Exam 2- Concepts

Concepts needed to be studied for upcoming exam

Liver cells exposed to alcohol have abundant…

Smooth ER, as more structures to detoxify the substances are required

Mitochondria have…

o Double membranes

o Cristae

o Their own DNA

Large numbers of ribosomes indicate high…

Protein production

Protein modification often occurs in the…

Golgi apparatus

Improper protein folding is frequently associated with the…

ER

The most abundant lipids in most membranes are…

Phospholipids

The structure of a phospholipid consists of…

A hydrophilic head, and a hydrophobic tail

Phospholipids can be arranged in bilayers. What does this mean?

The bilayers exist as a stable boundary between two aqueous compartments. The hydrophobic tails of the phospholipids point inwards (away) from the aqueous solution and are sheltered, and the hydrophilic heads of the phospholipids point outwards (towards) the aqueous solution

What is the function of cholesterol in cell membranes?

Cholesterol is essential for maintaining cell membrane integrity and fluidity

At relatively high temperatures, how does cholesterol affect the membrane’s fluidity?

Makes it less fluid

Why does cholesterol lower the temperature needed for a membrane to solidify?

Cholesterol hinders the close packing of the phospholipids, resulting in lower temperature requirements

Why is cholesterol referred to as a “fluidity buffer”?

Cholesterol helps resist the changes in a membrane’s fluidity that can be caused by changes in temperature

Membrane proteins are…

Amphipathic

Some membrane proteins can reside in what structure?

Phospholipid bilayer with their hydrophilic layers portruding and hydrophobic layers sheltered away from aqueoud solutions

In the fluid mosaic model, what directions do protein molecules drift in and where are they found?

They drift laterally, and are found in a fluid bilayer of phospholipids

How are proteins distrubuted in membranes?

They are often associated in long-lasting, specialized patches, where they carry out common functions

How is a membrane held together?

Hydrophobic interactions

How can lipids and proteins move in membranes?

Most can shift about sideways in the plane of the membrane

What does “flip flopping” mean in regards to a lipid’s movements?

In a rare case, the lipid can flip flop across the membrane and switch from one phospholipid layer to another

Proteins are much _____ than lipids and move more ____ than them

Larger, slowly

Many membrane proteins seem to be held immobile. This is due to their…

Attachment to the cytoskeleton or to the extracellular matrix (ECM)

Some membrane proteins seem to move in a highly directed manner. This is because…

They are driven along cytoskeletal fibers by motor proteins

A membrane remains fluid as temperature decreases until…

Phospholipids settle into closely packed arrangments and the membrane solidifies

What affects the temperature at which a membrane solidifies?

The types of lipids it is made of

If a membrane is rich in phospholipids with unsaturated hydrocarbon tails…

The membrane remains fluid to a lower temperature

The fluidity of a membrane affects both…

Its permeability and the ability of membrane proteins to move where they are needed

What happens when a membrane solidifies?

Its permeability changes, and enzymatic proteins in the membrane may become inactive if their activity requires movement within the membrane

What are the two major populations of membrane proteins?

Integral and peripheral

The majority of integral proteins are classified as

Transmembrane proteins

What shape are the amino acids coiled into for transmembrane proteins?

α helices

How long are the amino acids of transmembrane proteins?

20-30 in length

On the extracellular side, membrane proteins…

May attach to materials outside the cell

On the cytoplasmic side of the plasma membrane, some membrane proteins…

Are held in place by attachment to the cytoskeleton

Some functions of membrane proteins:

• Transport

• Enzymatic activity

• Signal transduction

• Cell recognition

• Intercellular joining

• Attachment to cytoskeleton and ECM

What is the role of carbohydrates in membranes?

Cells bind to use carbohydrates in order to recognize other cells on the extracellular surface of the plasma membrane

Appearance of membrane carbohydrates:

• Short

• Possess branched chains of fewer than 15 sugar units

Two types of membrane transport:

• Active

• Passive

Examples of active transport:

• Endocytosis

• Exocytosis

• Pinocytosis

• Phagocytosis

• Receptor-mediated endocytosis

Examples of passive transport:

• Simple diffusion

• Facilitated diffusion

• Osmosis

The cytoplasmic side of the membrane has a ____ charge

Negative

The extra cellular side of a membrane has a ____ charge

Positive

What does membrane potential affect?

Activity of excitable cells and transmembrane movement of all charged particles

What type of transport does membrane potential favor?

Passive

What are the two types of forces that drive the diffusion of ions across a membrane?

Chemical and electrical

An ion diffuses down its…

Electrochemical gradient

Main electrogenic pump found plants, fungi, bacteria…

Proton pump

ATP

ATP → ADP + Pi releases energy

Factors Affecting Enzyme Activity…

• Temperature

• pH

• Substrate concentration

• Enzyme concentration

Cellular respiration overall equation…

Glucose + Oxygen → Carbon Dioxide + Water + ATP

Glycolysis occurs in the…

Cytoplasm

Glycolysis produces…

Pyruvate, ATP, NADH

Krebs Cycle occurs in the…

Mitochondrial matrix

What does the Krebs Cycle produce?

CO2, NADH, FADH2, ATP

Where is the electron transport chain located?

Inner mitochondrial membrane

What does the Electron Transport Chain produce?

Most ATP

During cellular respiration, glucose is…

Oxidized

During cellular respiration, oxygen is…

Reduced

What does Lactic Acid Fermentation produce?

Lactic acid, NAD+

What does alcohol fermentation produce?

• Ethanol

• CO₂

• NAD⁺

Fermentation regenerates ____ so glycolysis can continue

NAD⁺

Why does changing the shape of an enzyme’s active site affect its activity?

Specific binding, induced fit, and catalysis cannot occur, which is needed in order for enzyme activity to be optimized

Why and when do intestinal cells active transport for glucose?

Into the intestinal cell (active transport via cotransport), A Na⁺/glucose cotransporter brings glucose into the cell together with Na⁺. Glucose is moved against its gradient, this is a form of active transport, indirectly powered by ATP that maintains the Na⁺ gradient (via Na⁺ pumps)

Why and when do intestinal cells use facilitated diffusion for glucose?

Out of the intestinal cell into the blood (facilitated diffusion), once inside, glucose concentration in the cell is higher than in the blood. Glucose then leaves the cell by facilitated diffusion through a carrier protein, moving down its concentration gradient into the bloodstream. No energy is required for this step; it is passive transport

Why are lysosomes needed to destroy engulfed bacteria?

When a white blood cell engulfs a bacterium, it traps it in a food vacuole. This vacuole then fuses with a lysosome. The lysosome contains digestive enzymes that work in an acidic environment and digest the bacterium into small molecules. Without lysosomes and their enzymes, the engulfed bacteria would remain intact and not be destroyed

How does increasing enzyme concentration increase reaction rate after substrate saturation?

If you increase enzyme concentration under saturation conditions, you are adding more active sites. Even though substrate is already abundant, there are now more enzyme molecules available to work on it

End product of aerobic cellular respiration

32 ATP

Anaerobic respiration consumes…

SO4²-,NO3-,CO3²-

In the equation C6H12O6 + 6O2 —> 6CO2 + 6H2O + Energy, what is oxidized?

C6H12O6 and 6CO2

In the equation C6H12O6 + 6O2 —> 6CO2 + 6H2O + Energy, what is reduced?

6O2 and 6H2O

In the equation CH4 + 2O2 —> CO2 + Energy + 2H2O, what is oxidized?

CH4 and CO2

In the equation CH4 + 2O2 —> CO2 + Energy + 2H2O, what is reduced?

2O2 and 2H2O

Glucose has approximately how much ATP?

32

What % of glucose is generated by substrate-level phosphorylation?

10

What % of glucose is generated by oxidative phosphorylation?

90

Private is converted to…

Acetyl CoA

Generates (per pyruvate)

• 1 GTP → 1 ATP

• 3 NADH → 9 ATP

• 1 FADH2 → 2 ATP

The complete oxidation of glucose produces how much ATP in eukaryotes? How much is actually used?

36 ATP, only 2 ATP used

Respiration makes about how much ATP?

38

The transfer of of e- and H+ the NAD+ is mediated by…

Dehydrogenase

When NAD accepts H+ and 2e-, what is the result?

NADH

NADH passes to…

The ETC

• Powered by redox reactions

• Uses energy from oxidation of organic molecules to produce ATP

Oxidative phosphorylation

Krebs Cycle generates ___ per pyruvate

1 GTP→1ATP

3NADH→9ATP

1FADH²→2ATP

ETC is embedded in the ___ and is the machinery of ___

Cristae, oxidative phosphorylation

Cytochromes present in the ETC

*b-c1

*c

*c oxidase

*cyt a

*cyt a3

Nonprotein in ETC

Ubiquinone

NADH dehydrogenase…

Flavoprotein

Chemiosmosis creates an ___ which provides energy for ___

H+ gradient, ATP synthesis

ATP synthase uses the flow of ___ to drive ___ of ATP

H+, phosphorylation

What type of force is the H+ gradient?

Proton-motive

Complete oxidation of glucose…

NADH = 3 ATP

FADH2 = 2 ATP

Small cells have a greater

Surface area:Volume ratio

Size of prokaryotic cells

1-10μm

Size of eukaryotic cells

10-100μm

What sets limits on the size of cells?

Cellular metabolism

ER

Accounts for >50% of the total membrane

What makes glycoproteins?

Rough ER

What 3 factors make up the cytoskeleton?

– Microtubules

– Microfilaments

– Intermediate filaments

Animal cells

– Covered by an elaborate extracellular matrix

• Collagen, proteoglycans, fibronectin

• Anchored by integrins

In isotonic solutions, plant cells become…

Flaccid