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AP Biology > The Cell > Flashcards

The Cell Flashcards

1
Q

Theory of endosymbiosis

A

Eukaryotic cells emerged when mitochondria and choloroplasts, once free-living prokaryotes, took up permanent residence inside other large cells

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2
Q

Eukaryotic Cell

A

● Internal membrances that compartmentalized the cell so that complex chemical reactions can be carried out efficiently in separate regions of a cell
● Nucleus bound by a double membrane
● All cells of the human body are eukaryotic cells
● DNA wrapped with histone proteins into chromosomes
● Ribosomes are largerr
● Metabolism is aerobic
● Cytoskeleton present
● Mainly multicellular with differentiation of cell types
● Cells are larger

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3
Q

Cell thoery

A

● All organisms are composed of cells
● All celss arise from preexisting cells
● Cell is the basic component of life

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4
Q

Prokaryotic Cell

A 
● Simple cells containing no nuclei or other internal membrances
● All bacteria are prokayotic cells
● No nucleus -- they have a nucleoid region, which is a non-membrane-bound region where the chromosome is located
● Circular, naked DNA
● Ribosomes are very small
● Metabolism is anaerobic or aerobic
● Cytoskeleton absent
● Mainly unicellular
● Cells are very small
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5
Q

Nucleolus

A

● Inside the nucleus
● Where ribosomal RNA (rRNA) is synthesized according to instructions from the DNA
- Large and small subunits of ribosomes are also assembled there
● Combines proteins imported from the cytoplasm with rRNA made in the nucleolus
● Nucleoli are not membrane-bound structures but are actually a tangle of chromatin and unfinished riosomal precursors

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6
Q

Ribosomes

A

● Protein factories
● Can be found free in the cytoplasm or bound to the endoplasmic reticulum
● Free ribosomes are associated with protein produced for the cell’s own use, while ribosomes attached to the ER are meant for export out of the cell

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7
Q

Peroxisomes

A

● Found in both plant and animal cells
● Contain catalase, which converts hydrogen peroxide (H2O2), a waste product of respiration in the cell, into water with the release of oxygen atoms
● They also detoxify alcohol in liver cells

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8
Q

Endomembrane System

A

● Regulates protein traffic and performs metabolic functions in cells
● Includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, vacuoles, and plasma membrane

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9
Q

Nucleus

A

● Contains chromosomes which are wrapped with special proteins into a chromatin network
● Surrounded by nuclear envelope

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10
Q

Nuclear envelope

A

● A selectively permeable membrane that separates the contents of the nucleus from the cyoplasm
● Contains pores to allow for the transport of molecules, like messenger RNA (mRNA), which are too large to diffuse directly through the envelope

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11
Q

Endoplasmic Reticulum

A

Membranous system of channels and flattened sacs that traverse the cytoplasm and account for more than half the total membranes in a eukaryotic cell

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12
Q

Rough Endoplasmic Reticulum

A

Studded with ribosomes and produces proteims

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13
Q

Smooth Endoplasmic Reticulum

A

● Assists in the synthesis of steroid hormones, like sex hormones, and of other lipids
● Stores Ca++ ions in muscle cells to facilitate normal muscle contractions
● Detoxifies drugs and poisons from the body

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14
Q

Golgi Apparatus

A

● Lies near the nucleus and consists of flattened membranous sacs stacked next to one another and surroundd by vesicles
● They process and package substances produced inthe rough ER and secrete hte substances to other parts of the cell or to the cell surface for export

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15
Q

Lysosomes

A

● Sacs of hydrolytic enzymes surrounded by a single membrane
● Principle site of intracellular digestion
● With the help of the lysosome, the cell continually performs autophagy
● Generally not found in plant cells

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16
Q

Hydrolytic enzymes

A

Digestive enzymes

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17
Q

Autophagy

A

The process of breaking down and recycling cell parts in a cell

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18
Q

Apoptosis

A

Programmed destruction of cells

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19
Q

Mitochondria

A

● Site of cellular respiration
● Have an outer double membrane and an inner series of membranes called cristae
● Contain their own DNA
● Constantly divide and fuse with each other in order to exchange DNA and compensate for one another’s defects

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20
Q

Vacuoles

A

● Membrane-bound structures used for storage
● Large vesicles derived from the ER and Glogi apparatus
● Mature plant cells generally have a single large central vacuole
● Many freshwater protists have contractile vacuoles

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21
Q

Contractile vacuoles

A

● Present in many freshwater protists

● Pump out excess water

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22
Q

Food vacuoles

A

Formed by the phagocytosis of foreign material

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23
Q

Chloroplast

A

● Contain the green pigment chlorophyll that abosrobs light energy and synthesizes sugar
● Found in plants and algae
● Double outer membrane and another inner membrane system called thylakoids

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24
Q

Cytoskeleton

A

● Complex mesh of protein filaments that extends throughout the cytoplasm
● Includes microtubules and microfilamnets

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25
Microtubules
Hollow tubes made of the protein tubulin that make up the cilia, flagella, and spindle fibers
26
Cilia / Flagella
● Move cells from one place to another | ● Consists of 9 pairs of microtubules organized around 2 singlest microtubules
27
Flagella
● Move cells from one place to another ● Consists of 9 pairs of microtubules organized around 2 singlest microtubules ● When present in prokaryotes, they are not made of microtubules
28
Spindle fibers
Help separate chromosomes during mitosis and meiosis and consist of microtubules organized into 9 triplets with no microtubules in the centre
29
Microfilaments
● Assembled from actin filaments | ● Help support the shape of the cell
30
Centrioles, centrosomes, and the Microtubule Organizing Centers
● Nonmembranous structures that lie outside the nuclear membranes ● Organize spindle fibers and give rise to the spindle apparatus required for cell division ● Two centrioles oriented at right angles to each other make up one centrosome ● Plant cells lack centrosomes, but have MTOCs
31
Cell wall
● One cell structure not found in animal cells ● Plants and algae have cell walls made of cellulose ● Cell walls of fungi are usually made of chitin
32
Chitin
Prokaryotes conssit of other polysaccharides and complex polymers
33
Primary cell wall
Immediately outside the plasma membrane
34
Second cell wall
Underneath the primary cell wall
35
Middle lamella
The thin gluey layer formed between the two new cells when a plant cell divides
36
Plasma Membrane
● Selectively permeable membrane that regulates the steady traffic that enters and leaves the cell ● Eukaryotic membrane consists of a phospholipid bilayer with proteins dispersed throughout the layer
37
Fluid mosaid model
S. J. Singer's description of the cell membrane
38
Integral proteins
Have nonpolar regions that completely span the hydrophobic interior of the cell membrane
39
Peripheral proteins
Loosely bound to hte surface of the cell membrane
40
Cholesterol molecules
Embedded in the interior of the bilayer to stabilize the cell membrane
41
Glycolipids
● Carbohydrates covalently bonded to lipids ● Extend from the external surface of the plasma membrane ● Signal molecules that distinguish one cell type from another
42
Glycoproteins
● Carbohydrates covalently bounded to protein ● Extend from the external surface of the plasma membrane ● Signal molecules that distinguish one cell type from another - Glycoproteins on the surface of red blood cells are responsible fo ABO and Rh blood types
43
Transport
● Movement of substances into and out of a cell | ● Can be either active or passive
44
Active transport
● Requires energy (ATP) ● Movement of molecules gainst a gradient ● Pumps or carriers, contractile vacuole, exocytosis, pinocytosis, phagocytosis, receptor-mediated endocytosis
45
Passive transport
● Requires no energy ● Movement of molecules down a concentration gradient from a region of high concentration to a region of low concentration until equilibrium is reached ● Examples are diffusion and osmosis
46
Diffusion
● Two types -- simple and facilitated | ● Random movement of molecules or other particles from a higher concentration to a lower concentration
47
Simple difusion
● Does not involve protein channels ● Examples if found in the glomerulus of hte human kidney, where solutes dissolved in the blood diffuse into Bowman's capsule of the nephron
48
Facilitated diffusion
Requires a hydrophilic protein channel that will passively transport specific substances across the membrane
49
Countercurrent exchange
● Special case of simple diffusion | ● The flow of adjacent fluids in opposite directions that maximizes the rate of simples diffusion
50
Osmosis
Specific type of diffusion of water across a membrane
51
Solvent
The substance that does the dissolving
52
Solute
The substance that dissolves
53
Hypertonic
Having greater concentration of solute than another solution
54
Hypotonic
Having lesser concentration of solute than another solution
55
Isotonic
Two solutions containing equal concentration of solutes
56
Osmotic potential
The tendency of water to move across a permeable membrane into a solution
57
Water potential
● psi ● Results from two factors -- solute concentration and pressure ● Water potential for pure water is zero ● the addition of solutes lowers water potential to a value less than zero ● Water will move across a membrane from the solution with the higher water potential to the solution with the lower water potential
58
Turgid
The swelling of the plant cells when water flow into the cell
59
Plasmolysis
Cell shrinking
60
Aquaporins
● Special water channel proteins found in certain cells that facilitate the diffusion of massive amounts of water across a cell membrane ● They do not affect the water potential gradient or the idrection of water flowing ● They affect the rate at which water diffuses down its gradient
61
Gated channels
Open and close in response to variables such as turgor pressure of a cell
62
Pumps/Carriers
Carry particles across the membrane by active transport
63
Sodium-potassium pump
Pumps Na+ and K+ ions across a nerve cell membrane to return the nerve to its resting state
64
Electron transport chain
Consists of proteins htat pump protons across hte cristae membrane
65
Contractile vacuoles
Pumps out excess water that has diffused inward because the cell lives in a hypotonic environment in freshwater Protista
66
Exocytosis
Occurs as vesicles release neurotransmitters into a synapse in nerve cells
67
Pinocytosis
● Cell drinking ● Uptake of large, dissolved, particles ● The plasma membrane invaginates around the particles and encloses them in a vesicle
68
Phagocytosis
● Engulfing of large particles or small cells by pseudopods | ● Cell membrane wraps around the particle and encloses it into a vacuole
69
Receptor-mediated endocytosis
● Enables a cell to take up large quantities of very specific substances ● A process by which extracellular substances bind to receptors on the cell membrane ● Once the ligand binds to the receptors, endocytosis begins ● The receptors, carrying the ligand, migrate and cluster along the membrane, turn inward, and become a coated vesicle that enters the cell ● This is the way cells take in cholesterol from the blood
70
Ligand
● The general name for any molecule that binds specifically to a receptor site of another molecule ● Never enters the cell
71
Bulk flow
● Overall movement of a fluid in one direction in an organism ● always from source to sink
72
Quorum sensing
● Simple bacterial cells respond to changes in population density ●Vibrio fisheri (bacteria) produces the bioluminsescne tsubstance luciferin that makes the bacteria glow - By using quorum sensing, V. fischeri produces luciferin only when its population is large enough that its bioluminescence can really be noticed
73
Gap junctions
● Permit the passage of materials directly from the cytoplasm of one cell to the cytoplasm of an adjacent cell ● In the muscle tissue of the heart, the flow of ions through the gap junctions coordinates the contractions of the cardiac cells
74
Plasmodesmata
Connect one plant cell to the next
75
Paracrine signaling
Release of local signals from one cell to nearby cells
76
Synaptic signaling
A neuron releases neurotransmitter into a synapse to stimulate an adjacent neuron to fire or muscle to contract
77
Long distance signaling
● Characteristic of the endocrine system in which hormones released by endocrine glands circulate in the blood to reach target organs or structures ● Three stages -- reception, transduction and response
78
Cell surface receptors
● Span the entire thickness of the membrane ● Are in contact with both the extracellular environment and hte cytoplasm ● ion channel receptors, G-protein-coupled receptors, protein kinase receptors
79
Hydrophilic signaling molecules
● Cannot diffuse through the membrane ● Bind to the part of the recptor on the cell surface that changes the shape on the cytoplasmic side of the same receptor
80
Second messenger
● Carried the signal from the hydrophilic signaling molecules ● The most common was cyclic AMP
81
Inon-channel receptors
● Involve an allosteric recepor that opens and husts a gate in a membrane allowing an influx of ions ● Acetylcholine receptor located in the plasma membranes of skeletal muscle cells is an example - Neurotransmitter acetylcholine binds to the allosteric receptor, which undergoes a conformational change that causes the opening of the channel
82
G-protein coupled receptors (GPCR)
● Span the entire cell membrane ● When a ligand binds to the extracellular domain of the receptor, it changes the conformation of the cytoplasmic side of the receptor - This then causes the G-protein in the alpha sub-unit to bind to and activate the enzyme adenylyl cyclase, activates mobile G protein to bind to GTP, which catalyzes the conversion of ATP to cAMP (second messenger) ● Cyclic-AMP activates other molecules inside a cell, which leads to a cellular response
83
Receptor Throsine Kinases (RTKs)
● Characterized by having enzymatic activity ● Spans the entire membrane and the part of the receptor that extends into the cytoplasm functions as a tyrosine kinases, an enzyme that catalyzes the transfer of phosphate groups from ATP to the amino acid tyrosine ● Before the ligand binds, the receptors exist as individual units - After binding, the individual units aggregate and activate the tyrosine kinase region which bonds to ATP ● Once fully activated, the receptor activates specific relay proteins which each lead to a cellular response
84
Hydrophobic chemical messengers
● Readily diffuse into the cell and switch a gene on or off in the nucleus ● Include steroids, thyroid hormones, Nitric oxide, bisphenol A (estrogen disruptor)
85
Transduction
● Once activated, the receptor converts a molecular signal into a cell response ● Often it requires a sequence of changes in a series of different molecules -- a signal transduction pathway
86
Signal transduction pathway
● Multi-step process in which a small number of extracellular signal molecules produce a major cellular response, a cascade effect ● It provides more oppotunities for coordination and regulation ● Exists in both yeast and animal cells and in bacteria and plants
87
Response
Transduction lead to a multitude of responses, either in the cytoplasm or in the nucleus
88
What are some characteristics that all cells share?
● They are all enclosed by a protective and selective barrier called a plasma membrance ● They all contain a semifluid substnace called cytosol in which subcellular components are suspended ● All cells contain ribosomes and genetic material in the form of DNA
89
What are cells small?
● The surface area of the plasma membrane limits the amount of material that can enter and leave the call -- diffusion rate ● Volume is proportional to how much energy the cell needs to survive ● SA : V = as big as possible ● When a cell grow larger, the SA does not keep up with the increase in volume ● Complex organisms consist of millionso f tiny cells carrying out different fucntions
90
Why don't cells look alike?
● Function dictates form and vice versa ● Different cell types have different overall appearances suited for each different function - The nerve cell, whose purpose is to send electrical impulses, is long and spindly - Fat cells are rounded, large, and istended - Cells that make up a tough peach pit resemble square building blocks
91
What are the roles of the cytoskeleton?
● Maintains the cell's shape ● Controls the position of organelles within the cell by anchoring them to the plasma membrane ● Involved with the flow of the cytoplasms, known as cytoplasmic streaming ● Anchors the cell in place by interacting with extracellular elements
92
What do microfilaments enable?
● Animal cells to form a cleavage furrow during cell division ● Ameoba to move by sending out pseudopods ● Skeletal muscle to contract as they slide along myosin filaments
93
What are the functions of proteins in the plasma membrane?
● Transport -- molecules, electrons, and ions are carried through channels, pumps, carriers, and electron trasnport chian, which manufacture ATP ● Enzymatic activity -- one membrane-bound enzyme is adenylate cyclase, which synthesizes cyclic AMP (cAMP) from ATP ● Signal transduction -- binding sites on protein receptors fit chemical messengers like hormones. Proteins changes shape and relays the message to the inside of the cell ● Cell to cell recognition -- some glycoproteins serve as identification flags htat are recognized by other cells ● Cell to cell attachments -- desmosomes, gap junctions, and tight junctions ● Attachment to the cytoskeleton and extracellular matrix -- helps maintain cell shape and stabilizes hte location of certain membrane proteins
94
What are some ways of communication between cells?
● Simple bacterial cells secrete molecules that enable them to respond to changes in their population density by a phenomenon called quorm sensing ● Multicellular organisms communicated through direct contact, gap junctions, paracrine signaling, long-distance signalling
95
What are the two examples of direct contact?
● Gap junctions in animal cells | ● Plasmodesmata in plant cells
96
How do small, nonpolar ligands bind to receptors?
They diffuse directly through the plasma membrane and bind to an intracellular receptor in the cytoplasm
97
Why is bisphenol A called estrogen disruptor?
● It mimics hormones like estrogen and sets up the estrogen signal pathway ● Believed to be responsible for problems in fetal development in humans
98
What are the four things to remember about signal transduction pathways?
● They are characterized by a signal, a transduction, and a response ● They are highly specific and regulated ● One signal molecule can cause a cascade effect, releasing thousands of molecules inside a cell ● These pathways evolved milions of years ago in a common ancestor

AP Biology (15 decks)

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