A&p Chapter 3 Cells

Front 1

Cells of the human body exhibit a broad diversity of morphologies (shapes)

Back 1

T

Front 2

According to the Cell Theory, cells are the basic structural and functional unit of living organisms.

Back 2

T

Front 3

Plasma membranes of human cells are non-selectively permeable.

Back 3

F

Front 4

Peripheral proteins of plasma membranes are imbedded in the lipid bilayer.

Back 4

F

Front 5

Plasma membranes are rigid, inflexible lipid-protein sheets.

Back 5

F

Front 6

Peripheral proteins can be used as transmembrane transport molecules.

Back 6

F

Front 7

The lipid bilayer of the plasma membrane is hydrophobic.

Back 7

T

Front 8

Amphipathic molecules have both hydrophobic and hydrophilic regions.

Back 8

T

Front 9

Cholesterol is primarily a
A. hydrophobic
B. hydrophilic
compound.

Back 9

A

Front 10

Passive membrane processes A. require
B. do not require
input of energy.

Back 10

B

Front 11

Ions diffuse through solution from a region of
A. higher concentration to a region of lower concentration
B. lower concentration to a region of higher concentration.

Back 11

A

Front 12

Membrane cholesterol is found associated with
A. phosphate heads
B. lipid tails
of the lipid bilayer.

Back 12

B

Front 13

The membrane transport process that requires a change in shape of the transport molecule is
A. channel-mediated diffusion
B. carrier-mediated diffusion

Back 13

B

Front 14

Membrane-spanning proteins
A. are
B. are not
amphipathetic.

Back 14

A

Front 15

Osmosis refers to the simple diffusion of
A. solutes
B. water

Back 15

B

Front 16

Water diffuses to a region of
A. higher solute concentration
B. lower solute concentration.

Back 16

A

Front 17

Lipid-soluble solutes
A. can
B. cannot
cross membrane layers via simple diffusion.

Back 17

A

Front 18

Cell Theory (4)

Back 18

1. A cell is the basic structural and functional unit of living organisms.
2. The activity of an organism depends on both the indl and the collective activities of its cells.
3. According to the principle of complementarity of structure and function, the biochemical activities of cells are dictated by the relative number of their specific subcellular structures.
4. Continuity of life from one generation to another has a cellular basis.

Front 19

Cells are composed of:

Back 19

carbon, hydrogen, nitrogen, oxygen and trace amounts of several other elements.

Front 20

Human cells have three main parts:

Back 20

plasma membrane
cytoplasm
nucleus

Front 21

Plasma Membrane

Back 21

a fragile barrier, outer boundary of the cell.

Front 22

Cytoplasm

Back 22

the intracellular fluid of cell that is packed with organelles, small structures that perform specific cell functions.

Front 23

Nucleus

Back 23

controls cellular activities and typically lies near the cell's center.

Front 24

Fluid Mosaic Model

Back 24

The FMM of membrane structure depicts the plasma membrane as an exceedingly thin structure composed of a double layer, or bilayer, of lipid molecules with protein molecules plugged in it. The proteins, many of which float in the fluid lipid bilayer, form a constantly changing mosaic pattern.

Front 25

Lipid Bilayer is composed of:

Back 25

mostly phospholipids
cholesterol
glycolipids

Front 26

Phospholipids

Back 26

Two parts:
- charged, polar head, hydrophobic (water-loving)
- uncharged, nonpolar tail, hydrophobic (water hating) made up of two fatty acid chains

Front 27

Glycolipids

Back 27

- lipids with attached sugar groups.
- found only on the outer plasma membrane surface and account for about 5% of the total membrane lipid.

Front 28

Membrane Proteins (64)

Back 28

proteins make up about half of the plasma membrane

- integral proteins
- peripheral proteins

Front 29

Integral Proteins

Back 29

- firmly imbedded in the lipid bilayer
- most are transmembrane proteins wihch span entire width altho some can protrude from one side only
- have both hydrophobic and hydrophilic regions
- some are enzymes but most are involved in transport

Front 30

Peripheral Proteins

Back 30

- not embedded in the lipid
- attach loosely to integral proteins

Front 31

Glycocalyx

Back 31

"sugar covering"
- fuzzy, sticky, carbohydrate-rich area at the cell serface. Enriched by glycolipids and glycoproteins secreted by the cell.
- provides highly specific biological markers by which approaching cells recognize each other.

Front 32

Membrane Junctions

Back 32

- tight junctions
- desmosomes
- gap junctions

Front 33

Tight Junctions

Back 33

- impermeable junctions that prevent molecules from passing through the intercellular space.
- however, some TJ's are somewhat leaky and may allow certain types of ions to pass.
- E.g.: TJ's bt epithelial cells lining the digestive tract keep digestive enzymes and microorganisms in the intestine from seeping into the bloodstream.

Front 34

Desmosomes

Back 34

" binding bodies"
- are anchoring junctions - mechanical couplings scattered like rivets along the sides of abutting cells that prevent their separation.
- bind neighboring cells together and contribute to a continuous internal network of strong "guy-wires"
- distributes tension throughout a cellular sheet and reduces the chance of tearing when it is subjected to pulling forces.
- abundant in tissues subjected to great mechanical stress, such as skin and heart muscle.

Front 35

Gap Junctions

Back 35

"bond"
- a communicating junction bt adjacent cells that allow ions and small molecules to pass from one cell to the next for intercellular communication.
- present in electrically excitable tissues, such as the heart and smooth muscle, where ion passage from cell to cell helps synchronize their electrical activity and contraction.

Front 36

Selective/Permeable Barrier

Back 36

the plasma membrane allows some substances to pass while excluding others.

Front 37

Passive Processes

Back 37

- substances cross the plasma membrane without any energy input from the cell.
- two main types of passive transport: diffusion and filtration

Front 38

Active Processes

Back 38

the cell provides the metabolic energy (ATP) needed to move substances across the membrane.

Front 39

Diffusion

Back 39

- the tendency of molecules or ions to move from an area of higher concentration to an area of lower concentration, down their concentration gradient.

Front 40

While the plasma membrane is a physical barrier to free diffusion because of its hydrophobic core, a molecule will diffuse through the membrane if the molecule is:

Back 40

1. lipid soluble
2. small enough to pass through membrane channels, or
3. assisted by a carrier molecule.

Front 41

Simple Diffusion

Back 41

- unassisted diffusion of lipid-soluble or very small particles
- nonpolar and lipid-soluble substances diffuse directly thru the lipid bilayer
- substances that diffuse thru include oxygen, carbon dioxide, and fat-soluble vitamins.
- bc oxygen concentration is higher in the blood, it diffuses into the cells
- carbon dioxide concentration is higher in cell so it diffuses into the blood.

Front 42

Facilitated Diffusion

Back 42

- assisted diffusion
- the transported substance either:
(1) binds to protein carriers in the membrane and is ferried across, or
(2) moves through water-filled protein channels
- certain molecules such as glucose, other sugars, some amino acids and ions are transported this way

Front 43

Carriers

Back 43

- transmembrane integral proteins that show specificity for molecules of a certain polar substance or class of substances too large to pass through membrane channels, such as sugars and amino acids
- carrier changes shape to facilitate transport
- is a protein carrier specific for one chemical, binding of substrate causes shape change in transport protein
- the substance moves down its concentration gradient like in simple diffusion
- glucose has higher concentration in blood so goes into cells
- carrier-mediated transport is limited by the number of protein carriers present, so if all are engaged, said to be saturated

Front 44

Channels

Back 44

- transmembrane proteins that transport substances, usually ions or water, through aqueous channels
- mostly ions selected on basis of size and charge
- like carriers, channels can be inhibited by certain molecules, show saturation and tend to be specific
- moves down its concentration gradient

Front 45

Osmosis

Back 45

- diffusion of a solvent such as water through a specific channel protein (aquaporin) thru the lipid bilayer.
- occurs whenever the water concentration differs on the two sides of a membrane
- if distilled water is present on both sides, no net osmosis occurs
- if solute concentration differs, water concentration differs (as solute concentration increases, water concentration decreases).
- extent to which water's concentration is decreased by solutes depends on the number, not the type of solute particles.

Front 46

Osmolarity

Back 46

the total concentration of all solute particles in a solution

Front 47

Tonicity

Back 47

the ability of a solution to change the shape or tone of cells by altering their internal water volume

Front 48

Isotonic Solutions

Back 48

- cells retain their normal size and shape (same solute/water concentration as inside cells; water moves in and out)

Front 49

Hypertonic Solutions

Back 49

- cells lose water by osmosis and shrink in a hypertonic solution (contains a higher concentration of solutes than are present inside the cells)
- cells immersed in hypertonic solutions lose water and shrink, or crenate

Front 50

Hypotonic Solutions

Back 50

Cells take on water by osmosis until they become bloated and burst (lyse) in a hypotonic solution is more dilute (contains a lower concentration of solutes than are present in cells)
- cells placed in a hypotonic solution pump up rapidly as water rushes into them
- e.g.: distilled water contains no solutes, so water continues to enter cells until they finally burst or lyse
-

Front 51

Uses of hyper- and hypo-tonic Solutions

Back 51

Hypertonic: used intravenously into the bloodstream of edematous patients (those swollen because water is retained in their tissues) to draw excess water out of that extracellular space and move it into the bloodstream to be eliminated by kidneys
- hyptonic solutions: may be used to rehydrate tissues of extremely dehydrated patients; can drink colas, apple juice, sports drinks

Front 52

Energy source for Simple Diffusion, Facilitated Diffusion and Osmosis

Back 52

kinetic energy

Front 53

Active Transport

Back 53

- like carrier-mediated facilitated diffusion, requires carrier proteins that combine specifically and reversibly with the transported substances
- transports substances against its concentration gradient

Front 54

Two Active Transport Processes

Back 54

- processes are distinguished according to their source of energy

- primary active transport
- secondary active transport

Front 55

Primary Active Transport

Back 55

- energy comes directly from hydrolysis of ATP
- performed across the plasma membrane by a solute pump, directly using energy of ATP hydrolysis
- hydrolysis of ATP results in the phosphorylation of the transport protein which causes the protein to change shape in such a manner that it pumps the bound solute across the membrane.
- ex moved: Na+, K+, H+, Ca2+, and others

Front 56

Sodium-Potassium Pump

Back 56

- ex of a primary active transport system
- K+ concentration is higher in cell
- Na+ concentration is higher outside of cell
- SP pump drives Na+ out of the cell against a steep concentration gradient and pumps K+ back in

Front 57

Secondary Active Transport

Back 57

- transport is driven indirectly by energy stored in ionic gradients created by operation of primary active transport pumps.
- secondary active transport systems are all coupled systems; that is, they move more than one substance at a time.

Front 58

Symport System

Back 58

- when two transported substances are moved in the same direction
e.g.: when Na+ moves down its gradient, it drags along glucose against its gradient into the cell

Front 59

Antiport System

Back 59

- move transported substances in opposite directions across the membrane
- e.g.: Ca2+, H+ (out of cells via antiporters)

Front 60

Vesicular Transport

Back 60

- fluids containing large particles and macromolecules are transported across cellular membranes inside membranous sacs called vesicles
e.g.: exocytosis, endocytosis, transcytosis

Front 61

Exocytosis

Back 61

- "out of the cell"
- vesicular transport processes that eject substances from the cell interior into the extracellular fluid

Front 62

Endocytosis

Back 62

- "within the cell"
- those in which the cell ingests small patches of the plasma membrane and moves substances from the cell exterior to the cell interior

Front 63

Transcytosis

Back 63

- moving substances into, across, and then out of the cell

Front 64

Substance, or Vesicular, Trafficking

Back 64

- moving substances from one area (or organelle) in the cell to another

Front 65

Energy for Vesicular Transport

Back 65

- energized by ATP (or in some cases another energy-rich compound, GTP - guanosine triphosphate)

Front 66

What are three types of Endocytosis that use clathrin-coated vesicles?

Back 66

- phagocytosis
- pinocytosis
- receptor-mediated endocytosis

Front 67

Phagocytosis

Back 67

"cell eating"
- the cell engulfs a large or solid material

Front 68

Phagosome

Back 68

- endocytotic vesicle formed when a particle binds to receptors on the cell's surface, cytoplasmic extensions called pseudopods form and flow around the particle and engulf it
- phagosome fuses with a lysosome and its contents digested or any indigestible content is ejected from the cell by exocytosis

Front 69

Phagocytes

Back 69

- cells that help police and protect the body by ingesting and disposing of bacteria, other foreign substances, and dead tissue cells
- move about by amoeboid motion

Front 70

Pinocytosis

Back 70

- "cell drinking"
- also called fluid-phase endocytosis
- infolding plasma membrane surrounds a very small volume of extracellular fluid containing dissolved molecules

Front 71

Receptor-mediated Endocytosis

Back 71

- the main mechanism for the specific endocytosis and transcytosis of most macromolecules by body cells
- receptors are plasma membrane proteins that bind only certain substances

Front 72

Exocytosis

Back 72

- process of E is typically stimulated by a cell-surface signal such as binding of a hormone to a membrane receptor or a change in membrane voltage, accounts for hormone secretion, neurotransmitter release, mucus secretion, and ejection of wastes
- substance to be removed from the cell is first enclosed in a protein-coated membranous sac, called a vesicle.
- vesicle migrates to the plasma membrane, fuses with it, and then ruptures, spilling the sac contents out of the cell

Front 73

Membrane Potential

Back 73

voltage across the membrane

Front 74

Plasma Membrane

Back 74

membrane made of a double layer of lipids (phospholipids, cholesterol, etc.) within which proteins are embedded. Proteins may extend entirely thru the lipid bilayer or protrude on only one face. Externally facing proteins and some lipids have attached sugar groups.

Front 75

Plasma Membrane Functions

Back 75

serves as an external cell barrier, and acts in transport of substances into or out of the cell. Maintains a resting potential that is essential for functioning of excitable cells. Externally facing proteins act as receptors (for hormones, neurotransmitters, and so on) and in cell-to-cell recognition

Front 76

Cytoplasm

Back 76

cellular region between the nuclear and plasma membranes. Consists of fluid cytosol containing dissolved solutes, organelles (the metabolic machinery of the cytoplasm), and inclusions (stored nutrients, secretory products, pigment granules)

Front 77

Cytoplasmic Organelles

Back 77

mitochondria
ribosomes
rough endoplasmic reticulum
smooth endoplasmic reticulum
golgi apparatus
lysosomes
peroxisomes
microtubules
intermediate filaments
centrioles

Front 78

Mitochondria

Back 78

- rodlike, double-membrane structures; inner member folded into projections called cristae
- contain own DNA, RNA and ribosomes and can reproduce themselves.

Front 79

Mitochondria Functions

Back 79

site of ATP synthesis
powerhouse of the cell

Front 80

Ribosomes

Back 80

- dense particles consisting of two subunits, each composed of ribosomal RNA and protein. Free or attached to rough endoplasmic reticulum.
- free ribosomes make proteins that function in the cytosol and imported into mitochondria; membrane-bound ribosomes synthesize proteins for cell membranes or for export.

Front 81

Ribosome Functions

Back 81

the sites of protein synthesis

Front 82

Rough Endoplasmic Reticulum

Back 82

- membrane system enclosing a cavity, the cisterna, and coiling thru the cytoplasm; ER is continuous with the nuclear membrane.
- externally studded with ribosomes

Front 83

Rough ER Functions

Back 83

- sugar groups are attached to proteins within the cisternae
- proteins are bound in vesicles for transport to the Golgi apparatus and other sides
- external face synthesizes phospholipids

Front 84

Smooth ER

Back 84

- membranous system of sacs and tubules
- free of ribosomes

Front 85

Smooth ER Functions

Back 85

- site of lipid and steroid (cholesterol) synthesis, lipid metabolism,a nd drug detoxification

Front 86

Golgi Apparatus

Back 86

- a stack of smooth membrane saces and associated vesicles close to the nucleus

Front 87

Golgi Apparatus Functions

Back 87

- packages, modifies, and segregates proteins for secretion from the cell, inclusion in lysosomes, and incorporation into the plasma membrane

Front 88

Lysosomes

Back 88

- membranous sacs containing acid hydrolases

Front 89

Lysosomes Functions

Back 89

sites of intracellular digestion

Front 90

Peroxisomes

Back 90

- membranous sacs of oxidase enzymes

Front 91

Peroxisomes Functions

Back 91

- the enzymes detoxify a number of toxic substances
- the most imp enzyme, catalase, breaks down hydrogen peroxide

Front 92

Microtubules

Back 92

- cylindrical structures made of tubulin proteins

Front 93

Microtubules Functions

Back 93

- support the cell and give it shape
- involved in intracellular and cellular movements
- form centrioles and cilia and flagella, if present

Front 94

Microfilaments

Back 94

- fine filaments composed of the protein actin

Front 95

Microfilaments Functions

Back 95

- involved in muscle contraction and other types of intracellular movement, help form the cell's cytoskeleton

Front 96

Intermediate Filaments

Back 96

- protein fibers; composition varies

Front 97

Intermediate Filaments Functions

Back 97

- the stable cytoskeletal elements
- resist mechanical forces acting on the cell

Front 98

Centrioles

Back 98

- paired cylindrical bodies, each composed of nine triplets of microtubules

Front 99

Centrioles Functions

Back 99

- organize a microtubule network during mitosis to form the spindle and asters. Form the basis of cilia and flagella.

Front 100

Inclusions

Back 100

- varied
- includes stored nutrients such as lipid droplets and glycogen granules, protein crystals, pigment granules

Front 101

Inclusions Functions

Back 101

- storage for nutrients, wastes, and cell products

Front 102

Cellular Extensions

Back 102

cilia
flagella
microvilli

Front 103

Cilia

Back 103

- short cell-surface projections; each cilium composed of nine pairs of microtubules surrounding a central pair

Front 104

Cilia Functions

Back 104

- coordinated movement creates a unidirectional current that propels substances across cell surfaces

Front 105

Flagella

Back 105

- like a cilium, but longer; only example in humans is sperm tail

Front 106

Flagella Functions

Back 106

- propel the cell

Front 107

Microvilli

Back 107

- tubular extensions of the plasma membrane; contain a bundle of actin filaments

Front 108

Microvilli Functionis

Back 108

- increase surface area for absorption

Front 109

Nucleus - What is Found?

Back 109

nuclear envelope
nucleoli
chromatin

Front 110

Nucleus

Back 110

- largest organelle
- surrounded by the nuclear envelope
- contains fluid nucleoplasm, nucleoli and chromatin

Front 111

Nucleus Functions

Back 111

- control center of the cell
- responsible for transmitting genetic information and providing the instructions for protein synthesis

Front 112

Nuclear Envelope

Back 112

- double-membrane structure pierced by pores
- outer membrane continuous with the ER

Front 113

Nuclear Envelope Functions

Back 113

- separates the nucleoplasm from the cytoplasm and regulates passage of substances to and from the nucleus

Front 114

Nucleoli

Back 114

- dense, spherical (non-membrane bounded) bodies, composed of ribosomal RNA and proteins

Front 115

Nucleoli Functions

Back 115

- site of ribosome manufacture

Front 116

Chromatin

Back 116

- granular, threadlike material composed of DNA and histone proteins

Front 117

Chromatin Functions

Back 117

- DNA constitutes the genes

Front 118

Cytoskeleton (87)

Back 118

- cell skeleton: an elaborate network of rods running thru the cytosol
- supports cellular structure and provides the machinery to generate various cell movements.

Front 119

3 Types of Rods in Cytoskeleton

Back 119

In order of increasing size:
- microfilaments
- intermediate filaments
- microtubules
None are membrane covered

Front 120

Centrosome

Back 120

- cell center
- acts as a microtubule organizing center
- contans paired centrioles

Front 121

Centrioles

Back 121

- small, barrel-shaped organelles oriented at right angles to each other
- the centrosome matrix is best known for generating microtubules and organizing the mitotic spindle in cell division

Front 122

Cell Life Cycle

Back 122

series of changes a cell goes through from the time it is formed until it reproduces.

Front 123

Two Major Periods of Cell Cycle

Back 123

1. Interphase - cell grows and carries on its usual activities.
2. Cell Division or Mitotic Phase - divides into two cells.

Front 124

Cell Division - Mitosis

Back 124

see pps. 97-99: 4 phases:
1. prophase
2. metaphase
3. anaphase
4. telophase

Front 125

Protein Synthesis

Back 125

pps. 100-107

Front 126

Developmental Aspects of Cells

Back 126

pps. 108-109