Biology Test 2

composed of phospholipids

phospholipid bilayer

attached to the outside and sometimes running through the bilayer

• They aren't rigid; they can move. Like cells are in a bubble of oil.
• Proteins are not locked in position.

Things are embedded in the membrane and can move.

• flexibility
• can seal itself
• portions can pinch off (also called vesicles)
• vesicles can fuse with another membrane

protein with a carbohydrate attached

cells to recognize a cell as yours

They have both hydrophobic and hydrophilic parts. That's how they get to stay in the bilayer without moving on through.

They go from outside to inside, all the way through the bilayer.

They just sit on one side of the membrane.

Helps keep the membrane fluid and helps control what goes in and out

Phospholipid bilayer is selectively permeable.

Some stuff can pass through and some can't (from inside or outside)

Cells still need polar stuff, so they use transport proteins to brings stuff.

It's small enough to pass through

• transport
• cell surface receptors
• cell surfacce identifiers
• enzymes
• attachments
• intercellular junctions

• bring stuff into the cell
• must be integral

• Chemicals interact with the proteins, but don't pass through them.
• Signal Transduction

• the protein takes the message from teh chemical and tells the cell
• a way of detecting things outside the cell

• can be integral or peripheral
• often glycoproteins
• recongize certain cells and how to deal with them
• helps immune system determine what needs to stay/go

some proteins in the membrane act as catalysts to allow reactions to happen

integral proteins attach on one side to the cytoskeleton for stability, on the other side to the extracellular matrix

holds the whole cell in place

• some proteins attach the cell to other cells.
• protein to protein bond of adjacent cells
• (AKA cell adhesion proteins)

• Diffusion
• Osmosis

net movement of substance from an area of higher concentration to an area of lower concentration

• Things still move fairly randomly, but attempts to find equilibrium.
• Substance becomes evenly (randomly) distributed.

Same thing happens with chemicals that can pass through the membrane (SIMPLE DIFFUSION)

Does not require energy; happens because the stuff wants to be equal.

solute molecule move directly through the membrane due to their own concentration gradient

• Happens when the cell wants a chemical that can't pass through the membrane, but there is still a greater concentration outside, the chemical can move through a transport protein.
• Also doesn't take energy.

diffusion of water through a selectively permeable membrane

... osmotic pressure increases to the point of lysis.

no net movement of water

equal solute concentration

higher [solute] outside than inside

• lower [water] outside than inside
• net loss of water from cell
• cell shrinks, crenation

lower [solute] outside than inside

• higher [water] outside than inside
• net flow of water into cell
• cell swells

• Cytoplasm pushes against the cell wall, making the cell inflexible
• turgor

• Cell membrane shrinks, pulls away from cell wall
• Plasmolysis
• Plant wilts

Yes, but it requires energy.

moving substances across the plasma membrane against the concentration gradient

• Has a high energy phosphate bond
• Cell breaks one of these bonds and takes some of its energy
• ATP >> ADP

Look it up.

Sodium-potassium pump

• 3 sodium pumped out, 2 potassium pumped in
• allows cell to control volume and maintain osmotic pressure

Look it up.

Yes, pinocytosis

• simple diffusion
• facilitated diffusion
• active transport
• exocytosis
• endocytosis

• phagocytosis
• pinocytosis

• "cell-eating"
• folds of plasma membrane surround particle to be ingested, forming small vacuole around it
• vacuole pinches off inside inside cell
• lysosomes fuse with vacuole and pour hydrolytic enzymes onto ingested material

• tiny droplets of fluid are trapped by folds of plasma membrane
• these pinch off into cytosol as small fluid-filled vesicles
• contents are slowly transferred to the cytosol

intercellular junctions

• anchoring
• tight
• gap

gap

cadherins lock together forming a desmosome

fibery things from anchoring junctions

• skin
• muscle

totally seal gaps between cells like they are zipped

intestines

two cells are joined by connexons that allow passage

• hollow tubes made of 6 protein strands (ish) that allow cells to exchange materials, electrical charges
• can open or close

• heart
• brain

capacity to do work

• kilojoules (kJ)
• 1 kilocalorie = 4.184 kJ

Calories really measure heat energy.

• potential
• kinetic

• It's called energy because of position or state, not because it's doing anything.
• stored energy

energy of motion

...be converted into another form.

... kinetic energy. And vice versa.

... kinetic energy (movement). And vice versa.

... chemical energy (photosynthesis).

Energy cannot be created or destroyed; it changes from one form to another.

Entropy is always increasing.

disorder, randomness

... loses useful energy as heat.

... be evenly dispersed.

• Organisms must be open systems.
• Organisms must continually obtain energy from their surroundings to do work.

Gibbs Free Energy (G)

energy available for work

• Most organisms have a certain amount of free energy.
• Most chemical reactions have a change in free energy.

• Exergonic reactions
• Endergonic reactions

• release energy
• are spontaneous

need input of energy

... provide energy for endergonic reactions.

Cells use ATP to link exergonic and endergonic reactions. (book figure)

• catabolism
• anabolism

• breakdown of large molecules into smaller ones
• exergonic
• Ex. starch -> glucose -> CO₂
• makes the energy needed for anabolism

• synthesis of large molecules from smaller ones
• endergonic
• Ex. amino acids -> protein --> muscle (anabolic steroids)

oxidation-reduction reactions (redox)

• involves the exchange of electrons
• oxidation = loss of electrons
• reduction = gain of electrons
• *drawing*

• NAD⁺
• accepts electrons as part of H atoms
• *drawing*

The cell controls the needed energy.

Cells produce enzymes to lower activation energy of specific reactions.

lower the amount of activation energy needed

biological catalysts, most are proteins.

• make certain reactions more likely to take place.
• increases rate of reaction.

Adding substrates changes the shape of the enzyme, bring the substrates close enough to react.

unchanged

gives the enzyme activity

region where substrates bind

any non-catalytic site

• Only produce enzymes when needed
• Some enzymes need allosteric activation

attach to allosteric sites of enzymes, deactivating them

• temperature
• pH
• enzyme and substrate concentration
• inhibitors

faster reaction

more reactions

temporarily stops or slows reactions by blocking active sites

temporarily stops or slows reactions by binding to an allosteric site

inhibitors permanently bind to enzymes, damaging them so they don't work anymore

cells obtain energy (ATP) from organic compounds

• This is aerobic respiration because it uses oxygen.
• Actually a series of smaller reactions

• exergonic
• catabolic

• 1. glycolysis: glucose --> 2 pyruvate
• acetyl CoA formation: pyruvate --> Acetyl CoA
• 2. citric acid cycle: acetyl CoA --> CO₂
• 3. electron transport: transfer electrons to O₂

cytoplasm

mitochondria

• occurs in the cytoplasm
• glucose --> 2 pyruvate

look it up.

look it up

• enters the citric acid cycle
• "acetyl" is converted in CO₂
• occurs in mitrondria matrix

• Krebbs Cycle
• TCA

• 2 CO₂
• 3 NADH
• 1 FADH₂
• 1 ATP

• 4 CO₂
• 6 NADH
• 1 FADH₂
• 2 ATP

• Electron (H) carriers
• Pass electrons to ETS
• Inner membrane of mitochondria

inner membrane has proteins that deal with the electrons

• Cells use pyruvate as an electron acceptor in fermentation process
• Not as effective as aerobic, still works

• Beta Oxidation
• Glycerol -->--> glyceraldehyde-3-phosphate --> glycolysis

fatty acids -->-->--> Acetyl CoA (which goes to CA cycle)

look it up