CELL GENERALITIES Flashcards
Lacks the membrane-bound structures
Prokaryotic cell
Possesses membrane surrounding the cell nucleus and organelle
Eukaryotic cell
● Stores and transmits genetic information DNA
Nucleus
● Responsible for transcription of mRNA
Nucleoulus
- ATP source
- Krebs cycle
- O2 phosphorylation
Mitochondria
Network of membranes
Endoplasmic Reticulum
- Protein synthesized by ribosomes is processed (in Golgi apparatus)
- Responsible for the translation of proteins
Rough Endoplasmic Reticulum
sites of protein synthesis
Ribosomes
- Enzymes for fatty acids and steroid synthesis
- Stores and releases calcium (more on muscle and cardiac
physiology)
Smooth Endoplasmic Reticulum
- Series of closely apposed flattened sacs
- Concentrates, modifies, and sorts proteins arriving from the rER
prior to their distribution.
Golgi Apparatus
Contains enzymes that are capable of digesting proteins, carbohydrates, lipids, nucleic acids, and other biological material
Lysosomes
- Provides structural support
- Gives structural strength to resist stretch
- Structural supporters and transport pathways
Cytoskeleton
Controls: location and communications of intracellular elements
Cytoskeleton
Mechanism: changing/maintaining shape and movement of the
Cytoskeleton
Separates the internal and extracellular environments
Plasma Membrane
- Composed of a bilayer of amphipathic lipids
- Physical barrier
Plasma Membrane
○ Monolayer structure containing a head and a tail
Micelles
○ Has a tail to tail arrangement
Liposomes
○ Acts as a protective barrier
Lipid bilayer
-The barrier becomes a regulator because:
■ Has a polar surface (has charges)
■ Has specialized membrane components
-Formed by the tail to tail arrangement of the phospholipid
molecules
inside layer and is soluble to fats(tail)
Hydrophobic
outside layer and soluble to water(head)
Hydrophilic
Other phospholipids Bilayer components:
- Cholesterol - stabilize the fluidity of the membrane at normal
temperature. - Sphingolipids
- Membrane proteins - help move large molecules from inside
to outside of the cell or vice versa. - Glycoconjugates - glucose conjugated to a protein.
FUNCTIONS OF PLASMA MEMBRANE
- Regulate the passage of substances into and out of the cell
● Detect chemical messengers arriving at the cell surface
● Link adjacent cells by membrane junctions
● Anchors cell to extracellular matrix
Protrude all the way through the membrane.
Integral proteins
Spans the cell membrane and provides cell communication
Integral proteins
- Provides structural CHANNELS (pores)
- Act as CARRIER proteins for transporting substances that could not penetrate the lipid bilayer
- Serves as RECEPTORS to H2O soluble chemicals such as peptide hormones
Integral proteins
Amphipathic
Integral proteins
Only to the surface and do not penetrate all the way through
Peripheral proteins
Primarily in the cytosolic (inner) side, attached to cytoskeleton elements that influence the cell shape and motility
Peripheral protein
Non-amphipathic
Peripheral protein
● Enable the cell to identify and interact with each other
● Usually extends to the extracellular fluid to form glycocalyx
Carbohydrates
TYPES AND ROLES OF MEMBRANE JUNCTIONS
● Desmosomes
○ Firm physical connections that hold adjacent cells
○ Example: Epithelial cells in the digestive tract
● Tight Junctions
○ Fuses adjacent plasma membranes (no space in between)
○ Well-developed in epithelial cells
○ Histologically basis: lumen to the blood vessels transport
○ Impermeable junctions that prevent molecules from passing
through intercellular space
○ Example: Tissues subjected to stress such as skin, heart, and
muscle
● Gap Junctions
○ Protein channels that link cytosol to facilitate electrical transmission
○ Communicating junction that allows ions and small molecules to pass for intercellular communication
○ Present in electrically excitable tissues such as smooth muscle and heart
Type of cell that generate mechanical force that produces movement
Muscle cell
Type of cell that Initiate and conduct electrical signals
Nerve cell
Connect, anchor, and support the structures of the body
Connective tissue cell
Create a protective barrier that selectively secretes and absorbs ions and organic molecules
Epithelial cell
Organs in the Nervous System
Brain, spinal cord, peripheral nerves and ganglia, special sense organs
Organs in the Musculoskeletal System
Cartilage, ligaments, bones, tendons, joints, skeletal muscle
Organs in the Digestive System
Mouth, pharynx, esophagus, stomach, intestines, salivary glands, pancreas, liver, gallbladder, pancreas
Organs in the Immune System
White blood cells, lymph vessels & nodes, spleen, thymus, and other lymphoid tissue
Circulatory System consists of:
Blood, heart, blood vessels
Defense against foreign invaders
Immune System
System responsible for Transport of blood
Circulatory system
Digestion and absorption of organic nutrients, salts, and water; excretion of waste materials
Digestive System
Support, protection, and movement of the body
Musculoskeletal system
Regulation & coordination of many activities in the body; detection of changes in internal and external environments; states of consciousness; learning; recognition
Nervous System
Organs of the Respiratory System
Nose, pharynx, larynx, trachea, bronchi, lungs
Organs of the Urinary System
Kidney, ureter, bladder & urethra
Organs of the Endocrine System
Organ secreting hormones such as pancreas, thyroid, testis, ovaries, hypothalamus, kidneys, pituitary, parathyroid, adrenals, intestines, thymus, heart, pineal gland
Organs of the Reproductive System
Ovaries, fallopian tubes, uterus, vagina, mammary glands, testes, penis
Organs of the Integumentary System
Skin
State of reasonably stable balance between physiology
variables
Homeostasis
○ Variables fluctuate within a predictable and often narrow
range
Homeostasis
○ The entire sequence of events
Homeostasis
○ Maintenance of a nearly constant internal environment
Homeostasis
maintain variables within
acceptable levels
Homeostasis
usually challenged by the external environment.
Physiological variables
● Negative Feedback
○ Opposite direction to the stimulus
○ Reverses a change in a controlled condition
○ E.g., Blood pH regulation (force exerted by blood as it
presses against the walls of the blood vessels
1. Inc blood pH or acidity (H+)
2. Receptors: peripheral and central
chemoreceptors
3. Control center: brain (medulla oblongata)
4. Effector organ: ventilatory muscles contract to
increase ventilation to eliminate Co2
○ E.g., Blood Glucose
■ Increased blood sugar will trigger the pancreas to release insulin for glucose reuptake
Positive Feedback
- An increase or decrease in the variable regulated brings
about responses that tend to move the variable in the
same direction (“positive to”) as the original stimulus.
○ Same direction as the stimulus
○ Strengthen or reinforce a change in one of the body’s
controlled conditions
○ ex: Normal Child Birth
1. Contractions of the uterus force the baby’s head into the cervix
2. Stimulus: Stretching of cervix
3. Receptor: Stretch sensitive nerve in the cervix
sends input
4. Input: Nerve impulse to the brain
5. Control Center: Brain interprets input and
release
6. Output: Oxytocin
7. Effector organ: uterus contract more forcefully
8. Baby’s body stretches cervix more
9. Positive feedback: Increasing stretching of the
cervix causes the release of more oxytocin which results in more stretching of the cervix
FACTORS UNDER HOMEOSTATIC CONTROL
Nutrients, gases, waste products, pH, salt and other electroclytes, temperature, volume and pressure
● Homeostasis is constantly being disrupted by:
○ Physical insults
■ Intense heat or lack of oxygen
○ Changes in the internal environment
■ Drop in blood glucose due to lack of food ○ Physiological stress
■ Demands of work or school ○ Disruptions
■ Mild and temporary (balance is quickly restored)
■ Intense and prolonged (severe infections)
COMPONENTS OF THE CONTROL SYSTEM
1 Stimulus (variable regulated)
2 Set-point of the variable (normal)
3 Receptor (the one that would receive the information)
4 Afferent pathway (the one that would send the information)
5 Integrating system (the one that would receive the information using our brain)
6 Efferent pathway (the one that would carry the message to the effectors)
7 Effectors (organs that would now cause a response )
8 Response
Receptor
○ Body structure that monitors changes in a controlled condition
○ Send input to the control center
■ Nerve ending of the skin in response to temperatures change
Control Center
○ Brain
○ Sets the range of values to be maintained
○ Evaluates input received from receptors and generates output
command
○ Nerve impulses, hormones
■ Brain acts as a control center receiving nerve impulses from skin temperature receptors
Effector
○ Receives output from the control center
○ Produces a response or effect that changes the controlled condition
■ Found in nearly every organ or tissue
■ Body temperature drops the brain send an impulse to the skeletal
muscle to contract
■ Shivering to generate heat
Storage pool in the body is affected by two events:
- Net gain
a. Gaining food through the GI tract, air from the lungs, or synthesized by the body - Net loss
a. Loss from metabolism and the excretion from body via
lungs, GI tract, kidneys, skin, menstrual flow
TOTAL BODY BALANCE:
NEGATIVE BALANCE
Loss > gain
TOTAL BODY BALANCE:
POSITIVE BALANCE
Gain > Loss
TOTAL BODY BALANCE:
STABLE
Gain = Loss
TOTAL BODY WATER COMPOSITION IN THE BODY
60% of the bodyweight ○ Distributed in the intracellular fluid or ICF (40%) and the extracellular fluid or ECF (20%). ○ ECF can be divided into: ■ Interstitial Fluid - 75% (3⁄4) of ECF ■ Plasma - 25% (1⁄4) of ECF
Specialized membrane between Interstitial fluid and plasma
Capillary wall
■ Exchange of fluid between the 2 compartments
most abundant cation in extracellular environment
Sodium
most abundant cation in intracellular environment
Potassium
MEMBRANE TRANSPORT PROTEINS
WATER CHANNELS
ION CHANNELS
- ligand gated
- voltage gated
- mechanically gated
SOLUTE CARRIERS
- uniporters
- symporters
- antiporters
- ATP dependent transporters
WATER CHANNEL
- Main route of water movement into and out of the cell
● Regulated by altering the AQUAPORINS in the membrane,
specifically their:
○ Number/quantity
○ Permeability
ION CHANNELS
○ Ligand-gated
■ Open when a specific molecule binds to it
○ Voltage-gated
■ Open when there is a change in membrane potential
○ Mechanically-gated
■ Open when physical deformation of the membrane occurs
TYPES OF ION CHANNELS ARE BASED ON:
○ Selectivity or Non-selectivity ■ Can be for one specific solute ■ Can allow passage of different solutes ○ Conductance ■ Higher concentration gradient ■ Ex: inward rectifier (greater conductance when ions move INTO the cell vs. out of the cell) ○ Gating
SOLUTE CARRIERS
Uniporters
Symporters/Co-transporters
Antiporters
ATP-Dependent Transporters
ATP-Dependent Transporters
● Uses ATP to drive the movement of molecules/ions across the membrane.
● Ex. Sodium-Potassium ATPase Pump uses ATP to transport 3 Na out of the cell and 2 K into the cell
Antiporters
● Couples the movement of two or more molecules/ions across the membrane.
● However, one is transported in the OPPOSITE direction.
● Ex. Sodium-Calcium Exchanger moves 1 Na into the cell and 1 Ca
out of the cell.
Symporters/Co-transporters
● Couples the movement of two or more molecules/ions across the membrane
● Transported in the SAME direction
● Ex. Sodium-Glucose Transporter (SGLT) transports 2 Na and 1
Glucose
Uniporter
● Transport a single molecule across the membrane
“Uni” - one, single
Example: GLUT2 Transporter Transports glucose into the cell
CHANNELS
conduit through membrane:
Intermittently open
CARRIERS
conduit through membrane:
Never open
CHANNELS
unitary event
Opening
CARRIERS
unitary event
Cycle of conformational change
Particle Translocated of Channels and Carrier
Smaller and Bigger
Translocation Rate of Channels and Carrier
Rapid and Slow
Can channels and carrier be saturated
No and Yes
● Molecules are constantly bouncing off of each other.
● These collisions generate energy that pushes molecules from one
direction to another.
● Molecules move from a high energy state to a low energy state.
Random Thermal Motion/Brownian Movement
Driving Forces affecting Movement
Chemical Driving Force and Electrical Driving Force Electrochemical Driving Force
Chemical Driving Force
● Occurs in the presence of a concentration gradient.
● A high frequency of collisions in the intracellular fluid will create more
energy and forcibly push solutes out of the cell.
● Movement of solute occurs from higher concentration to lower
concentration.
Electrical Driving Force
● Deals with solutes that have charges.
● There is net negative charge in the ICF because there are more
negatively charged ions in the ICF.
● There is a net positive charge in the ECF.
● Opposite charges attract, so negative charges in the ICF diffuse
greater to the outside of the cell and positive charges in the ECF diffuse greater to the inside of the cell.
Electrochemical Driving Force
Net driving force when chemical and electrical gradients are combined.
MEMBRANE TRANSPORT in which movement is along a gradient
PASSIVE
- Simple diffusion
- Facilitated Diffusion
- Osmosis
MEMBRANE TRANSPORT in which movement is against a gradient
ACTIVE
- primary active
- secondary active
MEMBRANE TRANSPORT in which movement requires a vesicle
VESICULAR
- Endocytosis
- Exocytosis
MEMBRANE TRANSPORT in which movement requires a vector
EPITHELIAL
- Paracellular
- Transcellular
Uses an integral protein, known as a transporter or carrier in transporting a molecule across a membrane
MEDIATED TRANSPORT SYSTEMS
3 PROCESSES OF MEDIATED TRANSPORT SYSTEM
a. Binding of the transported solute to a carrier
b. Conformational change of the carrier
c. Release of the transported solute to the other side of the
membrane
Facilitated diffusion and active transport
- Facilitated diffusion – w/o energy
- Active transport – w/ energy
Diffusion
● A process by which molecules move spontaneously from an era of HIGH CONCENTRATION to LOW CONCENTRATION
● Movement is along a gradient
● Molecules are in a continuous state of motion known as “Random
Thermal Motion”
● The warmer the environment, the more rapid is the movement
Factors that influence net flux can be explained by the following equation
Fick’s First law of diffusion
Stokes Einstein equation
Vander’s equation
●Relationship of Diffusion coefficient, area of membrane and concentration gradient to net diffusion
○ Increased Diffusion coefficient, area of membrane and concentration gradient = increase net diffusion
(faster)
● Relationship of membrane thickness to net diffusion
○ Increased membrane thickness = decrease net diffusion
(slower)
Fick’s First law of diffusion
● Relationship of Boltzmann’s constant and temperature to diffusion coefficient
○ Increased Boltzmann’s constant and temperature = increase diffusion coefficient
● Relationship of radius of macromolecule and viscosity of the medium to diffusion coefficient
○ Increased radius of macromolecule and viscosity of the medium = decrease diffusion coefficient
● Relationship of diffusion coefficient to net diffusion
○ Increased diffusion coefficient = INCREASED net diffusion
● Relationship of net diffusion to diffusion coefficient ○ No relationship
Stokes Einstein equation
● Increased net flux = increase diffusion
Vander’s Equation
The major factor limiting diffusion across the cellular membrane
hydrophobic interior of its lipid bilayer.
Directly related to the net flux are the following
○ Concentration gradient across the compartments
○ Surface area of permeable membrane
○ Temperature of the medium
Inversely related to net flux is
○ Mass of the molecule
reflects the ease with which the molecule is able to move through a given membrane
The numerical value of the permeability constants (kp) which the molecule is able to move through a given membrane. The greater the constant, the larger is the magnitude of the net flux.
● No energy required
PASSIVE TRANSPORT
