Biology (Cliff Notes) Flashcards
What is a peripheral protein?
Proteins that may attach loosely to the inner or outer surface of the membrane.
What is an integral protein?
Proteins that may be integrated into the membrane (are amphipathic.
What is transmembrane protein?
Proteins that are integral proteins that can span across the membrane, appearing at both surfaces.
What is the function of a channel protein?
Provide passageways for certain hydrophilic substances such as polar or charged molecules
What is the function of ion channels?
Provide passageways for ions. Ion-gated channels in nerve and muscle cells open in response to specific chemical or electrical stimuli.
What is a carrier protein?
Proteins that bind to specific molecules and carry them across the membrane after the protein undergoes a change in shape. Glucose is carried into the cell by a carrier protein.
What is a transport protein?
Proteins that use ATP to transport materials across the membrane. The use of ATP makes this transport active transport. (Na+-K+ pump uses ATP to maintain higher concentrations of Na+ and K+ on opposite sides of the membrane.
What is a recognition protein?
These proteins give each cell type a unique identification and distinction between “self” and foreign.
What is another term used to described recognition proteins?
They are also glycoproteins because they have short polysaccharide chains attached. The oligosaccharide part of the glycoprotein extends away from the surface of the membrane.
What is an adhesion protein?
Proteins that attach cells to neighboring cells and act as an anchor for the internal filaments and tubules that give stability to the cell
What is a receptor protein?
Proteins that provide binding sites for hormones or other trigger molecules.
What happens when a hormone or trigger molecule binds to a receptor?
In response to the hormone or trigger molecule, a specific cell response is activated.
What is the function of cholesterol in the plasma membrane of animal cells?
Provide rigidity
What is a sterol in plant cells?
A sterol is a substance related to cholesterol found in the cell membrane of plants and provides rigidity
Define glycocalyx and its function
Glycocalyx is a carbohydrate coat that covers the outer face of the cell wall of some bacteria and the outer face of the plasma membrane of certain animal cells. It consists of various oligosaccharides attached to glycolipids and glycoproteins. It may provide adhesive capabilities, act as a barrier to infection, of markers for cell-cell recognition
Define oligosaccharide
carbohydrates made up of less than 20 monosaccharides
What encloses the nucleus?
The nucleus is enclosed by a double membrane (two phospholipid bilayers) called the nuclear envelope.
What is enclosed in the nucleus?
The nucleus contains DNA, the hereditary information of the cell. It also contains nucleoli, which are concentrations of DNA in the process of manufacturing the components of ribosomes. The nucleus also serves as a the site for the separation of chromosomes during cell division.
How is DNA spread out in the nucleus?
In a threadlike matrix called chromatin.
When cells begin to divide, what happens to chromatin?
It condenses into rod-shaped bodies called chromosomes, each of which, before dividing, is made up of two long DNA molecules and various histone molecules.
What is the function of histones?
Histones serve to organize the lengthy DNA, coiling it into bundles called nucleosomes
What is a ribosome?
A ribosome assists in the assembly of amino acids into proteins.
Explain the process of ribosome formation
It’s 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.
Describe the ER and its function.
ER is made up of stacks of flattened sacs involved in the production of various materials.
Describe the Rough ER
When ribosomes are present, its called rough ER and here, glycoproteins are created by attaching polysaccharide groups to polypeptides assembled by ribosomes.
Describe the Smooth ER
ER without ribosomes and is responsible for various activities, such as the synthesis of lipids and hormones. In liver cells, it is involved in the breakdown of toxins, drugs, and toxic by-products from cellular reactions.
Describe the Golgi apparatus
A group of flattened sacs arrange like a stack of bowls that modify and package proteins and lipids into vesicles that bud from the outside surface of the Golgi.
What is a lysosome?
Vesicles from the Golgi that contain digestive enzymes. A low pH, favoring enzymatic activity, is maintained inside the lysosome (not viable in the cytoplasm if escaped).
Do lysosomes occur in plant cells?
No
What is peroxisome?
An organelle that breaks down various substances like H2O2 to form H2O and O2, fatty acids, and amino acids. They are common in liver and kidney cells.
What is the action of peroxisomes in plant cells?
They modify by-products of photorespiration, where CO2 is diverted from its use in photosynthesis.
What are peroxisomes called in germinating seeds?
Glyoxysomes, and they break down stored fatty acids to help generate energy for growth.
What is the main function of the mitochondria?
It carries out aerobic respiration (energy from carbs is converted to ATP)
Define the function of chloroplasts
Chloroplasts are plant organelles that carry out photosynthesis (convert light energy into chemical energy)
In decreasing diameter, name the protein fibers involved in establishing shape, and coordinating movements of the of the cytoskeleton
Microtubules, intermediate filaments, and microfilaments
Define microtubules
Protein fibers made from tubular and provide support and motility for cellular activities.
What guides the movement of chromosomes during cell division? Where is it found?
Microtubules, which are found in the spindle apparatus. They are also found in flagella and cilia
What are microfilaments?
They are protein fibers made from actin and they are involved in cell motility. They are found in muscle cells that move by changing shape (like phagocytes)
Describe the structure of flagella and cilia
Both consist of microtubules arrange in a “9+2” array - nine pairs of microtubules arranged in a circle surrounding a pair of microtubules
Define MTOC
Microtubule Organizing Centers (centrioles and basal bodies)
Describe the function of centrioles
A pair of centrioles make up centrosome, and they are MTOC just outside the nuclear envelope that give rise to the microtubules that make up the spindle apparatus used during cell division
Describe the function of basal bodies
MTOCs that are at the base of each flagellum and cilium which organize their development
Do plant cells contain centrioles?
No, only lower plants with motile sperm and flagella have basal bodies
What are vesicles and vacuoles?
Fluid-filled membrane-bound bodies
Define transport vesicles
Vesicles that move materials between organelles or between organelles and plasma membrane
Define food vacuoles
Temporary receptacles of nutrients that often merge with lysosomes, whose digestive enzymes break up the food
Define storage vacuoles
Vacuoles found in plants that store starch, pigments, and toxic substances
Define central vacuoles
Large bodies occupying most of the interior of certain plant cells. When fully filled, they exert turgor to maintain the rigidity in the cell wall. They also store nutrients and carry out functions otherwise assumed by lysosomes in animal cells.
Define cell wall
Cell walls are found in plants, fungi, protists, and bacteria. They develop outside the plasma membrane and provide support for the cell. It is mostly composed of cellulose, a polysaccharide made from beta-glucose.
What composes the cell wall of fungi
Usually cellulose or chitin, a modified polysaccharide of beta-glucose (one of the hydroxyl groups is replaced by nitrogen)
Define extracellular matrix
Found in animals (area between adjacent cells). It is occupied by fibrous structural proteins, adhesion proteins, polysaccharides secreted by the cells. The matrix provides mechanical support and helps bind adjacent cells. The most common substance in this region is collagen
What is the function of the cell junction?
Serves to anchor cells to one another or to provide a passageway for cellular exchange.
Define anchoring junction
Protein attachments between adjacent animal cells. One such junction, the desmosome, consists of proteins that bind adjacent cells together, providing mechanical stability to tissues.
What are desmosomes associated with that hold cellular structures together?
Protein filaments that extend into the interior of the cell
Define tight junctions
tightly stitched seams between animal cells which encircles each cell, providing a seal that prevents the passage of materials between cells (ie: cells lining digestive tract where materials are required to pass through cells to penetrate the bloodstream, instead of through intercellular spaces)
Define communicating junctions
Passageways between cells that allow the transfer of chemical or electrical signals
What are the two kinds of communicating junctions?
Gap junctions (in animal cells), and plasmodesmata (in plant cells)
Define gap junctions
narrow tunnels between animal cells that are made of proteins called connexins - prevent the cytoplasms of each cell from mixing, but allow passage of ions and small molecules.They are essentially proteins channels of two adjacent cells that are closely aligned.
Define plasmodesmata
narrow channels between plant cells. A narrow tube of ER, called desmotubule passes through the channel. Material exchange through this occurs through the cytoplasm surrounding the desmotubule
Name structures that are present in animal cells but not in plant cells
lysosomes, centrioles, and cholesterol
Name structures that are present in plant cells but not in animal cells
cell walls, chloroplasts, chloroplasts, and central vacuoles
What are eukaryotes?
All organisms except for bacteria, cyanobacteria, and archaebacteria
What are examples of prokaryotes?
Bacteria, cyanobacteria, and archaebacteria - all lack organelles and generally consist of a plasma membrane, a DNA molecule, ribosomes, cytoplasm, and a cell wall
Name differences between prokaryotes and eukaryotes
Define simple diffusion (or diffusion
The net movement of substances from an area of higher concentration to an area of lower concentration. In a state of equilibrium, molecules are uniformly distributed but continue to move randomly
Define osmosis
The diffusion of water molecules across a selectively permeable membrane. This creates hydrostatic pressure (osmotic pressure) in the body, and turgor in plant cells and microorganisms
Define dialysis
The diffusion of solutes across a selectively permeable membrane. The term is usually used when different solutes are separated by a selectively permeable membrane.
Define plasmolysis
The movement of water out of a cell that result in the collapse of the cell
Define facilitated diffusion
Diffusion of solutes or water through channel proteins in the plasma membrane.
Define countercurrent exchange *google?
Diffusion of substances between two regions in which substances are moving by bulk flow in opposite directions *ie: direction of water flow through fish gills is opposite to the flow of blood in the blood vessel. 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.
Define phagocytosis
“cellular eating” occurs when undissolved materials enter the cell through a vesicle fused in the plasma membrane that engulgs this material, forming a phagocytic vesicle. (WBCs engulf bacteria in this manner)
Define pinocytosis
“cellular drinking” occurs when dissolved substances enter the cell. The plasma membrane folds inward to form a channel allowing the liquid to enter then closes off the channel encircling the liwuid inside a vesicle.
Define receptor-mediated endocytosis
a form of pinocytosis that ocurs when specific molecules in the fluid surrounding the cell bind to specialized receptors that concentrate in coated pits in the plasma membrane. The pits, receptors, and specific molecules (ligands) folw inward and the vesicle is formed.
