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Intro to anatomy and physiology > Chapter 3 Cells > Flashcards

Chapter 3 Cells Flashcards

1
Q

what is a cell

A

the smallest unit of life
A cell continually carries out metabolic activities essential for life, as well as specialized functions, and adapts to changing conditions
Cells interact to form tissues, organs, and organ systems
The human body consists of 30 trillion cells that vary considerably in shape and size, yet have much in common

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2
Q

Differences in cell shape make different functions possible

A

Nerve cells have long extensions that conduct electrical impulses, while epithelial cells in the mouth are flat, thin, and densely packed, to provide a protective barrier

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3
Q

composite cell

A

includes many different cell structures; most cells contain most of these structures, but no cell contains all of them

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4
Q

A cell consists of three main parts:

A

Nucleus: Contains DNA (genetic material) and directs cell’s activities
Cytoplasm: Organelles and fluids that make up the majority of the cell; between nucleus and cell membrane
Cell membrane: Boundary that encloses the cell

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5
Q

organelles

A

Within the cytoplasm are specialized organelles (little organs) that perform specific functions for the cell
Organelles are suspended in a fluid called the cytosol

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6
Q

Cell membrane is also called plasma membrane

A

Boundary that contains the cell contents
Regulates the movement of substances in and out of the cell
Participates in signal transduction, a method of communication with other cells
Helps cells adhere to other cells

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7
Q

General Characteristics:

of cell membrane

A

Extremely thin, flexible, and elastic
Selectively permeable – regulates entry/exit of substances
Has complex surface features, with adaptations to increase surface area

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8
Q

Cell Membrane Structure: Lipids

A

Composed mainly of lipids and proteins, and some carbohydrates
The basic framework of the cell membrane consists of a double layer (bilayer) of phospholipids, with fatty acid tails turned inward and the water-soluble heads facing the surfaces
The phospholipids can move, forming a stable fluid film
Lipid-soluble molecules (respiratory gases, steroid hormones) can pass through the phospholipid portion of the membrane
Cell membrane is impermeable to water-soluble molecules
Embedded cholesterol molecules stabilize the membrane, and help make it less permeable to water-soluble substances

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9
Q

Cell Membrane Structure: Proteins

A

Many types of proteins are found in the cell membrane
Proteins are classified by their relationship to the phospholipid bilayer:
Integral: span width of bilayer; may protrude on 1 or both sides
Transmembrane: integral proteins that protrude on both sides
Peripheral: associate with one side of bilayer
Membrane proteins vary in shape: rodlike, globular, fibrous
Membrane proteins vary in function:
Some proteins function as receptors or growth factors on the cell surface, starting signal transduction
Other proteins transport ions or molecules across cell membrane, such as ion channels

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10
Q

Cell Membrane structure: proteins

Cell Identification

A

Other proteins have carbohydrates attached (glycoproteins) and are used for cell identification; this helps identify cells as “self,” protecting them from attack by the immune system

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11
Q

cytoskeleton

A

Proteins that protrude into the cell will anchor supportive rods and tubules, forming a cytoskeleton

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12
Q

cellular adhesion molecules

A

Membrane proteins called cellular adhesion molecules (CAMs) help determine a cell’s interactions with other cells

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13
Q

Cytoplasm

A

The cytoplasm makes up most of cell volume, and consists of a clear liquid (cytosol), a supportive cytoskeleton, and networks of membranes and organelles

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14
Q

Organelles:

Ribosomes

A

Tiny, spherical structures composed of RNA and protein
Provide structural support and enzyme activity for protein synthesis
Not membranous
Found in cytoplasm or bound to rough endoplasmic reticulum

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15
Q 
Organelles:
Endoplasmic reticulum (ER):
A

Made up of membrane-bound flattened sacs and vesicles
Functions as a transport network throughout the cell
2 types of ER:
Rough ER: contains ribosomes, and functions in protein synthesis
Smooth ER: does not contain ribosomes, and functions in lipid synthesis, absorption of fats, and metabolism of drugs

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16
Q

Organelles:

Vesicles

A

Membranous sacs

Store or transport substances within or between cells

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17
Q

Golgi apparatus:

A

Composed of flattened, membranous sacs
Refines, packages, and transports proteins formed in the rough ER
Vesicles formed in the ER travel to the Golgi apparatus, which may modify their contents by adding sugar molecules to the proteins, to stabilize their structure or to enable folding.
A new vesicle pinches off the Golgi apparatus and may then move to the cell membrane to secrete its contents to the outside (exocytosis)

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18
Q

Mitochondria

A

Elongated fluid-filled sacs
The inner membrane of the mitochondrion is folded into cristae, which increase surface area
House many chemical reactions that extract energy from nutrients (cellular respiration) and produce ATP
Store the energy in the chemical bonds of ATP
Very active cells contain thousands of mitochondria
Mitochondria have their own DNA and reproduce by dividing

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19
Q

Lysosomes:

A

Membranous sacs
Formed by budding off Golgi apparatus
Contain enzymes that break down nutrients, ingested materials, debris, worn out cell parts, cholesterol (in some cells), toxins, and drugs

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20
Q

Peroxisomes

A

Also membranous sacs
Contain a different set of enzymes than lysosomes
Their enzymes function in the breakdown of fatty acids and hydrogen peroxide, and detoxification of alcohol

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21
Q

cytoskeleton.

A

In the cytoplasm, there are several structures, which are not organelles, but rather part of the cytoskeleton.

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22
Q

Microfilaments and microtubules

A

Microfilaments and microtubules are thin, threadlike structures that serve as the cytoskeleton of the cell:

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23
Q

Microfilaments

A

made of the protein actin; cause various cellular movements; group together to form myofibrils in muscle

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24
Q

Microtubules

A

made of the globular protein tubulin, are attached in a spiral to form a long tube; important in cell division

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25
Intermediate fibers
made of different proteins in different cells, are abundant in skin cells and neurons
26
Other Cellular Structures: Centrosome
A non-membranous structure, made up of two hollow cylinders called centrioles, that function in the distribution of chromosomes during cell division; made of nine groups of three microtubules
27
Other Cellular Structures: Cilia
Motile extensions from the cell; short cilia are abundant on the free surfaces of certain epithelial cells and move in a wave (respiratory linings, for example) to move fluids or whole cells
28
Other Cellular Structures: Flagella
Another type of motile extension from cell; usually a cell only has 1 flagellum; the only human cell with a flagellum is a sperm cell; the flagellum allow the sperm to swim toward the egg cell
29
nucleus
The nucleus contains genetic material, DNA, which controls cell activities
30
nuclear envelope
The fairly large nucleus is surrounded by a double-layered nuclear envelope. Containing relatively large nuclear pores that allow the passage of certain substances
31
nucleoplasm
Contains a fluid called nucleoplasm
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The nucleolus
The nucleolus is a small, dense body in the nucleus, composed of RNA and protein; it is the site of ribosome production
33
Chromatin
Chromatin consists of loosely coiled fibers of protein and DNA found in the nucleus
34
chromosomes
Condensed DNA is referred to as chromosomes; this form of DNA is present during cell division
35
selective barrier
The cell membrane is a selective barrier, which controls which substances pass through it
36
Movements Into and Out of the Cell: | passive
Mechanisms of movement across the membrane may be passive, requiring no energy from the cell,
37
active
requiring cellular energy
38
passive transport mechanisms:
Examples of passive transport mechanisms: diffusion, facilitated diffusion, osmosis, and filtration
39
active transport mechanisms
Examples of active transport mechanisms: active transport, endocytosis, and exocytosis
40
Passive mechanisms: | Diffusion
Characteristics: Molecules move through the phospholipid bilayer from regions of higher concentration to regions of lower concentration. Source of Energy: Molecular motion Example: Exchange of oxygen and carbon dioxide in the lungs
41
Facilitated diffusion
Ions move through channels, or molecules move by carrier proteins, across the membrane from a region of higher concentration toward one of lower concentration. Molecular motion Movement of glucose through a cell membrane
42
Osmosis
Water molecules move through a selectively permeable membrane toward the solution with more impermeant solute (greater osmotic pressure). Molecular motion Distilled water entering a cell
43
Filtration
Smaller molecules are forced through porous membranes from regions of higher pressure to regions of lower pressure. Hydrostatic pressure Molecules leaving blood capillaries
44
Active mechanisms: | Active transport
Carrier molecules transport molecules or ions through membranes from regions of lower concentration toward regions of higher concentration. Cellular energy (ATP) Movement of various ions, sugars, and amino acids through membranes
45
Endocytosis: Pinocytosis
Membrane engulfs droplets containing dissolved molecules from surroundings. Cellular energy Uptake of water and solutes by all body cells
46
Phagocytosis
Membrane engulfs particles from surroundings. cellular energy White blood cell engulfing bacterial cell
47
Receptor-mediated endocytosis
Membrane engulfs selected molecules combined with receptor proteins Cellular energy Cell removing cholesterol molecules from its surroundings
48
Exocytosis
Vesicle fuses with membrane and releases contents outside of the cell. Cellular energy Neurotransmitter release
49
Cell Cycle: | Main phases
interphase, mitosis, and cytokinesis (division of the cytoplasm)
50
checkpoints
Whether the cell cycle progresses at certain times, called checkpoints, is controlled by interaction of special proteins
51
restriction checkpoint
A restriction checkpoint determines fate of cell: to continue cell cycle and divide, to enter a non-dividing stage as a specialized cell, or to die
52
Interphase
Phase of the cell cycle, before cell division begins, in which the cell grows and synthesizes new molecules, membranes, DNA, and organelles This is a time of great synthetic activity, rather than a time of rest
53
Cell Division: | 2 types of cell division
Meiosis: Only used for sperm & egg cell production Ensures that mature gametes have ½ the normal number of chromosomes as normal body cells Cell Division (Mitosis + Cytokinesis): More common type of cell division, used to increase number of cells Mitosis is division of the nucleus Cytokinesis is the division of the cytoplasm Regulated carefully, so that each of two daughter cells receives an exact copy of the original cell's genetic material (DNA)
54
Mitosis
Mitosis is described as a series of four stages, but the process is actually continuous:
55
Prophase
The first stage of mitosis DNA condenses into visible chromosomes (each consisting of two chromatids connected by a centromere) Centrioles migrate to opposite poles Microtubules of the cytoskeleton organize into spindle fibers The nuclear membrane and nucleolus disassemble
56
Metaphase
Spindle fibers attach to centromeres on the chromosomes | Chromosomes randomly align midway between centrioles
57
Anaphase
Sister chromatids are pulled apart Chromatids are now considered individual chromosomes Chromatids are pulled along the shortening spindle fibers toward opposite centrioles
58
Telophase
The final stage of mitosis Begins when the chromosomes have completed their migrations to opposite sides A nuclear envelope and nucleolus assemble for each forming cell The spindle fibers disassemble The chromosomes unwind, and take back their chromatin form
59
Cytokinesis (Cytoplasmic Division)
Begins during anaphase of mitosis, when cell membrane constricts around middle of cell
60
cleavage furrow
Constriction, called the cleavage furrow, continues throughout telophase; it eventually pinches the daughter cells apart
61
Contractile ring
Contractile ring of microfilaments attaches to inside of cell membrane; it divides the cytoplasm The two daughter cells may have slightly different amounts of cytoplasm and organelles, but they share identical genetic information
62
Cell Differentiation: | Differentiation
The process by which a cell develops/specializes into a specific type of cell with specialized functions Humans have >290 types of differentiated cells Cell differentiation allows cells to specialize by using different parts of the complete genome that is present in each cell; in each type of cell, some genes are “turned on” while others are “turned off”
63
Stem cells
retain the ability to divide without specialization; their presence in the cell allows for continuous growth and renewal
64
Progenitor cells
are daughters of stem cells that are partially specialized. Stem and progenitor cells allow cells to retain the ability to produce cells that will become the differentiated cells in each area of the body
65
Cell Death
Not all cells divide or differentiate; some die
66
Apoptosis
is a form of programmed cell death that is a normal part of development, rather than from injury or disease Removes overgrown tissues, damaged cells, extra cells in fetus Steps of apoptosis: Cell becomes rounded and bulges Nuclear membrane breaks down Chromatin condenses and enzymes cut up the chromosomes Cell shatters into many membrane-bound pieces Scavenger cells engulf and destroy the fragments

Intro to anatomy and physiology (4 decks)

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