Cellular Biology study guide Chapter 5

carrier proteins

Bind a specific single solute and transport it across the lipid bilayer (uniport transport)

Membrane Spanning Carrier Proteins

Binds to specific substances and transport them across the membrane

Glycolipids

lipids with attached carbohydrate groups

Cholesterol

Main sterol in animal membranes, is important for keeping the membranes fluid

What do transport proteins do?

Move particular ions and molecules, including water, in a directed way across the membrane

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

Calcium Pump (Ca2+)

Moves Ca2+ from the cytoplasm to the cell exterior, and from the cytoplasms into the vesicles of the endoplasmic reticulum (ER).

passive transport

Moves ions and molecules within the concentration gradient- higher to lower concentration

active transport

Moves ions or molecules against the concentration gradient- from lower to higher concentration

Primary Active Transport Pump

Moves positively charged ions (H+,CA2+, Na + and K+) across membranes

hypotonic solution

Strong walls prevent plant cells from bursting-osmotic pressure (turgor pressure) pushes cells tightly against their walls and supports soft tissues

Bulk endocytosis (pinocytosis)

Takes a drop of the aqueous extra cellular fluid (efc) surrounding the cells

receptor-mediated endocytosis

Target molecules are bound to receptor proteins on the outer surface cell

receptor-mediated endocytosis

Target molecules to be taken in are bound to receptor proteins on the outer cell surface

peripheral proteins

are held to membrane surfaces by non covalent bonds-hydrogen bonds and ionic bonds-formed with the polar parts of integral membrane proteins or membrane lipids

Proteins in cell-cell junctions

bind cells tightly together, as exemplified in gap junctions and tight junctions

cell adhesion proteins

bind cells together by recognizing and binding receptors or chemical groups on other cells

Osmosis

passive transport of water across a selectively permeable membrane

Where are proteins embedded?

phospholipid bilayer

Two major types of lipids in membranes

phospholipids and sterols

osmotic pressure

pressure that must be applied to prevent osmotic movement across a selectively permeable membrane

integral proteins

proteins embedded in the phospholipid bilayer.

H + Pumps

proton pump generates membrane potential and regulates pH in lysosomes and vacuoles

Receptor Proteins

recognize and bind molecules from other cells that act as chemical signals, such as hormones

Receptor proteins

recognize and bind molecules from other cells that act as chemical signals, such as hormones

What is the fluid mosaic model?

refers to the phospholipid molecules, which vibrate, flex back and forth, spin around their long axis, move sideways, and exchange places within the same bilayer half.

Antiport

solutes are transported in opposite directions

gated channels

switch between open, closed, or intermediate states

Three main functions of active transport

1. Uptake of essential nutrients from fluid surrounding cells, even when concentrations are higher in cells 2. Removal of secretory or waste materials from cells or organelles, even when concentrations are higher outside 3. Maintenance of intracellular concentrations of H+, Na+, K+, and Ca2+

low-density lipoprotein (LDL)

A complex of lipids and proteins, is the way cholesterol moves through the bloodstream

concentration gradient

A difference in the concentration of a substance across a distance.

Bulk endocytosis (pinocytosis) "cell drinking"

A drop of the aqueous fluid surrounding the cell- called extra cellular fluid (ECF) is taken into the cell together with any molecules that happen to be in the solution in the water.

Coated pit

A network of proteins (clathrin) coat and reinforce the cytoplasmic side

What do phospholipid molecules do?

Assemble into a bilayer (a later two molecules thick)

freeze fracture technique

Frozen cells were split into inner and outer halves, revealing the proteins embedded in the bilayers and their different patterns in the two halves

Phsopholipids

Have a polar electrically charged end containing a phosphate group, and a non polar uncharged end containing two non polar fatty acid tails

peripheral proteins

Held to membrane surfaces by non covalent bonds

If a solution surround a cell contains nonpenetrating solutes at higher concentrations than in the cell, the cell is what?

Hypertonic (water leaves and the cell shrinks)

If the solution surrounding a cell contains nonpenetrating solutes at lower concentrations than in the cell, the cell is what?

Hypotonic (water enters and the cells swell)

Phagocytes

In the bloodstream and protists such as amoeba, take in large particles or whole cells by phagocytosis

Cell-cell recognition proteins

In the plasma membrane identify a cell as part of the same individual or as a foreign, facilitate cell- cell linking, bind cells to the extracellular matrix (ECM) and link the ECM to the cytoskeleton

Na + K+ pump

In the plasma membrane of all animal cells moves 3 Na + out of the cell and 2 K+ into the cell in the same pumping cycle

channel proteins

Integral membrane proteins that form hydrophilic channels in the membrane through which water and ions can pass

What is phosphatidylcholine an example of?

Is an example of a phospholipid molecule

What does calcium pump regulate?

It regulates cellular activities such as secretion, microtubule assembly and muscle contraction

Transport of substances across a membrane against a concentration gradient requires what ?

It requires active transport - a process that requires energy output

Pinocytosis is nonspecific

It takes any solutes present in efc because the membrane lacks surface receptors for specific molecules

phospholipids and sterols are the two major types of what?

Lipid Membranes

primary active transport

The protein that transports a substance also hydrolyzes ATP to power the transport directly

secondary active transport

Uses an ion concentration gradient established by a primary pump as an energy source

Phagocytosis "cell eating"

Begins when surface receptors bind molecules on the substances to be taken in

Receptors with target molecules collect in a depression in the plasma membrane called

Coated pit

Transport

Controlled movement of specific ions and molecules across a membrane by membrane proteins

Membrane functions

Define the boundaries of cells and, in eukaryotes, the boundaries of compartments (organelles)

What do membranes do?

Defines the boundaries of cells and in eukaryotes, the boundaries of compartments Ex. Nucleus, mitochondria and chloroplasts

Molecular Insights

Describes the discovery of receptor- mediated endocytosis

Membranes are asymmetric

Different arrangements of membrane lipids and proteins occur in the two bilayer halves

What is passive transport a form of?

Diffusion

Fascilated Diffusion

Diffusion of polar and charged molecules through transport proteins in the hydrophobic lipid bilayer

Osmosis

Diffusion of water through a selectively permeable membrane

simple diffusion

Diffusion through the lipid part of a biological membrane

organelles of the endomembrane system

ER, Golgi Complex, lysosome, mitochondrion and chloroplast

What do membranes consist of?

Electrical properties and conduct signals when a cell receives an electrical, chemical, or mechanical stimulus

The differences in concentration ions and in electrical charge on the two sides of the membrane, constitutes a what?

Electrochemical gradient- form of potential energy

Where are integral proteins embedded?

Embedded deeply in the bilayer, whereas peripheral membrane proteins associate with membrane surfaces

Both Exocytosis and endocytosis require

Energy (ATP)

What does simple diffusion transport?

Non polar inorganic gases and organic molecules

Hydrophobic tail

Nonpolar, hates water

kiss and run mechanism

Occurs when a vesicles fuses with the plasma membrane, the vehicle contents are released from the cell, and then the vehicle reforms and moves back into the cell

Hydrophilic head

Polar end is hydrophilic and loves water

The concentration difference that drives diffusion, a concentration gradient is a form of what?

Potential energy

Tonicity

Property of a solution with respect to a particular membrane

fluid mosaic model

Proposes that the membrane consists of a fluid phospholipid bilayer in which proteins are embedded and float freely

Fluid Mosaic Model

Proposes that the membrane consists of a fluid phospholipid bilayer in which proteins are embedded and float freely.

Glycoproteins

Protein molecules with carbohydrate groups attached. Found on outer surface of cell membranes

nonpenetrating solutes

Proteins and other molecules that cannot pass through a membrane that is impermeable to them but freely permeable to water

Endocytosis

Proteins and other substances are trapped in pitlike depressions that bulge inward from the plasma membrane and pinch off as an endocytic vesicle

The "mosaic" part of the fluid mosaic model

Refers to membrane proteins, most of which float individually in the fluid lipid bilayer, like icebergs in the sea.

Mosiac

Refers to membrane proteins-most float individually in the lipid bilayer, some are attached to the cytoskeleton

fluid

Refers to the phospholipid molecules, that constantly move and exchange places within the same layer

Exocytosis

Secretory vesicles bud from the golgi complex move through the cytoplasm and contact the plasma membrane

Membrane Spanning Channel Proteins

Selectively regulate transport of specific ions or water through the membrane

polar molecule

Small enough to slip between the hydrocarbon tails of phospholipid molecules in a fluid bilayer

hypertonic solution

Stems and leaves wilt- in extreme cases, plant cells shrink so much that they retract from their walls (plasmolysis)

The lipid bilayers form what?

The lipid bilayer forms the structural framework of membranes and is a barrier to the passage of most water-soluble molecules

What is the glycocalyxes function?

The main function is to protect cells against chemical and mechanical damage

osmotic pressure

The term for pressure that must be applied to a solution to prevent water movement across a membrane

membrane potential

The voltage across a cell's plasma membrane.

What do glycolipids and glycoproteins do?

They form a surface coat called the glycocalyx

plasma membrane

Thin layer of lipids and proteins, seperates cells from its surroundings

secondary active transport

Transport is indirectly driven by ATP hydrolysis

enzymatic proteins

confer specific properties on the membranes with them

biological membranes

consist of lipids and proteins assembled into a thin film

recognition proteins

in the plasma membrane identify a cell as part of the same individual or as foreign

integral proteins

embedded in the phospholipid bilayer

ion channels

facilitate the transport of ions

transport proteins

form channels that allow selected polar molecules and ions to pass across a membrane

symport

the solute moves through the membrane channel in the same direction as the driving ion

Aquaporins

water channel proteins

Isotonic

when the concentration of two solutions is the same