To have enzyme/substrate concentrations high enough so that rates of reactions are reasonable to support life (Rates of Reaction)

Rates of Diffusion Rates of Transport Reactions can occur without interference

(conflicting reactions can happen simultaneously)

Local environments can allow different reactions to happen

Specialization (different cells can do different things)

Damage can be contained

Reactions can be ordered by embedding them into membranes

• What cells move?– Embryonic, cancer, single, during cell

division, healing, nerve cells (reach out filopodia – if a connection is used its strengthened – if not – its destroyed), macrophages, protozoans

• Types of Movement– amoeboid, cilia, flagella, muscle

contraction, intracellular transport

250 cells fit on a period Ridge on a finger – 20 cells wide 1” patch of skin = million cells in top

layer Exceptions

› Egg› Muscle cell – 1.5” long› Nerve – extentions spine to toes

Phospholipid bilayer Protein Channels (for small and charged atoms or

molecules)› Open› Gated› Shape change› Active Transport channels

Receptors› Endocytose ligand› Sets off a series of chemical reactions› Opens gated channels› Turn on genes› Secrete a hormone

Marker or Signal Proteins – identifies the cell Attachment proteins

› Cell to cell attachment› Attachment to the cytoskeleton› Attachment to the ECM proteins

Woman dies after water-drinking contest Water intoxication eyed in ‘Hold Your Wee for a Wii’ contest death A woman who competed in a radio station’s contest to see how much water she could drink without going to the bathroom died of water intoxication, the coroner’s office said Saturday. Jennifer Strange, 28, was found dead Friday in her suburban Rancho Cordova home hours after taking part in the “Hold Your Wee for a Wii” contest in which KDND 107.9 promised a Nintendo Wii video game system for the winner.“She said to one of our supervisors that she was on her way home and her head was hurting her real bad,” said Laura Rios, one of Strange’s co-workers at Radiological Associates of Sacramento. “She was crying and that was the last that anyone had heard from her.”Initially, contestants were handed eight-ounce bottles of water to drink every 15 minutes.“They were small little half-pint bottles, so we thought it was going to be easy,” said fellow contestant James Ybarra of Woodland. “They told us if you don’t feel like you can do this, don’t put your health at risk.”Ybarra said he quit after drinking five bottles. “My bladder couldn’t handle it anymore,” he added.After he quit, he said, the remaining contestants, including Strange, were given even bigger bottles to drink.“I was talking to her and she was a nice lady,” Ybarra said. “She was telling me about her family and her three kids and how she was doing it for kids.”

Diffusion – high to low due to random motion of molecules

Osmosis – diffusion of water Simple diffusion – thru phospholipid

bilayer – driven by kinetic energy of the molecules or atoms themselves

Facilitated diffusion – using the help of protein channels (open, gated, or shape change) – dependent on concentration, # of channels – driven by kinetic energy of the molecules – may also use an electrochemical gradient› Electrochemical gradient – molecules also move

toward the opposite charge

Eggciting Osmosis

res onion osmosis

Salt poisoning - Germany4 year old dies by accidentJust read in the paper that a woman killed her 4-year old stepchild by

making her eat too much salt: Apparently, the two were preparing a pudding,

and the child accidentally put in two table-spoons of salt instead of sugar.

The stepmother got angry and forced the child to eat the pudding. The child

died in intensive care a day later. Apparently, a court now ruled that the

stepmother does not have to go to jail, because it is not general knowledge

that excessive salt-consumption is fatal, so the death was considered

accidental / negligent behavior.

The newspaper says that consuming more than 1 g of salt per 1 kg of body

weight within a short span of time is usually fatal. Any of our natural

science / medicine buffs can confirm this? It's total news to me!

 

Facilitated Diffusion Channels

open gated shape change

Active Transport Channels

Active Transport – low to high movement using protein channel pump – pumps using energy (ATP) provided by the cell

Co-Transport – combo of active transport and fac. diffusion. Cells pump H+ which then binds to molecule to be transported. The H+ molecule combo then diffuses thru a fac. diffusion channel.

Exocytosis – (secretion) – wrapping molecules in a membrane vesicle inside the cell – having it fuse with the cell membrane and dump the contents outside the cell (with or against conc. Gradient – big stuff like proteins

Endocytosis – engulfing large particles with part of the cell membrane and bringing them into the cell in a vesicle.› Pinocytosis (liquids)› Phagocytosis (solids)› Receptor-Mediated endocytosis

Protects the DNA from cytosolic enzymes that would destroy it

Provides a small space to maximize enzyme/substrate concentrations so that replication and mRNA production is efficient

Provides the right environment for those chemical reactions

Organizes the DNA to control gene expression through the nuclear matrix

Move stuff across cell surfaces like mucus

Moves some single-celled protozoans like paramecia

Flagella Longer and only 1/cell – sperm or

up to 6 on bacteria, also found on protozoa

For swimming

Breakdown glucose and uses the released energy to make ATP from ADP

The inner mitochondrial membrane is in-folded to create more surface area = more e.t.c.’s so more efficient cell respiration

Have their own DNA and ribosomes, comes only from the mother

Can copy themselves and make their own proteins

For photosynthesis – create sugar from inorganic materials – carbon dioxide and water using the sun’s energy to excite the electrons – the excited electrons are stored in the covalent bonds shared between the C and H atoms

They also have their own DNA and ribsomes

Collecting the sun’s energy happens in the thylakoid membranes which are stacked and have huge amounts of surface area

The chemical reactions to then make the sugar happen in the stroma where the correct enzymes are

Vacuoles

Animal vacuoles can store water, wastes, nutrients – small and fairly numerous

Plant vacuoles take up the majority of the cytoplasm of the cell › They can actively transport salt to the interior so

water will flow in creating turgor pressure› Pigments also stored here

Protozoans have food vacuoles (from endocytosed food then fuses with lysosome) and Paramecium have contractile vacuoles to squeeze out water to keep the osmostic balance

Ribosomes – Protein synthesis - aa are bonded together in a chain based on the sequence of mRNA copied from the DNA

If proteins are destined for a particular location such as the cell membrane or are to be secreted, a signal sequence directs the ribosome to the RER

Protein enters the RER from the ribosome Folds into the correct shape Is modified – may be cut some, carbs added

etc. Is transported to the Golgi

Modifies (add location signals) to the protein so it goes to where it’s supposed to)

Molecules that match specific docking proteins on the motor proteins are added to the protein so it “jumps on to the right microtubule

Packages (wraps it in a piece of its own membrane)

Has receptors for binding proteins Fuses with old cell parts, bacteria, or

macromolecules in vesicles and breaks them into components

Digest old worn out cell parts to keep the cell unclogged and able to function normally

In macrophages, digest all of the junk that they endocytose like whole bacteria, dried blood, damaged bone, etc.

In single cells – they fuse with the endocyotic membrane and become food vacuoles

Specialized functions in different cells In all cells, can make phospholipids Makes cholersterol Makes steriod hormones Detoxifies drugs and alcohol Sequesters calcium in muscle cells

Duplicate and move to the cell poles and reforms the cytoskeletal microtubules into spindle fibers to separate the chromosomes

Plant cells don’t have them but do have a centrosome

Cytoskeleton

Made out of many protein fibers (microfilaments) and microtubules

The microfilaments are for structure and shape of the cell

Microtubules act as train tracks for motor proteins to transport stuff through the cell

Determines the cell’s shape and therefore what DNA is read – must be attached to nuclear matrix and is attached to the cell membrane and ECM

Clump or RNA and proteins that will become the ribosomes

Plants – cellulose – helps create turgor presssure, provides structure

Bacteria - chitin

Tight Junctions – between epithelial cells – proteins that hook the cells together tightly so that there is no leakage between the cells

Desmosome – tight junction with extra reinforcing proteins tying the cytoskeletons of neighboring cells together – keeps cells from ripping apart

Gap Junctions – found in smooth muscle – tiny protein tunnels that ions can pass through from cell to cell

Square or rectangular Form Leakproof Linings and barriers Selectively secrete and absorb

Big cell bodies with many short extensions to receive information and one long axon to send information

Fast signal transmission since almost touch the cells they are communicating with with their extensions

Long tube-shaped cells packed with contractile proteins and many nuclei

Tight junctions between cells – each muscle is connected to an axon for quick communication

Spindle-shaped cells surrounding hollow organs to squeeze the contents to move them

Have gap junctions so contract all together

Cells not joined – separated by ECM Amt. and type of matrix gives the tissue it’s

characteristics Matrix is always a mix of fibrous proteins and

liquid)

Bone is strong and supports weight because:Bone is mostly matrix

Matrix is hardened with calcium

Stores fat away from enzymes but also used for cushioning and insulation

Little matrix – more about the cells

Makes up tendons, ligaments, underneath of skin – has to be really strong

Almost entirely matrix – fibrous proteins with very little liquid