• Membrane is considered a mosaic of lipids, proteins,and carbohydrate molecules 
• Membrane exhibits properties that resembles a fluid because lipids and proteins can move relative to eacotherwise within the membrane 

• transmembrane proteins: one or more regions that are physically embedded in the hydrophobic region of the phospholipid bilayer
• lipid-anchored protein: covalent attachment of a lipid to an amino acid side chain within a protien

• length of fatty acyl tails, (shorter=less likely to interact making the membrane more fluid)
• presence of double bonds in acyl tails (double bonds create kinks in the fatty acyl tails, making it more difficult for neighboring tails to interact and making the bilayer more fluid)
• Presence of cholesterol (cholesterol tends to stabilize membranes, effects depend on temperature)

• Yes
• depending on cell type, 10-70% of membrane proteins may be restricted in movement
• integral membrane proteins may be bound to components of the cytoskeleton , restricting thier lateral movement
• membrane proteins may be attached to molecules that are outside the cell, such as interconnected network of proteins forming the extracelluar matrix

• cytosol and endomembrane system work together to synthesize most of the lipids (in Eukaryotes)
• process occurs at cytosolic leaflet of smooth ER
• fatty acid building blocks are made via enzymes in cytosol or are taken into cell from food

• most trnsmembrane proteins are directed here...besides those that go to the mitochondria
• from here membrane proteins are transferred via vesicles to other regions of the cell

• the process of adding (covalently attaching) a sugar (carbohydrate) to a protein or lipid
• Glycolipid-carbohydrate to lipid
• Glycoprotein-carbohydrate to protein
• N-linked=attachment of carbohydrate to nitrogen atom of asparagine side chain
• O-linked=occurs only in Golgi, addition of sugars to oxygen atom of serine or theonine side chains
• can serve as recogniton signals for other cellular proteins (play a role in cell surface recognition)

• essential molecules enter
• metabolic intermediates remain
• waste products exit

• passive transport=no energy input, down or with gradient (examples are passive diffusion-diffusion of a solute through a membrane without transport protein, and facilitated diffusion-diffusion of a solute through a membrane with the aid of a transport protein
• Active transport=requires energy, up or against gradient

• creates a barrier to hydrophilic molecules and ions due to hydrophobic interior
• rate of diffusion depends on chemisry of solute and its concentration
• gases and a few small, uncharged molecules can passively diffuse across
• Ions and large molecules diffuse slowly

• relatively constant internal environment different from their external environment
• transmembrane gradient: concentration of a solute is higher on one side of a membrane than the other
• ion electrochemical gradient: both an electrical gradient and chemical gradient

 measure of the osmotonic pressures gradient (as defined by the water potential of the two solutions) of two solutions separated by a semipermeable membranes

3 kinds

1. isotonic
2. hypertonic
3. hypotonic

• water diffuses through a membrane from an area with more water to an area with less water
• if the solutes cannot move, water movement can make the cell shrink or swell as water leaves or enter the cell
• osmotic pressure-the tendency for water to move into any cell

provide a passageway for the movement of ions and hydrophilic molecules across a membrane

there are two classes: channels and transporters

• type of transport protein
• direct diffusion of ions or molecules
• most gated
• aquaporins

• "carriers"
• conformational change transports solute
• Principal pathway for the uptake of organic molecules such as sugars, amino acids, and nucleotides
• 3 types (uniporter, symporter, antiporter

against a gradient and requires energy, from low concentration region to high concentration region

Primary active transport uses a pump: directly uses energy to transport solute

Secondary active transport: use pre-existing gradient to drive transport of solute

ATP driven Ion pumps generate ion electrochemical gradients

Na+ and K+ transported agains their gradients by using the ATP from hydrolysis

3 Na+ exported and 2K+ imported

antiporter, electrogenic pump exort 1 net positive charge

transport large molecules such as proteins and polysaccharides, and even very large particles

material inside the cell packaged into vessicles and excreted into the extracellular medium

transport large molecules such as proteins and polysaccharides, and even very large particles

Plasma membrane invaginates, or folds inward, to form a vesicle that brings substances into the cell

receptor-mediated endocytosis

pinocytosis

phagocytosis

over 200 that are grouped into a few general categories

cells joined together forming continuous sheets to cover or line body surfaces

(dermal also forms a layer of cells)

animal: classified by a number of layers, hallmark is many connections

Plant: tightly woven together layers like animals, may be replaced by periderm with age-bark

1. cell division
2. cell growth
3. differentiation
4. migration
5. apoptosis
6. cell connections

network of material secreted from the cells forming a commplex meshwork outside of cells

major component of certain parts of plants and animals...bone and cartilage and the woody parts in plants

in animals ECM helps to support, strengthen, cell signalling and organize cells

major macromolecules of ECM are proteins (large fibers) and polysaccharides (give a gel-like character)

Adhesive

Fibronectin and laminin

adhere ECM components together and to the cell surface

structural

collagen provides tensil strength (main protein found in bone, cartilage, tendon, skin)

Elastin provides elasticity (expands and returns to original shape)

2nd major component (protein first)

in vertebrates glycosaminoglycans (GAGs) are most abundant...

long, unbranched polysaccharides with a repeating disaccharide unit

highly negatively charge attracts positive ions and water

proteoglycans and GAGs resist compression (form gel-like component)

Chondroitin sulfate-cartilage

hyaluronic acid-found in skin, eyes, joint fluid

chitin important ECM in invertebrates (exoskeleton)

adhere cells to each other and to the ECM

animals cells have a more varied group of junctions

3 types (anchoring, tight, gap)

need to respond to changing environment

adaptation of cellular esponse is critical for survival

glucose acts as a signal to yeast cells to increase in number of glucose transporters and enzymes allowing efficient uptake and use of glucose

Cells need to communicate with eachother (cell-cell communication)

signals between cells

cell junctions allow signaling molecules to pass from one cell to another

signal between cells

some molecules are bound to the surface of cells and serve as signals to cell coming in contact with them

signals between cells

cells secrete signaling molecules that bind to their own cell surface or neighboring cells of the same type

signals between cells

signal does not affect cell secreting the signal but does influence cells in close proimity (synaptic signaling)

signal between cells

signals (hormones) travel long distances and are usually longer lasting

1. receptor activation
2. signal transduction
3. cellular response

step 1 cell signaling

signaling molecules bind to receptor

step 2 cell signaling

activated receptors stimulates sequence of charges-signal transduction pathway

3rd step in cell signaling

several different processes

• alter activity of 1+ enzymes
• alter structural protein functions
• change gene expression-transduction factor

signaling molecule

binds noncovalently to receptor with high degree of specificity

binding and releasing between receptor and ligand relatively rapid

ligands alter receptor structure conformation change

once a ligand is released, the receptor is no longer activated

enzyme-linked

G-protein-coupled

ligand-gated ion channels

found in all living species

extracellular domain binds signal

causes intracellular domain to become functional catayst

most are protein kinases (add phosphate to target=phosphorylation)

G-protein coupled receptors (GPCR)

(surface cell receptor)

• found in all eukaryotes, common in animals
• 7 transmembrane segments
• activated receptors binds to G proteins
• releases CDP and inds GTP instead
• GTP causes G protein to disassociate
• beta subunit an b/y dimer interact with other proteins in a signaling pathway

ligand-gated ion channels

(cell surface receptor)

• plant and animal cells
• ligand bindng causes ion channels to open and ions to flow through the membrane
• animals-signals between nerve and muscle cells or beteen 2 nerve cells

inside the cell

Estrogen receptros

estrogen passes through membrane and binds to receptor nucleus

dimer of estrogen-receptor complexes binds to DNA and acts as a transcription factor: regulte transcription of specific genes

part of cellular response

activated by signaling molecule binding to cell surface receptor

enzyme-linked receptor

G-protein-coupled receptors

signal amplification: binding of signal receptor can cause the synthesis of many cAMP that activate PKA, each PKA can phosphorylate many proteins

Speed: in one experiment a substantial amount of cAMP was made withing 20 seconds after addition of signal

cellular response caused by a given signaling molecule depends on the type of cell responding to signal

variation in response determined by types of proteins that each cell makes, such as receptors and signal transduction proteins

hormones coordinate cellular activities in multicellular animals

(hormone signaling-fight or flight)

different effects throghout body

lungs: relax airways endabling greater oxygen uptake

Heart: stimulates to beat faster

caffeine inhibits phosphodiesterase:enyme removes cAMP once a signaling molecule is no longer present

Inhibition causes cAMP to persist for longer so heart beats faster

• programmed cell death
• cell shrinks and forms rounder shape
• -due to destruction of nucleus and cytoskeleton
• Plasma membrane froms blebs
• -irregular extensions that break away

is a category of enzyme-linked receptors that is found in animals

recognize various types of signaling molecules (growth factor: homone that acts to stimulate cell growth or division)

Epidermal growth factor (EGF) (stimulates epidermal cells to divide)

signals binding to cell surfaces are first messenger

many signals transduction pathways lead to production of second messangers

relay signals inside cells (cAMP, Ca2+, diacylglycerol and inositol triphosphate)

a way to activate G protien to influence signal transduction pathway

1. alpha subunit can activate phospholipase C (binds to it)
2. Diacylglycerol (DAG) and inositol triphhosphate (IP3) made from plasma membrane phospholipid
3. Ca2+ channels in ER open
4. Variety of effect of Ca2+ on cell behavior

• breakdown of reactants
• used for recycling
• used to obtain energy for endergonic (energy required) reactions
• energy stored in intermediates (ATP and NADH)

• biosynthetic reactions
• make large macromolecules or smaller molecules not available from food

1. substrate-level phosphorylation: (enzyme directly transfers phosphate from one molecule to another molecule)
2. oxidative-phosphorylation: (energy stored in an electrochemical gradient is used to make ATP from ADP and Pi)

oxidation: removal of e-

reduction: addition of e-

redox reaction: e- removed from one molecule i added to another

e- removed by oxidation (redox reaction) are used to create energy intermediates like NADH

NAD+ --- NADH = reduced

NADH --- NAD+ = oxidation

oxidiaed to make ATP

can donate e- during synthesis reactions

process by which living cells obtain energy from organic molecules

primary aim to make ATP and NADH

aerobic respiration uses oxygen (o2 consumed and CO2 released)

focus on glucose but other organic molecules also used

C6H12O6 + 6O2----6CO2 + 6H2O

There are 4 metabolic pathways

1. glycolysis
2. breakdown of pyruvate to an acetly group
3. citric acid cycle
4. oxidative phosphorylation

stage 1 of glucose metabolism

Glycolysis

occur with or without oxygen

steps in glycolysis nearly identical in all living species

10 steps 3 phases

energy investment

cleavage

energy liberation

stage 2 of glucose metabolism

breakdown of pyruvate to an acetyl group

in eukaryotes, pyruvate is transported to the mitocondrial matrix

broken down by pyruvate dhyrogenase

molecule of CO2 removed from each pyruvate

remaining acetyl group attached to CoA to make acetyl CoA

1 NADH is made for each pyruvate

stage 3 of glucose metabolism

Citric Acid Cycle

metabolic cycle (particular molecules enter while others leave, involving a series of organic molecules regenerated with each cycle

Acetyl is removed from Acetyl CoA and attached to oxaloacetate to form citrate or citric acid

series of steps releases 2 CO2, 1 ATP, 3NADH, and 1 FADH2

oxaloacetate is regenerated to start the cycle again

stage 4 of glucose metabolism

oxidative phosphorylation

high energy e- removed from NADH and FADH2 to make ATP

typically requires oxygen

oxidative process involves e- transport chain

phosphorylation occurs by ATP synthase

group of protein complexes and small organic molecules embedded in the inner mitochondrial membrane

can accept and donate e- in a linear manner in a series of redox reactions

movement of e- generates H+ electrochemical gradient/proton-motive force

(excess of positive charges outside of matrix)

enzyme harnesses free energy as H+ flow through membrane embedded region

energy conversion-H+ electrochemical gradient or proton motive force converted to chemical bond energy in ATP

Rotary machine that makes ATP as it spins