Topic 2- Tissue types and movements of molecules across Plasma membrance Flashcards
What is a cell
Cell: basic structural and functional unit of living organisms, smallest unit of life which can replicate independently(200 different types of cells)
What is Differentiation
process whereby cells assume their specialised structure and function
cytoplasm
Water substance contains electrolytes, organic molecules and organelles
Mitochondria
Powerhouse which produces ATP
Rough Endoplasmic Reticulum
site of protein production(ribosomes)
Smooth endoplasmic reticulum
Synthesis of lipids
Cell detoxification
Golgi Apparatus
Modify, concentrate and package proteins and lipids from the ER
Lysosomes
Breakdown foreign or damaged material
Membrane surrounds organelle to separate the ‘nasty’ enzymes from the cell
Cytoskeleton
Transport of intracellular organelles
Cell motility, division and contractility
Plasma Membrane
Semipermeable membrane which defines cell boundaries
Nucleus
Central control of all function i.e. DNA, growth, metabolism and reproduction
Plasma Membrane characteristics
Defines the cells boundary
Separates the intracellular and extracellular spaces (inside and outside of the cell)
Dynamic structure which alters to facilitate cellular requirements
phospholipid
Polar hydrophilic head (water loving)
Derived from glycerol conjugated to nitrogenous compounds
Non polar hydrophobic tail (water fearing)
Two long chain fatty acids
One fatty acid is saturated (straight) which the other is unsaturated (kinked)
Bilayer
Spontaneously forms a bilayer with hydrophilic heads faced outwards and hydrophobic tails forced inwards together
Structure is relatively weak and will separate if sufficient force is placed
cholesterol
Fills the gaps between unsaturated fatty acid tails
Stabilise and regulate the fluidity of the phospholipid bilayer
Proteins
Functional units within the plasma membranes
Integral proteins: incorporated within the membrane goes through both sides of the membrane
Transport channels or carriers
Enzymes
Receptors i.e. detects interactions with hormones
Peripheral proteins: embedded within the inner or outer surface
Cell recognition and cell to cell interactions i.e. glycoproteins
Cytoskeleton anchorage facilitates shape and placement of particular proteins
membrane junctions determined by?
Glycoproteins (glue like)
Wavy contours of the membrane (tongue and groove)
Special cell junctions
Desmosomes
Disk-shaped junctions that form cells into tissue
Found in areas that can be stretched prevents tearing due to arrangement of protein filaments i.e. found in organs subject to mechanical stress – heart
Due to cross-linkage of proteins which are densely accumulated at the cytoplasmic surface of each cell and in the extracellular space between cells
Tight Junctions
The joining of the extracellular surfaces of two adjacent cells
Occurs in a band around the entire circumference of the cell
Blocks extracellular pathway between cells impermeable
Found in epithelial cells in the intestinal tract keeps enzymes and microbes from the blood
Gap junction
Protein channels linking the cytosol of adjacent cells
Attached to each other via hollow cylinders connexons
-Composed of transmembrane proteins
Allow small molecules to pass through ions, simple sugars
Found in variety of cell types i.e. cardiac cells and smooth muscle
-Present in electrical excitable tissue where ion passage between cells enables synchronisation of their electrical activity and contraction
interstitial fluid
a solution which bathes and surrounds cells
interstitial fluid characteristics
main component of extracellular fluid containing hormones, fatty acids, amino acids, vitamins, neurotransmitters, hormones, sugars and wastes
Cells must be able to attain the correct balance of components for appropriate function
passive transport
No energy required
Diffusion or osmosis
Down concentration gradients to achieve equilibrium
Active transport
Requires energy (ATP)
Low high concentration against the gradient
Requires carrier proteins which combine specifically with the transport substance
-Phosphorylation of the protein facilitates movement
-E.g. hydrogen, sodium, potassium
when is bulk transport used
Substances which cannot be moved across the plasma membrane moved by bulk transport
Endocytosis
Bulk transport into the cell
Cell membrane extends outwards and surrounds particles outside of the cell
Forms a vesicle and can be released inside the cytoplasm
Exocytosis
Bulk transport out of the cell
Particles are transported in a vesicle to the cell membrane
Vesicle and cell membrane fuse together releasing the contents
what does diffusion depend on?
Diffusion depends on: molecule, size, charge, solubility and kinetic energy of the particles involved
Simple Diffusion
Non-polar or lipid molecules diffuse directly through the plasma membrane
Channel mediated facilitated diffusion
Transmembrane channels (proteins) facilitate diffusion via water filled channels
Selective depending on channel size and charge
Leak channels always open allowing movement according to concentration gradients
Chemically gated channels chemically/ligand gated channels open when the appropriate chemical binds
Voltage gated channels open and close in response to changes in membrane potential
Mechanical gated channels open in response to deformation of membrane i.e. via sensory receptors
Carrier mediated facilitated diffusion
Transmembrane proteins (carriers) transport certain polar molecules which are too large
Alteration in the shape of the channel facilitate movement
Factors affecting the rate of diffusion
Size of the chemical substance (smaller = faster)
Temperature (hotter = faster)
Difference in concentration (larger difference = faster)
Osmosis
Passive transport of water from low solute concentration to high solute concentration
Osmolarity
the number of solute particles present in a 1L of solution (~300 mOsmol/L in our cells)
i.e. 1 M NaCl = 2 Osmol/L solution depends on the dissociation of the solute
Tonicity
the ability of a solution to change the shape or tone of cells by altering the cells internal water volume
isotonic
solutions which have the same number of molecules, or the same osmolarity as our cells
Cells retain normal shape due to no fluid movement
Hypertonic
solutions which have a higher number of molecules than those seen in the cell
Cells shrink/crenate
Hypotonic
he solution is more dilute than those in the cells
Cells swell/lyse
ATP
Adenosine Triphosphate
Glucose, fatty acids and amino acids are sources of energy for ATP synthesis
Production: Metabolic pathways
-Product of one enzyme reaction becomes the substrate for the next
-Inefficient -> Heat is bi-product
ATP-ADP cycle (occurs within mitochondria)
-When bonds are broken, energy is released
———–ATP -> ADP + Pi + energy
———–Faciliated through ATPase
Glycolysis (anaerobic)
The breakdown of 6-carbon glucose into two 3-carbon pyruvic acid units
The hydrogens removed join with the hydrogen carrier NAD+ to form NADH
Although some energy is needed to start glycolysis, there is an overall net gain of 2 ATP
Occurs in the cytoplasm
Krebs Cycle
Pyruvate moves into the mitochondria
Pyruvic acid Acetyl CoA produces NADH as a by-product
2 Acetyl CoA produced per glucose i.e. 1 Acetyl CoA per pyruvate molecule
FADH2 is also produced
NAD and FAD are carrier molecules that transport hydrogen atoms and electrons
1 ATP produced per Acetyl CoA
Electron Transport Chain
High energy electrons help pump H+ across the inner mitochondrial membrane creating a concentration gradient
ATP synthase – site of ATP production H+ flow through, capturing energy
Hydrogen combines with oxygen to form water
Aerobic respiration
Aerobic: with O2
The presence enables pyruvic acid acetyl CoA
Anaerobic
Anaerobic: without O2
Undergoes purely glycolysis
Production of NADH ‘clogs’ up glycolysis
Pyruvic acid Lactic acid which enables NADH to provide its electrons to it
Lactic acid build-up causes pain
Paracrine/Autocrine
Local communication:
Paracrine: Adjacent or close cells
Autocrine: Same cell
-Involved in positive feedback loops to perpetuate a response
Hormones
Part of the endocrine system:
Slow but long lasting
Long range chemical messengers
The blood carries the messenger to other sites in the body, where they exert their effects on their target cells some distances from their site of release.
Only the target cells of a particular hormone have receptors
Neurotransmitter
Nervous System:
Short range chemical messengers
Secreted at synapse
Exerts effects dendrites of post-synaptic neuron or neuromuscular junction (muscle cell)
Fast-response
Short lasting because cleared by reuptake, enzyme degeneration
Prevents any unwanted signals
Excitatory or inhibitory
Control of hormones release
Hormone release results from gland stimulation, however patterns may vary
-Spurts
-Evenly
-Sporadically as needed
Controlled by:
-Humoral stimuli (chemical changes in blood nutrients, iron levels)
-Neural Stimuli (nerve fibres stimulates glands)
-Hormonal stimuli (can attach to a gland, which triggers to release another hormone)
compare hormones and neurotransmitters based on duration, speed of response, transport and clearance
duration
hormone= prolonged
Neurotransmitter=immediate
Speed of response
Hormone= slow
Neurotransmitter=fast
Transport
Hormone= blood stream
Neurotransmitter= across synapse
Clearance
Hormones= Enzyme degradation
Neurotransmitter= Reuptake/diffusion
Epithelial tissue
A sheet of cells that covers a body surface or lines a body cavity – form body boundaries
Function: protection, absorption, filtration, excretion, secretion – defends on structure
Forms in the body;
Covering and lining epithelium
Covering and lining epithelium: forms the outer layer of the skin, dips into and lines the open cavities of the urogenital, digestive and respirator systems and covers the walls and organs of closed ventral body cavity
Granular epithelium
Glandular epithelium: surrounds the glands of the body
Main characteristics of epithelium tissue
polarity, specialised contacts, supported by connective tissue, Avascular and innervated, regeneration, simple or stratified
Polarity
Polarity: all epithelia have an apical (top) surface and a lower attached basal (bottom) surface that differ in structure and function
Apical sections often have microvilli (small extensions which increase SA) or motile cilia (slender protuberances that beat in waves)
Specialised contacts
Specialised contacts: epithelial cells fit close together and form continuous sheets tight junctions and desmosomes
Support by connective tissue
Supported by connective tissue: reinforces the epithelium and helps resist tearing and stretching
Avascular and innervated
Avascular and innervated: no blood tissues but supplied by nerve fibres
Nourished by diffusion of nutrients from blood vessels in underlying connective tissue
Regeneration
Regeneration: regenerative capacity given adequate nutrition
Classification of Epithelia: (number of cell layers) (cell shape)
simple or stratified
Simple or stratified (2 or more layers): simple for absorption and filtration and stratified for durability and protection
Connective tissue
Tissue that connects, supports, binds or separates other tissues or organs
Highly vascular with exception of cartilage
What are the three main components of connective tissue?
Ground substances(clear, colourless, viscous fluid that fills the space between the cell and fibres
Fibres
Cells
–Ground substances+fibres= extracellular matrix
–composition of each component differs in different tissues resulting in versatility
What are the three types of fibres
collagen. elastic and reticular
Collagen
Collagen: fibrous protein – extremely tough and provides high tensile strength
Cross link and bundle together into thick fibres
Elastic
Elastic: long thin fibres (elastin) which form branching networks which allow stretching and recoil
Reticular
Reticular: short, fine collagenous fibres which branch extensively to form a delicate network
Important around other tissue types – form fuzzy nets which allow more ‘give’ than collagen
Specific cell types
-blast, -cyte fat cells
-blast immature, non-differentiated cells
Actively proliferating and secrete the ground substance and the fibres characteristic of their particular matrix
-cyte mature
Maintain the health of the matrix
Can revert to their active/immature state to repair and regenerate the matrix
Fat cells: store nutrients
Muscle Tissue
Make ~50% of body mass
Cardiac muscle: contracts the heart to pump blood
Skeletal muscle: moves bones and other structures
Smooth muscle: changes shape to facilitate bodily functions
Characteristics
Nervous Tissue
Nervous tissue is found in the central and peripheral nervous systems
The brain, spinal cord and nerves
Regulates and controls body function
Well vascularised (supplied by blood vessels)
Simple squamous
