U2 C4 - A Tour of The Cell

Common structures found in most animal and plant cells

the nucleus endoplasmic reticulum ribosomes vesicles mitochondria

Tell me all about the nuclear envelope

- Double membrane that isolates nucleus from the rest of the cell - Perforated by nuclear pores which regulate the entry and exit of molecules - Studded on outer surface by ribosomes - Continuous with membranes of endoplasmic reticulum - Underlined by nuclear lamina which maintain the shape of the nucleus (scaffolding structure to hold the shape of the nucleus. without it, the nucleus would collapse)

Structures unique to animal cells

- centrosomes (micro tubular organizing center) - lysosomes - cilia and flagella (only animal cells are mobile; plant cells don't need them)

Structures unique to plant cells

- chloroplasts - plastids - cell walls - central vacuoles (huge and water filled!)

What are the basics of eukaryotic cells?

- has a nucleus - has most of the DNA in the nucleus - has many membranous organelles -is typically 10-100μm in diameter

What are the basics of prokaryotic cells?

- has no nucleus - has most of the DNA in the nucleoid - has no membrane-bound organelles - has typically 1-5μm in diameter

What are the 3 major components of the cytoskeleton?

1. Thin microfilaments of actin protein 2. Medium-sized intermediate filaments of various proteins 3. Thick microtubules of tubulin protein

The diameter of a typical eukaryotic cell is approximately ten times the diameter of a typical prokaryote. What is the ratio of the volume of typical eukaryotic:prokaryotic cells? 10:1 1000:1 100:1

1000:1 As the diameter of a cell increases, other dimensions also change. For two cells of approximately equivalent shape but different diameters, surface area increases as the square of diameter, and volume increases as the cube of diameter. Thus, if a eukaryotic cell is ten times the diameter of a prokaryote, its surface area will be one hundred (102) times that of the prokaryote and its volume will be one thousand (103) times that of the prokaryote.

Explain what centrosomes and centrioles are

A centrosome comprises two microtubule rings known as centrioles. Its main function is to organize the microtubules and provide a structure to the cell. It also pulls the chromatids apart during cell division. PLANT CELLS DON'T HAVE CENTROSOMES

Extracellular matrix (ECM) and name its functions!

A complex meshwork of proteins and carbohydrates that are synthesized and released by cells Functions: - Support and protect cells - Provide supportive external scaffolding - Segregate tissues from one another - Regulate cell proliferation, differentiation, and migration - Regulate interactions with other cells and with the environment

Plastids

A diverse group of double-membrane organelles involved in photosynthesis, pigment storage, or food (photosynthetic products) storage AN EXAMPLE IS THE CHLOROPLAST They have their own DNA fruit colorflower colorstarchlipids 2 membrnaes Found only in plants and photosynthetic protists. ONLY FOUND IN PLANTS AND ALGAE and they are unique to the kind of organism!

The Endomembrane System

A group of internal membrane-enclosed organelles in eukaryotic cells that work together to regulate protein traffic and perform metabolic functions

Define the nucleus and list the three parts of the nucleus

A large membrane-bound organelle that contains three major parts - the nuclear envelope - chromosome - nucleolus

What is the cytoskeleton?

A network of protein fibers extending throughout the cytoplasm. Organizes the cell's shape, structures, and activities

Not from lecture slides (mastering bio practice problems) What is a protist?

A protist is any eukaryotic organism that is not an animal, plant, or fungus. Examples of protists include algae, amoebas, euglena, plasmodium, and slime molds.

The Golgi Apparatus

A set of stacked and flattened membrane sacs called cisternae (each membrane sac has different enzymes in it) Shipping and receiving center for secretory and membrane proteins - receives proteins from ER - modifies proteins - sorts and packages materials into transport vessicles - vesicles from ER fuse with "receiving" face; vesicles carrying final product bud off "shipping face" This is like the post office! The Golgi adds different attachments to different proteins like lipids or carbohydrates. Helps fold the proteins into its 3d structure (I think she said this in class....double check!)

What is a granum?

A stack of thylakoids

Cell walls

A supportive and protective extracellular structure made of overlapping cellulose microfibrils embedded in other polysaccharides and proteins. Usually consist of multiple layers - Primary cell wall: relatively thin and flexible - Middle lamella: thin layer between primary walls of adjacent cells - Secondary cell wall (in some cells): added between the plasma membrane and primary cell wall Only in plants The cell wall is a permeable structure to biological molecules. The cell wall is not solid. It has a lot of spaces to allow molecules to diffuse freely through. It covers the plasma membrane, which is selectively permeable. So, the plasma membrane will filter out the good and bad molecules

Myosin

An actin-binding motor protein

Endoplasmic reticulum

An interconnected network of membrane sacs or tubules continuous with the outer nuclear membrane Typically makes up at least 50% of the total cellular membrane Important in the synthesis, modification, and transport of biological molecules Has both rough and smooth membranes, usually continuous with each other

Desmosomes

Anchoring junctions between animal cells Linking and anchoring proteins connect networks of intermediate filaments of adjacent cells Join cells in tissues that are repeatedly stretched (skin, intestines, heart), keep cells from being pulled part, and contribute to tissue stability

Tight Junctions

Animals only Formed by strands of transmembrane proteins that seal adjacent cells Leakproof barriers Found in fluid-filled hollow organs (e.g. bladder, stomach)

Gap Junctions

Animals only Formed of transmembrane protein tubes called connections and filled with cytosol (these are like tunnels! The tunnels are lined with amino acids) Small hydrophlic moleucles may pass, but proteins and organelles cannot (simply due to size) Allow cells to communicate, to share nutrients, to cooridnate by transferring chemcial or election signals (e.g. muscle cell contractions)

Ribosomes and the two types

Are workbench for protein synthesis. They are complexes of ribosomal RNA and protein 2 types: - Free ribosomes: the site of the synthesis of cytoplasmic proteins - Membrane-attached ribosomes: the site of the synthesis of proteins that function within the endomembrane system or are destined for export from the cell

Chloroplasts

Capture light energy Specialized orgnaelles found in plants and algae The sites of photosynthesis which contain chlorophyll, as well as enzymes and other molecules that function in photosynthesis Contains DNA and ribosomes

What are the membrane sacs in the golgi apparatus called

Cisternae

Cell junctions and list the different types

Direct physical contact between neighboring cells - Plasmodesmata - Tight junctions - Desmosomes - Gap junctions

Chromosomes

Discrete units that organize DNA Each chromosome: one long DNA molecule associated with proteins

What are the two basic cell types?

Eukaryotic and prokaryotic cells

The nuclear lamina is a meshwork of fibrous proteins called lamins. Lamins are synthesized by a. Rough ER-attached ribosomes b. Smooth ER-attached ribosomes c. Free ribosomes in cytosol d. Free ribosomes inside hte nucleus e. Mitochondrial ribosomes

Free ribosomes in cytosol This is the answer because the ribosomes can't be fully assembled in the nucleus so they can't function here. In the nucleus (the nucleolus to be more specific), the proteins imported from the cytoplasm are assembled with rRNA into large and small subunits of ribosomes. these subunits then exit the nucleus through the nuclear pores to the cytoplasm where a large and a small subunit can assemble into a ribosome.

A mutation that disrupts the ability of an animal cell to add carbohydrate modifications to proteins would most likely cause defects in its Golgi apparatus and extracellular matrix microtubules and Golgi apparatus nuclear lamina nuclear lamina and extracellular matrix

Golgi apparatus and extracellular matrix

The rough ER

Has a bunch of ribosomes studded on its outer surface. A factory of secretory proteins which are typically glycoproteins (proteins covalently bonded to carbohydrates) A factory of membrane lipids Distributes transport vesicles -- proteins surrounded by membranes

The smooth ER

Has no attached ribosomes on its surface Smooth ER is the site to synthesize lipids (fats, oils, and steroids), or to metabolize carbohydrates, or detoxify drugs and poisons, or to store calcium ions Has enzymes to break down glycogen if needed (polysaccharide of glucose) to provide glucose molecules

Microtubules

Hollow rods constructed from tubulin Have a centrosome: a "microtubule-organizing center" in animal cells where tubulin dimers assemble into microtubules. The centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring - Maintenance of cell shape - Movement of organelles - Segregation of chromosomes during mitosis and meiosis - Cellular locomotion

Which statement about extracellular structures (plant cell walls and the extracellular matrix of animal cells) is correct? Proteins and lipids are common components of extracellular structures. All extracellular structures form barriers to separate adjacent cells. Extracellular structures store energy in the form of polysaccharides for subsequent metabolism by the cell. Information can be transmitted from these extracellular structures to the cytoplasm.

Information can be transmitted from these extracellular structures to the cytoplasm. Extracellular structures provide mechanical and chemical signals that are transmitted across the plasma membrane to the interior of the cell.

Why isn't the mitochondrion classified as part of the endomembrane system? It is not involved in protein synthesis It has a double membrane structure It produces a special class of transport vesicles It is not derived from the endoplasmic reticulum or Golgi

It is not derived from the endoplasmic reticulum or Golgi

What are vacuoles? Name and describe the different types.

Large spherical membrane-bound structures. 1.) Food vacuoles: formed by phagocytosis 2.) Contractile vacuoles: found in many freshwater protists that pump excess water out of cells 3.) Central vacuoles: found in many mature plant cells that provide turgor pressure against the cell wall and serve as a repository for hazardous wastes, nutrients, or concentrate pigments. The central vacuole pushes other organelles towards the outside of the cell. For instance, it pushes the chloroplasts to the edge of the cell which will help it perform photosynthesis better

Lysosomes

Lysosomes are the cell's waste disposal and recycling center in animal cells A membranous sac of hydrolytic enzymes that can digest macromolecules Contain digestive enzymes for destruction of materials, cells, or worn-out/defective organelles Has an internal pH of about 5 (acidic). The lysosomal enzymes are only active in an acidic envrionement with this pH of 5. So, if a lysosome were to bust inside the cell, the hydrolytic enzymes wouldn't destroy the cell because they can only be active in a pH of 5 and the pH of the whole cell isn't 5. Plays an important role in phagocytosis: fuse with food vacuoles and digest food into basic nutrients Plays an essential role in autophagy: to recycle the cell's own organelles and macromolecules

Extracellular matrix of animal cells

Made up of glycoproteins such as collagen, proteoglycans, and fibronectin Binds to cell-surface receptor proteins in the plasma membrane called integrins

Cilia and Eukarotic Flagella

Microtubule-containing extensions of the plasma membrane Cilia: hair-like structures, short and numerous, found ONLY in eukaryotic cells. Cilia beat in unison and the beating helps move materials across the surface of the tissue or to move an entire cell Flagella: whip-like structures, long but only one or two. A flagellum rotates in a corkscrew motion and is used to move an entire cell, such as animal sperm cells Both cilia and eukaryotic flagella contain microtubules in a "9+2" arrangement A basal body that anchors the cilium or flagellum Dynein drives the bending movements of a cilium or flagellum Cilia and Eukayrotic Flagella have similar molecular structure even though they seem different!

All cells come from pre-existing cells through _____

Mitosis or meiosis or binary fission

Name all the membrane-enclosed organelles in the endomembrane system

Nuclear envelope Endoplasmic reticulum Golgi apparatus lysosomes Vacuoles Plasma membrane

Plasmodesmata

Plants only Channels linking adjacent cells, allowing for movement of large molecules serve as cytoplasmic bridges to facilitate efficient exchange of signaling molecules between neighboring cells Lined with plasma membrane and filled with cytosol Continuous from one cell to another

Which statement correctly describes an endomembrane function? Products of the ER are usually modified during their transit from the cis to the trans region of the Golgi apparatus. The lumen of the endoplasmic reticulum (ER) is continuous with the cell nucleus. Secretory proteins in transit from one part of the cell to another are carried in lysosomes.

Products of the ER are usually modified during their transit from the cis to the trans region of the Golgi apparatus. (The cis and trans regions of the Golgi apparatus act as receiving and shipping departments. As molecules move from the cis to the trans face of the Golgi apparatus, they are usually modified.)

Not from lecture slides (mastering bio practice problems) Why is the answer to this question wrong? And, what is the correct answer? Question: Consider a protein that is made in the rough endoplasmic reticulum. When the synthesis of the protein is complete, the protein is located in the ER membrane. Where else in the cell might this protein be found? Answer: in the internal space of the Golgi apparatus, being modified before the protein is excreted

Proteins that are inserted into the rough ER membrane are membrane proteins, not soluble proteins to be excreted. Remember, in the question it said that after the synthesis of this protein was complete, it didn't leave the ER. if it were to leave the ER, it would go to the golgi but in this case it's not leaving the cell. Correct answer: embedded in the plasma membrane, functioning in the transport of molecules into the cell

Which of the following statements is a plausible description of some aspect of protein secretion from prokaryotic cells? In prokaryotes, the ribosomes that are involved in the synthesis of secreted proteins are located outside of the cell. The mechanism of protein secretion in prokaryotes is probably the same as that in eukaryotes. Proteins that are secreted by prokaryotes may be synthesized on ribosomes that are associated with the cytoplasmic surface of the plasma membrane. Prokaryotes are unlikely to be able to secrete proteins because they lack an endomembrane system.

Proteins that are secreted by prokaryotes may be synthesized on ribosomes that are associated with the cytoplasmic surface of the plasma membrane.

Cells use _____ to copy DNA to make proteins

RNA

Intermediate Filaments

Rope-like fibers made of multiple strands of fibrous proteins A number of different varieties, each one made up fo a different type of protein More permanent cytoskeleton elements than the other two classes - Maintenance of cell shape - Anchorage of nucleus and certain other intracellular structures - Formation of nuclear lamina

Just look Not from lecture slides (mastering bio practice problems)

The observation that chloroplasts and mitochondria each contain their own DNA and synthesize some of the proteins that function in these organelles suggests that chloroplasts and mitochondria must divide each time the cell containing them divides The fact that chloroplasts and mitochondria contain DNA that encodes for some of their proteins means that these organelles must divide each time the cell that contains them divides.

Mitochondria

The powerhouse of the cell, as it produces ATP The cites of cellular respiration Round, oval, or tubular organelles enclosed with a double membrane Contains mitochondrial DNA (AKA it has its own DNA! This DNA is circular) and its own ribosomes Smooth outer membrane Inner membrane folded into many cristae The acidic intermembrane compartment (more acidic than matrix) The mitochondiral matrix The amount of mitochondria per cell varies. For instance, in muscle cells, there will be many mitochondria because it needs the ATP to make the muscle contractions

Not from lecture slides (mastering bio practice problems) Where are the ribosomes for mitchondria found?

The ribosomes in the mitochondria are found in the matrix of the mitochondria, not in the intermembrane space.

Nucleolus and what is it composed of?

The site of ribosome synthesis and assembly. Composed of ribosomal RNA (rRNA), DNA, proteins, and ribosomes

What do microfilaments and microtubules have in common?

They are able to assemble and disassemble quickly. They usually work together/interact with motor proteins to produce motility

Microfilaments

Thin solid rods built from two intertwined strands of actin Highly dynamic structures Tracks for the movement of myosin, an actin binding motor protein - Maintenance and change of cell shape - Cell motility - Cytokinesis of animal cells - Muscle contraction - Cytoplasmic streaming in plant cells

What makes up the chloroplast?

Thylakoids: membranous sacs, stacked to form a granum Stroma: the internal fluid

True or false: every part of the cell need to be closed to the external environment

True

True or false: the number of chromosomes an organism has doesn't indicate its complexity

True

Which of the following molecules is required to build cilia or flagella?

Tubulin

The components of the endomembrane system are either continuous or connected through transfer by ____

Vesicles

Why aren't viruses living organisms?

Viruses do not have cells so they can't multiply. They can't reproduce on their own.

Do plants have mitochondria?

YES! Plants need ATP so they have mitochondria too!!!

Can you find an internal membrane in a prokaryotic cell?

Yes! In order to maximize surface area, internal membranes are formed so it's not just a plasma membrane

Do plants have an extracellular matrix?

Yes! The cell wall of plant cells is a type of extracellular matrix. This is because the cell wall is made of cellulose and other molecules

Do prokaryotes have chromosomes and DNA?

Yes, they have both. Just because they don't have a nucleus doesn't mean they don't have chromosomes.

If a treatment were available that would disrupt the nuclear lamina in living cells, what would you expect to be the most likely immediate consequence for the cell? a change in the shape of the nucleus the inability of the nucleus to divide during cell division closure of nuclear pores disrupting transport of materials into and out of the nucleus the loss of chromosome function

a change in the shape of the nucleus

Consider two cells with the same volume but with very different surface areas due to differences in their shapes. The cell with the larger surface area is likely to __________.

be involved in the rapid uptake of compounds from the cell's environment be involved in the rapid uptake of compounds from the cell's environment

In a liver cell detoxifying alcohol and some other poisons, the enzymes of the peroxisome remove hydrogen from these molecules and

combine the hydrogen with oxygen molecules to generate hydrogen peroxide.

All cells contain ____ and ____

cytoplasm and cytosol

All cells are enclosed by ____ a. a cell wall mainly composed of cellulose b. a cell wall mainly composed of phospholipids c. a plasma membrane mainly composed of cellulose d. a plasma membrane mainly composed of phospholipids and proteins

d. a plasma membrane mainly composed of phospholipids and proteins

Prokaryotes may have membranous structures such as ____ a. only the plasma membrane b. chromosomes c. the cell wall d. the plasma membrane and internal membranes

d. the plasma membrane and internal membranes

____ provide strong adhesion a. Desmosomes b. Tight junctions c. Gap junctions d. Plasmodesmata

desmosomes

_____ give strength to tissues a. Desmosomes b. Tight junctions c. Gap junctions d. Plasmodesmata

desmosomes

A 9 + 2 arrangement of microtubules, consisting of nine doublets of microtubules surrounding a pair of single microtubules, is associated with which of the following structures? centrioles only motile cilia and centrioles eukaryotic flagella and motile cilia both eukaryotic and bacterial flagella eukaryotic flagella only

eukaryotic flagella and motile cilia

Not from lecture slides (mastering bio practice problems) Which is/are most likely to be involved in the process of producing proteins for a chloroplast or mitochondrion?

free cytoplasmic ribosomes

____ and ____ allow direct communication between cells a. Desmosomes b. Tight junctions c. Gap junctions d. Plasmodesmata

gap junctions and plasmodesmata

Not from lecture slides (mastering bio practice problems) Chloroplasts and mitochondria are thought to have started as prokaryotes. One piece of supports for this hypothesis is these organelles prokaryotic-type ribosomes. These ribosomes are probably most similar to ribosomes found __________. free in the cytoplasm of eukaryotes on the rough ER in bacterial cells The first two answers are correct. The first three answers are correct.

in bacterial cells Like the ribosomes in bacteria, the ribosomes in the mitochondria are smaller than those found free in the cytoplasm or bound to endoplasmic reticulum in the eukaryotes.

If plant cells are grown on media containing radioactively labeled thymine for one generation, where will radioactively labeled macromolecules be detected? only in the nucleus and chloroplasts only in the nucleus in the nucleus, mitochondria, and chloroplasts only nucleus and mitochondria

in the nucleus, mitochondria, and chloroplasts

Movement of vesicles within the cell depends on what cellular structures?

microtubules and motor proteins

What types of proteins are synthesized somewhere other than the rough ER? secreted proteins mitochondrial membrane proteins plasma membrane proteins nuclear envelope proteins

mitochondrial membrane proteins Most mitochondrial proteins, as many as 99%, are made outside of the mitochondrion itself, in the liquid cytoplasm that fills the entire cell.

Not from lecture slides (mastering bio practice problems) Which of these membranes are likely to have a lipid composition that is most distinct from the others? endoplasmic reticulum Golgi apparatus lysosome membrane mitochondrial outer membrane plasma membrane

mitochondrial outer membrane The mitochondria are not part of the endomembrane system and must synthesize their own lipids.

Do plants have centrioles?

no

The chemical reactions involved in respiration in prokaryotic and eukaryotic cells are virtually identical. In eukaryotic cells, ATP is synthesized primarily on the inner membrane of the mitochondria. In light of the endosymbiont theory for the evolutionary origin of mitochondria, where would you expect most ATP synthesis to occur in prokaryotic cells? on the endoplasmic reticulum on the plasma membrane on the nucleoid membrane in the cytoplasm

on the plasma membrane

When a potassium ion (K+) moves from the soil into the vacuole of a cell on the surface of a root, it must pass through several cellular structures. Which of the following correctly describes the order in which these structures will be encountered by the ion?

primary cell wall →→ plasma membrane →→ cytoplasm →→ vacuole

_____ are cellular machines that synthesize proteins

ribosomes

Which structure is the site of the synthesis of proteins destined for export from the cell? lysosomes Golgi vesicles rough ER free cytoplasmic ribosomes smooth ER

rough ER this is because the rough ER has ribosomes that are BOUND TO IT!! Membrane-attached ribosomes are the site of the synthesis of proteins that function within the endomembrane system or are destined for export from the cell

Vinblastine, a drug that inhibits microtubule polymerization, is used to treat some forms of cancer. Cancer cells given vinblastine would be unable to carry out which of the following processes? migrate by amoeboid movement extend pseudopods separate chromosomes during cell division maintain the shape of the nucleus form cleavage furrows during cell division

separate chromosomes during cell division

Chromatin

the material of which the chromosomes of organisms other than bacteria (i.e., eukaryotes) are composed. It consists of protein, RNA, and DNA.

____ form a watertight seal and prevent material from passing between cells a. Desmosomes b. Tight junctions c. Gap junctions d. Plasmodesmata

tight junctions