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BIOL 235 > Chapter 3: Cellular Level > Flashcards

Chapter 3: Cellular Level Flashcards

1
Q

Cells (3 main parts)

A

The basic, living, structural and functional units of the body
1. Plasma membrane
2. Cytoplasm
3. Nucleus

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2
Q

Plasma membrane

A

The cell’s flexible outer surface, separating the cell’s internal and external environments (selective barrier + communicator)

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3
Q

Cytoplasm

A

All cellular contents between the plasma membrane and the nucleus made of 2 key components:
1. Cytosol = intracellular fluid (ICF)
2. Organelles

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4
Q

Nucleus

A

Organelle that houses most of a cell’s DNA

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5
Q

Fluid mosaic model

A

Describes the plasma membrane as a continually moving sea of fluid lipids that contain a mosaic of proteins

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6
Q

3 types of lipid molecules in the plasma membrane

A
  1. Phospholipids = 75%
  2. Cholesterol = 20%
  3. Glycolipids = 5%
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7
Q

Phospholipids

A

Amphipathic molecules with a polar (hydrophilic) head and 2 non-polar (hydrophobic) tails

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8
Q

4 membrane proteins

A
  1. Integral proteins
  2. Transmembrane proteins
  3. Peripheral proteins
  4. Glycocalyx
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9
Q

Integral Membrane Proteins

A

Extend into or through the lipid bilayer and firmly embedded in it (amphipathic)

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10
Q

Transmembrane proteins

A

Span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid

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11
Q

Peripheral proteins

A

Not firmly embedded in the membrane + support the plasma membrane, anchor integral proteins and participate in moving materials / organelles within cells

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12
Q

Glycocalyx membrane proteins

A

A sugary coat made of the carbohydrate group of glycolipids and glycoproteins; varies from cell to cell and therefore acts as the molecular “signature” of cells for recognition

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13
Q

6 functions of membrane proteins

A
  1. Ion channels
  2. Carrier (transporters)
  3. Receptors
  4. Enzymes
  5. Linkers
  6. Cell-identity markers
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14
Q

What is meant by membrane fluidity

A

Membrane lipids and proteins easily rotate and move sideways in their half of the bilayer

Fluidity increases with double bonds & higher temperatures

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15
Q

Membrane selective permeability

A

The plasma membrane permits some substances to pass more readily than others b/c of the non-polar hydrophobic interior

The lipid biyler of the plasma membrane is:
- highly permeable to non-polar molecules (O2, CO2)
- Moderately permeable to polar, uncharged molecules (H2O)
- Impermeable to ions and large, uncharged polar molecules (glucose)

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16
Q

Transmembrane proteins

A

Act as channels and carriers to increase the plasma membrane’s permeability to ions and uncharged polar molecules that, unlike H2O and urea, cannot cross the lipid bilayer unassisted

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17
Q

Plasma membrane electrical gradient

A

The inner surface of the plasma membrane is MORE negatively charged and the outer surface is MORE positively charged

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18
Q

Electrochemical gradient of the plasma membrane

A

Combines influence of the concentration gradient and the electrical gradient to help move substances across the plasma membrane

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19
Q

Plasma membrane concentration gradient

A

A difference in the concentration of a chemical, such as inside and outside the plasma membrane

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20
Q

3 types of membrane transport

A
  1. Passive
  2. Active
  3. Vesciles
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21
Q

Passive membrane transport

A

Substances move down their concentration / electrical gradient to cross the membrane via diffusion, using only its own kinetic energy from particles that are moving

3 types:
1. Simple diffusion
2. Facilitated diffusion
3. Osmosis

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22
Q

Define active membrane transport and what are the 2 types

A

An active process requiring energy (usually ATP) to allow carrier proteins (transmembrane proteins) to move solutes across the plasma membrane against a concentration gradient / electrical gradient

2 types:
1. Primary active transport
2. Secondary active transport

Substances transported:
- Polar / charged solutes

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23
Q

What is membrane transport using vesicles (3 types)

A

An active process in which tiny spherical membrane sacs transport substance into or out of cells using ATP
1. Endocytosis: into the cell
2. Exocytosis: out of the cell
3. Transytosis: Both

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24
Q

What is simple diffusion

A

A passive process in which substances move freely through the lipid bilayer of the plasma membranes of cells without the help of membrane transport proteins

Substances transported:
- Nonpolar molecules: O2, CO2, fatty acids, steriods, fat-soluble vitamins
- Polar molecules: H2O, urea, alcohol

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25
Q

What is facilitated diffusion

A

A passive process in which polar/highly charged substances move through the lipid bilayer via one of two integral membrane proteins:
1. Channel-mediated facilitated diffusion
2. Carrier-mediated facilitated diffusion

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26
Q

Channel-mediated facilitated diffusion

A

A solute moves down its concentration gradient across the lipid bilayer through a membrane channel (e.g., K+ and Cl- or Na+ and Ca2+) at certain sites

Gated channels = when part of the channel protein acts as a plug, changing shape in one way to open the pore and in another way to close it

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27
Q

Carrier-mediated facilitated diffusion

A

A passive process in which a carrier (or transporter) moves a solute down its concentration gradient across the plasma membrane (e.g., glucose, fructose, vitamins)

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28
Q

Transport maximum

A

An upper limit on the number of carrier available in the plasma membrane to participate in carrier-mediated facilitated diffusion

Once all carrier are occupied the transport maximum is reached aka is fully saturated

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29
Q

What are the 3 steps of transporting glucose across the plasma membrane

A

Occurs via carrier-mediated facilitated diffusion
1. glucose binds to a specific type of carrier protein (glucose transporter - GluT) on the outside surface of the membrane
2. transporter undergoes a change in shape, glucose passes through the membrane
3. transporter releases glucose on the other side of the membrane

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30
Q

What are the 3 types of solutions created via osmosis

A
  1. Isotonic = any solution in which a cell maintains its normal shape and volume
  2. Hypotonic (grow) = a solution that has a lower concentration of solutes
  3. Hypertonic (shrink) = has a higher concentration of solutes
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31
Q

What is osmosis

A

A passive process by which water moves through a selectively permeable membrane from an area of lower solute concentration (i.e., higher water concentration) to an area of higher solute concentration (i.e., lower water concentration) via one of 2 methods:
1. Via simple diffusion
2. Via water channels + aquaporin integral membrane proteins

32
Q

Tonicity

A

A measure of a solution’s ability to change the volume of a cell by altering its water content

33
Q

Lysis

A

The rupture of other types of cells due to placement in a hypotonic solution

34
Q

What is primary active transport and what substances does it transport

A

Energy derived from hydrolysis of ATP changes the shape of a carrier protein, which “pumps” a substance across a plasma membrane against its con- concentration gradient

Substances transported:
- Na+, K+
- Ca2+, H+
- I-, Cl-
- Other ions

35
Q

What is secondary active transport and what substances does it transport

A

Coupled active transport of 2 substances across the plasma membrane using energy stored in a Na+ or H+ concentration gradient during primary active transport using anti ports and symports

  1. Antiporter: move Na+ (or H+) and another substance in opposite directions across the membrane
  2. Symporter: move Na+ (or H+ and another substance in the same direction across the membrane

Substances transported:
- Antiport: Ca2+, H+
- Symport: glucose, amino acids

36
Q

What are the 4 steps of the sodium potassium pump

A

Objective: maintain a low concentration of Na+ and a high concentration of K+ in the cytosol

  1. 3 Na+ in cytosol bind to protein pump
  2. Binding triggers hydrolysis of ATP into ADP + P which causes a change in shape, expelling 3 Na+ into ECF
  3. 2 K+ bind and trigger release of P group from protein pump, triggers change in shape
  4. Reverts to original shape and releases 2 K+ into the cytosol and the cycle repeats
37
Q

What is endocytosis and what are the 3 sub-types

A

A transport vesicle used to move materials into a cell; includes 3 types:
1. Receptor-mediated
2. Phagocytosis
3. Bulk-phase (pinocytosis)

38
Q

What is receptor-mediated endocytosis and what are the 6 steps

A

A selective process by which cells take up specific ligands (molecules that bind to specific receptors) trigger infolding of a clathrin-coated pit that forms a vesicle containing ligands

Transported substances (ligands):
- Cholesterol
- Transferrin
- Vitamins
- Antibodies
- Hormones

6 steps:
1. Binding: LDL particle binds to plasma membrane from the ECF
2. Vesicle formation: Vesicle forms from invagination of the plasma membrane and pinches off
3. Uncoating: Cathrin-coated vesicle loses its coat and become uncoated
4. Fusion: vesicle fuses with an endoscope and LDL particles separate from their receptors
5. Recycling of receptors: receptors become transport vesicles that return to the plasma membrane
6. Degradation in lysosomes: lysosomes containing digestive enzymes break down large protein/lipid molecules of the LDL into amino acids, fatty acids and cholesterol

39
Q

What is phagocytosis endocytosis and how does it happen

A

“Cell eating” is a form of endocytosis in which the cell engulfs large solid particles into a cell after pseudopods engulf it to form a phagosome.

Examples:
1. Macrophages = in body tissues
2. Neutrophils = white blood cells

Transported substances:
- Bacteria
- Viruses
- Aged/dead cells

40
Q

What is bulk-phase endocytosis and what substances does it transport

A

“Cell drinking”; movement of ECF into a cell by infolding of plasma membrane to form a vesicle (does not involve receptors)

Substances transported:
- Solutes in ECF

41
Q

What is exocytosis and what substances does it transport

A

Movement of substances out of a cell in secretory vesicles that fuse with the plasma membrane and release their contents into the ECF

Substances transported:
- Neurotransmitters
- Hormones
- Digestive enzymes

42
Q

What is transcytosis and what substances does it transport

A

Movement of a substance through a cell as a result of endocytosis on one side and exocytosis on the opposite side

Substances transported:
- Antibodies across endothelial cells

E.g., substances btw blood plasma and interstitial fluid

43
Q

What is the cytoplasm of a cell and its 2 components

A

Consists of all the cellular contents between the plasma membrane and the nucleus

2 components:
1. Cytosol
2. Organelles

44
Q

What is the cytosol (ICF) of a cell, its purpose and structure

A

The fluid portion of the cytoplasm that surrounds organelles and contains dissolves/suspended components (e.g., ions, glucose)

Purpose:
The site of many chemical rxns required for cell existence

Structure:
Cytoskeleton = a network of 3 types of protein filaments that extends throughout the cytosol

45
Q

What are the 3 types of protein filaments that make up the cytoskeleton

A
  1. Microfilaments
  2. Intermediate filaments
  3. Microtubules
46
Q

What are microfilaments?

A

Thinnest protein filament of the cytoskeleton of a cell (aka cytosol) that:
1. generate movement
2. provide mechanical support to anchor cytoskeleton to integral proteins

47
Q

What are intermediate filaments?

A

Thickest protein filament of the cytoskeleton of a cell (aka cytosol) that:
1. stabilize the position of organelles
2. Help attach cells to one another

48
Q

What are microtubules?

A

Largest protein filament made of tubulin in the cytoskeleton of a cell (aka cytosol) that:
1. Help determine cell shape
2. help secretory vesicles move
3. include cilia and flagella

49
Q

What are organelles?

A

Specialized structures within the cytosol of a cell that have characteristic shapes, and they perform specific functions in cellular growth, maintenance, and reproduction

50
Q

What is a centrosome?

A

Microtubule organizing organelle of a cell, located near the nucleus

51
Q

What are cilia?

A

Short, hairlike projections (organelles) that extend from the surface of the cell and coordinate movement of fluid along the surface of a cell (e.g., in cells of the respiratory tract)

52
Q

What are flagella?

A

Long projections (organelles) that extend from the surface of a cell and move the cell (e.g., sperm cell tail)

53
Q

What is the endoplasmic reticulum? What are its 2 forms?

A

A organelle that is a network of membranes in the form of flattened sacs or tubules

2 forms:
1. Rough ER = continuous with nuclear membrane + studded with ribosomes  produces secretory proteins, membrane proteins and organellar proteins
2. Smooth ER = extends from the rough ER + no ribosomes  synthesizes fatty acids and steroids (estrogen and testosterone)

54
Q

What is the Golgi complex?

A

An organelle made of small flat membranous sacs called cisterns that accepts proteins / enzymes at the cis face / via transport vesicles from the rough ER and packages them into secretory, membrane or transport vesicles for delivery to their final destination via the trans face (exit)

55
Q

What are lysosomes?

A

An membrane-enclosed vesicles (organelle) that forms from the Golgi complex and degrades proteins delivered to them in vesicles

Fxns:
- Digest molecules that enter the cell via endocytosis
- Recycle cell structures/organelles during autophagy (regeneration)
- Destroy an entire cell during autolysis

56
Q

What are peroxisomes?

A

Organelles that contain oxidases, enzymes that can oxidize (remove hydrogen) from organic substances to prevent cell death and self-replication

E.g., found in the liver

57
Q

What are proteasomes?

A

Organelles that help with the continuous destruction of unneeded, damaged, or faulty proteins is the function of tiny barrel-shaped structures consisting of four stacked rings of proteins around a central core called

58
Q

What are mitochondria? What are their 4 main structures?

A

An organelle that generates most of the ATP through aerobic (oxygen-requiring) respiration and is self-replicating

4 structures:
1. External mitochondria membrane
2. Internal mitochondrial membrane
3. Mitochondrial cristae
4. Mitochondrial matrix

59
Q

What is the nucleus and its functions?

A

Consists of a nuclear envelope with pores, nucleoli and chromosomes which exist as a tangled mass of chromatin in interphase cells

Functions:
- Nucleus pores control the movement of substances btw the nucleus and cytoplasm
- Nucleoli produce ribosomes
- Chromosomes consist of genes that control cellular structures and direct cellular functions

60
Q

What is gene expression and name its 2 steps

A

Refers to the use of a gene’s DNA as a template for the synthesis of a specific protein and occurs in 2 steps
1. Transcription
2. Translation

61
Q

What is transcription?

A

The first step of gene expression; during which the information encoded in a specific region of DNA is transcribed (copied) to produce a specific molecule of RNA (ribonucleic acid) in the nucleus of a cell

Base pairs (DNA –> RNA):
A –> U
T –> A
G –> C
C –> G

62
Q

What are the 3 types of RNA made from DNA during transcription?

A
  1. mRNA = directs the synthesis of a protein
  2. rRNA = joins with ribosomal proteins to make ribosomes
  3. tRNA = binds to an amino acid and holds it in place on a ribosome until it is incorporated into a protein during translation
63
Q

What is RNA polymerase?

A

An enzyme that catalyzes transcription of DNA and attaches at the promoter (a special nucleotide sequence and the segment of DNA where transcription begins)

64
Q

Compare introns vs. exons

A

During transcription, not all parts of a gene code for a protein:

Introns = regions within a gene that do not code for parts of proteins

Exons = the regions within a gene that do code for segments of a protein

65
Q

What is a terminator in the context of transcription

A

A special nucleotide sequence where transcription of the DNA strand ends

When RNA polymerase reaches the terminator, the enzyme detaches from the transcribed RNA molecule and the DNA strand

66
Q

What is translation?

A

The second step of gene expression; a process when nucleotide sequence in an mRNA molecule specify the amino acid sequence of a protein, which is carried out by ribosomes in the cytoplasm

67
Q

What are the 7 steps of translation

A

Starts at the A site –> P site (where the chain is located) –> E

  1. An mRNA molecule binds to the small ribosomal subunit at the mRNA binding site
  2. The large ribosomal subunit attaches to the small ribosomal subunit–mRNA complex, creating a functional ribosome
  3. The anticodon of another tRNA with its attached amino acid pairs with the second mRNA codon at the A site of the ribosome
  4. A component of the large ribosomal subunit catalyzes the formation of a peptide bond between methionine and the amino acid carried by the tRNA at the A site
  5. Following the formation of the peptide bond, the resulting two- peptide protein becomes attached to the tRNA at the A site
  6. After peptide bond formation, the ribosome shifts the mRNA strand by one codon
  7. Protein synthesis ends when the ribosome reaches a stop codon at the A site, which causes the completed protein to detach from the final tRNA
68
Q

Polyribosome

A

When several ribosomes attached to the same mRNA during translation

69
Q

What is cell division? What are the 2 types?

A

The process by which cells reproduce themselves

2 types:
1. Somatic cell division
2. Reproductive cell division

70
Q

What is somatic cell division?

A

One of two types; When a cell undergoes a nuclear division called mitosis and a cytoplasmic division called cytokinesis to produce 2 genetically identical cells with the same # of chromosomes as the original cell

E.g., any cell of the body other than germ cells

71
Q

What is reproductive cell division?

A

One of two types; Consists of a special two-step division called meiosis, in which the number of chromosomes in the nucleus is reduced by half and produces gametes

72
Q

What is the cell cycle? What are the 3 main phases?

A

Mitosis: When a somatic cell duplicates its contents and divides in two (human cells, such as those in the brain, stomach, and kidneys, contain 23 pairs of chromosomes, for a total of 46)

Phases:
1. Interphase (G1, S, G2)
2. Mitosis M phase (prophase, metaphase, anaphase, telophase, cytokinesis)

73
Q

What is interphase?

A

The first step of the somatic cell cycle when a cell is not dividing but replicates its DNA and produces additional organelles and cytosolic components in anticipation for division

74
Q

What is mitosis (M phase)?

A

The second step of the somatic cell cycle when a cell is dividing and results in the formation of two identical cells, consists of a nuclear division (mitosis) and a cytoplasmic division (cytokinesis) to form two identical cells

75
Q

What is meiosis?

A

Sexual reproduction = the reproductive cell division that occurs in the gonads (ovaries and testes), produces gametes in which the number of chromosomes is reduced by half; genetic recombination occurs during meiosis

BIOL 235 (4 decks)

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