Cell structure and function Flashcards by Logan Harris

What makes cells in different tissues of the same animal different?

Gene Expression

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Biomembrane properties

-Fluid mosaic (hydrophylic heads and hydrophobic tails)
-Phospholipids are amphipathic (charged hydrophilic head and uncharged hydrophobic tail)
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Lipid rafts

Special regions in the membrane that select phospholipids based on their tails, also help select certain transmembrane proteins

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2 Forms of bulk transport

Endocytosis

- Exocytosis

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When will a cell membrane have equal distribution of phospholipid molecules

When the cell dies

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5 Functions of the cell membrane

Mechanical and structure barrier
Selective permeability
Carrier-mediated transport
Bulk transport
Markers and signaling

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Mechanical and structure barrier description

A cell membrane maintains the physical integrity of the cell and forms a barrier between in and outside

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Selective permeability description (passable things)

Gases (CO2, N2, O2)
Small uncharged polar molecules (ethanol)
Some water (about 20%) and some urea will also pass through

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Carrier-mediated transport description

Proteins in cell membranes allow transport of specific molecules across the membrane in either direction

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Endocytosis

Process in which secretory vesicle contents are moved into the cell (from the extracellular fluid) via the cell membranes

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Exocytosis

Process by which contents of secretory vesicles are moved out of the a cell (from the intracellular fluid) via the cell membrane.

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Markers and signaling description

Proteins called surface protein markers embedded in the cell membrane identify the cell, enabling cells to recognize and communicate with each other

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2 types of membrane proteins

Integral proteins

- Peripheral proteins

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Integral proteins

Such as ion channels or receptors are embedded in and anchored to the cell membrane

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Peripheral proteins

Are not embedded in the membrane

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6 functions of membrane proteins

ion channels
Transporters
Receptors
Enzymes
Cell recognition(identity) proteins
Linker proteins

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Ion channels

Pore-forming membrane proteins that gate the flow of ions across the cell membrane, help regulate cell volume, and control the flow of ions across secretory and epithelial cells

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Transporters

Membrane proteins are required to enable the specific passage or transport of selected substances across membranes

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Receptors

Specialized integral membrane proteins that take part in communication between the cell and the outside world. Activated by hormones, neurotransmitters and other chemicals

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Enzymes

Catalysts for biochemical: ATPases, hydrolases, oligosaccharidases, peptidases, lipases, etc.

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Cell Recognition (identity) proteins

ID tags, usually glycoproteins that allow the body’s immune system to identify cells (important in cell/cell recognition)

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Linker proteins

Face the cytoplasm and interact with the cytoskeleton or face the exterior and interact with the extracellular matrix; both types can affect the shape and movement of the cell

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What things can cross the plasma membrane freely

Gases (CO2, N2, O2)
small uncharged polar molecules (Ethanol)
Small amounts of water and urea

Aquaporins

-transmembrane channels
-Made of 4 subunits
-selective for water
-found throughout cellular life
help manage osmotic imbalances, and are much more permeable that the plasma membrane itself

Osmolarity

The measure of osmotic strength, different from osmolality

Does the concentration or the size of molecules affect the osmolarity?

Only the concentration (count) | 150 mM NaCl = 300 mOsmol/L

Normal mammalian tonicity

275-290 mOsmol/L | -extracellular and intracellular osmotic pressures can vary 5-7%

Hypotonic solution

Inside of cell has higher concentration than outside (water flows into cell, cell lyses)

Isotonic solution

Concentration in and out of cell is equal (water flows through cell, cell is in normal state)

Hypertonic solution

Concentration is higher outside of cell than inside (water flows out of cell, cell shrivels)

Total body water distribution

2/3 intracellular fluid | 1/3 extracellular fluid (interstitial fluid and plasma(in blood))

Colloid osmotic pressure or oncotic pressure

Created by osmotic pressure due to large molecules in the plasma. Counteracts vascular system pressure (equal to about 28 mmHg)

3 potential causes of edema

- Increased capillary permeability - Decrease oncotic pressure - Increased hydrostatic pressure

Hydrostatic pressure

Equal to mean blood pressure. | Force exerted in blood vessels that forces fluid into the interstitial space

Selective permeability (impassable things)

- Large uncharged polar molecules (glucose) - Ions (K+, Cl-, etc..) - Charged polar molecules (amino acids, ATP, glucose 6-phosphate)

Types of passive transport

- Diffusion - Facilitated diffusion - osmosis

Passive transport

Substances diffuse spontaneously down their concentration gradients, rate can be increased by transport proteins in membrane

Diffusion

Hydrophobic molecules and (at a slow rate) very small uncharged polar molecules can diffuse through the lipid bilayer

Facilitated diffusion

Many hydrophilic substances diffuse through membranes with assistance of channel or carrier proteins

How does membrane permeability affect entropy

No permeability means no effects of entropy

What factors are involved in an IV drug delivery

- Reflection coefficient - Permeability of the capillary wall (effective osmotic pressure) - Area of the capillary wall - Concentration difference at the capillary wall (delta concentration) - Permeability of the cell membrane - Area of the cell membrane

Reflection coefficient

How easily a drug diffuses

Do all drugs have the same reflection coefficient?

No. Different chemicals have varying reflection coefficients

Do all membranes have the same permeability

No. Membranes have different (partial) permeabilities

What is electricity

Is the flow of electrons, can also come from ions (lithium ion batteries)

Voltage is the measure of what

Potential

What is the difference in current and voltage between a D and an AAA battery

The voltage is the same in both batteries, but the current is much higher in a D battery.

What is current

The flow of electricity

Is it possible for a cell to have no current but still have potential?

Yes

Given ion concentrations, what equation is needed to determine the equilibrium potential inside and outside of a cell

The Nernst Equation, use to solve for one ion at a time. Effective with only passive transport

The Nernst equation solves for ideal equilibrium (is theoretical), why is the actual equilibrium different?

- Channels leak differently - Their permeabilities vary - Active versus passive transport - Other ions and compartments

NaCl ATPase (pump)

Brings in 2 K+ and sends out 3 Na+ | -Observed in all eukaryotic cells

Types of cotransport

- Antiporters | - Symporters

Antiporter

Exchange solutes, driving them in opposite directions

Symporter

Carry secondary solutes in parallel as a byproduct of transport

Why do electrolytes hydrate

Because of coupled transport; The NaCl pump sends Na out of the cell (against its gradient), so when it flows back into the cell it drags sugar with it (coupled transport). -Gatorade contains electrolytes (salt) and Dextrose (sugar), So the increased amount of Na pulls the dextrose into the cell with it

How do cells use voltage gradients

To drive other processes. Cells are like ionic batteries