- undergo change in shape to trans locate a solute across a membrane. - specific molecule transported down its concentration gradient.

LECTURE 5 Flashcards by wajih tar

What are three ways for molecules to move across the membrane

1) diffusion (active transport)
2) facilitated diffusion
3) active transport

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Diffusion (active transport)

Occurs best with small hydrophobic molecules (O2), which are soluble in the bilayer.

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(Active transport) When a molecule is more once treated on one side of a membrane

Diffusion occurs until equilibrium is reached

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Which molecules are from best to warts at diffusing across the membrane in active transport

Hydrophobic = BEST

Small uncharged polar = POOR

Large uncharged polar - RARE

Charges (small or large) = NEVER

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Osmosis

Diffusion of water, but solute (sugar) cannot pass.

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During osmosis, where dos water move from

Water moves from a place of Low solute concentration to higher clout ion concentration

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Tonicity

The relative contraction of a solute in two solution separated by age range that it cannot pass.

hypotonic
isotonic
hypertonic

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Hypotonic (less solute)

ANIMAL: influx of water causes osmotic lysis (Lysed). Water going in

PLANT: turger pressure, turgid (normal)

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Isotonic

ANIMAL: normal (water going in and out)

PLANT: flaccid (water going in and out)

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Hypertonic (more solute)

ANIMAL: shriveled (water going out)

PLANT: plasmolyzed, cell shrinks, membrane pulls always from cell wall = plasmolysis

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Types of diffusion or active transport

osmosis

- tonicity

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Facilitated diffusion

Passive transport aided by proteins (transport proteins)

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Two types of transport proteins

channel proteins

- carrier proteins

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Channel proteins

A specific channel protein per one type of molecule, cell conditions determine whether closed or open

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Two examples of channel proteins

Aquaporins: facilitates osmosis

Ion channel: allows specific ions

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Carrier proteins

undergo change in shape to trans locate a solute across a membrane.
specific molecule transported down its concentration gradient.

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Active transport

Used to move a substance against the concentration gradient

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Active transport requires energy, which kind?

ATP

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Why do cells do active transport

to concentrate nutrients in the cell
to expel waste
establish (chemical/voltage) gradients

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What kinds of proteins are involved in active transport

Carrier proteins, each septic to one substance

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Animal cells Martin a high concentration of ____ and a low concetration of _____

High concentration of K+ and a low concentration of Na+

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How do cells maintain Na and K levels, and what kind of energy does it use?

Sodium-potassium pump, uses ATP

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ATP

Adenosine triphosphate, breaks down ADP +Pi and released energy

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ADP

Adenosine diphosphate

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Phosphate

Active trap org allows cells to establish and maintain

Concentration gradients

What are the steps (6) to the sodium-potassium pump?

1) cytoplasmic Na+ binds to the sodium-potassium pump. 2) Na+ blinding stimulates phosphorylation by ATP. 3) phosphorylation causes the protein to change its shape. Na+ expelled 4) K+ bonds and triggers release of phosphate groups 5) loss of phosphate restore proteins original shape 6) K+ released, cycle repeated

Because there are 3 Na going out for every 2 K going in, what does this cause

An imbalance in charge across the membrane, (more negative inside), causing ions to move

Membrane potential

The unique distribution of anions and cations across the plasma membrane.

Tow forces drive the diffusion of ions across the membrane

- a difference in concentration (chemical force) | - a different in charge (electrical force)

What do the 2 forces that drive ions to diffuse across membrane make

Electrochemical gradient

What kind of molecule flow done the electrochemical gradient

Charged molecules

Pumps are responsible for creating

Electrogenic pumps

For animals, an important electrogenic pump is the

Sodium-potassium pump

For planets, fungi, and bacteria the electrogenic pump is a

Proton pump.

Cotransporters

Transports a second substance against its own concentration gradient.

How can Big molecules (polysaccharides) be transported? And what does it involve?

Bulk transporting mechanisms involving the formation of vesicles

The membrane for bulk transport is

flexible and can bend into different shapes- pinching off into vesicles. This requires energy

Exocytosis

Exporting substances out of the cell

Processes of bulk transport

Exocytosis and endocytosis

3 types of endocytosis

1) phagocytosis 2) pinocytosis 3) receptor-mediated

Phagocytosis

Cell eating (vacuole)

Pinocysis

Cell drinking (vesicle)

Receptor-mediated

A mechanism involving receptors to import specific things

Recpetors are a sspecofc type of

Protein

Receptors receive chemical signals from _____

Ligands

Receptors-mediated endocytosis

Receptors binds to a ligand that the cell needs to uptake. Clathrin binds to these receptors on the inside of the cell, gathering them into a pit shape which forms the vesicle. Clathrin is released, ligand is consumed, receptors make their way back to the membrane.

Clathrin is a

Coat protein that helps facilitate vesicle formation

An example of receptor-mediated endocytosis is

Fat delivery to cells.

What kind of proteins transport fat to cells via the bloodstream

Lipoproteins

A lipoproteins has a surface

Monolayer of phospholipid and cholesterol

Lipoprotiens core consists of

Triacylglycerols and/or cholesterol

Which specific proteins associate with the fat droplet

Apolipoprotiens

When recpetors on the recipients cell recognize the apoprotein they promote

Endocytosis and the uptake of the fats.

LDL means

Low density lipoprotein

HDL means

High density lipoproteins

LDL

Low in density, high in cholesterol

HDL

High in density due to high protein / lipid ratio.

What do the proteins and lipid in HDL do?

They remove access cholesterol from blood vessels and transport it to the liver.

Which cholosterol is good / bad

HDL= good LDL = bad

Primary active transport

Systems that perform active transport using ATP directly mediate (EXAMPLE: Na+ / K+ pump)

Secondary active transport

Systems that use carrier proteins driven by ion gradients

Three descriptions of carrier proteins

1) uniporters 2) symporters 3) antiporters

Aniporters

transports only one type of molecule

Symporters

Transports two different molecules in the same direction

Antiporters

Transports two different molecule in opposite directions

Types of transport review card

1) passive transport -diffusion across membrane, NO energy use 2) active transport - uses energy to move solute against gradients 3) bulk transport - diffusion across plasma membrane using exocytosis and endocytosis

The cell membrane is a

Fluid barrier that separates the cell interior from the exterior

Is the cell membrane strong?

Bacterial cell walls

Provides shape and protection.

Both bacteria and animal cells both contian a

Much higher concentration of many molecules, compared with their environment.

Bacterial cells walls are made of

Peptidoglycan

What are the tow major classes of cells walls and how are they distinguished?

1) gram positive 2) gram negative They are distinguished based on how they are stained

Gram positive bacteria

- simple cell wall structure - thick layer of peptidoglycan - NO outer layer

Gram negative bacteria

- complex cell wall structure - thinner layer of peptidoglycan - outer membrane - carbohydrate portion of lipopolysacchrdies. (Causes fever due to lipopolysacchrides)