Unit 3 - Cell Structure & Structure/Function of Plasma Membranes

In the context of cell biology, what do we mean by form follows functions? What are at least two examples of this concept?

"Form follows function" refers to the idea that the function of a body part dictates the form of that body part. As an example, compart your arm to a bat's wing. While the bones of the two correspond, the parts serve different functions.

Describe how microfilaments and microtubules are involved in the phagocytosis and destruction of a pathogen by a macrophage.

A macrophage engulfs a pathogen by rearranging its actin microfilaments to bend the plasma membrane around the pathogen. Once the pathogen is sealed in an endosome inside the macrophage, the vesicle is walked along microtubules until it combines with a lysosome to digest the pathogen.

Vacuole

A membrane-bounded sac, somewhat larger than a vesicle, which functions in cellular storage and transport

Prokaryote

A unicellular organism that lacks a nucleus and other membrane-bound organelles

Compare and contrast the boundaries that plant, animal, and bacteria cells use to separate themselves from their surrounding environment.

All 3 cell types have a plasma membrane that borders the cytoplasm on its interior side. In animal cells, the exterior side of the plasma membrane is in contact with the extracellular environment. However, in plant and bacteria cells, a cell wall surrounds the outside of the plasma membrane. In plants, the cell wall is made of cellulose, while in bacteria the cell wall is made of peptidoglycan. Gram-negative bacteria also have an additional capsule made of lipopolysaccharides that surrounds their cell wall.

Explain how the formation of an adult humans follows the cell theory:

All humans are multicellular organisms whose smallest building blocks are cells; adult humans begin with the fusion of a male gamete cell with a female gamete cell to form a fertilized egg (single cell); that cell then divides into two cells, which each divides into two more cells, and so forth until all the cells of the human embryo are made; as the embryo passes through all the developmental stages to make an adult human, the cells that are added arise from division of existing cells.

Why are plasma membranes arranged as a bilayer rather than a monolayer?

Because the phospholipids that create it are amphiphilic (hydrophilic head, hydrophobic tail). If the plasma membrane was a monolayer, the hydrophobic tails of the phospholipids would be in direct contact with the inside of the cell. Since the cytoplasm is largely made of water, this interaction would not be stable, and would disrupt the plasma membrane of the cell as the tails were repulsed by the cytoplasm (in water, phospholipids spontaneously form spherical droplets with the hydrophilic heads facing outward to isolate the hydrophobic tails from the water). By having a bilayer, the hydrophilic heads are exposed to the aqueous cytoplasm and extracellular space, while the hydrophobic tails interact with each other in the middle of the membrane.

What are the structural and functional similarities and differences between mitochondria and chloroplasts?

Both are enveloped in a double membrane, and both make ATP. Both have DNA. Mitochondria can be found in both the animal and plant cell while chloroplasts are only found in the plant cell.

What are the similarities and differences between the structures of centrioles and flagella?

Centrioles and flagella are alike in that they are made up of microtubules. In centrioles, two rings are arranged at right angles to one another. This arrangement does not occur in flagella.

How do cilia and flagella differ?

Cilia and flagella are alike in that they are made up of microtubules, Cilia are short, hair-like structures. Flagella, in contrast, are long, hair-like structures; when flagella are present, a cell has just one or two.

Microtubule

Cytoskeletal system's widest element; it helps the cell resist compression, provides a track along which vesicles move through the cell, pulls replicated chromosomes to opposite ends of a dividing cell, and is the structural element of centrioles, flagella, and cilia

Pathogenic E. coli have recently been shown to degrade tight junction proteins during infection. How would this provide an advantage to the bacteria?

E. coli infections generally cause food poisoning, meaning that the invading bacteria cross from the lumen of the gut into the rest of the body. Tight junctions hold the epithelial layer that lines the digestive tract together so that the material that crosses into the body is tightly regulated. One way E. coli can avoid this regulation is to destroy the tight junctions so that it can enter the body between the epithelial cells, rather than having to go through the cells.

Explain how the extracellular matrix function

Functions in the healing and growth of the tissue

Chlorophyll

Green pigment in plants that captures the light energy that drives the light reactions of photosynthesis

What are the advantages and disadvantages of each of these types of microscopes?

Light microscope: + easily obtained and the light beam doesn't kill the cells - Limited in the amount of detail that they can reveal Electron microscope: + you can view intricate details - bulky and costly, preparation for the microscopic examination kills the specimen

How does the structure of a plasmodesma differ from that of a gap junction?

Plasmodesmata, which a plant cell needs for transportation and communication. Gap junctions are necessary in animal cells for transportation and communication.

You already know that ribosomes are abundant in red blood cells. In what other cells of the body would you find them in great abundance? Why?

Ribosomes are abundant in muscle cells as well because muscle cells are constructed of the proteins made by the ribosomes.

In your opinion, is the nuclear membrane part of the endomembrane system? Why or why not?

Since the external surface of the nuclear membrane is continuous with the rough endoplasmic reticulum, which is part of the endomembrane system, then it is correct.

Vesicle

Small membrane-bound sac that functions in cellular storage and transport; its membrane is capable of fusing with the plasma membrane and the membranes of the endoplasmic reticulum and Golgi apparatus

Explain why not all microbes are harmful:

Some microbes are beneficial For instance, E. coli bacteria help break down fiber in the diet.

Antibiotics are medicines that are used to fight bacterial infections. These medicines kill prokaryotic cells without harming human cells. Which part or parts of the bacterial cell do you think antibiotics target? Why?

The cell wall would be targeted by antibiotics as well as the bacteria's ability to replicate. This would inhibit the bacteria's ability to reproduce.

In your everyday life, you have probably noticed that certain instruments are ideal for certain situations. For example, you would use a spoon rather than a fork to eat soup because a spoon is shaped for scooping, while soup would slip between the tines of a fork. The use of ideal instruments also applies to science. In what situation(s) would the use of a light microscope be ideal, and why?

When viewing a small living organism, especially when the cell has been stained to reveal details.

In what situation(s) would a transmission electron microscope be ideal, and why?

When viewing the cell's internal structures, because many of the internal structures have membranes that are not visible by the light microscope.

In what situation(s) would the use of a scanning electron microscope be ideal, and why?

When you want to view the minute details of a cell's surface, because its beam of electrons moves back and forth over the surface to convey the image.

Cell Theory/Unified Cell Theory

a biological concept that states that one ore more cells comprise all organisms; the cell is the basic unit of life; and new cells arise from exiting cells

Golgi apparatus

a eukaryotic organelle made up of a series of stacked membranes that sorts, tags, and packages lipids and proteins for distribution

Cilium (cilia, plural)

a short, hair-like structure that extends from the plasma membrane in large numbers and is used to move an entire cell or move substances along the outer surface of the cell

Bacteria that lack fimbriae are less likely to _____. a) Adhere to cell surfaces b) Swim through bodily fluids c) Synthesize proteins d) Retain the ability to divide

a) Adhere to cell surfaces

Which of the following organelles relies on exocytosis to complete its function? a) Golgi apparatus b) vacuole c) mitochondria d) endoplasmic reticulum

a) Golgi apparatus

Tay-Sachs disease is a genetic disorder that results in a destruction of neurons due to a buildup of sphingolipids in the cells. Which organelle is malfunctioning in Tay-Sachs? a) Lysosome b) Endoplasmic reticulum c) Peroxisome d) Mitochondria

a) Lysosome

Which of the following is not a component of the endomembrane system? a) Mitochondrion b) Golgi apparatus c) Endoplasmic reticulum d) Lysosome

a) Mitochondrion

What problem is faced by organisms that live in freshwater? a) Their bodies tend to take in too much water. b) They have no way of controlling their tonicity. c) Only salt water poses problems for animals that live in it. d) Their bodies tend to lose too much water to their environment.

a) Their bodies tend to take in too much water.

In plant cells, the function of the lysosomes is carried out by _____. a) Vacuoles b) Peroxisomes c) Ribosomes d) Nuclei

a) Vacuoles

What is the primary function of carbohydrates attached to the exterior of cell membranes? a) identification of the cell b) flexibility of the membrane c) strengthening the membrane d) channels through membrane

a) identification of the cell

Which plasma membrane component can be either found on its surface or embedded in the membrane structure? a) protein b) cholesterol c) carbohydrate d) phospholipid

a) protein

Microscope

an instrument that magnifies an object

Light microscope

an instrument that magnifies an object using a beam visible light passed and bent through a lens system to visualize a specimen

Electron microscope

an instrument that magnifies an object using an electron beam that passes and bent through a lens system to visualize a specimen

The _____ is the basic unit of life. a) Organism b) Cell c) Tissue d) organ

b) Cell

In humans, _____ are used to move a cell within its environment while _____ are used to move the environment relative to the cell. a) Cilia, pseudopodia b) Flagella; cilia c) Microtubules; flagella d) Microfilaments; microtubules

b) Flagella; cilia

Which of the following have the ability to disassemble and reform quickly? a) Microfilaments and intermediate filaments b) Microfilaments and microtubules c) Intermediate filaments and microtubules d) Only intermediate filaments

b) Microfilaments and microtubules

The process by which a cell engulfs a foreign particle is known as: a) Endosymbiosis b) Phagocytosis c) Hydrolysis d) Membrane synthesis

b) Phagocytosis

Peroxisomes got their name because hydrogen peroxide is: a) Used in their detoxification reactions b) Produced during their oxidation reactions c) Incorporated into their membranes d) A cofactor for the organelle enzymes

b) Produced during their oxidation reactions

A scientist compares the plasma membrane composition of an animal from the Mediterranean coast with one from the Mojave Desert. Which hypothesis is most likely to be correct? a) The cells from the Mediterranean coast animal will have more fluid plasma membranes. b) The cells from the Mojave Desert animal will have a higher cholesterol concentration in the plasma membranes. c) The cells' plasma membranes will be indistinguishable. d) The cells from the Mediterranean coast animal will have a higher glycoprotein content, while the cells from the Mojave Desert animal will have a higher lipoprotein content.

b) The cells from the Mojave Desert animal will have a higher cholesterol concentration in the plasma membranes.

Imagine a cell can perform exocytosis, but only minimal endocytosis. What would happen to the cell? a) The cell would secrete all its intracellular proteins. b) The plasma membrane would increase in size over time. c) The cell would stop expressing integral receptor proteins in its plasma membrane. d) The cell would lyse.

b) The plasma membrane would increase in size over time.

Which transport mechanism can bring whole cells into a cell? a) pinocytosis b) phagocytosis c) facilitated transport d) primary active transport

b) phagocytosis

Which of the following is most likely to have the greatest concentration of smooth endoplasmic reticulum? a) A cell that secretes enzymes b) A cell that destroys pathogens c) A cell that makes steroid hormones d) A cell that engages in photosynthesis

c) A cell that makes steroid hormones

The key components of desmosomes are cadherins and _____. a) Actin b) Microfilaments c) Intermediate filaments d) Microtubules

c) Intermediate filaments

In what important way does receptor-mediated endocytosis differ from phagocytosis? a) It transports only small amounts of fluid. b) It does not involve the pinching off of the membrane. c) It brings in only a specifically targeted substance. d) It brings substances into the cell, while phagocytosis removes substances.

c) It brings in only a specifically targeted substance.

What happens to the membrane of a vesicle after exocytosis? a) It leaves the cell. b) It is disassembled by the cell. c) It fuses with and becomes part of the plasma membrane. d) It is used again in another exocytosis event.

c) It fuses with and becomes part of the plasma membrane.

Which of the following are only in plant cells? a) Gap junctions b) Desmosomes c) Plasmodesmata d) Tight junctions

c) Plasmodesmata

When viewing a specimen through a light microscope, scientists use _____ to distinguish the individual components of cells. a) A beam of electrons b) Radioactive isotopes c) Special stains d) High temperatures

c) Special Stains

Which of the following sequences correctly lists in order the steps involved in the incorporation of a proteinaceous molecule within a cell? a) Protein synthesis of the protein on the ribosome; modification in the Golgi apparatus; packaging in the endoplasmic reticulum; tagging in the vesicle b) Synthesis of the protein on the lysosome; tagging in the Golgi; packaging in the vesicle; distribution in the endoplasmic reticulum c) Synthesis of the protein on the ribosome; modification in the endoplasmic reticulum; tagging in the Golgi; distribution via the vesicle d) Synthesis of the protein on the lysosome; packaging in the vesicle; distribution via the Golgi; tagging in the endoplasmic reticulum

c) Synthesis of the protein on the ribosome; modification in the endoplasmic reticulum; tagging in the Golgi; distribution via the vesicle

Many viruses enter host cells through receptor-mediated endocytosis. What is an advantage of this entry strategy? a) The virus directly enters the cytoplasm of the cell. b) The virus is protected from recognition by white blood cells. c) The virus only enters its target host cell type. d) The virus can directly inject its genome into the cell's nucleus.

c) The virus only enters its target host cell type.

How does the sodium-potassium pump make the interior of the cell negatively charged? a) by expelling anions b) by pulling in anions c) by expelling more cations than are taken in d) by taking in and expelling an equal number of cations

c) by expelling more cations than are taken in

The principal force driving movement in diffusion is the __________. a) temperature b) particle size c) concentration gradient d) membrane surface area

c) concentration gradient

Water moves via osmosis _________. a) throughout the cytoplasm b) from an area with a high concentration of other solutes to a lower one c) from an area with a high concentration of water to one of lower concentration d) from an area with a low concentration of water to higher concentration

c) from an area with a high concentration of water to one of lower concentration

Nucleus

cell organelle that houses the cell's DNA and directs ribosome and protein synthesis

Eukaryotic cell

cell that has a membrane-bound nucleus and several other membrane-bound compartments or sacs

Ribosome

cellular structure that carries out protein synthesis

Nucleoid

central part of a prokaryotic cell's central part where the chromosome is located

Gap junction

channel between two adjacent animal cells that allows ions, nutrients, and low molecular weight substances to pass between cells, enabling the cells to communicate

Plasmodesma (plural, plasmodesmata)

channel that passes between adjacent plant cells' cell walls, connects their cytoplasm, and allows transporting of materials from cell to cell

Organelle

compartment or sac within a cell

Intermediate Filament

cytoskeletal component, comprised of several fibrous protein intertwined strands, that bears tension, supports cell-cell junctions, and anchors cells to extracellular structures

Prokaryotes depend on _____ to obtain some materials and to get rid of wastes. a) Ribosomes b) Flagella c) Cell division d) Diffusion

d) Diffusion

Which of the following organisms is a prokaryote? a) Amoeba b) Influenza A virus c) Charophyte algae d) E coli

d) E coli

Congenital disorders of glycosylation are a growing class of rare diseases. Which organelle would be most commonly involved in the glycoprotein disorder portion of the group? a) RER b) Ribosomes c) Endosomes d) Golgi apparatus

d) Golgi apparatus

Which of the following do not play a role in intracellular movement? a) Microfilaments and intermediate filaments b) Microfilaments and microtubules c) Intermediate filaments and microtubules d) Only intermediate filaments

d) Only intermediate filaments

Diseased animal cells may produce molecules that activate death cascades to kill the cells in a controlled manner. Why would neighboring healthy cells also die? a) The death molecule is passed through desmosomes b) The death molecule is passed through plasmodesmata c) The death molecule disrupts the extracellular matrix d) The death molecule passed through gap junctions

d) The death molecule passed through gap junctions

Which of the following is surrounded by two phospholipid bilayers? a) The ribosomes b) The vesicles c) The cytoplasm d) The nucleoplasm

d) The nucleoplasm

Active transport must function continuously because __________. a) plasma membranes wear out b) not all membranes are amphiphilic c) facilitated transport opposes active transport d) diffusion is constantly moving solutes in opposite directions

d) diffusion is constantly moving solutes in opposite directions

Which characteristic of a phospholipid contributes to the fluidity of the membrane? a) its head b) cholesterol c) a saturated fatty acid tail d) double bonds in the fatty acid tail

d) double bonds in the fatty acid tail

What is the combination of an electrical gradient and a concentration gradient called? a) potential gradient b) electrical potential c) concentration potential d) electrochemical gradient

d) electrochemical gradient

n which situation would passive transport not use a transport protein for entry into a cell? a) water flowing into a hypertonic environment b) glucose being absorbed from the blood c) an ion flowing into a nerve cell to create an electrical potential d) oxygen moving into a cell after oxygen deprivation

d) oxygen moving into a cell after oxygen deprivation

55) Which of the following is found both in eukaryotic and prokaryotic cells? a) Nucleus b) Mitochondria c) Vacuole d) ribosomes

d) ribosomes

Nuclear envelope

double-membrane structure that constitutes the nucleus' outermost portion

Cytyplasm

entire region between the plasma membrane and the nuclear envelope, consisting of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals

Endomembrane system

group of organelles and membranes in eukaryotic cells that work together modifying, packaging, and transporting lipids and proteins

Central Vacuole

large plant cell organelle that regulates the cell's storage compartment holds water, and plays a significant role in cell growth as the site of macromolecule degradation

Desmosome

linkages between adjacent epithelial cells that form when cadherins in the plasma membrane attach to intermediate filaments

Extracellular matrix

material secreted from animal or fungal cells that provides mechanical protection and anchoring for the cells in the tissue

Lysosome

organelle in an animal cell that functions as the cell's digestive component; it breaks down proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles

Plasma membrane

phospholipid bilayer with embedded (integral) or attached (peripheral) proteins, and separates the cell's internal content from its surrounding environment

Chloroplast

plant cell organelle that carries out photosynthesis

Tight Junction

protein adherence that creates a firm seal between two adjacent animal cells

Cytoskeleton

protein fiber network that collectively maintains the cell's shape, secures some organelles in specific positions, allows cytoplasm and vesicles to move within the cell, and enables unicellular organisms to move independently

Chromatin

protein-DNA complex that serves as the chromosomes' building material

Centrosome

region in animal cells made of two centrioles that serves as an organizing center for microtubules

Smooth Endoplasmic Reticulum

region of the endoplasmic reticulum that has few or no ribosomes on its cytoplasmic surface and synthesizes carbohydrates, lipids, and steroid hormones; detoxifies certain chemicals (like pesticides, preservatives, medications, and environmental pollutants), and stores calcium ions

Cell Wall

rigid cell covering comprised of various molecules that protects the cell, provides structural support, and gives shape to the cell

Nucleoplasm

semi-solid fluid inside the nucleus that contains the chromatin and nucleolus

Endoplasmic reticulum

series of interconnected membranous structures within eukaryotic cells that collectively modify proteins and synthesize lipids

Peroxisome

small, round organelle that contains hydrogen peroxide, oxidizes fatty acids and amino acids, and detoxifies many poisons

Chromosome

structure within the nucleus that contains chromatin that contains DNA, the hereditary material

Mitochondria (singular: mitochondrion)

the cellular organelles responsible for carrying out cellular respiration, resulting in the production of ATP, the cell's main energy-carrying molecule

Cytosol

the cytoplasm's gel-like material in which cell structures are suspended

Microfilament

the cytoskeleton system's narrowest element; it provides rigidity and shape to the cell and enables cellular movements

Nucleolus

the darkly staining body within the nucleus that is responsible for assembling ribosomal subunits

Flagellum (plural, flagella)

the long, hair-like structure that extends from the plasma membrane and is used to move the cell

Rough Endoplasmic Reticulum (RER)

the region of the endoplasmic reticulum that is studded with ribosomes and engages in protein modification and phospholipid synthesis