Chapter 2 Cell Theory

Question 1

Organelle

Answer 1

An internal functional structure that is located within the cytosol of a cell

Question 2

Plasma membrane

Answer 2

A dynamic barrier that surrounds the cytosol of the cell.
- The Membrane surrounding organelle maintains internal environment that allows the organelle to carry out its particular function

Question 3

Nucleus

Answer 3

• Contains almost all the DNA in a eukaryotic cell.

Question 4

Nuclear envelope

Answer 4

A two-layer membrane that encloses the nucleus of a eukaryotic cell
- Consists of two lipid bilayers that are folded together. The outer bilayer of the membrane is continuous with the membrane of another organelle, the endoplasmic reticulum (ER).
Allows water and gas to run freely.
System of transporters and pumps controls the passage of molecules between the nucleus and the cytosol.

Question 5

The endomembrane system

Answer 5

a group of interacting organelles between the nucleus and the plasma membrane.

Question 6

Lysosome

Answer 6

Vesicles that contain powerful digestive enzymes.

A small, membrane-bound organelle that contains digestive enzymes that aid in waste disposal

Question 7

Cytoskeleton

Answer 7

A dynamic system of filaments that provides cell structure, helps with cell division, and enables the cell and inner organelles to move around
Bettween the nucleoplasm and plasma membrane

Question 8

Microfilament

Answer 8

A fibre structure made from actin that is part of the cytoskeleton & is located in the cytosol of cells
- Strengthen or change the shape of eukaryotic cells.

Question 9

Flagellum

Answer 9

A whip like tail that is used in propulsion of both prokaryotic and eukaryotic cells

Question 10

Cell Wall

Answer 10

The outer barrier of a plant cell; the cell wall surrounds the plasma membrane and gives structure to the plant
- Water and many solutes easily cross it on the way to and from the plasma membrane.

Question 11

Primary wall

Answer 11

A cellulose coating that surrounds a plant cell
The primary wall thin and pliable, which allows the growing plant cell to enlarge. Starts secreting a material onto the inner surface of the primary wall. This material forms a firm secondary wall

Question 12

Secondary wall

Answer 12

A coating that is added to a plant cell wall; it is more rigid and often thicker than the primary cell wall

Question 13

Extracellular Matrix (ECM)

Answer 13

A molecular system that supports and protects a cell; a cell’s environment
Non-living, complex mixture of fibrous proteins and polysaccharides is secreted by cells and varies with the type of tissue. It supports and anchors cells, separates tissues, and functions in cell signaling.

Question 14

Cell junction

Answer 14

A structure that allows cells to interact with each other and the surrounding environment

Question 15

Cystic fibrosis

Answer 15

Cystic fibrosis (CF) is a genetic disorder that impairs the lungs and gastrointestinal tract.  
	- Caused by mutations to a single gene that codes for a protein called the cystic fibrosis transmembrane conductance regulator, or CFTR. In properly functioning cells, CFTR acts as a membrane transport protein.

Question 16

Fluid Mosaic Model

Answer 16

The idea that a biological membrane consists of a fluid phospholipid bilayer, in which proteins are embedded and float freely

Question 17

What is in the Fluid Mosaic Models

Answer 17

It Consists of lipid molecules in which proteins are embedded and float freely.
- Exist in a double layer, called a bilayer, that is less than 10 nm
- Some components have carbohydrate groups linked to them, forming glycolipids and glycoproteins that face the exterior of the cell.
Play a role in cell recognition and cell–cell interactions.

Question 18

Glycolipid

Answer 18

Any membrane lipid that is bound to a carbohydrate

Question 19

Glycoprotein

Answer 19

A membrane component that contains a sugar, or carbohydrate, bound to an amino acid

Question 20

Membrane Asymmetry

Answer 20

The proteins and other components of one half of the lipid bilayer differ from those that make up the other half of the bilayer.
This reflects the differences in the functions performed by each half of the membrane.

Question 21

The Role of Phospholipids in Cell Membranes

Answer 21

• Phospholipids contain two fatty acid tails, which are usually linked to glycerol, a phosphate group, and a compound such as choline
  Their structure make them important for membrane function since the fatty acid tails of a phospholipid are very hydrophobic (nonpolar), whereas the phosphate-containing head group is charged and hydrophilic (polar).
  When added to an aqueous solution, large numbers of phospholipids form a bilayer, or a structure that is two lipid molecules thick
  A bilayer forms spontaneously in water because of the tendency of the non-polar hydrophobic fatty acids to aggregate together while the polar heads associate with water.
  These arrangements are favored because they represent the lowest energy state, and therefore are more likely than any other arrangement to occur.

Question 22

Fluidity of the cell Membrane

Answer 22

Fluidity of the lipid bilayer is dependent on how densely the individual lipid molecules can pack together.
This is influenced by the composition of the lipid molecules that make up the membrane as well as the temperature.
Fatty acids composed of saturated hydrocarbons tend to have a straight shape, which allows the lipids to pack together more tightly.
In comparison, the double bonds in an unsaturated fatty acid bend its structure, so the lipid molecules are less straight and more loosely packed.
At any given temperature, the fluidity of a membrane is related to the degree to which the membrane lipids are unsaturated. The more unsaturated a membrane is, the lower its gelling temperature.

Question 23

Sterol

Answer 23

A type of steroid with an OH group at one end and a non-polar hydrocarbon chain at the other
Sterols also influence membrane fluidity.

Question 24

Transport Membrane Proteins

Answer 24

Many substances cannot freely diffuse through membranes. Instead, a specific compound may be able to cross a membrane by way of a hydrophilic protein channel. Alternatively, shape shifting may allow some membrane proteins to shuttle molecules from one side of a membrane to the other.

Question 25

Membrane Proteins with Enzymatic Activity

Answer 25

Some membrane proteins such as those associated with respiration and photosynthesis, are enzymes.

Question 26

Triggering signal Membrane Proteins

Answer 26

Membrane proteins may bind to specific chemicals, such as hormones. Binding to these chemicals triggers changes on the inner surface of the membrane, starting a cascade of events within the cell.

Question 27

Attachment and recognition membrane proteins

Answer 27

Proteins that are exposed to both the internal and external membrane surfaces act as attachment points for a range of cytoskeleton elements, as well as components involved in cell–cell recognition, and bond to the extracellular matrix. For example, surface proteins can recognize elements of disease-causing microbes that may try to invade cells, triggering an immune response.

Question 28

Integral Membrane Protein

Answer 28

A protein that is embedded in the lipid bilayer
Have at least one region that interacts with the hydrophobic core of the membrane. However, most integral proteins are transmembrane proteins. They span the entire membrane bilayer and have regions that are exposed to the aqueous environment on both sides of the membrane.

Question 29

Peripheral Membrane Protein

Answer 29

A protein on the surface of the membrane
- Held to membrane surfaces by noncovalent bonds (hydrogen bonds and ionic bonds), usually by interacting with the exposed portions of integral proteins as well as directly with membrane lipid molecules.
Are on the cytosol side of the membrane, and some are part of the cytoskeleton

Question 30

What organelles do not have a membrane?

Answer 30

Ribosomes, Centriole

Question 31

Microtubule

Answer 31

A long, hollow cylinder that consists of subunits of the protein tubulin. Form dynamic scaffolding for many cellular processes, rapidly assembling when they are needed and disassembling when they are not.

Question 32

Passive Transport

Answer 32

The movement of a substance across a membrane without expending energy.
- Driven by diffusion

Question 33

Diffusion

Answer 33

The net movement of a substance from a region of higher concentration to a region of lower concentration.
This occurs because molecules are in constant motion and, in an ideal closed environment, tend to become uniformly distributed in space.
Diffusion is the primary mechanism of solute movement within a cell and between cellular compartments separated by a membrane. If molecules are more concentrated in one region of a solution or on one side of a membrane, molecules random motions causes them to become evenly distributed
As diffusion proceeds, there is a net movement of molecules in one direction until the concentrations on both sides of the membrane become equal.

Question 34

What does The Rate of Diffusion Depend on?

Answer 34

Rate of diffusion depends on the concentration difference, or concentration gradient, existing in two areas or across a membrane.
The larger the gradient, the faster the rate of diffusion is. The molecules or ions continue to move from one region to another. However, THERE IS NO NET CHARGE in concentration.

Question 35

Dynamic Equilibrium

Answer 35

The state in which continuous action results in balanced conditions

Question 36

What is the selective permeability of membranes

Answer 36

Membranes have selective permeability, (some molecules can diffuse very rapidly across a membrane while other molecules are unable to transit the membrane without assistance).
Size & charge, determine what can move across a membrane.

Question 37

Simple Diffusion

Answer 37

The ability of substances to move across a membrane unassisted.
Very small non-polar molecules, are soluble in the hydrophobic interior of a membrane and move between sides
Non-polar steroid hormones and non-polar drugs can cross a membrane.
Small uncharged molecules, such as waterable to move quite rapidly across a membrane.

Question 38

Facilitated Diffusion

Answer 38

The facilitated transport of ions and polar molecules through a membrane via protein complexes
The movement of the molecules and ions is driven by diffusion based on a concentration gradient across the membrane. When equilibrium is reached and there is no longer a concentration gradient, facilitated diffusion stops. Carried out by transport proteins

Question 39

Transport Protein

Answer 39

An integral membrane protein that provides a pathway for molecules to cross a membrane

Question 40

Channel Protein

Answer 40

A hydrophilic pathway in a membrane that enables water and ions to pass through

Question 41

Carrier protein

Answer 41

A protein that binds to a molecule and transports it across the lipid bilayer

• Carrier proteins also form passageways through the lipid bilayer. Diffusion is the driving mechanism for moving a solute down its concentration gradient, is unable to pass membrane without carrier proteins.
• When transporting, carrier protein changes shape, allowing the solute to move from one side of membrane to other. Change in shape distinguishes how carrier proteins and channel proteins function.

Question 42

Osmosis

Answer 42

The passive diffusion of water across a membrane
- The inward or outward movement of water by osmosis develops forces that can cause cells to swell or shrink.
Water diffuses from an area of lower solute concentration (high water concentration) to an area of greater solute concentration (low water concentration) and is therefore influenced by any difference or change in solute concentration on either side of a membrane.

Question 43

Hypertonic

Answer 43

The property of a solution that has a higher solute concentration than another solution

Question 44

Hypotonic

Answer 44

The property of a solution that has a lower solute concentration than another solution

Question 45

Active transport

Answer 45

The movement of substances across membranes against their concentration gradient using pumps
- Using “pumps,” active transport is able to concentrate specific compounds inside cells and push others out
The term “active” refers to the fact that the cell has to expend energy, which is usually in the form of ATP, to pump molecules across a membrane.

Question 46

Primary Active Transport

Answer 46

All primary active transport pumps move positively charged ions, across membranes. The concentration gradients that are established by these active transport pumps underlie functions that are absolutely essential for cellular life.
EXAMPLE: An H+ pump (also called a proton pump) in the plasma membrane pushes hydrogen ions from the cytosol to the cell exterior.

Question 47

Electrochemical Gradient

Answer 47

The combined effects of a difference in electrical potential energy and a difference in the concentration gradients of these ions.
Combined effects of the voltage and the differences in ion concentrations create an electrochemical gradient. An electrochemical gradient is a form of stored potential energy that can be used for other transport mechanisms.
EX: The electrochemical gradient across the plasma membrane is involved in the movement of ions associated with nerve impulse transmission.

Question 48

Secondary Active Transport

Answer 48

• A secondary active transport pump uses the concentration gradient of an ion, established by a primary pump, as its energy source.
  Secondary active transport is facilitated by symport and antiport.

Question 49

Symport

Answer 49

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

Question 50

Antiport

Answer 50

The driving ion moves through the membrane channel in one direction, providing the energy for the active transport of another molecule in the opposite.

Question 51

Exocytosis

Answer 51

Moves proteins and waste out of the cells
Secretory vesicles move through the cytosol and contact the plasma membrane. The vesicle membrane fuses with the plasma membrane, releasing the contents of the vesicle to the exterior of the cell.

Question 52

Endocytosis

Answer 52

Moves aggregate molecules into the cell
Proteins and other substances are trapped in a depression that bulges inward from the plasma membrane.
The depression pinches off as an endocytic vesicle.

Question 53

Bulk - Phase Endocytosis

Answer 53

Extracellular water is taken in, along with any molecules that happen to be in solution in the water. No binding by surface receptors takes place.

Question 54

Receptor Mediated Cytosis

Answer 54

The molecules to be taken in are bound to the outer cell surface by receptor proteins).
The receptors bind to only certain molecules—primarily proteins or molecules carried by proteins.
After binding, the receptors collect into a pit coated with a network of proteins, called clathrin, that reinforce the cytosol side. The coated pit then breaks free of the membrane to form a vesicle. In the cytosol, the vesicle loses its clathrin coating and may fuse with a lysosome. Enzymes within the lysosome then digest the cargo, breaking it down into smaller molecules that are useful to the cell

Question 55

Phagocytosis

Answer 55

The pathway in which cells engulf bacteria, parts of dead cells, viruses, or other foreign particles.