Human Morph & Func Ch 2

What is energy used for?

• Power muscle

• Pump blood

• Absorb nutrients

• Exchange respiratory gases

• Synthesize new molecules

• Establish cellular ion concentrations

What is the "energy currency" for cells?

ATP

What is the primary fuel for the first step in cellular

respiration (glycolysis)?

carbohydrates

What are the benefits of fats in cellular respiration?

provide fatty acids needed for cellular respiration (citric acid cycle) as acetyl-CoA

What is the main energy source during prolonged exercise or fasting?

fat

What is the benefit of proteins in cellular respiration?

serve as a last resort for energy production

What are the functions of proteins?

primarily used for repair and synthesis of cellular components

What issues can contribute to disruptions in cellular respiration?

- mitochondrial disorders

- metabolic disorders

- cancer

- diabetes

- aging

What does the breakdown of glucose lead to?

the formation of carbon dioxide and water

What is the glucose oxidation equation?

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O

Where does glycolysis occur?

in the cytosol

Where does the citric acid cycle and electron transport system occur?

mitochondria

At what stage is oxygen the final electron acceptor?

oxidative phosphorylation

What is ATP formed from in oxidative phosphorylation?

ADP

What's the difference between substrate-level phosphorylation and oxidative phosphorylation?

Substrate-level forms ATP from energy directly released

from a substrate

When does oxidative phosphorylation occur?

during glycolysis and citric acid cycle

How much ATP is produced from Glycolysis?

2 NADH → 6 ATP

How much ATP is produced during Intermediate stage?

2 NADH → 6 ATP

How much ATP is produced from Citric Acid Cyle?

- 6 NADH → 18 ATP

- 2 FADH2 → 4 ATP

How much ATP is produced total?

34 but some ATP used during cellular respiration, so net ATP is 30

What happens when oxygen is insufficient?

- Activity of electron transport chain decreases

- Cell becomes more dependent upon glycolysis

- Glycolysis eventually shuts down

- NAD+ must be regenerated for glycolysis to continue

Describe what happens when activity of electron transport chain decreases.

• Levels of NADH and FADH2 accumulate

• Decreased levels of NAD+ and FAD

Describe what happens when cell becomes more dependent upon glycolysis.

Requires NAD+ to continue

Describe what happens when glycolysis eventually shuts down.

triggers a catastrophic energy crisis that can lead to cellular dysfunction, lactic acidosis, and eventual cell death

How is NAD+ regenerated?

Hydrogen transferred from NADH to pyruvate -> Pyruvate converted to lactate -> Enables glycolysis to continue

Individuals with respiratory or cardiovascular disease who have trouble regenerating NAD+ also experience what issue?

decreased ability to deliver oxygen to cells

What are the general functions of a cell?

- Maintain integrity and shape of a cell

- Obtain nutrients and form chemical building blocks

- Dispose of wastes

- cell division

Why is cell division beneficial?

Help maintain tissue by providing cells for new growth and replacing dead cells

What is the purpose of the plasma membrane?

• Serves as physical barrier between cell and fluid that surround it (interstitial fluid)

• Regulates movement into and out of a cell

• Establishes and maintains electrochemical gradient

• Functions in cell communication

Describe membrane transport?

Process of obtaining and eliminating substance across the plasma membrane

Describe passive transport.

- Do not require energy

- substance move down concentration gradient from area of more substance to area of less

Describe active transport.

- Require energy

- Substance moves up its concentration gradient

- Membrane-bound vesicle must be released (vesicular transport)

Describe diffusion.

movement of particles from an area of higher concentration to an area of lower concentration until they spread out

For what molecules is diffusion beneficial for?

or small charged or polar solutes

Describe channel-mediated diffusion.

- Movement of small ions through water-filled protein channels

- Channels specific for one ion type

Describe leak channels.

Continuously open

Describe gated channels.

Opens in response to stimulus for fraction of second

What is Channel-mediated diffusion essential for?

normal function of muscle and nerve cells

Describe carrier-mediated diffusion.

Small polar molecules assisted across membrane by

carrier protein which binds to carrier protein shape

• Moves substances down their gradien

What is a uniporter?

carrier transporting only one substance

What determines the max rate of substance transport?

The number of channels and carriers

Define osmosis.

passive movement of water via a semipermeable membrane

- membrane is also selective for certain solutes

What are the two ways water is moved via osmosis?

- slipping between molecules in the phospholipid bilayer

- aquaporins

What are aquaporins?

integral protein water channels

Define osmotic pressure.

the pressure exerted by movement of water across a semipermeable membrane due to a difference in solution concentration

Describe hydrostatic pressure.

pressure exerted by a fluid on the inside wall of a container

Define tonocity.

The ability of a solution to change pressure or volume of a cell via osmosis

Define isotonic.

No net movement of water inside/outside the cell in the cytosol

Define hypertonic.

water leaves the cell

Define hypotonic.

water enters the cell

Define active transport.

the movement of solute concentration from lower to higher concentration

What determines whether the movement in active transport is primary or secondary?

the source of energy

Describe primary active transport.

energy used directly from the breakdown of ATP leads to phosphorylation

Define phosphorylation.

addition of phosphate groups to transport proteins, changing its shape and moving the protein across the membrane

What are ion pumps?

cellular protein pumps that move ions across a membrane

What is vesicular transport also known as?

bulk transport

Describe vesicular transport.

involves energy input to transport large molecules across a membrane using a vesicle

What is a vesicle?

membrane-bounded sac filled with material

What are the two kind of vesicular transport?

exocytosis and endocytosis

Describe exocytosis.

vesicle releases its contents from the cell via fusion of vesicle and plasma membrane (requires ATP)

Describe endocytosis.

uptake of substances from outside of cells via formation of invagination which pinches off to form vesicle

What is endocytosis used for?

- uptake of materials for digestion

- retrieval of membrane regions from exocytosis

- regulation of membrane protein composition

What are the three types of junctions?

- tight junctions

- desmosomes

- gap junctions

Describe tight junctions.

rows of proteins linking cells to prevent passing of substances

- requires materials

Which kind of junction maintains the polarity of epithelia?

tight junctions

Describe desmosomes.

composed of proteins that bind neighboring cells.

What are hemidesmosomes?

anchor basal layer of cells of the epidermis to underlying components

Describe gap junctions.

form tiny, fluid-filled tunnels, providing direct passageway for substances to travel between cells