Biology, The Cell. Prokaryotes and Eukaryotes

TRUE

(TRUE or FALSE?) A smooth endoplasmic reticulum exhibits all of the following activities: 1. manufacturing lipids 2. manufacturing hormones 3. breaking down toxins

False. Microtubules actually originate from basal bodies or centrioles (microtubule organizing centers, or MTOCs), not from the plasma membrane.

(TRUE or FALSE?) Microtubules originate from the plasma membrane.

True.

(TRUE or FALSE?) Only animal cells, not plant cells, have plasma membranes that contain cholesterol.

False. Both animals and plants have cells with mitochondria and have ribosomes attached to ER

(TRUE or FALSE?) Only animals cell (not plant cells) have mitochondria and have ribosomes attached to ER.

TRUE

(TRUE or FALSE?) When there is a concentration gradient, water will move across a membrane unassisted by ATP or channel proteins. In contrast, solutes (the dissolved substances) cannot cross the membrane unassisted.

False. The flagella of all eukaryotic cells (including a few plant groups such as ferns and mosses) contain microtubules with the 9+2 arrangement.

(TRUE or FALSE?) only animal cells have flagella and cilia with a "9 + 2" microtubule arrangement.

False. Both animals and plants have cells with mitochondria and have ribosomes attached to ER

(TRUE or FALSE?) only plant cells have ribosomes attached to the endoplasmic reticulum.

False

(TRUE or FALSE?) solutes (the dissolved substances) can cross the membrane unassisted.

fungi

chitin is often found in the cell walls of _________.

Prokaryotes

generally consist of only a plasma membrane, a DNA molecule, ribosomes, cytoplasm, and often a cell wall. Do not have a nucleus

polysaccharides, cellulose (as in plants), or chitin (as in fungi).

The cell walls of archaebacteria contain various [...], but not peptidoglycans.

peptidoglycans

The cell walls of bacteria and cyanobacteria, when present, are constructed from [...].

mitochondrion

The cellular structure that is involved in producing ATP during aerobic respiration is the

peptidoglycans

a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria, forming the cell wall.

endosymbiosis.

Biologists commonly agree that chloroplasts found in eukaryotes have their ancestry in cyanobacteria, via a process called [....]

they both have a plasma membrane, ribosomes, and DNA. Also, many prokaryotes have a cell wall, a structure they have in common with the eukaryotic cells of plants and fungi. DNA is packaged differently (naked DNA molecules in prokaryotes compared to DNA associated with proteins in eukaryotes) prokaryotic ribosomes are smaller than those of eukaryotes prokaryotic flagella do not contain microtubules, and that prokaryotic cells lack a nuclear membrane and the various eukaryotic organelles. the cell walls of bacteria and cyanobacteria contain peptidoglycans, unlike the cellulose and chitin of plants and fungi.

Compare and contrast the cellular characteristics of prokaryotes and eukaryotes.

The plasma membrane is composed of a bilayer of phospholipids. A molecule of phospholipid consists of two fatty acids and a phosphate group attached to a glycerol component. The fatty acid tails represent a hydrophobic region of the molecule, while the glycerol-phosphate head is hydrophilic. The phospholipids are arranged into a bilayer formation with the hydrophilic heads pointing to the outside and the hydrophobic tails pointing toward the inside. As a result, the plasma membrane is a barrier to most molecules. In plants, fungi, and bacteria, the membrane deposits cellulose or other polysaccharides on the outside of the membrane to create a cell wall. The cell wall provides support to the cell. Embedded in the phospholipid bilayer are various proteins and, in animals cells, cholesterol molecules. This mixture of molecules accounts for the fluid mosaic model of the plasma membrane, that is, a highly flexible lipid boundary impregnated with various other molecules.

Describe the structure of the plasma membrane and the various ways in which the plasma membrane permits interactions with the outside environment.

The plasma membrane is a selectively permeable membrane. Small molecules, like O2 and CO2, readily diffuse through the membrane. The movement of larger molecules is regulated by proteins in the plasma membrane. There are several kinds of these proteins. Channel proteins provide passage for certain dissolved substances. Transport proteins actively transport substances against a concentration gradient. The glycocalyx, consisting of the oligosaccharides from glycolipids, recognition proteins, and other glycoproteins, provides adhesion or participates in cell-to-cell interactions. Receptor proteins recognize hormones and transmit their signals to the interior of the cell. Various substances can be exported into the external environment by exocytosis. In exocytosis, substances are packaged in vesicles that merge with the plasma membrane. Once they merge with the membrane, their contents are released to the outside. In an opposite kind of procedure, food and other substances can be imported by endocytosis. In endocytosis, the plasma membrane encircles the substance and encloses it in a vesicle.

Describe the various activities that occur within cells and the methods that cells use to separate these activities from one another.

Actin

Microfilaments are made up of the protein ________.

D. Facilitated Diffusion. Note that this question asks about solutes moving down a concentration gradient across a plasma membrane and without ATP.

Movement of solutes across a plasma membrane from a region of higher solute concentration to a region of lower solute concentration with the aid of proteins...

A. Active Transport. The energy requirement indicates active transport.

Movement of solutes across a plasma membrane requiring the addition of energy.

B. Bulk Flow. The movement of urine through the urinary tract is by bulk flow, a collective movement of all substances moving in the same general direction. This is in contrast to diffusion, osmosis, and other molecular motions, in which the motion of particular molecules with respect to other molecules is being described.

Movement of urine through the urinary tract.

C. Osmosis. Note that this question asks about water moving down a gradient.

Movement of water across a membrane from a region of higher concentration of water to a region of lower concentration of water without the end of protein.

E. Plasmolysis If the solute concentration is higher outside than inside the cell, water moves out of the cell (by osmosis), resulting in the collapse of the cell.

Movement of water out of a cell resulting in the collapse of the plasma membrane.

1. nucleoli 2. chloroplasts 3. mitochondria 4. Golgi bodies

Prokaryotes lack:

mitochondrion. chloroplast.

Respiration takes place in the ______________. ATP is also produced in the _____________, but that is from photosynthesis.

A. Ribosomes

Which of the following cellular structures are common to both prokaryotes and eukaryotes? A. Ribosomes B. Nucleoli C. Chloroplasts D. Mitochondria E. Golgi bodies

Flagella

[...] when present in prokaryotes, are not constructed of microtubules.

Fats. proteins. Mitochondria.

_______ usually originate from smooth ER; ______ originate from ribosomes or rough ER; ______ are often found near areas requiring a great deal of energy (ATP). And polysaccharides have various origins.

cellulose

____________ is the main constituent of plant cell walls.

peptidoglycans

___________________ are found in the cell walls of bacteria and cyanobacteria.

cyanobacteria

a phylum of bacteria that obtain their energy through photosynthesis, and are the only photosynthetic prokaryotes able to produce oxygen.

Eukaryotes

include all organisms except for bacteria, cyanobacteria, and archaebacteria