The Cellular Level of Organisation Flashcards

1
Q

Cell theory

A
  1. Cells are the building blocks of all organisms
  2. All cells come from the division of preexisting cells
  3. Cells are the smallest units that carry out life’s essential physiological functions
  4. Each cell maintains homeostasis at the cellular level
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2
Q

Cytology

A

The study of cellular structure and function

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3
Q

Two types of human cells

A

Sex cells (sperm and oocytes) and somatic cells (all other cells)

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4
Q

Functions of the plasma membrane

A
  1. To seperate the cytoplasm from the extracellular fluid
  2. To control entry and exit of ions, nutrients, wastes, and secretions
  3. To sense changes in extracellular fluid through receptors
  4. To stabilise tissues
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5
Q

Phospholipid bilayer

A

Hydrophilic heads on the outside and hydrophobic tails on the inside

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6
Q

Function of cholesterol in the plasma membrane

A

To stiffen the plasma membrane, making it less fluid and less permeable

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7
Q

Two types of membrane proteins

A

Integral: part of the structure of the plasma membrane
Peripheral: bound to inner or outer surface of the membrane, easily separated from it

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8
Q

Anchoring proteins

A

Attach the plasma membrane to other structures and stabilise its position

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9
Q

Recognition proteins (identifiers)

A

Recognise other cells as normal or abnormal

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10
Q

Enzymes

A

Catalyse reactions in both cytosol and extracellular fluid (can be integral or peripheral)

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11
Q

Receptor proteins

A

Sense specific extracellular ions or molecules called ligands

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12
Q

Carrier proteins

A

Bind solutes and transport them across the plasma membrane

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13
Q

Intergral protein channel

A

Allow ion and small water-soluble substances to move across the plasma membrane

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14
Q

Why do ions need a protein channel to enter a cell?

A

They don’t dissolve in lipids and thus cannot cross the phospholipid bilayer

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15
Q

Rafts

A

Areas marking the location of anchoring proteins and some kinds of receptor proteins that are confined to specific areas of the plasma membrane

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16
Q

Why do most integral proteins drift across the surface of the membrane?

A

Because the membrane phospholipids are fluid at body temperature

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17
Q

Complex carbohydrates of the plasma membrane

A

Proteoglycans, glycoproteins, and glycolipids

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18
Q

Carbohydrate layer on plasma membrane

A

Glycocalx

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19
Q

Functions of the glycocalx

A
  1. To form a viscous layer that lubricates and protects the plasma membrane
  2. To anchor the cell in place with stickiness
  3. Glycoproteins and glycolipids can function as receptors
  4. Cells involved in the immune response recognise glycoproteins and glycolipids as normal or abnormal
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20
Q

Cytoplasm

A

The general term for the material between the plasma membrane and the membrane that surrounds the nucleus

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21
Q

Cytosol

A

The intracellular fluid made made from water and various dissolved and insoluble material

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22
Q

Which contains more proteins: cytosol or extracellular fluid?

A

Cytosol

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23
Q

Organelles

A

Internal structures of cells that perform most of the tasks that keep a cell alive and functioning normally

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24
Q

Two types of organelles

A

Non-membranous: not completely enclosed by membranes, and all of their components are in direct contact with the cytosol
Membranous: isolated from the cytosol by phospholipid membranes

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25
Q

Inclusions

A

Masses of insoluble materials e.g. glycogen granules and pigment granules

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26
Q

Cytoskeleton

A

Internal protein framework that gives the cell strength and flexibility

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27
Q

Protein that makes up microfilaments

A

Actin

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28
Q

Function of microfilaments

A
  1. To anchor cytoskeleton to integral proteins of the plasma membrane
  2. Determine the consistency of the cytosol (dense, flexible network = cytosol has gelatinous consistency, widely dispersed = cytosol is more fluid)
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29
Q

Additional microfilament in skeletal muscle cells

A

Thick myosin filaments, which interact with thin actin filaments to cause contraction

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30
Q

Terminal web

A

A layer of actin filaments present in cells that form a layer or lining, e.g. the lining of the intestinal tract

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31
Q

Components of the cytoskeleton

A

Microfilaments, intermediate filaments and microtubules

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32
Q

Function of intermediate filaments

A
  1. To strengthen the cell and help maintain its shape
  2. To stabilise the position of organelles
  3. To stabilise the position of the cell with respect to surrounding cells
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33
Q

Protein that makes up microtubules

A

The globular protein tubulin

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34
Q

What is the most durable cytoskeletal element?

A

Intermediate filaments

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35
Q

Function of microtubules

A
  1. To give the cell strength, maintain its shape, and anchor the position of major organelles
  2. To change the shape of the cell, and to assist in cell movement
  3. To move vesicles or other organelles within the cell through motor proteins
  4. To distribute duplicated chromosomes containing DNA to opposite ends of the dividing cell (to act as spindle apparatus)
  5. To form structural components of organelles, such as centrioles and cilia
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36
Q

Which element makes up the most of the cytoskeleton?

A

Microtubules

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37
Q

Which cytoskeletal element is made of molecules that assemble and disassemble?

A

Microtubules

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38
Q

Microvilli

A

Small, finger-shaped projections of the plasma membrane

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39
Q

Function of the microvilli

A

To increase the surface area of the cell

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40
Q

Which cells are covered with microvilli

A

Cells involved in actively absorbing material e.g. cells lining the digestive tract

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41
Q

Centrosome

A

Region of cytoplasm located next to nucleus in the cell, microtubule-organising centre of animal cells

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42
Q

Where do microtubules generally begin in the cell?

A

Centrosome

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43
Q

Centrioles

A

A pair of cylindrical structures that aid in the formation of the spindle apparatus needed in the movement of chromosomes in cell division

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44
Q

Arrangement of centrioles

A

9+0 array

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45
Q

Cilia

A

Fairly long, slender extensions of the plasma membrane

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46
Q

Two types of cilia

A

Nonmotile primary cilium: detects environmental stimuli

Multiple motile cilia: beat rhythmically to move fluids and secretions across the cell surface

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47
Q

Arrangement of nonmotile primary cilium

A

9+0 array

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48
Q

Arrangement of motile cilia

A

9+2 array

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49
Q

Arrangement of basal body

A

9+0 array

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50
Q

What is the basal body made of?

A

Centrioles

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51
Q

Strokes of motile cilia

A

Power stroke: relatively stiff

Return stroke: relatively flexible

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52
Q

Where are motile cilia found?

A

Cells lining the respiratory and reproductive tracts, and various other locations in the body

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53
Q

Ciliopathies

A

A wide range of human disorders caused by defective primary cilia

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54
Q

Flagellum

A

Long, whip-like extension of the plasma membrane

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55
Q

Arrangement of the flagellum

A

9+2 array

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56
Q

Which is the only type of human cell that has a flagellum?

A

Sperm cells

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57
Q

Ribosomes

A

The organelles responsible for protein synthesis

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58
Q

Composition of ribosomes

A

60% RNA and 40% protein

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59
Q

Two subunits of ribosomes

A

A small ribosomal subunit and a large ribosomal subunit which both contain special proteins and ribosomal RNA (rRNA)

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60
Q

What must happen before protein synthesis begins?

A

A small and large ribosomal subunit in the cytoplasm must join together with a strand of messenger RNA (mRNA)

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61
Q

Two major types of ribosomes

A

Free ribosomes: scattered throughout the cytoplasm (the proteins they make directly enter the cytosol)
Fixed ribosomes: temporarily fixed to the endoplasmic reticulum (the proteins they make enter the ER, modified and packaged for use, and then secreted)

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62
Q

Proteasomes

A

Organelles containing protein-digesting (proteolytic) enzymes, or proteases, that remove and recycle damaged or denatured proteins and play a role in the immune response

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63
Q

Recycling of damaged proteins

A

Cytoplasmic enzymes attach chains of ubiquitin (molecular “tags”) to proteins destined for recycling. Tagged proteins are quickly transported into a proteasome where they are rapidly disassembled into amino acids and small peptides, which are released into the cytoplasm.

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64
Q

Endoplasmic reticulum (ER)

A

A network of intracellular membranes continuous with the nucleus envelope, which surrounds the nucleus

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65
Q

Functions of the ER

A
  1. Synthesis of proteins, carbohydrates and lipids
  2. Storage of synthesised molecules or materials
  3. Transport within the ER
  4. Absorb toxins and neutralise them with enzymes
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66
Q

Cisternae

A

Chambers within the ER that store water

67
Q

Two types of ER

A
Smooth ER (SER): no fixed ribosomes
Rough ER (RER): fixed ribosomes
68
Q

Functions of the SER

A
  1. Synthesis of phospholipids and cholesterol for plasma membrane, ER, nuclear membrane and Golgi apparatus
  2. Synthesis of steroid hormones
  3. Synthesis and storage of glycerides in liver and fat cells
  4. Synthesis and storage of glycogen in skeletal muscle and liver cells
  5. Absorption of calcium ions in muscle cells, neurons and other types of cells
  6. Detoxification of drugs in liver and kidney cells
69
Q

Functions of the RER

A

To synthesis proteins through the fixed ribosomes and then chemically modify and packaged for export to the Golgi apparatus

70
Q

Transport vesicles

A

Small, membranous sacs that pinch off from the tips of the cisternae of the RER and then deliver their contents to the Golgi apparatus

71
Q

Functions of the Golgi apparatus

A
  1. Modifies and packages secretions for release from the cell
  2. Adds or removes carbohydrates to or from proteins to chain their structure and function
  3. Renews or modifies the plasma membrane
  4. Packages special enzymes within lysosomes for use in the cytoplasm
72
Q

Protein synthesis

A
  1. A gene on DNA produces mRNA, the template for protein synthesis
  2. mRNA leaves the nucleus and attaches to a free ribosome in the cytoplasm or a fixed ribosome on the RER
    3a. Proteins constructed on free ribosomes are released into the cytosol for use within the cell
    3b. Protein synthesis on fixed ribosomes occurs at the RER. The newly synthesised protein folds into its 3D shape.
  3. The proteins are modified within the ER. Regions of the ER then bud off, forming transport vesicles containing modified proteins and glycoproteins
  4. The transport vesicles carry the proteins and glycoproteins towards the Golgi apparatus. The transport vesicles then fuse to create the forming (cis) face of the Golgi apparatus.
  5. Multiple transport vesicles combine to form cisternae on the cis face. Further packaging and modification occur as the cisternae move towards the maturing (trans) face.
  6. The trans face generates vesicles that carry modified proteins away from the Golgi apparatus.
  7. Lysosomes: released into the cell
    Secretory vesicles: fuse with the plasma membrane and empty their products outside the cell by exocytosis
    Membrane renewal vesicles: add new lipids and proteins to the plasma membrane
73
Q

Lysosomes

A

Vesicles that provide an isolated environment for potentially dangerous chemical reactions and contain digestive enzymes that break organic polymers into monomers

74
Q

Lysosomes functions

A
  1. To fuse with the membrane of a damaged organelle
  2. To fuse with an endosome containing fluid or solid materials from outside the cell
  3. The lysosomal membrane breaks down during autolysis following cellular injury or death
75
Q

Which is smaller: lysosomes or peroxisomes?

A

Peroxisomes

76
Q

How are peroxisomes produced?

A

Through the division of exisiting peroxisomes

77
Q

Function of peroxisomes

A

To break down organic molecules and protect the cell from free radicals

78
Q

Mitochondria

A

The organelles that produce ATP for the cell

79
Q

Structure of mitocondria

A

Double membrane - outer membrane surrounds the organelle, inner membrane folds to create cristae which surrounds the matrix of the mitochondrion

80
Q

Why is the inner membrane of the mitochondria folded?

A

To increase SA

81
Q

Aerobic metabolism

A
  1. Glycolysis - glucose molecules are broken down into 2 molecules of pyruvate which are then absorbed the the mitochondrion
  2. A CO2 molecule is removed from each pyruvate molecule
  3. Remnants of the pyruvate molecules undergo the citric acid cycle (CO2 released from cell, electron transferred from H to O
  4. Energy released allows enzymatic conversion of ADP to ATP
82
Q

Which membranous organelle isn’t in communication with the others through vesicles?

A

Mitochondria

83
Q

Membrane flow

A

The continuous movement and exchange of membrane segments

84
Q

Structure of the nucleus

A

Nuclear envelope - double membrane separated by a narrow perinuclear space
Nuclear pores - openings in the nuclear envelope that receive chemical communication
Nucleoplasm - contains nuclear matrix (network of fine filaments)
Nucleoli - synthesise rRNA, ribosomal subunites (made of RNA, enzymes and proteins called histones)
Nucleosome - DNA winded around histones
Chromatin - tangle of fine filaments (non-dividing cells)
Chromosomes - tight structures just before division begins

85
Q

Why doesn’t DNA flow out of nuclear pores?

A

DNA molecules are too big

86
Q

Composition of amino acids

A

Three nitrogenous bases = 1 amino acid

87
Q

Gene

A

Functional unit of heredity, the sequence of nucleotides of a DNA strand that specifies the amino acids needed to produce a certain protein

88
Q

Gene activation

A

A process in which the portion of the DNA molecule containing a gene uncoils and the histones are temporarily removed

89
Q

Transcription

A

The synthesis of RNA from a DNA template

90
Q

mRNA

A

Carries the information needed to synthesis proteins

91
Q

Coding strand of DNA

A

The strand containing the triplets that specify the sequence of amino acids in the polypeptide

92
Q

Template strand of DNA

A

The strand containing the complementary triplets that will be used as a template for mRNA production

93
Q

mRNA transcription

A
  1. Once DNA strands have separated and histone have been removed, the enzyme RNA polymerase binds to the promoter of a gene on the template strand
  2. At the “start signal, RNA polymerase strings template strand nucleotides and complementary nucleotides in the nucleoplasm together through covalent bonding creating mRNA strand. T is never used in mRNA strand
  3. At the “stop” signal, the enzyme and mRNA strand detach from the DNA strand
94
Q

Codon

A

Three-base mRNA sequence with nitrogenous bases complementary to those of the triplets in the DNA strand

95
Q

RNA processing

A

A process in which noncoding intervening sequences (introns) are snipped out and the remaining coding segments (exons) are spliced together

96
Q

Translation

A

The formation of a linear chain of amino acids (polypeptide) using the information from an mRNA strand

97
Q

Initiation (process of translation)

A
  1. Amino acids provided by tRNA (tail of tRNA binds to amino acid)
  2. tRNA anticodon bonds with a complementary mRNA codon
  3. Small and large ribosomal subunits join together and enclose mRNA and tRNA (large ribosomal subunit has three sites for RNA binding: E, exit; P, polypeptide binding; A, arrival)
98
Q

Anticodon

A

Loop made by tRNA containing three nitrogenous bases

99
Q

Elongation (process of translation)

A
  1. Ribosome moves one codon father. Another tRNA arrives at A, carrying amino acid 2, initiation repeats, ribosomal enzyme attaches amino acid 1 to amino acid 2
  2. A third tRNA arrives at the A, tRNA at E leaves
  3. Elongation continues until it reaches a stop codon
100
Q

Termination (process of translation)

A

A protein release factor bonds with the stop codon, releasing the polypeptide

101
Q

Signalling pathway

A

Form intracellular signalling molecules

102
Q

Types of membrane permeability

A

Impermeable, freely permeable and selectively permeable

103
Q

Diffusion

A

The net movement of a substance from an area of higher concentration to an area of lower concentration

104
Q

Concentration gradient

A

Difference between the high and low concentrations of a substance

105
Q

Factors influencing diffusion rates

A
  1. Distance (shorter = faster)
  2. Ion and molecule size (smaller = faster)
  3. Temperature (hotter = faster)
  4. Concentration gradient (steeper = faster)
  5. Electrical gradient
106
Q

Simple diffusion

A

Alcohols, fatty acids, steroids, water, dissolved gases (oxygen and CO2), and lipid-soluble drugs can diffuse through the plasma membrane the membrane

107
Q

Channel-mediated diffusion

A

Ions and water-soluble compounds must enter the cell through channel-mediated diffusion

108
Q

Leak channels

A

Membrane channels that are always open

109
Q

Osmosis

A

Water molecules tend to flow across a selectively permeable membrane toward the solution with the higher solute concentration, because that is where the concentration of water is lower

110
Q

Osmotic pressure

A

An indication of the force with which pure water moves into a solution as a result of its solute concentration

111
Q

Aquaporins

A

Abundant water channels

112
Q

Hydrostatic pressure

A

Pressure generated from pushing against a fluid

113
Q

Osmolarity

A

The total solute concentration in an aqueous solution

114
Q

Tonicity

A

The effects of various osmotic solutions on cells

115
Q

Isotonic

A

Equal solute concentration

116
Q

Hypotonic

A

The solution with the lower solute concentration

117
Q

Hypertonic

A

The solution with the higher solute concentration

118
Q

Hemolysis

A

When a RBC is put into a hypotonic solution, it swells up and bursts

119
Q

Crenation

A

When a RBC is put into a hypertonic solution, it shrinks

120
Q

Carrier-mediated transport

A

The process in which integral proteins bind specific ions or organic substrates and carry them across the plasma membrane

121
Q

Characteristics of carrier-mediated transport

A
  1. Specificity
  2. Saturation limits
  3. Regulation
122
Q

Symport mechanism

A

The carrier protein (symporter) transports 2 different molecules or ions through a membrane in the same direction

123
Q

Antiport mechanism

A

The carrier protein (antiporter) transports 2 different molecules or ions in opposite directions

124
Q

Facilitated diffusion

A

The process in which substances are passively transported across the membrane by carrier proteins. The molecule binds to the receptor site on the carrier protein, the protein changes shape, moving the molecule across the membrane and into the cytoplasm e.g. glucose

125
Q

Active transport

A

Process in which a high-energy bond provides the energy needed to move ions or molecules across the membrane

126
Q

Ion pumps

A

Carrier proteins that actively transport the cations: sodium, potassium, calcium and magnesium

127
Q

Primary active transport

A

The process of pumping solutes against a concentration gradient using energy from ATP

128
Q

Sodium-potassium pump

A

The sodium ion concentration is high in the extracellular fluid, but low in the cytoplasm (and vice versa for potassium). Leak channels allow sodium ions to diffuse into the cell and potassium ions to diffuse out. Homeostasis requires that sodium ions be ejected and potassium ions be reclaimed

129
Q

How many sodium and potassium ions are moved per 1 ATP molecule?

A

3 sodium ejected and 2 potassium reclaimed

130
Q

Secondary active transport

A

The transport mechanism itself does not require energy from ATP, but the cell often needs to expend ATP at a later time to preserve homeostasis

131
Q

Endocytosis

A

The process in which extracellular materials can be packaged into vesicles at the cell surface and imported into the cell

132
Q

Three major types of endocytosis

A
  1. Receptor-mediated endocytosis
  2. Pinocytosis
  3. Phagocytosis
133
Q

Receptor-mediated endocytosis

A

The process in which cholesterol and iron irons enter the cell through clathrin-coated pits

134
Q

Pinocytosis

A

The formation of endosomes filled with extracellular fluid (a pocket forms in the plasma membrane that then pinches off)

135
Q

Phagocytosis

A

The formation of endosomes (called phagosomes) containing solid objects (cytoplasmic extensions called pseudopodia surround the object and their membranes fuse to form a phagosome which then fuses with lysosome whose enzymes digest its contents

136
Q

Exocytosis

A

The process in which a vesicle forms inside the cell and fuses with the plasma membrane

137
Q

Transcytosis

A

The process in which endocytosis produces vesicles on one side of the cell that are discharged through exocytosis on the other side of the cell

138
Q

Charges of the surfaces of the plasma membrane

A

The cytoplasm-facing surface has a slight negative charge with respect to the extracellular surface (only in relation to surfaces - not relevant to contents)

139
Q

Causes for the charges on the surfaces of the plasma membrane

A

Cytoplasm-facing surface: negative due to negatively charged protein anions that are too large to pass through any membrane ion channels
Extracellular surface: positive due to sodium cations

140
Q

Potential difference

A

When positive and negative charges are held apart

141
Q

Membrane potential

A

The potential difference across the plasma membrane

142
Q

Resting membrane potential

A

The membrane potential in an unstimulated or undisturbed cell

143
Q

Apoptosis

A

The genetically controlled death of cells

144
Q

Interphase

A

The stage of the cell life cycle between mitotic division

145
Q

G0 phase

A

An interphase cell in a non-dividing state

146
Q

DNA replication

A
  1. Helicases unwind the DNA strands while DNA polymerase bind to exposed nitrogenous bases
147
Q

Mitosis

A

The duplication of the chromosomes in the nucleus and their separation into 2 identical set

148
Q

Cytokinesis

A

The division of the cytoplasm during mitosis, beginning in late anaphase and continuing through telephase

149
Q

Miotic rate

A

Rate of cell division

150
Q

Phases of mitosis

A

Prophase, metaphase, anaphase and telophase

151
Q

Growth factors

A

Various natural body substances derived from food can stimulate the division of specific types of cells

152
Q

Telomeres

A

Terminal segments of DNA associated proteins

153
Q

Functions of telomeres

A

To attach chromosomes to the nuclear matrix and protect the end of the chromosomes from damage during mitosis

154
Q

Repressor genes

A

Genes that inhibit cell division

155
Q

Tumor

A

A mass produced by abnormal cell growth and division

156
Q

Benign tumour

A

The cells usually remain in the tissue where the tumour originated

157
Q

Malignant tumour

A

The cells aren’t confined to originating tissue

158
Q

Primary tumour

A

Tumour of origin

159
Q

Invasion

A

The tumour spreading process

160
Q

Cause of cancer

A

The abnormal proliferation of any of the cells in the body

161
Q

Oncogenes

A

Mutated genes

162
Q

Mutagens

A

Agents that can cause a mutation

163
Q

Carcigonens

A

Cancer-causing agents

164
Q

Cellular differentiation

A

The development of specific cellular characteristics and functions that are different from the original cell