Chapter 6

Centrosomes

In animal cells microtubules grow out from a region near the nucleus and considered a "microtubule-organizing center" Function: compression-resisting girders.

Cytoplasmic streaming

In plant cells appears to involve both actin-mysosin interactions and sol-gel conversions. Its a circular flow of cytoplasm

Phagocytosis

A form of intercellular digestion in which a cell engulfs a smaller organism or food particle

Nucleous

(nucleoli) A dense structure visible in the non-diving nucleus, synthesizes ribosomal RNA and combines it with protein to assemble ribosomal subunits, which then pass through nuclear pores to the cytoplasm where it then assembles into a ribosome.

Microtubules

A hollow rod of tubulin protein in the cytoplasm of almost all eukaryotic cells. Tubulin polymers. Made up of a and B-tubulin. Functions: Maintains cell shape cell motility (cilia and flagella) Chromosome separation in cell division Vesicle movements Fungi and almost all plant cells lack centrosomes with centrioles but still have well organized microtubules.

Mitochondrial Matrix

Contains many enzymes as well as mitochondrial DNA and ribosomes; enclosed by the inner membrane. Enzymes in the matrix aid in cellular respiration. Proteins that function in respiration are built into the inner membrane.

Endoplasmic reticulum (ER)

Continous with the nuclear envelope and encloses a network of interconnected tubules or compartments called cisternae. Has smooth and rough ER

Pseudopodium

A cellular extension of amoeboid cells used in moving and feeding

Chromatin

A complex of DNA and protein making up chromosomes.

Explain how the ultrastructure of cilia and flagella relate to their functions (mechanism involving the motor protein).

A core of microtubules sheathed by the plasma membrane, a basal body that anchors the cilium or flagellum and a motor protein called dynein, which drives the bending movements of a cilium or flagellum.

Nuclear Envelope

A double membrane perforated by pores that regulate the movement of materials between the nucleus and the cytoplasm. Its continuous with ER.

Lysosome

A membrane-enclosed sac of hydrolytic enzymes that a cell uses to digest macromolecules. Hydrolytic enzymes and lysosomal membrane are made by rough ER and then transferred to the golgi apparatus for further processing. The 3D shapes of proteins and digestive enzymes protect vulnerable bonds from enzymatic attack and spare them from being destroyed. Functions: Breakdown of ingested substances, cell macromolecules, and damaged organelles for recycling.

Transport Vesicle

A membranous compartment used to enclose and transport materials from one part of a cell to another

Cytoskeleton

A network of protein fibers extending throughout the cytoplasm. Types: microtubules, microfilaments, and intermediate filaments. Function in cell motility (of both internal structures and the cell as a whole), and transmit mechanical signals from the cell's surface to its interior. Very important for animal cells bc they lack cell walls. Fluorescence micrograph used to see it.

Glycoprotein

A protein covalently bonded to a carbohydrate.

Motor Protein

A protein that interacts with cytoskeletal elements and plasma membrane molecules, allowing the whole cells to move along fibers outside the cell.

Integrin

A receptor protein that span the plasma membrane and bind, via other proteins, to microfilaments of the cytoskeleton.

Vesicle

A sac made of membrane in the cytoplasm

Cytosol

A semifluid medium in a cell in which are located organelles

Thylakoid

A series of flattened sacs within chloroplasts

Cilium

A short hair-like cellular appendage with a microtubule core

Golgi Apparatus

After leaving the ER, many transport vesicles travel to the golgi apparatus. Functions: modification of proteins, carbohydrates on proteins, and phospholipids. Synthesis of polysaccharides. Golgi vesicles are engaged in the transfer of material b/t parts of the golgi and other structures. Consists of flattened sacs, called cisternae. Consists of two types of golgi stacks: cis face and trans face.

Transport Protein

Allows hydrophilic substances to avoid contact with the lipid bilayer by passing thru them. also called channel proteins Function by having a hydrophilic channel that certain molecules or atomic ions use as a tunnel through the membrane.

Describe the function of the extracellular matrix in animal cells.

Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM). The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin. ECM proteins bind to receptor proteins in the plasma membrane called integrins.

Organelle

Any several membrane-enclosed structures with specialized functions, suspended in the cytosol of the eukaryotic cells

Prokaryotic Cell

Are cells with no nucleus or membrane-enclosed organelles

Cell Wall

Are composed of microfibrils of cellulose embedded in a matrix of polysaccharides and protein.

Gap Junction

Are cytoplasmic connections that allow for the exchange of ions and small molecules between cells through protein-lined pores. Cell junction in animal tissues

Centriole

Are each composed of nine sets of triplet microtubules arranged in a ring, and replicates before animal cell division. Is associated with the centrosomes- both help microtubule assembly in animal cells, but are not essential for eukayotes. Fungi and almost all plant cells lack centrosomes with centrioles but still have well organized microtubules.

Explain the structure and role of centrioles.

Centrioles are each composed of nine sets of triplet microtubules arranged in a ring, is associated with the centrosome and replicates before cell division.

Plasmodesma

Channels in plant cell walls through which the plasma membranes of bordering cells connect, thus linking most cells of a plant into a living continuum.

Briefly describe the energy conversions carried out by mitochondria and chloroplasts.

Chemical energy conversion encloses a mitochondrion building enzymes and proteins in the inner membrane. Light Energy stores energy (starch) by absorbing light to the thylakoids.

Explain the significance of the cis and trans sides of the Golgi apparatus.

Cis and trans face regions help direct the vesicles to the plasma membrane or to other organelles Cis: located near ER. A vesicle that comes from the ER can add its membrane and the contents of its lumen to the cis face by fusing with the golgi. Trans: gives rise to the vesicles that pinch off and travel to other sites. Products of the ER are modified during the transit from the cis face to the trans face regions.

Ribosomes

Composed of protein and ribosomal RNA. Carries out protein synthesis. Cells active in protein synthesis have prominent nucleoli. Builds proteins in 2 cytoplasmic locations: free ribosomes are suspended in the cytosol and bound ribosomes are attached to the outside of the ER or nuclear envelope.

Proteoglycan

Consists of a small core protein with many attached carbohydrate chain

List the components of the endomembrane system, and describe the structure and function of each component.

Consists the nuclear envelope: a double membrane perforated by pores that regulate the movement of materials between the nucleus and the cytoplasm. endoplasmic reticulum: continuous with the nuclear envelope and encloses a network of interconnected tubules or compartments called cisternae. Golgi apparatus consists of a stack of flattened sacs. lysosome are membrane-enclosed sacs of hydrolytic enzymes used by animal cells to digest macromolecules. Vacuoles are formed as a result of phagocytosis. and are large membrane-bounded vesicles.

Name two different kinds of vacuoles, giving the function of each kind.

Contractile vacuole pump excess water out of freshwater protists, thus maintaining a suitable concentration of ions and molecules inside the cell. Central vacuole is found in mature plant cells, and solution inside it is called cell sap-which is the cell's main repository of inorganic ions: potassium and chloride. Plays a major role in cell growth of plant cells, which enlarge as the vacuole absorbs water.

Nucleoid

In a prokaryotic cells ONLY, and where the DNA is concentrated in a region that is not membrane-enclosed

Chromosomes

DNA (and protein) is organized into units and located within the nucleus. We have 46 and our sex cells have 23.

Eukaryotic cell

Have a true nucleus enclosed in a nuclear envelope and numerous organelles suspended in cytosol.

Endoplasmic Reticulum

Extensive network of membrane-bounded tubules and sacs. Active in membrane synthesis and other synthetic and metabolic processes. It contains Rough and Smooth ER. Membrane separates lumen from cytosol and continuous with the nuclear envelope.

Plastids

Family of closely related plant organelles in with chloroplast is a specialized member of. Type: Amyloplast-a colorless organelle that stores starch in roots and tubers. Chromoplast-has pigments that give fruits and flowers ther orange and yellow hues.

Intermediate Filaments

Fibrous proteins supercoiled into thicker cables; like twisted rope. Made up of Keratins, Lamina, and other proteins. Functions: Mechanical durability (desmosomes) Maintains cell shape Anchors nucleus and other organelles formation of nuclear lamina

Stroma

Fluid outside the thylakoids. Contains the chloroplast DNA and ribosomes and many enzymes.

Cristae

Folds of the inner membrane create a large surface area and encloses the mitochondrial matrix.

Actin

Form a network just inside the plasma membrane and the core of small cytoplasmic extensions called microvilli. Responsible for muscle contraction along with myosin. What microfilaments are made out of.

Food vacuole

Formed as a result of phagocytsis

Distinguish between free and bound ribosomes in terms of location and function.

Free ribosomes are used within the cytosol. Bound ribosomes, attached to the endoplasmic reticulum or nuclear envelope, usually make proteins that will be included within membranes, for packaging into organelles (lysosomes), or exported from the cell.

Smooth ER

Lacks ribosomes

Dynein

Large motor proteins, composed of several polypeptides. Responsible for bending in organelles. Performs a complex cycle caused by changes in the shape of the protein with ATP giving the energy to make these changes. ATP drives the sliding of the microtubules doublets past each other as two feet, composed of motor proteins, alternately attach doublets, pull down, release, and reattach.

Compare the structure, and functions of microtubules, microfilaments and intermediate filaments.

Microtubules have hollow rods constructed of columns of globular proteins called tubulins. Microtubules change length through the addition or subtraction of tubulin dimers. They also provide the supporting framework of the cell. microtubules serve as tracks along which organelles move with the aid of motor molecules. Microfilaments are solid rods consisting of a twisted double chain of molecules of the globular protein actin. Actin filaments are microfilaments function in support forming a network just inside the plasma membrane and the core of small cytoplasmic extensions called microvilli. Intermediate filaments are intermediate in size between microtubules and Microfilaments are more diverse in their composition. Intermediate fibers appear to be important in maintaining cell shape. The nucleus is securely held in a web of intermediate filaments, and the nuclear lamina lining the inside of the nuclear envelope is composed of intermediate filaments.

Explain the roles of peroxisomes in eukaryotic cells.

Peroxisomes are oxidative organelles filled with enzymes that function in a variety of metabolic pathways such as: Produces hydrogen peroxide as a byproduct, then converts it to water. Also breaks down fatty acids for energy or detoxifying alcohol and other poisons.

Describe two examples of intracellular digestion by lysosome.

Phagocytosis- is when lysosomes fuse with food vacuoles, whose enzymes digest the material ingested. digestion products (simple sugars, amino acids, and other monomers) pass in the cytosol and become nutrients for the cell. Some human cells also carry out phagocytosis-Macrophages= a type of white blood cell that helps defend the body by engulfing and destroying bacteria. Autophagy: process where lysosomes use their hydrolytic enzymes to recycle the cell's own organic material. A damaged organelle or small amount of cytosol becomes surrounded by a double membrane, and a lysosomes fuses with the outer membrane. The lysosomal enzymes dismantle the enclosed material, and the monomers are returned to the cytosol for reuse. W/ help from lysosomes, cells continue to renew themselves.

Describe the basic structure of a plant cell wall.

Plant cell walls are composed of microfibrils made of the polysaccharide cellulose, which are synthesized by cellulose snythase and then embedded in a matrix of polysaccharides and proteins.

Name the intercellular junctions found in plant and animal cells and list the function of each type of junction.

Plasodesmata are channels in plant cell walls through which the plasma membranes of bordering cells connect, thus linking most cells of a plant into a living continuum. Three intercellular junctions between animal cells are tight junction where proteins hold adjacent cell membranes tightly together, creating an impermeable seal across a layer of epithelial cells, Demosomes (anchoring junctions) are reinforced by intermediate filaments and rivet cells into strong sheets, Gap junctions (communicating junctions) are cytoplasmic connections that allow for the exchange of ions and small molecules between cells through protein-lined pores.

Distinguish between prokaryotic and eukaryotic cells.

Prokaryotes are cells with no nucleus or membrane-enclosed organelles. Eukaryotic cells have a true nucleus enclosed in a nuclear envelope and numerous organelles suspended in cytosol.

Tight junction

Proteins hold adjacent cell membranes tightly together, creating an impermeable seal across a layer of epithelial cells. Cell junction in animal tissue

Desmosomes

Reinforced by intermediate filaments and rivet cells into strong sheets. Cell junction in animal tissue Attach muscle cells to each other in a muscle. Muscle tear involves the rupture of desmosomes.

Rough ER

Ribosomes are attached to the cytoplasmic surface

Vacuole

Sac that buds from the ER, Golgi, or plasma membrane. Important part of the endomembrane system. its selective in transporting solutes. Functions: digestion, storage, waste disposal, water balance, cell growth, and protection.

Mitochondrion

Site of cellular respiration. Found in all eukaryotes. Enclosed by 2 membranes; each a phospholipid bilayer with embedded proteins. Outer membrane is smooth. Inner membrane is convoluted with infoldings called cristae. It divides the mitochondrion into two internal compartments: intermembrane space-the narrow region b/t the inner and outer membranes. and the second is the mitochondrial matrix.

Microfilament

Solid thread of two intertwined strands of actin, each a polymer of actin subunits. Made up of Actin Functions: Maintains cell shape cytoplasmic streaming cell motility (pseudopod movement) muscular contraction cell divison

Central Vacuole

Surrounded by a vacuolar membrane and enclosing a solution called cell sap. Stores organic compounds and inorganic ions for the cell. Functions: Storage Hydrolysis of macromolecules Breakdown of waste products Plant growth

Nucleus

Surrounded by the nuclear envelope (double membrane) perforated by nuclear pores- pores regulate entry and exit of material. Houses chromosomes, which are made of chromatin (DNA & proteins); contains nucleoli-where ribosomal subunits are made.

Describe the functions of the cytoskeleton.

The cytoskeleton is a network of protein fibers that give mechanical support, function in cell motility (of both internal structures and the cell as a whole), and transmit mechanical signals from the cell's surface to its interior. It also interacts with special proteins called motor proteins to produce cellular movements.

Plasma Membrane

The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell's chemical composition.

Cellular respiration

The metabolic process that uses oxygen to generate ATP by extracting energy from sugars, fats, and other fuels.

Collagen

The most abundant glycoprotein in the extracellular matrix (ECM). Forms strong fibers that are embedded in a network of proteoglycan complexes

Ribosomal RNA (rRNA)

The most abundant type of RNA, which together with protein makes up ribosomes

Explain the role of the nucleolus in protein synthesis.

The nucleolus, a dense structure visible in the non-dividng nucleus, synthesizes ribosomal RNA and combines it with protein to assemble ribosomal subunits, which then pass through nuclear pores to the cytoplasm.

Briefly explain how the nucleus controls protein synthesis in the cytoplasm.

The nucleus directs protein synthesis by synthesizing messenger RNA (mRNA) according to instructions provided by the DNA. The mRNA is then transported to the cytoplasm via the nuclear pores. Once an mRNA molecule reaches the cytoplasm, ribosomes translate the mRNA's genetic message into the primary structure of a specific polypeptide.

Chloroplast

The site of photosynthesis in plants and algae. Convert solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from carbon dioxide and water.

Compare the structure and functions of smooth and rough ER.

The smooth ER: has no ribosomes on it. Its enzymes are involved in synthesizing phospholipids and steroid (including sex hormone), carbohydrate metabolism, and detoxification of drugs and poisons. Smooth ER also aids in storage and release of calcium ions during muscle contraction. The rough ER: studded with ribosomes. makes new membranes from the cell. Aids in synthesis of secretory and other proteins from bound ribosomes. Adds carbohydrates to proteins to make glycoproteins. Enzymes built into the membrane assemble phospholipids, and membrane proteins formed by bound ribosomes are inserted into the ER membrane.

Identify the three functional compartments of chloroplast. Explain the importance of compartmentalization in chloroplast function.

The stroma is in the inner membrane that is a fluid surrounding a membraneous system of flattened sacs called thylakoids, inside of which is the thylakoid space. Photosynthetic enzymes are embedded in the thylakoids, which may be stacked together to form structures called granum.

Extracellular matrix (ECM)

The substance in which animal tissue cells are embedded. Main ingredients are glycoproteins and other carbohydrate-containing molecules. Some cells are attached to the ECM by fibronectin.

Cytoplasm

Thick liquid residing between the cell membrane holding all organelles, except for the nucleus

Myosin

Thousands of actin filaments are arranged parallel to one another along the length of a muscle cell, interdigitated with thicker filaments made of a protein called MYOSIN. Acts as a motor protein by walking along the actin filaments. Contraction of the muscle cell results from actin and myosin filaments sliding past one another, shortening the cells.

Active Transport

To pump a solute across a membrane against its gradient requires work; cell must expand energy. The transfer proteins that must move solutes AGAINST their concentration gradient are called carrier proteins.

Describe the structure of a mitochondrion and explain the importance of compartmentalization in mitochondrial function.

Two membranes, each a phospholipid bilayer with unique embedded proteins, encloses the mitochondrion. A narrow intermembrane space exists between the smooth outer membrane and the convoluted inner membrane, called cristae, create a large surface area and encloses the mitochondrial matrix. Many respiratory enzymes, mitochondrial DNA, and ribosomes are housed in this matrix. Other respiratory enzymes and proteins are built into the inner membrane.

Granum

a stack of thylakoids in a chloroplast

Peroxisome

are roughly spherical and often have granular or crystalline core thats a dense collection of enzymes. Are oxidative organelles filled with enzymes that remove hydrogen atoms from substrates and transfer them to oxygen, thus producing hydrogen peroxide (H2O2). They function in a variety of metabolic pathways, such as using oxygen to break down fatty acids that are sent to the mitochondria and used for fuel for cellular respiration. Also detoxifying alcohol and other poisons in the liver by transferring hydrogen from poisons to oxygen.

Nuclear Lamina

netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope

Autophagy

process where lysosomes use their hydrolytic enzymes to recycle the cell's own organic material. A damaged organelle or small amount of cytosol becomes surrounded by a double membrane, and a lysosomes fuses with the outer membrane. The lysosomal enzymes dismantle the enclosed material, and the monomers are returned to the cytosol for reuse. W/ help from lysosomes, cells continue to renew themselves.

Contractile Vacuole

pumps excess water out of freshwater protists, thus maintaining a suitable concentration of ions and molecules inside the cell.

ER membrane

separates the internal compartment of the ER called the ER lumen from the cytosol