

tight junctions, gap (communicating) junctions, and desmosomes (anchoring junctions.

What is the role of a tight junction?

prevent leakage of extracellular fluid. ex found in skin

What is a gap/communicating junction?

junction that creates cytoplasmic channels. ions, sugars, amino acids, and small molecules pass through. necessary for cell communication.

What is the role of an anchoring junction or desmosomes ?

fasten cells together in tight sheets. attach muscle cells to each other, some times muscle tears are due to the rupture of desmosomes.

If a cell is exposed to cyanide where will the cyanide be found?

In the mitochondria, cyanide binds to molecule involved in producing ATP

What are considered eukaryotic organisms?

protists, fungi, animals, and plants

What are organelles in animal cells but not plant cells?

lysosomes, centrosomes with centrioles, flagella(but present in some plant sperm)

What organelles are present in plant cells but not animal cells?

chloroplasts, central vacuole, cell wall, plasmodesmata

What are integrins?

receptor proteins built into the plasma membrane