Physiology Unit 1

What are the 4 major Categories of Cells

1) Epithelial

2) Muscle

3) Connective

4) Neurons

Epithelial Cells

Form-sheet like layers of cells that function as a barrier

Where are Epithelial Cells?

they line external body surfaces and hollow organs

Muscle Cells

specialized cells designed to contract (shorten)

What are the two categories of muscle cells?

Voluntary: flexing bicep

Involuntary: pumping blood, mixing food in the stomach

What are the 3 Types of muscle cells?

1) Skeletal

2) Smooth

3) Cardiac

Connective tissues are…

a diverse set of cells that connect or “link” body structures

What are the 4 types of connective tissues?

1) Bone

2) Tendons

3) Fats

4) Blood

Many connective tissues have…

extensive extracellular matrix

Neurons

communicate with each other and other body cells

4 Components of Neurons

1) Have branches to receive (dendrites) or send (axon) signals

2) Receive information from receptors or other neurons (afferent)

3) Transmit information to muscles, glands, or other neurons (efferent)

4) Significant neuronal processing occurs in the brain and spinal cord

What 4 primary macromolecules are all cells made up of?

1) Proteins

2) Nucleic Acids

3) Polysaccharides

4) Lipids

Lipids are…

not soluble in water (hydrophobic) and have a heterogeneous structure

3 Functions of Lipids

1) Membrane structure

2) Energy Storage

3) Signaling: Intracellular, Intercellular

Many lipids have…

LONG hydrophobic tails

Lipids that have a hydrophilic “water-loving” head group and hydrophobic tails are called?

amphipathic

Example of amphipathic lipids

phospholipids

What is the hydrophobic nature of membranes?

to make a barrier for water soluble substances: ions, glucose, amino acids

Cell plasma membrane is what?

a lipid bilayer

What is the cell plasma membrane composed of?

Amphipathic Phospholipids, and associated proteins (some proteins act as transporters to regulate traffic across the membrane)

4 Aspects in Variety of Lipids

1) Degree of Saturation (number of double bonds) affect fatty acid structure

2) Saturated FA are straight, can therefore pack together tightly

3) Unsaturated FA are kinked and don’t pack together tightly

4) Degree of saturation affects fluidity of lipids/membranes

Triglycerides are a major form of?

energy storage

Where are fatty acids stored/metabolized?

adipose cells to help maintain blood glucose/energy levels near homeostasis

Steroids (derived from cholesterol) are…

major signaling molecules (cholesterol helps form the plasma membrane)

Polysaccharides/Carbohydrates are…

the most abundant class of organic molecules found in nature, derived from photosynthesis.

Functions of Carbohydrates

1) Building blocks of other macromolecules

2) Energy Source (glucose)

3) Modify structure/function of other macromolecules

Are carbohydrates polar or nonpolar?

Polar-dissolve in water

Monosaccharides are…

building blocks for other macromolecules such as polysaccharides and nucleotides (ring shaped structures)

Monosaccharides join via…

glycosidic bonds to form polymers called polysaccharides

Polysaccharides function?

1) Energy Glucose - Major input to ATP production

Glycogen storage in animal cells

2) Modify structure/function of other macromolecules: glycolipids- outside membrane

glycoproteins: postranslational- affects trafficking/folding

DNA is typically…

a right handed double helix that stores the genetic code in the nucleus.

What is DNA’s backbone

sugar-phosphate with nitrogenous bases (A,T,C,G)

What are the names of the DNA monomers?

Pyruvates: Adenine, Guanine

Pyrimidines: Thymine, Uracil, Cytosine

Structure of a Nucleotide

Phosphate group (negative charge), 5 carbon sugar, and monomer base

Nucleic Acids are templates for proteins, what are the steps?

1) Synthesis of mRNA in the nucleus

2) Movement of mRNA into cytoplasm via nuclear pore

3) Synthesis of protein

Central Dogma of Molecular Biology

DNA → RNA → Protein

Transcription

DNA → RNA

Translation

RNA → Protein

Proteins perform?

Most cellular functions

\-Ubiquitous “workhorses” for the cell

Nucleic Acids function?

Store and express genetic code

\-3 nucleotides = 1 amino acid

Aspects of DNA

Nuclear Storage of Code

\-Double Stranded

\-Antiparallel

\-Complementary

Aspects of RNA?

Expression of Code

\-single stranded

\-U

\-Functions in Cytoplasm

How many different Amino Acids make up proteins?

20

How many hydrophobic amino acids?

9

\-1/2 of R groups

\-tend to be on interior of protein

How many hydrophillic amino acids?

6

\-1/3 of R groups

\-tend to cluster on Protein surface

How many amino acids are charged?

\-1/3

\-Ionic interactions

\-affects how the protein folds

Nucleotides are also involved in…

energy transfer and cell signaling

\-phosphate bonds break to use energy

Minor modifications in protein shape can…

dramatically affect its function

\-acetylcholine receptors change shape upon ligand binding and allows NA+ influx

Amino Acids are linked to form…

polypeptides/proteins Via peptide Bonds

\-protein primary sequence is Directional: amino end (n-terminal) to carboxyl end (c- terminus)

Proteins are all different sizes and shapes and…

perform a multitude of cellular functions

proteins folding information comes from…

which specific amino acids are present (R-group)

\-protein folding (structure) dictates function

Kinesin

motors of train, walks along a microtubule track

tubulin

binds other tubulin (train tracks)

Some proteins function as Enzymes which…

“speed up” chemical reactions

\-Some require ATP others don’t

\-enzymes increase likelihood of chemical reaction

What do ATP synthetase positions ADP and PO4 do?

sufficiently close to allow them to chemically interact (bond) generating ATP (product)

About Anabolic chemical reactions?

Require energy input

\-synthesize large molecules from small

\-energy is stored as “potential energy

\-need to be coupled with catabolic reactions

\-enzymes increase likelihood of reactions

About catabolic reactions

release energy

\-break down large molecules into smaller molecules (glycolysis)

\-occur spontaneously- but are sped up by enzymes

What is the Frist Law of Thermodynamics?

Energy can be neither created nor destroyed but instead can only change form

Are chemical reactions reversible?

Yes

\-Law of Mass Action determines direction of reaction

\-Increased concentration of reactants tends to push reaction forward towards products

\-increased concentration of products tends to push reaction in reverse

Are enzymes specific for substrates?

Yes

\-substrates have to fit just right into the enzyme active site

\-Enzyme folding is critical to ensure correct amino acids line active sites

\-Many enzymes require cofactors or coenzymes to form appropriate folded active site

Factors that Affect Enzyme Catalyzed reaction rates?

\-temperature and PH

\-enzyme/substrate concentration

\-Affinity (strength of association) of enzyme for substrate

\-allosteric reactions

Higher substrate concentration means…

faster reaction rate because they are more likely to bond with the enzymes

\-plateau: all active sites full

Increasing the affinity…

increase the rate of reaction

How do allosteric interactions affect enzyme catalytic rates?

\-chemical modulator binds enzyme at different location than active site changes enzyme conformation

\-some allosteric modulators activate enzymes while other inhibit

\-competitive inhibitors bind directly in the active site and compete with substrate

Enzyme Functions are affected by…

covalent modifications

\-typically post-transitional modifications

\-often reversible

Cells are compartmentalized into organelles which…

localize specific proteins and have distinct functions

What are many plasma membrane functions carried out by?

proteins

What do protein transporters aid in?

required to aid in moving most substances in/out of cells

\-most substances need protein help (ions, glucose, amino acids)

What do protein receptors help do in the cell?

Signal things to happen inside the cell

\-complicated intracellular signal transduction cascades are mediated by various proteins

What are adherens junctions?

proteins that help cells adhere to each other to form tissue/organs

What do specialized tight junctions do?

form impermeable barriers in epithelial tissues that line special organs

\-claudin and occludin proteins form intercellular “ridges”

\-don’t allow passage of solutes between cells

\-solutes must cross epithelial cell plasma membrane

What do gap junctions do?

allow rapid intercellular transport

\-quick communication allow tissue to function as a unit

\-connexins form channels/pores

\-small molecules quickly diffuse to neighboring cell

\-relatively common in heart, smooth muscle, neurons

membrane bound nucleus is…

the information center of the cell (stores and protects DNA)

\-surrounded by nuclear envelope

\-DNA replication and transcription takes place in here

\-Nuclear pores allow macromolecules to pass (mRNA, proteins)

All cells contain the same DNA T/F

True

\-DNA is packaged by histone proteins

\-most DNA is semi-packaged (chromatin/interphase DNA)

\-Mitosis= chromosomes

Only some DNA directly codes for…

protein

\-roughly 20,000 genes are scattered throughout the human genome

\-much of the rest of the DNA helps regulate gene expression

Transcription of DNA into RNA Occurs in…

the nucleus

Steps of transcrition

1) RNA polymerase binds to promoter

2) DNA uncoils and seperates

3) Free RNA nucleotide aligns and is added to new RNA strand; RNA synthesis begins

4) RNA polymerase moves down DNA; RNA elongates

After processing, where is mRNA released

into the cytoplasm

What do ribosomes do

\-attach to mRNA and translate it into protein

\-Ribosomes “read” triplet nucleotide code (starts AUG)

Translation Overview

1) Initiation: start at 5’ AUG

2) Elongation: AA shuttled in by tRNA and linked via polypeptide bond

3) Termination: UAG stop codon reached and protein factor releases polypeptide

Secretory Pathway polypeptides have special sequence:

1) ER

2) Transport Vesicle

3) Golgi

4) Secretory vesicle

5) Plasma membrane

Endoplasmic reticulum

network od flate membrane sacs contiguous with nuclear envelop

\-Rough ER: ribosomes synthesize secretory pathway proteins initial processing of proteins occurs in rough ER

\-Smooth ER: lipid synthesis, Ca storage

Golgi Complex

\-Processing/Sorting station for membrane bound and secretory proteins

\-close prozimity to ER

\-Membranous complex with vesicles fusing and being released

\-synthesis of complex polysaccarhides

Endosomes are…

intermediate “sorting vesicles” between golgi, lysosomes, and plasma membrane

Microtubules

Dynamic cell “skeleton” involved in:

\-intracellular movement of organelles and vesicles

\-mitotic spindle formation during mitosis

\-specialized cell motility

What 3 different parts is a cytoskeleton composed of?

1) Microfilament: actin monomers

2) Intermediate filaments: variety of proteins

3) Microtubules: tubulin monomers

What are the two ATP dependent motor proteins?

Kinesin

Dynein

Kinesin

\-moves vesicles towards cell periphery

dynein

moves vesicles back in towards nucleus

Actin

forms a dynamic meshwork just beneath the plasma membrane of all cells

\-plays a role in the maintenance of cell shape and whole-cell movement

What other role does actin play in muscle…

\-a linear scaffold that myosin can move/shorten

Neurofilament expression levels…

helps determine axon diameter

\-axonal diameter partially dictates velocity of electrical conduction down the axon (larger diameter=faster conductance)

Lysosomes are…

membrane bound organelle full of macromolecule recycling enzymes

\-sequesters hydrolases (cutting proteins)

\-non-selective digestion of proteins, lipids, carbs, nucleic acids

\-material from inside and outside of the cell can be sent to lysosomes

Phagocytized material (bacteria) is delivered to lysosomes for…

digestion and constituent macromolecule recycling

Mitochondria produces…

ATP for the cell

\-all cells have mitochondria but they are enriched in cells with high energy demand

ATP provides…

the energy for most cellular processes

\-transfers energy from metabolic breakdown of macromolecules into useful energy for cellular processes

\-Transient energy storage = all ATP is used up within 90 secs

Describe the mitochondrial structure

Outer Membrane: porins let molecules in and out.

Matrix: pyruvate oxidation and TCA cycle

Inner membrane: Electron transport and oxidative phosphorylation

Glucose metabolism

C6H12O6 + 6O2 = 6CO2 + 6 H2O + energy

initiates in cytoplasm and finishes inside mitochondria.

Net = 38 ATP

Where does glycolysis occur…

in cytosol

\-pyruvate enters mitochondrial matrix via outer membrane porins

\-A series of 10 enzymes convert glucose into 2 pyruvate + NADH + ATP

Pyruvate enters…

the mitochondrial matrix and is converted into ACetly CoA by pyruvate dehydrogenase which links to the TCA cycle