Cells

Question 1

Cell

Answer 1

Smallest structural and functional unit of life

Question 2

Cell theory

Answer 2

1. The cell is the smallest unit of life
2. All organisms are made of one or more cells
3. Cells only arise from other cells

Question 3

What are the 3 main parts of a human cell?

Answer 3

1. Plasma membrane
2. Cytoplasm
3. Nucleus

Question 4

Plasma membrane

Answer 4

The outer boundary of the cell, which acts as a selectively permeable barrier.

Question 5

Cytoplasm

Answer 5

The intracellular fluid packed with organelles, small structures that perform specific cell functions

Question 6

Nucleus

Answer 6

An organelle that controls cellular activities. Typically, the nucleus lies near the cell’s center

Question 7

Extracellular materials

Answer 7

Substances contributing to body mass that are found outside the cells

Question 8

What are the major classes of extracellular materials?

Answer 8

1. Extracellular fluid
2. Cellular secretions
3. Extracellular matrix

Question 9

What is the fluid mosaic model?

Answer 9

Describes the plasma membrane as a phospholipid bilayer with embedded proteins, arranged as a fluid mosaic

Question 10

What are the functions of the plasma membrane?

Answer 10

1. Physical barrier, separates cytoplasm from extracellular fluid
2. Selective permeability: determines which substances enter/exit cell
3. Communication: proteins interact w/ chemical messengers to relay message to cell interior
4. Cell recognition: cell surface carbohydrates allow cells to recognize each other

Question 11

Integral proteins

Answer 11

Proteins that are firmly inserted into the lipid bilayer making up the plasma membrane, have both hydrophilic and hydrophobic regions

Question 12

Peripheral proteins

Answer 12

Proteins that aer not embedded in the lipid bilayer that makes up the plasma membrane

Question 13

Glycolipid

Answer 13

A lipid with sugars attached

Question 14

Glycoprotein

Answer 14

A protein with sugars attached

Question 15

Glycocalyx

Answer 15

“sugar covering”; fuzzy, sticky, carbohydrate-rich area at the cell surface created by the sugars of glycoproteins and glycolipids

Question 16

What are the three types of cell junctions?

Answer 16

1. Tight junctions
2. Desmosomes
3. Gap junctions

Question 17

Tight junction

Answer 17

Area where plasma membranes of adjacent cells are tightly bound together by integral proteins, forming an impermeable barrier.

Question 18

Desmosomes

Answer 18

Cell junction composed of thickened plasma membranes joined by filaments. Serve as anchoring junctions

Question 19

Gap junction

Answer 19

Communicating junction between adjacent cells

Question 20

Passive transport

Answer 20

Substances cross the plasma membrane without any energy input from the cell

Question 21

Active transport

Answer 21

The cell provides the metabolic energy (usually ATP) needed to move substances across the plasma membrane

Question 22

Diffusion

Answer 22

The movement of particles (molecules or simple ions) from an area where they are in higher concentration to an area where they are in lower concentration

Question 23

What three factors influence the speed of diffusion

Answer 23

1. Concentration gradient (larger difference in concentration = fast diffusion)
2. Molecular size (smaller particles diffuse more rapidly)
3. Temperature (higher temp = fast diffusion)

Question 24

Simple diffusion

Answer 24

The unassisted transport across a plasma membrane of a lipid-soluble or very small particle.

Lipid solubility and size are the two criteria that determine how easily a substance will pass by simple diffusion.

Question 25

Facilitated diffusion

Answer 25

Passive transport process used by certain large or charged molecules that are unable to pass through the plasma membrane unaided. Involves movement through channels or movement facilitated by a membrane carrier.

Question 26

Carriers

Answer 26

Transmembrane proteins that are specific for transporting certain polar molecules or classes of molecules that are too large to pass through membrane channels

Question 27

Channels

Answer 27

Transmembrane proteins that transport substances, usually ions, through aqueous (water-filled) channels from one side of the membrane to the other

Question 28

Osmosis

Answer 28

The movement of water through a selectively permeable membrane

Question 29

Aquaporins

Answer 29

Transmembrane proteins that form water channels and allow single-file movement of water molecules

Question 30

Osmolarity

Answer 30

The total concentration of all solute particles in a solution

Question 31

Tonicity

Answer 31

A measure of the ability of a solution to cause a change in cell shape or tone by promoting osmotic flows of water.

Question 32

Isotonic solutions

Answer 32

Have the same concentrations of nonpenetrating solutes as those found in cells. Cells exposed to isotonic solutions retain their normal shape, and exhibit no net loss or gain of water

Question 33

Hypertonic solutions

Answer 33

Have a higher concentration of nonpenetrating solutes than seen in the cell. Cells immersed in hypertonic solutions lose water and shrivel, or crenate

Question 34

Hypotonic solutions

Answer 34

More dilute (contain a lower concentration of nonpenetrating solutes) than cells. Cells placed in a hypotonic solution plump up rapidly as water rushes into them

Question 35

Primary active transport

Answer 35

The energy to do work comes directly from hydrolysis of ATP by transport proteins called pumps

Question 36

Secondary active transport

Answer 36

Transport is driven by energy stored in concentration gradients of ions created by primary active transport pumps

Question 37

Sodium-potassium pump

Answer 37

A primary active transport system that simultaneously drives out of the cell against a steep gradient and pumps back in

Question 38

Vesicular transport

Answer 38

Cellular energy is used to move large substances, or large amounts of a substance, across cellular membranes inside bubble-like, membranous sacs called vesicles

Question 39

Transcytosis

Answer 39

Moves substances into, across, and then out of the cell

Question 40

Vesicular trafficking

Answer 40

Moves substances from one area (or membranous organelle) in the cell to another.

Question 41

Endocytosis

Answer 41

Means by which fairly large extracellular molecules or particles enter cells

Question 42

Phagocytosis

Answer 42

Engulfing of solids by (phagocytic) cells

Question 43

Pinocytosis

Answer 43

Engulfing of extracellular fluid by cells. Also called fluid-phase endocytosis

Question 44

Receptor-mediated endocytosis

Answer 44

The type of endocytosis in which engulfed particles attach to receptors before endocytosis occurs.

Question 45

Exocytosis

Answer 45

Mechanism by which substances are moved from the cell interior to the extracellular space as a secretory vesicle fuses with the plasma membrane.

Question 46

Resting membrane potential

Answer 46

The voltage that exists across the plasma membrane during the resting state of an excitable cell; typically ranges from -50 to -90 millivolts depending on cell type.

Question 47

What primarily determines the resting membrane potential?

Answer 47

Determined mainly by the concentration gradient of potassium and by the differential permeability of the plasma membrane to K+ and other ions

Question 48

Cell adhesion molecules

Answer 48

Surface glycoproteins involved in maintaining cell-to-cell or cell-to-extracellular matrix associations.

Question 49

Membrane receptors

Answer 49

A large, diverse group of integral proteins that serve as binding sites for signaling molecules.

Question 50

What are the three major elements of cytoplasm?

Answer 50

- Cytosol: viscous, semitransparent fluid in which the other cytoplasmic elements are suspended - Inclusions: chemical substances that may or may not be present, depending on cell type - Organelles: metabolic machinery of the cell, each performs its own specific job

Question 51

Mitochondria

Answer 51

Cytoplasmic organelles responsible for ATP generation for cellular activities.