Biology: Ch. 2 Cells Flashcards
Cell
Basic functional unit of all living things
Plasma membrane (Cell membrane)
- Bounds the cell & encloses the nucleus and cytoplasm
- Separates internal metabolic events from external environment
- Controls movement into and out of the cell
- Phospholipid bilayer
Cytoplasm
Consists of organelles suspended in the cytosol
Cytosol
Consists of water and dissolved substances such as proteins and nutrients
Peripheral proteins
Attach loosely to the inner or outer surface of the protein
Integral proteins
Extend into the membrane; amphipathic
Transmembrane proteins
Integral proteins that span across the membrane and appear at both surfaces
Fluid mosaic model
Mosaic nature of scattered proteins within a flexible matrix of phospholipid molecules
Phospholipid membrane
- Selectively permeable
- Allows small, uncharged, polar molecules (H2O & CO2), hydrophobic molecules (O2 & lipid-soluble molecules) to pass
Channel proteins
Open passageways for hydrophilic substances (polar and charged molecules)
Ion channels
Passage of ions
Gated channels
Ion channel in nerve and muscle cells that responds to chemical or electrical stimuli
Porins
Allow passage of certain ions and small polar molecules
Aquaporins
Increase passage rate of H2O molecules in kidneys and plant roots
Carrier proteins
Binding to specific molecules (glucose) induces change of shape which transfers the molecule across
Transport proteins
Use ATP
Active transport
When energy is used to transport materials
Na+-K+ pump
Uses ATP to maintain higher concentrations of Na+ and K+ on opposite sides of the membrane; active transport
Recognition proteins
Gives each cell a unique identification which allows them to make a distinction between self and foreign; glycoprotein
Glycoprotein
Protein with a short polysaccharide chain attached
Adhesion proteins
- Attach cells to neighboring cells
- Provide anchors for internal filaments and tubules
Receptor proteins
Binding sites for hormones or other trigger molecules
Cholesterol
Distributed throughout lipid bilayer providing rigidity to the plasma membranes of animal cells; sterols provide similar function in plants
Glycocalyx
- Carbohydrate coat covering the outer face of the cell wall (some bacteria) or plasma membrane (certain animal cells)
- Consists of various oligosaccharides attached to membrane phospholipids and proteins
- Can provide adhesive capabilities, barrier to infection, cell-to-cell recognition
Organelles
Bodies within the cytoplasm that physically separate the various metabolic reactions
Nucleus
- Bounded by nuclear envelope
- Contains DNA in form of chromatin
- One or more nucleoli
- Site for separation of chromosomes
Nuclear envelope
Consists of 2 phospholipid bilayers
Chromatin
DNA which is spread out within the nucleus as a threadlike matrix
Chromosomes
Condensed form of chromatin when cell begins to divide; made up of two long DNA molecules and various histone molecules
Histones
Organize the DNA into bundles (nucleosomes)
Nucleosomes
Bundles of DNA which make up the histones
Nucleoli
Concentrations of DNA in the the process of manufacturing the components of ribosomes
Ribosomes
- Subunits are manufactured in the nucleus and consist of RNA molecules and proteins
- 60S + 40S = 80S
- Assist in the assembly of amino acids into proteins
S value (Svedberg unit)
How readily a product forms a sediment in a centrifuge; larger value = larger heavier products
Endoplasmic reticulum (ER)
- Stacks of flattened sacs that produce various materials
- Smooth and rough
Rough ER
- Ribosomes are present
- Create glycoproteins by attaching polysaccharide groups to polypeptides
Smooth ER
- Synthesis of lipids and hormones
- Breakdown of toxins, drugs, and toxic by-products in liver cells
Golgi apparatus (Golgi complex or Golgi body)
- Group of flattened sacs arranged like a stack of bowls
- Modify and package proteins and lipids into vesicles
Vesicles
Spherical sacs that bud from the Golgi apparatus which migrate to and merge with the plasma membrane to release contents outside the cell
Lysosomes
Vesicles from Golgi apparatus the contain digestive enzymes (low pH) that break down food, cellular debris, and foreign invaders (bacteria)
Peroxisomes
- Breakdown H2O2, fatty acids, and amino acids
- Liver and kidney cells: breakdown toxic substances
- Plant cells: modify by-products (CO2) of photorespiration
- Germinating seeds: (called glyoxysomes) breakdown stored fatty acids to help generate energy for growth
Mitochondria
Carry out aerobic respiration
Aerobic respiration
Process in which energy (ATP) is obtained from carbohydrates
Chloroplasts
Carry out photosynthesis
Photosynthesis
Plant process of incorporating energy from sunlight into carbohydrates
Three protein fibers & function
- Microtubules, intermediate filaments, microfilaments
- Establish shape of or coordinate movements of the cytoskeleton
Cytoskeleton
Internal structure of the cytoplasm
Microtubules
- Made of protein tubulin
- Provide support and motility for cellular activities
- Found in the spindle apparatus and flagella and cilia
Spindle apparatus
Guides the movement of chromosomes during cell division
Intermediate filaments
Provide support for maintaining the shape of the cell
Microfilaments
- Made of protein actin
- Involved in cell motility
- Found in muscle cells and cells that move by changing shape (phagocytes)
Flagella
Long, few, move in snake-like motion
Cilia
Short, many, move in back-and-forth movement
Structure of flagella and cilia
Microtubules arranged in a “9+2” array–nine pairs of microtubules arranged in a circle surrounding a pair of microtubules
Function/structure of centrioles and basal bodies
- Act as microtubule organizing centers (MTOCs)
- 9 triplets of microtubules arranged in a circle
Centrioles
- Pair of centrioles in centrosome gives rise to the microtubules that make up the spindle apparatus
- Lacking in plant cells
Basal bodies
- Organize the development of flagellum and cilium
- Present in lower plants
Vacuoles and vesicles
Fluid-filled, membrane-bound bodies
Transport vesicles
Move materials between organelles or between organelles and the plasma membrane
Food vacuoles
Temporary receptacles of nutrients; merge with lysosomes which break down the food
Storage vacuoles
In plants; store starch, pigments, and bacteria
Central vacuoles
- Large bodies occupying most of the interior of certain plant cells
- Exert turgor (pressure) on cell wall which fully filled which maintains rigidity
- Store nutrients and carry out lysosome-like functions
Cell walls
- Found in plants, fungi, protists, and bacteria
- Develop outside the plasma membrane and provide support
- Made of cellulose in plants and cellulose or chitin in fungi
Extracellular matrix
- In animals; area between adjacent cells
- Provides mechanical support and helps bind adjacent cells together
- Occupied by fibrous structural proteins, adhesion proteins, and polysaccharides secreted by the cell (common substance is collagen)
Cell junctions
Anchor cells to one another or provide passageway for cellular exchange
Anchoring junctions
- Protein attachments between adjacent animal cells
- Ex. desmosome
Desmosome
- Consists of proteins that bind adjacent cells together
- Provides mechanical stability to tissues
- Associated with protein filaments that extend into the cell and hold cellular structures together
Tight junctions
- Tightly stitched seams between animal cells
- Junction completely encircles each cell producing seal that prevents passage of materials between cells
- Present in lining of digestive tract
Communicating junctions
- Allow the transfer of chemical or electrical signals
- Types: Gap junctions and plasmodesmata
Gap junctions
- Narrow tunnels between animals cells consisting of proteins called connexins, which prevent the cytoplasms of each cell from mixing but allow passage of ions and small molecules
- Allow communication through exchange of materials or transmission of electrical impulses
Plamodesmata
- Narrow channels between plant cells
- Narrow tube of ER, called a desmotubule, surrounded by cytoplasm and the plasma membrane, passes through the channel (material exchange occurs through this cytoplasm)
Present in plant cells, absent in animals cells
Cell walls, chloroplasts, central vacuoles
Present in animal cells, absent in plant cells
Lysosomes, centrioles, cholesterol
Eukaryotes
All organisms except for bacteria, cyanobacteria, and archaebacteria (prokaryotes)
Prokaryotes
Lack all organelles; consist of plasma membrane, DNA molecule, ribosomes, cytoplasm, and often a cell wall
Difference of prokaryotes
- No nucleus
- Hereditary material: single “naked” DNA molecule
- Ribosomes are smaller (50S + 30S = 70S)
- Cell walls made from peptidoglycans (except archaebacteria which contain polysaccharides)
- Flagella are not constructed of microtubules
Selectively permeable membrane
Allows only specific substances to pass
Hypertonic
Higher concentration of solutes
Hypotonic
Lower concentration of solutes
Isotonic
Equal concentration of solutes
Bulk flow
Collective movement of substances in the same direction in response to force or pressure; blood in blood vessel
Passive transport
Movement down concentration gradient; no energy required
Simple diffusion
Net movement of substances from an area of higher concentration to an area of lower concentration as a result of random and constant motion of molecules
Osmosis
- Diffusion of water across selectively permeable membrane
- Hydrostatic pressure (or osmotic pressure) may build up; turgor pressure in plants
Dialysis
Diffusion of solutes across selectively permeable membrane which different solutes are separated
Plasmolysis
Movement of water out of a cell (osmosis) that results in the collapse of the cell
Facilitated diffusion
- Diffusion of solutes or water through channel proteins in the plasma membrane
- Aquaporins increase the rate of transfer of water by facilitated diffusion
Countercurrent exchange
Diffusion of substances between two regions in which substances are moving by bulk flow in opposite directions
Active transport
- Movement of solutes against a gradient; requires energy
- Transport proteins transfer small ions, amino acids, and monosaccharides
Vesicular transport
Uses vesicles or other bodies in the cytoplasm to move macromolecules or large particles across the plasma membrane
Exocytosis
Vesicles fuse with plasma membrane and release contents to the outside of the cell
Endocytosis
Capture of a substance outside of the cell when the plasma membrane merges to engulf it; enters cytoplasm enclosed in a vesicle
Phagocytosis
Cellular eating; when undissolved material enters the cell–plasma membrane wraps around the solid material and engulfs it
Pinocytosis
Cellular drinking; when dissolved substances enter the cell–plasma membrane folds inward to form a channel allowing the liquid to enter
Receptor-mediated endocytosis
- Form of pinocytosis when specific molecules bind to specialized receptors in coated pits
- Pits, receptors, and molecules (ligands) fold inward and formation of a vesicle follows
