Cell Biology
What are chloroplast and describe their function (Plant Cells)
Chloroplasts carry out photosynthesis, the plant process of incorporating energy from sunlight into carbohydrates.
What are peripheral membrane proteins
Proteins may attach loosely to the inner or outer surface of the membrane without going through it
Fungi and most plant cells do not contain a _____ as their MTOC
centrosome
if the solute concentration is lower outside the cell than it is inside the cell, the environment is _____
hypotonic
in a _____ environment, water will travel via osmosis from the external environment and into the cell
hypotonic
The movement of macromolecules in or out of the cell is called both transport and consists of two types (Vesicular transport uses vesicles or other bodies in the cytoplasm to move macromolecules or large particles across the plasma membrane. Types of vesicular transport are described here)
1)Exocytosis describes the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell. This is common when a cell produces substances for export. 2) Endocytosis describes the capture of a substance outside the cell when the plasma membrane merges to engulf it. The substance subsequently enters the cytoplasm enclosed in a vesicle. There are three kinds of endocytosis. THERE ARE THREE TYPES OF ENDOCYTOSIS: • Phagocytosis: ("cellular eating") occurs when undissolved material enters the cell. The plasma membrane wraps around the solid material and engulfs it, forming a phagocytic vesicle. Phagocytic cells (such as certain white blood cells) attack and engulf bacteria in this manner. • Pinocytosis: ("cellular drinking") occurs when dissolved substances enter the cell. The plasma membrane folds inward to form a channel allowing the liquid to enter. Subsequently, the plasma membrane closes off the channel, encircling the liquid inside a vesicle. • Receptor-mediated endocytosis: a form of pinocytosis, occurs when specific molecules in the fluid surrounding the cell bind to specialized receptors that concentrate in coated pits in the plasma membrane. The membrane pits, the receptors, and their specific molecules (called ligands) fold inward and the formation of a vesicle follows. Proteins that transport cholesterol in blood (low-density lipoproteins, or LDLs) and certain hormones target specific cells by receptor-mediated endocytosis.FF
How do prokaryotic cells differ from eukaryotic cells
1. Prokaryotes do not have a nucleus. 2. The hereditary material in prokaryotes exists as a single "naked" DNA molecule without the proteins that are associated with the DNA in eukaryotic chromosomes. 3. Prokaryotic ribosomes are smaller (70S, with 50S and 30S subunits) than those of eukaryotes (80S, with 60S and 40S subunits). 4. The cell walls of bacteria and cyanobacteria, when present, are constructed from peptidoglycans, a polysaccharideprotein molecule. The cell walls of archaebacteria contain various polysaccharides, but not peptidoglycans, cellulose (as in plants), or chitin (as in fungi). 5. Flagella, when present in prokaryotes, are not constructed of microtubules
Important vocabulary when talking about the movement of substance in a cell
1. The movement of substances may occur across a selectively permeable membrane (such as the plasma membrane). A selectively permeable membrane allows only specific substances to pass. 2. The substance whose movement is being described may be water (the solvent) or it may be the substance dissolved in the water (the solute). 3. Movement of substances may occur from higher to lower concentrations (down the concentration gradient) or the reverse (up or against the gradient). 4. Solute concentrations between two areas may be compared. A solute may be hypertonic (a higher concentration of solutes), hypotonic (a lower concentration of solutes), or isotonic (an equal concentration of solutes) relative to another region. 5. The movement of substances may be passive or active. Active movement requires the expenditure of energy and usually occurs up a gradient.
Describe the Golgi apparatus and its function
A Golgi apparatus modify and package proteins and lipids into vesicles, small, spherically shaped sacs that bud from the outside surface of the Golgi apparatus. Vesicles often migrate to and merge with the plasma membrane, releasing their contents to the outside of the cell.
A smooth endoplasmic reticulum exhibits all of the following activities EXCEPT: A. assembling amino acids to make proteins B. manufacturing lipids C. manufacturing hormones D. breaking down toxins E. breaking down toxic cellular by-products
A. Ribosomes assemble amino acids into proteins. Such activity would be found associated with rough endoplasmic reticulum.
What is active transport
Active transport is the movement of solutes against a gradient and requires the expenditure of energy (usually ATP). Transport proteins in the plasma membrane transfer solutes such as small ions (Na+ , K+ , Cl- , H+ ), amino acids, and monosaccharides across the membrane.
Describe Peroxisomes and their function
Animals: Peroxisomes break down various substances, including hydrogen peroxide (H2O2) (forming H2O and O2.), fatty acids, and amino acids. Peroxisomes are common in liver and kidney cells where they break down toxic substances. Plants: In plant cells, peroxisomes modify by-products of photorespiration, a process by which CO2 is diverted from its use in photosynthesis. In germinating seeds, peroxisomes (called glyoxysomes) break down stored fatty acids to help generate energy for growth.
What is bulk flow driven by
Bulk flow is the collective movement of substances in the same direction in response to a force or pressure. Blood moving through a blood vessel is bulk flow.
Describe what cell Junctions are and list the main types that are commonly found in cells
Cell junctions serve to anchor cells to one another or to provide a passageway for cellular exchange. They include the following: ■ Anchoring junctions are protein attachments between adjacent animal cells. One such junction, the desmosome, consists of proteins (including the protein keratin) that bind adjacent cells together, providing mechanical stability to tissues. Desmosomes are also associated with protein filaments that extend into the interior of the cell and serve to hold cellular structures together. ■ Tight junctions are tightly stitched seams between animal cells. The junction completely encircles each cell, producing a seal that prevents the passage of materials between the cells. Tight junctions are characteristic of cells lining the digestive tract where materials are required to pass through cells (rather than intercellular spaces) to penetrate the blood stream. ■ Communicating junctions are passageways between cells that allow the transfer of chemical or electrical signals. Two kinds of communicating junctions occur, as follows: • Gap junctions are narrow tunnels between animal cells that consist of proteins called connexins. The proteins prevent the cytoplasms of each cell from mixing, but allow the passage of ions and small molecules. In this manner, gap junctions allow communication between cells through the exchange of materials or through the transmission of electrical impulses. Gap junctions are essentially channel proteins of two adjacent cells that are closely aligned. Because the proteins of each cell extend beyond the plasma membranes before they meet, a small gap occurs between the two plasma membranes. • Plasmodesmata (singular, plasmodesma) are narrow channels between plant cells. A narrow tube of endoplasmic reticulum, called a desmotubule, surrounded by cytoplasm and the plasma membrane, passes through the channel. Material exchange through a plasmodesma apparently occurs through the cytoplasm surrounding the desmotubule.
What are Centrioles (Animal Cell) and basal bodies and describe their function
Centrioles and basal bodies act as microtubule organizing centers (MTOCs). A pair of centrioles (enclosed in a centrosome) located outside the nuclear envelope gives rise to the microtubules that make up the spindle apparatus used during cell division. Basal bodies are at the base of each flagellum and cilium and appear to organize their development. Plant cells lack centrioles and only lower plants (such as mosses and ferns) with motile sperm have flagella and basal bodies.
Explain the function of cholesterol (Animal Cell) in the phospholipid bilayer (plasma/cell membrane)
Cholesterol makes up around 30-50% of a eukaryotic cell membrane. Cholesterol is also amphipathic, which allows it to interact with various regions of the phospholipid bilayer. The ability of cholesterol to interact with the cell membrane is beneficial to the overall fluidity of the membrane. Several factors influence the fluidity of a membrane; they are temperature, cholesterol, and fatty acid saturation in the phospholipid tails. In plant cells, related substances (sterols) provide a similar function.
which of the following components are the most prevalent in extracellular Matrix a) tubulin b) actin c) collagen d) keratin a)intermediate filaments
Collagens are the most abundant protein in the ECM. In fact, collagen is the most abundant protein in the human body and accounts for 90% of bone matrix protein content. Collagens are present in the ECM as fibrillar proteins and give structural support to resident cells.
which of the following holds the phospholipid bilayer together a) surface tension b) covalent bonds c) phospholipid head attraction d) electrostatic attraction between phosphate groups e) hydrogen bonding
D
The movement of molecules during diffusion can be described by all of the following EXCEPT: A. Molecular movements are random. B. Net movement of solute molecules is from a region of higher concentration to a region of lower concentration. C. Each molecule moves independently of other molecules. D. Solute molecules always move down the concentration gradient. E. Net movement of gas molecules is from a region of higher concentration to a region of lower concentration.
D. Since the motion of the molecules is random, at any particular moment there are sure to be some molecules moving against the concentration gradient. It is only the net movement of molecules that moves down the gradient
What type of porin is found in kidney's and plant roots
DAT Pro-Tip: there is a particular type of porin (aquaporin) found in the kidney and plant roots. These allow water to flow more rapidly than simple diffusion alone.
What are Flagella and Cilia describe their functions
Flagella and cilia are structures that protrude from the cell membrane and make wavelike movements. Flagella and cilia are classified by their lengths, by their numbers per cell, and by their movement: Flagella are long, few, and move in a snakelike motion; cilia are short, many, and move with a back-and-forth movement. A single flagellum propels sperm. The numerous cilia that line the respiratory tract sweep away debris. Structurally, both flagella and cilia consist of microtubules
hypotonic solution
If the solute concentration is lower outside the cell than it is inside the cell, the environment is hypotonic. In this case, water will travel via osmosis from the external environment and into the cell. In this way, an animal cell will swell and eventually burst in a process called lysis.
hyper-tonic solution
If the solute concentration outside a cell were higher, it would be called a hypertonic environment. Here, water will leave the cell via osmosis in an attempt to reduce the solute concentration outside the cell. The loss of fluid causes the cell to shrivel. DAT Pro-Tip: if a cell in a hypertonic environment has a cell wall (as in a plant cell), the cell membrane will dehydrate/shrink away from the cell wall in a process called plasmolysis.
what are the components of The extracellular Matrix
In biology, the extracellular matrix (ECM) is a three-dimensional network of extracellular macromolecules, such as collagen, enzymes, and glycoproteins, that provide structural and biochemical support to surrounding cells.
Definition: Cell induction (cell signaling)
Induction, in embryology, process by which the presence of one tissue influences the development of others. Certain tissues, especially in very young embryos, apparently have the potential to direct the differentiation of adjacent cells.
Describe the two types of integral membrane proteins
Integral proteins: may extend into the membrane. Transmembrane proteins: may span across the membrane, appearing at both surfaces. Like phospholipids, integral proteins are amphipathic, with the hydrophobic regions embedded in the membrane and the hydrophilic regions exposed to the aqueous solutions bordering the membrane.
integrins interact with the ECM to signal for _____
Integrins are transmembrane proteins that connect cells to the ECM via fibronectin/laminin proteins Responsible for: growth/division/differentiation/apoptosis
isotonic solution
Isotonic solutions are those where the extracellular and intracellular environments have the same solute concentrations. Animal cells prefer isotonic environments because they will be in water balance. In other words, they will not lose or gain too much fluid volume.
Describe lysosomes and their function (Animal Cell)
Lysosomes are vesicles from the Golgi apparatus that contain digestive enzymes. They break down food, cellular debris, fat and foreign invaders such as bacteria. A low pH (acidic), favorable to the activity of the enzymes, is maintained inside the lysosome. As a result, any enzyme that might escape from the lysosome remains inactive in the neutral pH of the cytosol. Lysosomes do not occur in plant cells.
what is the difference between microfilaments and microtubules
Microtubules are usually discussed with microfilaments. Although they are both proteins that help define cell structure and movement, they are very different molecules. While microfilaments are thin, microtubules are thick, strong spirals of thousands of subunits. Those subunits are made of the protein called tubulin Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other proteins in the cell. Microtubules are major components of the cytoskeleton. They are found in all eukaryotic cells, and they are involved in mitosis, cell motility, intracellular transport, and maintenance of cell shape. Microtubules are composed of alpha- and beta-tubulin subunits assembled into linear protofilaments.
What are microtubules and describe their function
Microtubules, intermediate filaments, and microfilaments are three protein fibers of decreasing diameter, respectively. All are involved in establishing the shape of or in coordinating movements of the cytoskeleton, the internal structure of the cytoplasm. • Microtubules are made of the protein tubulin and provide support and motility for cellular activities. They are found in the spindle apparatus, which guides the movement of chromosomes during cell division, and in flagella and cilia (described in the following section), structures that project from the plasma membrane to provide motility to the cell. • Intermediate filaments provide support for maintaining the shape of the cell. • Microfilaments are made of the protein actin and are involved in cell motility. They are found in muscle cells and in cells that move by changing shape, such as phagocytes (white blood cells that wander throughout the body attacking bacteria and other foreign invaders)
Describe the mitochondria and their function (Animal Cell)
Mitochondria carry out aerobic respiration, a process in which energy (in the form of ATP) is obtained from carbohydrates, they are often more numerous near areas of major cellular activity.
Diagram: Plant vs Animal Cells
Note that plant cells can generally be distinguished from animal cells by the following: 1. Plant Cells: The presence of cell walls (cellulose), chloroplasts, and central vacuoles 2. Animal Cells: The presence of lysosomes, centrioles, and cholesterol
Describe Passive Transport (5 different types)
Passive transport processes describe the movement of substances from regions of higher to lower concentrations (down a concentration gradient) and do not require expenditure of energy: 1. Simple diffusion, or diffusion, is the net movement of substances from an area of higher concentration to an area of lower concentration. This movement occurs as a result of the random and constant motion characteristic of all molecules (atoms or ions), motion that is independent from the motion of other molecules. Since, at any one time, some molecules may be moving against the gradient and some molecules may be moving down the gradient (remember, the motion is random), the word "net" is used to indicate the overall, eventual result of the movement. Ultimately, a state of equilibrium is attained where molecules are uniformly distributed but continue to move randomly. 2. Osmosis is the diffusion of water molecules across a selectively permeable membrane. When water moves into a body by osmosis, hydrostatic pressure (osmotic pressure) may build up inside the body. Turgor pressure is the osmotic pressure that develops when water enters the cells of plants and microorganisms. 3. Dialysis is the diffusion of solutes across a selectively permeable membrane. The term dialysis is usually used when different solutes are separated by a selectively permeable membrane. 4. Plasmolysis is the movement of water out of a cell (osmosis) that results in the collapse of the cell (especially plant cells with central vacuoles). 5. Facilitated diffusion is the diffusion of solutes or water through channel proteins in the plasma membrane. Note that water can pass through the plasma membrane without the aid of specialized proteins, but aquaporins increase the rate of transfer by facilitated diffusion. 6. Countercurrent exchange describes the diffusion of substances between two regions in which substances are moving by bulk flow in opposite directions. For example, the direction of water flow through the gills of a fish is opposite to the flow of blood in the blood vessels. Diffusion of oxygen from water to blood is maximized because the relative motion of the molecules between the two regions is increased and because the concentration gradients between the two regions remain constant along their area of contact.
List the common types of proteins found in the plasma membrane and their functions
Proteins in the plasma membrane provide a wide range of functions and include the following: • Channel proteins provide open passageways through the membrane for certain hydrophilic (water-soluble) substances such as polar and charged molecules. • Ion channels allow the passage of ions across the membrane. In nerve and muscle cells, ion channels called gated channels open and close in response to specific chemical or electrical stimuli to allow the passage of specific ions (such as Na+ and K+ ). • Porins are proteins that allow the passage of certain ions and small polar molecules through membranes. Aquaporins, found in the plasma membranes of certain cells (such as those found in kidneys and plant roots), dramatically increase the passage rate of H2O molecules. • Carrier proteins bind to specific molecules, which are then transferred across the membrane after the carrier protein undergoes a change of shape. The passage of glucose into a cell is by a carrier protein. • Transport proteins use energy (ATP) to transport materials across the membrane. When energy is used for this purpose, the materials are said to be actively transported, and the process is called active transport. The Na+ - K+ pump, for example, uses ATP to maintain higher concentrations of Na+ and K+ on opposite sides of the plasma membrane. • Receptor proteins provide binding sites for hormones or other trigger molecules. In response to the hormone or trigger molecule, a specific cell response is activated. • Recognition proteins give each cell type a unique identification. This provides for a distinction between cell types, between self cells and foreign cells, and between normal cells and cells infected with viruses. Recognition proteins are glycoproteins because they have short polysaccharide chains (oligosaccharides) attached. The oligosaccharide part of the glycoprotein extends away from the surface of the membrane. • Adhesion proteins attach cells to neighboring cells or provide anchors for the internal filaments and tubules that give stability to the cell.
What are ribosomes and describe their function
Ribosome subunits are manufactured in the nucleus and consist of RNA molecules and proteins. The two subunits, labeled 60S and 40S, move across the nuclear envelope and into the cytoplasm where they are assembled into a single 80S ribosome. In the cytoplasm, ribosomes assist in the assembly of amino acids into proteins.
Describe the cell theory
The cell theory states that: 1) all living things are composed of cells 2)cells are the basic functional unit of life 3) cells arise only from pre-existing cells 4) cells carry their genetic information in the form of DNA
What is the cytoplasm and what does it consist of
The cytoplasm consists of specialized bodies called organelles suspended in a fluid matrix, the cytosol (aqueous intracellular fluid) which consists of water and dissolved substances such as proteins and nutrients.
What is the endoplasmic reticulum and describe its function
The endoplasmic reticulum, or ER, consists of stacks of flattened sacs involved in the production of various materials. They appear as a series of maze-like channels, often closely associated with the nucleus. Rough ER: When ribosomes are present (characterized by the presence of membrane-bound ribosomes), the ER (called rough ER) is responsible for creating glycoproteins, and various other proteins. Smooth ER: without ribosomes, is responsible for various activities, including the synthesis of lipids and hormones, especially in cells that produce these substances for export from the cell. In liver cells, smooth ER is involved in the breakdown of toxins, drugs, and toxic by-products from cellular reactions.
Describe the extracellular region and the processes that might occur there
The extracellular region is the area outside the plasma membrane. The following may occur in this region: ■ Cell walls are found in plants, fungi, protists, and bacteria. They develop outside the plasma membrane and provide support for the cell. In plants, the cell wall consists mainly of cellulose, a polysaccharide made from β-glucose. The cell walls of fungi are usually made of cellulose or chitin. Chitin is a modified polysaccharide differing from cellulose in that one of the hydroxyl groups is replaced by a group containing nitrogen. ■ The extracellular matrix is found in animals, in the area between adjacent cells (beyond the plasma membrane and the glycocalyx). The area is occupied by fibrous structural proteins, adhesion proteins, and polysaccharides secreted by the cells. The matrix provides mechanical support and helps bind adjacent cells together. The most common substance in this region is the protein collagen.
What is the nucleolus and describe its function
The nucleolus makes ribosomal subunits from proteins and ribosomal RNA, also known as rRNA. It then sends the subunits out to the rest of the cell where they combine into complete ribosomes. Ribosomes make proteins; therefore, the nucleolus plays a vital role in making proteins in the cell.
Describe the nucleus, its function
The nucleus is bounded by the nuclear envelope consisting of two phospholipid bilayers, each similar to the plasma membrane. The nucleus contains DNA (deoxyribonucleic acid), the hereditary information of the cell. Normally, the DNA is spread out within the nucleus as a threadlike matrix called chromatin. When the cell begins to divide, the chromatin condenses into rod-shaped bodies called chromosomes, each of which, before dividing, is made up of two long DNA molecules and various histone (protein) molecules. The histones serve to organize the lengthy DNA, coiling it into bundles called nucleosomes. Also visible within the nucleus are one or more nucleoli, concentrations of DNA in the process of manufacturing the components of ribosomes. The nucleus also serves as the site for the separation of chromosomes during cell division.
Describe the phospholipid membrane (cell membrane)
The phospholipid membrane is selectively permeable. Only small, uncharged, polar molecules (such as H2O and CO2) and hydrophobic molecules (nonpolar molecules like O2 and lipid-soluble molecules such as hydrocarbons) freely pass across the membrane. In contrast, large polar molecules (such as glucose) and all ions are impermeable. The plasma membrane (cell membrane) bounds the cell and encloses the nucleus and cytoplasm. Its main function is to separate internal metabolic events from the external environment and controls the movement of materials into and out of the cell.
What is Transfection (bacteria)
Transfection is the process of deliberately introducing naked or purified nucleic acids into eukaryotic cells.
What are vacuoles and vesicles and describe their functions
Vacuoles are membrane-bound sacs within the cytoplasm of a cell that function in several different ways. In mature plant cells, vacuoles tend to be very large and are extremely important in providing structural support, as well as serving functions such as storage, waste disposal, protection, and growth. • Transport vesicles move materials between organelles or between organelles and the plasma membrane. • Food vacuoles are temporary receptacles of nutrients. Food vacuoles often merge with lysosomes, whose digestive enzymes break down the food. • Storage vacuoles in plants store starch, pigments, and toxic substances (nicotine, for example). Plant: • Central vacuoles are large bodies occupying most of the interior of certain plant cells. When fully filled, they exert turgor, or pressure, on the cell walls, thus maintaining rigidity in the cell. They also store nutrients and carry out functions otherwise assumed by lysosomes in animal cells.
After a laboratory experiment, a student washes her hands with soap water and notices her skin absorb the water and wrinkles. This is because the students cells are ______ to the _____ soap water a) hypertonic, hypotonic b) hypotonic, hypertonic c) hypertonic, hypotonic d) hypertonic, hypotonic e) isotonic, hypertonic
a) hypertonic, hypotonic Explanation: with respect to the question, when the skin absorbs water, it is hinting that the skin cells contain more solutes in the surrounding water. Therefore, we can say that the skin cells are hypertonic relative to the hypotonic soap water.
cell walls are unique carbohydrate-based structures that lie _______ in certain types of cells that do not make collagen and therefore cannot make an ECM
above the cell membrane
Why do animals not have a cell wall
animal cells secrete collagen and make an ECM, so they do not have a cell wall.
_____ are unique carbohydrate-based structures that lie above the cell membrane in certain types of cells that do not make collagen and therefore cannot make an ECM
cell walls
hard, non-living structural polysaccharide that makes up the cell wall of a plant cell
cellulose
_____ determine the placement of the nucleus and organelles
centrioles
The most common fibrous structural protein in the ECM is a protein called _____
collagen
the _____ primarily functions to provide mechanical support in the area between adjacent animal cells
extracellular matrix (ECM) junctions
the protein building block of prokaryotic flagella is called _____
flagellin
Basal bodies are found at the base of each _____
flagellum and cilium
if the solute concentration outside a cell were higher, it would be called a _____ environment
hypertonic
in a _____ environment, water will leave the cell via osmosis in an attempt to reduce the solute concentration outside the ce
hypertonic
What are the 2 types of membrane proteins
integral proteins and peripheral proteins
What type of molecules cannot travel directly across the bilayer
large, hydrophilic
found in the cell walls of certain bacteria
peptidoglycans
What are the 3 main components of a cell membrane
phospholipids; cholesterol; proteins
which cell types have cell walls?
plants; fungi; bacteria; archea
Movement of water out of a cell resulting in the collapse of the plasma membrane is called
plasmolysis
if a cell in a hypertonic environment has a cell wall, it will experience _____
plasmolysis
form the cell walls in archaea
polysaccharides
What are 3 common types of membrane proteins
receptors; adhesion proteins; recognition proteins (glycoproteins)
the loss of intracellular fluid in hypertonic environments causes the cell to _____
shrivel
animal cells will _____ in hypotonic environments
swell/lyse
the protein building block of eukaryotic flagella is called _____
tubulin
