Lecture 3: Cells and Tissues
Bio 219
Dr. Adam Ross
Cell Physiology
Cell Physiology
• Brief review of organelles
• Should be mostly review
• Cell surrounded by plasma membrane
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Lipid bilayer
Also surrounds organelles
Polar heads face aqueous environments
Non-polar tails face inwards away from polar aqueous environment
Nucleus
• Site where DNA is stored
• Transcription happens here
• DNA to mRNA
• Gene expression can be regulated by a number of factors
• Contains nucleolus
Rough Endoplasmic Reticulum
• Associated with the ribosome
• Non membrane bound organelle (ribosome)
• Makes proteins from mRNA
• Also folds proteins
Ribosome
• Protein machinery responsible for translating mRNA into polypeptides
• See Previous Lecture
Smooth E.R.
• Synthesizes lipids, phospholipids, and steroids
• Carbohydrate metabolism
• Detoxification of drugs
• Gluconeogenesis
Mitochondria
• Produces ATP
• H+ ion gradient drives ATP-synthase
• Created by electron transport chain
Cell Membrane
• Lipid bilayer also contains other non-phospholipid elements
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Cholesterol
Glycoproteins
Receptor proteins
Surface proteins
Glycolipids
Plasma Membrane
Carbohydrate
Glycoprotein
Plasma
membrane
Embedded
protein
Cholesterol
Extracellular
fluid
Glycolipid
Outer surface
of plasma
membrane
Plasma
membrane
Inner surface
of plasma
membrane
Phospholipid
bilayer
Cytoplasm
Surface
protein
Filaments of
cytoskeleton
Three basic ways to transport things
• Pores
• Non gated channels. Always open
• Channels
• Gated pores, allow transport when open
• Carriers
• Opens upon presentation of thing to be transported
• Generally unidirectional
Pores, channels and carriers
• Pores- always open
• Aquaporin channels in kidney
• Look like a straight, open tube
• Channels
• Alternatively open and closed
• Allow specific things to pass
• Ion channels regulate cell membrane potential
• Carriers
• Two gates that are never open at same time
• Never provides continuous path
Membrane proteins have diverse functions
• Ionotropic receptor (type of gated channel)
• Nicotinic acetylcholine receptor (nAChR)
• Voltage gated channel
• Opens in response to changes in electrical potential
• Metabotropic receptor
• β-adrenergic
• Transport proteins
• Na-K ATPase
• Structural Proteins
• Integrin
Ionotropic receptors
• Binding of ligand to receptor opens ion channel
• Allows ions to enter or leave cell, changing the electrical potential or activity
of a cell or downstream messenger
• nAChR
• In skeletal muscle; allows for communication between nerves and muscles
• Binding of acetylcholine to nAChR, opens a cation channel which starts the
process of muscle contraction
• There are also voltage gated ion channels
• Open in response to changes in cell electrical potential
nAChR
Metabotropic receptors
• Binding of ligand causes metabolic cascade of G-proteins
• This cascade used second messengers to change activity of some cellular
parameter
• In the heart muscarinic acetylcholine receptors are used to slow heart rate
• Use of heterotrimeric G-protein
Metabotropic vs ionotropic
Transport proteins
• Transport can be active or passive
• Example: Glucose transporters (GLUT)
Cotransporters
• Can also be called exchangers
• Exchange one molecule or ion for another
• Generally driven by the inward Na+ gradient
• Many examples
• Na/Glucose
• K/Cl
Connective proteins
• Surface proteins that aid in cell to cell adhesion
• Integrin is one example
• Interacts with extracellular matrix to help provide cell stability
• Tight junctions
• Make gaps between cells impenetrable
• Made up of a number of proteins
• Gap junctions
• Allow for electrical communication between cells
• Via direct cell to cell exchange of ions and/ or small molecules
• Found in most cells in solid tissue
Integrin
Tight junctions
Gap junctions
Membrane has a diverse array of functions
• Protect cell from pathogens
• Maintain proper salt-water balance
• And corresponding membrane potential
• Respond to signaling ligands via surface receptors
• Endo and Exocytosis
• Anchor cell in place
• Communication with neighboring cells
4 basic tissue types
• Epithelial
• Connective
• Neuronal
• Muscular
Epithelial tissue
• Continuous sheets of cells
• Squamous, columnar, cuboidal
• Boundary covering internal environment (ECF) from external
environment
• Covering/ lining epithelia
• Protection/ absorption
• Skin
• GI tract
• Secretory epithelia
• Exocrine and endocrine glands
Types of epithelial tissue
• Squamous
• Flattened sheet of cells
• Columnar
• Tall column shaped cells
• Cubodial
• Cube shaped cells
• Simple
• Single layer of epithelial cells
• Compound/ Stratified
• Multiple layers of cells
Squamous epithelia
• Simple
• Single layer
• Often a mediator of filtration and diffusion
• Stratified
• Multiple layers
• Only one layer of cells is attached to the basement membrane
• Good for areas with lots of abrasion
Squamous epithelia
Simple: Glomerulus on top,
Bowman’s capsule on bottom
Stratified: Human epidermis
Columnar epithelia
• Simple
• Single layer of column shaped cells
• Most organs of human digestive tract
• Stratified
• Secretion and protection
• Urethra, vas deferens, uterus, eye, anus
• Pseudostratified
• Appears to be stratified
• Actually only one layer of cells
• Linings of upper respiratory tract (ciliated)
• Male vas deferens (non-ciliated)
• Ciliated
• Columnar cells have cilia attached to the apical membrane
• Used to trap debris
Columnar epithelia
Simple (stomach)
Cubodial epithelia
• Simple
• Single layer of cube shaped cells
• Kidney tubules, glandular ducts
• Stratified
• Sweat, mammary, and salivary glands
• Often times only top layer is cuboidal, other layers are other cell types
Cubodial epithelia
Pig kidney
Parotid gland (stratified)
Functions of epithelial
• Exchange
• Simple squamous; alveoli
• Transport
• Simple columnar; small intestine & simple cuboidal; renal tubule
• Ciliated
• Pseudostratified; trachea & simple ciliated columnar; uterine tube
• Protective
• Stratified squamous; skin
• Secretory
• Glandular; endocrine and exocrine glands
Connective tissue
• Major support tissues of the body
• Most abundant and diverse tissue type
• Storage site for fat
• Composed of cells and extracellular matrix
• Considered to be two parts of one thing
• Cells are tissue specific
• ECM is mostly protein fibers used for anchoring and support
Types of connective tissue
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Many different types of connective tissue:
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2.
3.
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5.
6.
Areolar
Adipose
Dense (Tendons and Ligaments)
Cartilage
Bone
Blood
Loose connective tissue (Fibroblasts)
Loose adipose tissue
Adipose (fat) tissue
• Found under skin, around kidneys
and heart
• Functions in energy storage and insulation;
cushioning for organs
Dense connective tissue
Dense connective tissue
• Found in tendons and ligaments
• Forms strong bands that attach
bone to muscle or bone to bone
Cartilage
Cells = chondrocytes
Bone
Bone- functions
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Functions:
1.
2.
3.
4.
Protects and supports internal structures
Facilitates movement along with muscles
Stores lipids, calcium, and phosphorus
Produces blood cells
Bone
Bone
• Found in the skeleton
• Functions in support, protection
(by enclosing organs), and movement
Blood
Blood
• Found within blood vessels
• Transports nutrients, gases, hormones, wastes;
fights infections
Blood
• Blood consists of liquid (plasma) and formed elements including:
• Red Blood Cells (RBC) - transports oxygen to body cells.
• White Blood Cells (WBC) - fight infection
• Platelets—cell fragments necessary for clotting of the
blood.
Connective tissues
Neuronal tissue
• Designed to transmit information from one part of the body to
another
• Uses electrochemical signals
• Action potentials
• Neurotransmitters
• Synapses
• Also includes support cells for the cells sending the messages
(neurons)
• Microglia, astrocytes, schwann cells, etc
Nervous tissue
Axon
Dendrite
Cell body
Neuron
Neuroglia
Muscular tissue
• Cardiac, skeletal, and smooth muscle in the body
• Produces force to move body, pump blood, or help move digested
food.
• Relies on the interaction of actin and myosin to produce force
• Different muscle tissues have different properties
• Will cover in depth during muscle lecture
Skeletal muscle
• Voluntary
• Striated
• Activated by acetylcholine release at synapse
• Majority of body’s energy and blood are used here
Skeletal muscle
Cardiac muscle
• Only in the heart (duh.)
• Involuntary
• Striated
• No direct neural control
Smooth muscle
• Involuntary
• Non striated
• Involved in digestive process