1.1. Cell Physiology Flashcards
Passive Transport Processes
- Requires no energy (ATP)
- Diffusion
- Osmosis
Diffusion
- Random movement due to intrinsic kinetic energy movement is down a concentration gradient (downhill) does not require
- There should be Concentration Gradient
Net Diffusion
Movement from high to low concentration
Osmosis
Diffusion of water or solvent molecules across a selectively permeable membrane from a region of higher water concentration to one of lower water concentration
Osmotic Pressure
- Force required to prevent membrane of water across cell membrane
- The higher the concentration, the higher the osmotic pressure
Isotonic
- Equal osmotic pressures
- Equal solute concentration
- Isotonic environments show no effect on cells
- Isotonic solutions are not helpful in food presentation
- Water does not move
- Cells remain intact
Hypotonic
- Lower osmotic pressure
- Lower concentration of solute
- Hypotonic environments cause cells to swell (water moves by osmosis)
- Hypotonic solutions are not helpful in food presentation
- Has lower concentration of solutes and a higher concentration of water relative to the cytoplasm of the cell
Lysis (Hypotonic)
Cells swell enough to rupture
Hemolysis (Hypotonic)
Bursting of RBC
Hypertonic
- Have comparatively higher osmotic pressure
- High concentration
- Hypertonic environments cause cells to shrink (water molecules move out of the cells by exosmosis, faster than they enter the cell)
- Hypertonic solutions are helpful in food presentations
- Cell shrinkage = Crenation
Diffusion Through Membrane Channels
- Passive diffusion of a substance down its electrochemical gradient
- Passes through channels, and some channels are open all the time, while some are gated
Facilitated Diffusion
- Passive but mediated
- Movement of molecules down a concentration gradient
- There are transmembrane proteins that act as transporters
- Maximum diffusion rate is limited by the number of transporters
- Transports polar or charged solutes (glucose, fructose, galactose, urea, and some vitamins)
Filtration
- Passive transport
- Movement of water and solutes through a membrane or through a capillary wall by hydrostatic pressure
- If diffusion occurs by means of a concentration gradient, filtration occurs through presence of pressure gradient (there is a difference in pressure on both sides)
- Transports Filtrate (solute-containing fluid)
Active Transport Processes
- Mediated transport requiring energy in the form of Adenosine Triphosphate (ATP)
- Movement of molecules is against the concentration gradient
- Molecules can move from a region of lower concentration to a region of higher concentration (which is why energy is required)
Primary Active Transport
- Involves solute pumps wherein substance is transported against its concentration gradient
- Makes use of transmembrane proteins that require Adenosine Triphosphate or ADP
(Sodium pumps / Potassium pumps)
Secondary Active Transport
- Coupled transport of 2 substances
- Energy is supplied by a sodium ion or hydrogen concentration gradient
- Involves the presence of
ANTIPORTERS - opposite direction
SYMPORTERS - same direction
Vesicular Transport
- Movement of substances into and out of the cells in the vesicle occurs.
- Requires energy in the form of ATP
Vesicle
- Small membranous sac formed by budding off from an existing membrane
2 Forms of ATP
Endocytosis - movement into the cell
Exocytosis - movement of substances out of the cell
Endocytosis
Substances brought into the cell by endocytosis are surrounded by a piece of plasma membrane, which buds off inside the cell to form a vesicle containing the ingested substances
2 Types of Endocytosis
PHAGOCYTOSIS - Ingestion of large particles (bacteria, viruses, aged cells, or dead cells)
PINOCYTOSIS - Ingestion of extracellular fluid
Phagocytosis
(1) Begins as the particle binds to a plasma membrane receptor, causing the cell to extend projections of its plasma membrane in cytoplasm called PSEUDOPODS (2) that surround the particle
(3) and portions of their membrane fused to form a vesicle that enters the cytoplasm
(4) Vesicles fuse with 1 or more lysosomes
(5) Lysosomal enzymes break down the ingested material
- Only occur in PHAGOCYTES (specialize in engulfing and destroying bacteria and foreign substance
- Include white blood cells and macrophages
- Protect body from diseases
Exocytosis
- Secretion, deliberation of materials from a cell
- Secretory Vesicles (membrane-enclosed vesicles) used with the plasma membrane, and release their contents into the extracellular fluid
2 Types of Cell
SECRETORY CELLS - Liberate digestive enzymes, hormones, mucous, and other secretions
NERVE CELLS - Release substances called neurotransmitters via Exocytosis
Cell Cycle
Sequence of changes that a cell undergoes, from the time it forms until it duplicates its contents, and divides itself into two
2 Major Periods of Cell Cycle in Somatic Cells
INTERPHASE - when a cell is not dividing MITOSIS PHASE (M Phase) - when the cell is dividing
Cell Cycle 1: Interphase
- Cell replicates its deoxyribonucleic acid (DNA)
- Manufactures additional organelles and cytosolic components, in anticipation of cell division
- G1
- S Phase
- G2
Cell Cycle 1: Interphase G1
- Cell becomes metabolically active
- Duplicates organelles and cytotoxic components
Cell Cycle 1: Interphase S Phase
DNA and centrosome are replicated
Cell Cycle 1: Interphase G2
- Cell growth continues
- Enzymes and other proteins are synthesized
Cell Cycle 2: Mitosis Phase
Prophase
Metaphase
Anaphase
Telophase
Cell Cycle 2: Mitosis Phase Prophase
- Chromatid fibers condense chromosomes that are visible under the microscope
- Condensation process may prevent the entangling of the long DNA strands
- Each prophase chromosome consists of identical, double-stranded chromatids, which are held together by CENTROMERE
- Later, pericentriolar material of two centrosomes start to form the MITOTIC SPINDLE (football-shaped assembly of microtubules)
- Lengthening of the microtubules between centrosomes pushes centrosomes to opposite poles of the cell
- Spindle extends from pole to pole, then nucleolus and nuclear envelope break down
Cell Cycle 2: Mitosis Phase Metaphase
- Centromeres of the chromatid pairs are aligned along the microtubules of the mitotic spindle
- METAPHASE PLATE (at exact center of the mitotic spindle)
Cell Cycle 2: Mitosis Phase Anaphase
- Centromeres split, separating the two members of each chromatid pair, which move to opposite poles of the cell
- Once separated, chromatids are now called CHROMOSOMES
- As chromosomes are pulled by the microtubules of the mitotic spindle during anaphase, they appear to be V shaped
- The pull is caused by the Depolymerization Process
Depolymerization Process
Removal of tubulin proteins from the spindle fibers which will cause the shortening of spindle fibers
Cell Cycle 2: Mitosis Phase Telophase
- Begins after chromosomal movement stops
- Identical set of chromosomes, now at opposite poles of the cell, uncoil and revert to the thread-like chromatid form
- New nuclear envelope forms around each chromatin mass, nucleoli appears, and eventually the mitotic spindle breaks
- Cells are reconstructed
Mitosis
- Cell Division undergone by somatic cells and primordial germ cells
- Parent cell with the diploid number of chromosomes, divides to form two daughter cells, each with the same number and identical set of chromosomes
Cytokinesis
- Begins late in anaphase, with formation of a cleavage furrow, a slight indentation of the plasma membrane, that extends around the center of the cell
- Microfilaments in cleavage furrow pull the plasma membrane progressively inward, constricting the center of the cell like a belt around a waist
- After cytokinesis, there are 2 new and separate cells, each with equal portions of cytoplasm and organelles, and identical sets of chromosomes
- When cytokinesis is complete, interphase can begin
Meiosis
- Cell Division that is undergone by reproductive cells, wherein a parent cell divides to form daughter cells, each with a haploid number of chromosomes
Protein Synthesis
- DNA serves as the master blueprint for protein synthesis
- GENE is a DNA segment that carries the information building one protein or polypeptide chain.
- Much of the cellular machinery is devoted to synthesizing large numbers of diverse
The instructions for protein synthesis are found in the DNA in the nucleus.
Protein synthesis involves transcription and translation
Proteins
- Key substances for all aspects of cell life
- Determine the physical and chemical characteristics of cells
