Chapter 3 The Cell Flashcards
Basic Process of Cells
- Cell metabolism
- Transport of substances
- Communication
- Cell reproduction
Cell Metabolism
sum of all chemical reactions that cell caries out to maintain life:
1. Anabolic reactions (build up)
2. Catabolic reactions (break down)
3. Oxidation-reduction (conversion)
Anabolic reactions
building reactions, small molecules bonded together to form macromolecules
Catabolic reactions
break down macromolecules into smaller molecules
Oxidation-reduction
reactions convert energy into ATP for cells to fuel its process
Transport
Substances the cell has produced or ingested and transports to a variety of destinations
Communication
Communicates between itself, its surrounding environment, and other cells (chemical and electrical signals)
Cell reproduction
By cell division, process necessary for growth and development and replacement of old, damaged cells
Animal cell components
-Plasma membrane
-Cytoplasm : cytosol, organelles, cytoskeleton
-Nucleus
Plasma membrane
phospholipid bilayer that surrounds each cell, isolating internal structures and process from external environment. (creates barrier)
Functions:
-provides structural support, means of communication with its surrounding and other cells, and cell identification.
-Defines intracellular space (contains intracellular fluid, ICF or cytosol), separates it from extracellular space.
Cytoplasm consist of
- Cytosol
- Organelles
- Cytoskeleton
Cytosol
intracellular fluid; mostly water dissolved solutes, inclusions, and proteins (site of many important chemical reactions)
Organelles
cellular machines with very specific functions, suspended in cytosol. Separate potentially damaging chemical reactions from surrounding cell structures
Cytoskeleton
network of protein filaments, creates and maintains shape, hold organelles in place, provides transportation for substances within cell
Nucleus
-Most cells contain a nucleus
-Single roughly spherical organelle
-Enclosed in phospholipid bilayer
-Contains most of cells DNA, primary location for making most RNA
- DNA and RNA control organelle function by coding for and synthesizing proteins
Cell size and diversity
-Enable performance of specialized functions
ex: Structure Function core principle
Structure of Plasma Membrane
Phospholipid
(Within the plasma membrane) Allows plasma membrane to form effective barrier between ECF and cytosol
-Interact with water in both fluid compartments without falling apart.
-Repel water, keeping ECF and cytosol separated.
Polar (head)
Head of phospholipid (hydrophilic)
Non polar (2 tails)
2 tails of phospholipid (hydrophobic)
Amphiphilic
Phospholipids are amphiphilic:
-Phosphate group (hydrophilic polar head) on the outside
-Two fatty acids (hydrophobic tails) in the middle
Membrane proteins
Main component of plasma membranes: 2 types
1. intergal proteins
2. peripheral proteins
Integral proteins
Span entire membrane, ‘transmembrane’ proteins
Peripheral protiens
found only on one side of membrane or other
Functions of Membrane proteins
- Channels
2.Carrier proteins
3.Receptors
4.Enzymes - Structural support
6.Link
Channels
Transmembrane proteins allow certain substances to cross membrane and pass into or out of cell
Carrier proteins
integral proteins bind, change shape, and directly transport substances into and out of cell
Receptors
Bind to chemical messengers (ligands), trigger sequence of events within cell.
ex: cell to cell communication
Enzymes
Speed up chemical reactions, vital to maintaining homeostasis
Structural Support
When bound to cytoskeleton:
-Give cells shape
-Help maintain structural integrity
Link
link adjacent cells to one another (zipper):
-Anchor cells within tissue
-Allow cell-to-cell communication
Cholesterol
Lipid; stabilizes plasma membranes fluid structure during temp changes
Glycolipids and Glycoproteins
Carbohydrate bond to either lipid or protein; identify cell as part of the body (cell recognition)
Agonists
Mimic ligands’s actions; stimulate receptor.
ex: narcotic pain killers such as morphine mimic actions of endorphins
Antagonists
Inhibit ligands actions by blocking receptor.
ex: antihistamines block receptors for histamine.
Selective Permeability
Allows certain molecules to cross , prohibits passage of other molecules. Critical to survival of cell.
Passive Transport
Substance crosses plasma membrane by not requiring energy.
- Diffusion
-Simple and Facilitated - Osmosis
Active Transport
Substance crosses plasma membrane by requiring energy
Variable determining how substance is able to move across plasma membrane
- Type of substance
- Plasma membrane permeability to substance
- Concentration of substances in cytosol and ECF
Concentration Gradient
Force that drives many types of passive transport
-High concentration; means more molecules
-Low concentration; means less molecules
Diffusion
Movement of solute molecules from high concentration to low concentration, until equilibrium (no net movement) is reached.
Simple Diffusion
Mostly non-polar solutes (oxygen, carbon dioxide, lipids and hydocarbons) pass through phospholipid bilayer without membrane protein.
Facilitated Diffusion
Charged or polar solutes (ions and glucose) cross phospholipid bilayer with help of membrane protein (carrier or channel).
Osmosis
Passive process, where solvent (usually water) moves across membrane.
-Water moves from area with lower concentration of solute (more water molecules) across membrane to area with higher concentration of solute (less water molecules)
Water movement across plasma membrane
- Through channel proteins- aquaporins (primary route for osmosis of water)
- Through phospholipid bilayer directly
Osmosis Pressure
Driving force exerted by solute molecules
-Causes water molecules to move until equilibrium reached.
-Pressure applied to solution to prevent water from moving into it by osmosis
Hydrostatic Pressure
Force water exerts on walls of its container
Osmosis V Diffusion
*Diffusion – movement of solute across plasma membrane from higher solute concentration to lower solute concentration (with concentration gradient)
*Osmosis – movement of solvent across plasma membrane from area of lower solute concentration to area of higher solute concentration
Tonicity
Way to compare osmotic pressure gradients between two solutions: cytosol and ECF
Isotonic Solution
Both fluids have approximately the same concentration of solute, no net movement of water across plasma membrane, no volume changes in either fluid compartment .
-Normally ECF is isotonic to cytosol
Hypertonic ECF Solution
Solute concentration of ECF if higher than inside cell, more water molecules inside cell than outside, osmotic pressure gradient pulls water out of cell, cell shrink (crenates), loses water by osmosis.
- Greater ability to cause osmosis than cytosol
Hypotonic ECF Solution
Solute concentration of ECF if lower than inside cell, more water molecules in ECF than inside cell, osmotic pressure gradient pulls water into cell, cell swells and possible ruptures, will gain water.
-Less ability to cause osmosis than cytosol
Active Transport
Require energy (ATP) to proceed as solutes move against concentration gradients (low to high concentration)
-Primary active transport
-Secondary active transport
3 Types of Pumps in plasma membrane
- Uniport
- Symport
- Antiport
Uniport
Transport single substance through membrane in one direction (into or out of cell)
Symport
Transport two or more substances through membrane in same direction (into or out of cell)
Antiport
Transport two or more substances in opposite directions through membrane
Primary Active Transport
*Sodium-potassium pump (Na+ / K+) pump or(Na+ / K+) ATPase) – most vital for maintenance of Na+and K+concentration gradient homeostasis
*Na+concentration is ten times greater in ECF than cytosol; K+ concentration is ten times greater in cytosol than ECF
*Pump maintains steep concentration gradients by transporting 3Na+out and 2K+ into cell(against concentration gradients) for every ATP molecule hydrolyzed
Secondary Active Transport
Uses ATP indirectly to fuel transport pump.
Electrophysiology
Charge separation exists across plasma membrane.
-Thin layer of positive charges lines outside of membrane, thin layer of negative charges lines inside of membrane.
-Separation of charges creates electrical gradient, provides energy for work
Membrane Potential
Electrical potential across plasma membrane
Resting membrane potential
Membrane potential when cell is at rest; measured in millivolts (mV); value is negative, meaning inside of cell is more negative than surrounding ECF
Vesicles
Small sacs filled with large molecules too big to transport by other means
-Requires ATP
-Enclosed in phospholipid bilayer; allows fusion with or formation from plasma membrane or other membrane bound organelles
Endocytosis
Fluid, molecules taken into cells; 2 types:
1. Phagocytosis
2. Pinocytosis
Phagocytosis
“Cells eating”
Cells ingest large particles like bacteria , dead, or damaged cells or parts of cell
Pinocytosis
“Cell drinking” or Fluid phase endocytosis
Cells engulf fluid droplets from ECF
Receptor - mediated endocytosis
Special form of pinocytosis
-Receptors fills vesicles with specific molecules (cholesterol, hormones, iron)
Exocytosis
Large molecules exit cell (secretion), vesicles fuse with plasma membrane, opening into ECF.
Transcytosis
Molecules brought into cell by endocytosis, transported across cell to opposite side, and secreted by exocytosis
Organelles
Cellular machinery with specific functions vital to maintaining homeostasis. Can be membrane bound or not enclosed.
Membrane Bound
mitochondria, peroxisomes, endoplasmic reticulum, Golgi apparatus, and lysosomes;
-functions could be destructive to rest of cell
Organelles not enclosed in membrane
ribosomes and centrosome
Mitochondria
“Power Plant”, provide majority of ATP (membrane bound)
-Each has own DNA , enzymes and ribosomes
-Double layered, smooth outer membrane, inner membrane highly folded cristae
Mitochondria Outer Layer
Large channels allow molecules from cytosol to enter inner membrane space (between two phospholipid bilayers)
Mitochondria Inner Layer
More selective , transports only necessary solutes into matrix (innermost space) using specific transport proteins
Mitochondria Matrix
Contains mitochondria DNA, proteins, and enzymes specific for breakdown of organic fuels by oxidative catabolism (produces ATP)
Peroxisomes
(membrane bound) organelles, use oxygen to oxidize organic molecules and produce hydrogen peroxide.
*Oxidize toxins (like alcohol) in liver and kidney to less toxic compounds.
*Break down fatty acids into smaller molecules; used for ATP production or other anabolic reactions
*Synthesize certain phospholipids; critical to plasma membranes of specific cells of nervous system
Ribosomes
Tiny granular non membrane bound organelle. Site of protein synthesis:
–Composed of large and small subunits; each made of ribosomal proteins and ribosomalRNA (rRNA)
–Free in cytosol; usually make proteins needed within cell itself
–Bound to membranes of other cellular structures; produce proteins destined for export outside cell, for export to lysosomes, or for insertion into membrane
Endomembrane System
Form vesicles that exchange proteins and other molecules; synthesize, modify, and package molecules produced within cell.
Components of Endomembrane System
–Plasma membrane
–Nuclear envelope
–Endoplasmic reticulum (ER)
–Golgi apparatus
–Lysosomes
Endoplasmic Reticulum (ER)
Large folded phospholipid bilayer continuous with nuclear envelope. 2 forms:
- Rough ER (RER) - ribosome attached to membrane
- Smooth ER (SER)- no ribosome
Golgi Apparatus
Between the RER and plasma membrane.
-Group of flattened membranous sacs filled with enzymes and other molecules.
Products packaged in Golgi can be:
–Secreted from cell (exocytosis)
–Become part of plasma membrane
–Sent to lysosome
Lysosomes
Organelles responsible for digestion of worn out cells or cellular components for recycling.
*Contain digestive enzymes (acid hydrolases)
*Macromolecules broken down into smaller subunits; released to cytosol for disposal or reused to manufacture new macromolecules.
Cytoskeleton
Dynamic structure:
*Gives cell its characteristic shape and size; creates internal framework
*Provides strength, structural integrity; anchoring sites’ support plasma and nuclear membranes and organelles
*Allows for cellular movement where protein filaments are associated with motor proteins
*Performs specialized functions in different cell type
Types of Filaments
Cytoskeleton contains three types of long protein filaments:
*Actin filaments *Intermediate filaments *Microtubules
Actin Filaments
(microfilaments)
Thinnest filament, composed of two intertwining strands of actin subunits.
*Provide structural support, bear tension, and maintain cell’s shape
*Involved in cellular motion when combined with motor protein myosin
Intermediate Filaments
Ropelike, made of different fibrous proteins including keratin, strong more permanent structures.
*Form much of frame work of cell; anchor organelles in place
*Help organelles and nucleus maintain both shape and size
*Help cells and tissues withstand mechanical stresses
Microtubes
Largest filaments, hollow rods or tunes composed of tubulin. Can be rapidly added or removed, allow for size and shape changes within cell.
*Maintain internal architecture of cell; keep organelles in alignment
*Motor proteins dynein and kinesin allow transport of vesicles along microtubule network
Centrosome
Gel matrix containing tublin subunits
Centrioles
Ring of nine groups of three microtubules (critical for cellular division) without it cells cannot divide
Basal Bodies
Modified microtubules on internal surface of plasma membrane where flagella and cilia originate
Inner framework of cytoskeleton
-Microvilli
-Cilia
-Flagella
Microvilli
Finger like extensions of plasma membrane with actin filament core
- help maintain shape
- increase surface are of cells in organs specialized for absorption
Cilia
–Hair-like projections composed of microtubules and motor proteins
–Move in unison to propel substances past cells
Flagella
-Solitary; longer than cilia
–Found only on sperm cells
–Beat in whiplike fashion; propel entire cell
*Flagella and cilia are structurally similar to centrioles except they contain two central microtubules not found in centrioles
Nucleus
Governing body that directs activities of other cellular components; largely determines type of proteins and production rate
-DNA is housed here
-plans (genes) within DNA are executed by several different types of RNA
Nuclear Envelope
Membrane that surrounds nucleoplasm (cytosol-like gel containing many components – water, free nucleotides, enzymes, other proteins, DNA, and RN
Inner membrane (nuclear envelope)
lines interior of nucleus; supported by network of intermediate filaments (nuclear lamina)
Outer Membrane (nuclear envelope)
studded with ribosomes; continuous with endoplasmic reticulum
Nuclear pores (nuclear envelope)
large protein complexes; connect nucleoplasm with cytoplasm; allows substances to move between two locations
Chromatin
One extremely long DNA molecule and associated proteins; organize and fold molecule to conserve space:
–Nucleosome – strand of DNA coiled around group of histone proteins; like beads on string
–Reduces length of strand by about one-third
Chromosomes
Chromatin threads that coil tightly and condense into chromosomes
-Human cells contain two sets of 23 chromosomes: one maternal and one paternal set (46 total)
Sister Chromatids
Identical copies of each chromosome , made in preparation for cell division, connected to one another at centromere
Nucleoli
(Singular, nucleolus) Nuclear region responsible for synthesis of ribosomal RNA and assembly of ribosomes.
Protein Synthesis
AKA Translation
-Manufacturing proteins from DNA blueprint using RNA
DNA-Transcription-mRNA-Translation-Protein
Gene expression
Production of protein from specific gene. 2 processes:
- Transcription
- Translation
Gene
Long chain of nucleotides, determines , determines sequence of amino acids in specific protein
4 Nucleotides in DNA
A, T,G,C
-Each set of three nucleotides (triplet) represents different amino acid. Each amino acid may be represented by more than one triplet
Codon
3-nucleotide sequence of mRNA copy is Codon.
Genetic Code
List of which amino acid is specified by each DNA triplet
Mutations
Changes in DNA due to mistakes in copying DNA or induced by agents (mutagens)
- mutagens: uv light , radiation, chemicals, viruses
-bases for many diseases (cancer)
Transcription
Process of making mRNA (transcript), exits nucleus through nuclear pore into cytoplasm to ribosomes.
3 stages:
-Initiation
-Elongation
-Termination
RNA Polymerase
Enzyme builds transcript, bind to gene, brings in complementary nucleotides, linking them together to form mRNA
Initiation
Beginning of transcription; protein transcription factors bind to Promoter region near gene on template strand of DNA; RNA polymerase also binds to promoter; DNA unwinds with aid of enzyme helicase
Elongation
RNA polymerase- enzyme that elongates the mRNA transcript.
Termination
When last triplet of gene is reached and newly formed pre-mRNA molecule is ready for modification
Introns
noncoding sections of gene that do not specify amino sequence
Exons
Sections that do specify amino acid sequence
RNA Processing
Introns in pre-mRNA must be removed and exons spliced together
Transcription completion
mRNA exits nucleus through Nuclear Pore, enters cytosol and ready for translation into PROTEIN
Translation
Occurs at ribosomes.
-Sequence of mRNA is translated into amino acid sequence with transfer RNA (tRNA)
-tRNA - made in nucleus. picks up specific amino acids and transfers to ribosome
-Nucleotides is translated into amino acids
Anticodon
Sequence of three nucleotides one one end of tRNA complementary to codon of mRNA
tRNA structure
one end is the anticodon and another end carries specific amino acid molecule. (which amino acid is determined by anticodon)
Three binding sites of tRNA
- A site (amino site) - binds to incoming tRNA carrying amino acid
- P site (peptidyl site) - amino acid is removed from its tRNA and added to growing peptide chain
- E site (exit site) - empty tRNA then exits ribosome and is free to pick up another amino acid
Initiation (Translation)
Initiator tRNA brings mRNA start codon in ribosomes P site
Elongation (Translation)
Next tRNA binds to open A site, then allows two amino acids to be linked by peptide bond. The first tRNA exits from E site, second tRNA moves to P site, and A site is open for next tRNA to bind
Termination (Translation)
End of translation, when ribosome reached stop codon on mRNA and new peptide is released
Posttranslational modification
Newly formed polypeptides must be modified, folded properly; sometimes combined with other polypeptides to become fully functional protein
Cell theory
Cells cannot spontaneously appear; must come from division of cells that already exist; all forms of life result from repeated rounds of cell growth and division
Cell Cycle
Ordered series of events from formation of cell to its reproduction by cell division
Cell division
Required for growth and development as well as for tissue repair and renewal
Main phases of cell cycle
Interphase and M phase
Interphase
Period of growth and preparation for cell division; 3 subphases:
- G1 phase (1st gap)
- S phase (synthesis)
- G2 phase (2nd gap)
G1 Phase
Cell performs normal daily metabolic activities (production of new organelles, cytoskeleton, and other proteins); prepares cell for next phase
S Phase
(synthesis)
DNA synthesis (replication) occurs; vital for cell to proceed to next phase
-chromatin unwinds, each base pair is duplicated using existing DNA strands as template to build new strand
G2 Phase
cellular growth; proteins required for cell division are rapidly produced and centrioles are duplicated
Helicase
enzyme that separates DNA strands
Primase
enzyme that builds RNA primer on exposed DNA strands
DNA Polymerase
enzyme that adds nucleotides to RNA primer. enzyme can only add to existing chain of nucleotides
M phase
(cell division) Two overlapping processes: mitosis and cytokinesis
Semiconservative replication
End result is two identical double helices each with one old and one new strand. Then moves to G2 phase.
Mitosis
Newly replicated genetic material is divided between two daughter cells.
Cytokinesis
Cell’s proteins, organelles, and cytosol are divided equally between two daughter cells
Interphase
–Nuclear envelope encloses nucleus
–Centriole pairs duplicated
–Nucleus and nucleolus are clearly visible; individual chromosomes not distinguishable
Mitosis
Division of genetic material . 4 stages:
- Prophase
- Metaphase
- Anaphase
- Telophase
