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Cell biology > Cells, cell junctions, transport > Flashcards

Cells, cell junctions, transport Flashcards

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1
Q

Define eukaryotic cell.

A

Eukaroyte cells have membrane bound organelles, linear DNA found in nucleous, DNA with intrones and exones bound on histone proteins.

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2
Q

Why are cells the fundamental building blocks of life?

A

the basic structural, functional, and biological unit of all known living organisms

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3
Q

Give 2 functions of the Golgi-apparatus.

A

Transport of lipids from smooth ER and proteins from rough ER. Modification of proteins such as phosphorylarion and glucosylation.

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4
Q

Which cell organelles are surrounded by a double membrane layer?

A

Mitochondria has smooth outer layer and folded inner layer.

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5
Q

What are the similarities and differences between a lysosome and a peroxisome?

A

Lysosome breaks down macromolecules (intracellular digestion)
Peroxisome is a membrane-bound organelles (excreted
by Golgi) that contain enzymes for
oxidation (oxidase) of amino acids and
detoxifying (catalase) harmful
substances
deals with free radicals, has catalase and peroxidase.

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6
Q

What are the main functions of the cytoskeleton? Describe its composition.

A

Actin filament, long peptides. Microtubule which can act as intracellular transport but costs ATP. Important for cilia and flagella. Intermediate filaments tough and can link organelles, cells and to the extracellular matrix.

• highly dynamic structure
• 3 different filament types
• mechanical strength 
• responsible for cell shape and 
movements/transport
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7
Q

Define nuclear lamina.

A

meshwork of nuclear
intermediate filament proteins that supports
and strengthen the nuclear envelope

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8
Q

What is a motor protein?

A

Dynein and kinesin
Drive intracellular transport
Move in opposite directions
Play an important role in movement and positioning of organelles within eukaryotic
cell –e.g. during cell division and nerve cells

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9
Q

How does skeletal muscle contraction work?

A

Actin filaments slide against myosin filaments
shortening of sarcomeres without changing the length of each
filament

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10
Q 
(Which cell organelles are present in a plant cell but not in an animal cell? What is the
function of these organelles?)
A

Chloroplast: photosynthesis: sunlight to glucose

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11
Q

What are cell membranes made of? How are these components arranged?

A

Lipid bilayer with hydrophilic heads and hydrophobic tails, hydrophilic heads out

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12
Q

Describe the composition of a phospholipid.

A

molecule has a hydrophilic “head” containing a phosphate group and two hydrophobic “tails” derived from fatty acids, joined by an alcohol residue

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13
Q

Why has a cell a lipid bilayer?

A 
Physical and protective barrier
•Regulate transport
•Allow cell-recognition and cell communication
•Mechanical properties
• continuity
• capacity for movement and expansion
•Internal membrane (eukaryotes)
• enclosing an intracellular compartment
• differences in protein membranes –responsible for giving each organelle its distinctive character

Bilayers spontaneously close in on themselves to form sealed
compartments = energetically most favourable

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14
Q

Which molecule plays an important role in membrane fluidity?

A

fluidity modulated by cholesterol
Cholesterol makes the bilayer stronger, but less fluid and less permeable
unsaturation makes bilayer more fluid

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15
Q

Review how lipids move in the bilayer.

A

lateral diffusion, flexion, rotation, flip flop (last one is rare)

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16
Q

How can the fluidity of a cell membrane be changed?

A

More cholesterol

lenght and grade of saturation
how closely packed it is

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17
Q

What are the functions of membrane proteins?

A

Transport, receptor, enzyme, anchor

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18
Q

What kind of membrane transport proteins do exist?

A

Transporter (binding site, high specificity)

Channel (pore, discriminate on size and electrical charge)

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19
Q

Define glycocalyx and describe its function.

A

carbohydrate layer, sugar coat on extracellular site of lipid bilayer.

Protection cell surface from mechanical and chemical damage/stress
• Example: water-absorbing sugars give a slimy structure that helps
motility and prevents sticky cells
• Important in cell-cell recognition and cell-adhesion
• Example: lectin recognizes specific glycocalyx on neutrophils

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20
Q

What is the difference between active and passive transport? Give an example of each type.

A

Active transport against concentration gradient and requires ATP. Eg. transport of glucose. Passive transport does not require ATP, can be channel mediated or transporter mediated. Aquapourins allow water to flow through, a passive transport.

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21
Q

Describe the working mechanism of Na/K pump?

A

An electrogenic transmembrane ATPase.
The Na⁺/K⁺-ATPase enzyme is active (i.e. it uses energy from ATP). For every ATP molecule that the pump uses, three sodium ions are exported and two potassium ions are imported; there is hence a net export of a single positive charge per pump cycle.

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22
Q

Define symporter, antiporter, and uniporter.

A
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23
Q

Draw a neuron and label the cell body, axon, dendrite, and nerve terminal.

A

Looks like a tree, in which tree top is cell body, trunk is axon and roots are terminal branches. Dendrites are branches on the tree.

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24
Q

Describe the process of nerve cell signalling.

A

Action potential, nerve impulses. A travelling wave on the axon. Ion channels in axon are voltage gated. Wave of depolarisation.

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25
Why is action potential referred as “all-or-none”?
If a stimulus is strong enough, an action potential occurs and a neuron sends information down an axon away from the cell body and toward the synapse. ... The action potential is always a full response. There is no such thing as a "strong" or "weak" action potential. Instead, it is an all-or-nothing process
26
Which type of membrane proteins (channel) in the nerve terminal will be activated by a nerve impulse?
Voltage gated Ca2+ channels in nerve terminals convert electrical signal into a chemical signal Transmitter-gated ion channels at postsynaptic cell gives electrical signal
27
What is a protein signal sequence?
to direct the protein to a particular destination eg. ER signal sequence
28
Describe protein transport through nuclear pores.
``` Meshwork of proteins: small water-soluble molecules can pass the nuclear pore (unselective). Larger molecules and macromolecular complexes: • Nuclear localisation signal recognized by nuclear import receptor • Requires energy (GTP) • Fully FOLDED conformation ```
29
Give the differences and similarities between protein transport through the membrane of the nucleus and the mitochondria.
Through membrane to nucleus occurs fully folded. Through membrane on mitochondria and chloroplasts unfolded. Chaperone helps to fold corrected when entered.
30
What is a protein translocator?
Protein translocators are proteins on inner membrane of mitochondria and chloroplast
31
How are water-soluble proteins (made on the ER) released in the ER lumen?
SRP signal recognition particle binds to ER sequence and ribosome. Ribosomes move to translocator and release SRP. Synthesised into ER lumen.
32
How are transmembrane proteins released in the ER?
Single pass. Through protein translocator. The finished protein extends on both sides of membrane, in ER lumen and in cytosol. Double pass. Through protein translocator.
33
What is vesicular transport? Describe vesicle budding and vesicle docking.
Budding: Protein coat: example is the clathrin coated vesicle. Docking: Vesicle moved by motor proteins of cytoskeleton, docking by t snare and fuses with cell membrane.
34
Which protein plays a role in choosing the cargo molecule (within the process of vesicle budding)?
Protein adaptin plays important role in choosing cargo
35
Define exocytosis
exocytosis: transport from trans-Golgi to plasma membrane. Unregulated eg. plasma membrane. Regulated eg. secretory proteins.
36
Name 2 different pathways for exocytosis.
Unregulated eg. plasma membrane. Regulated eg. secretory proteins
37
Name 3 different types of endocytic pathways.
1. Pinocytosis = cellular drinking, by all cells 2. Phagocytosis = cellular eating, by phagocytic cells like macrophages, neutrophils 3. Receptor-mediated endocytosis = specific uptake (to avoid large volumes or unnecessary compounds)
38
Cells in epithelia are polarized. Explain the term “polarized”.
APICAL side: at luminal area BASAL side: at basal lamina BASAL LAMINA: sheet of collagen and laminin –link to other tissue
39
Name 3 types of cell junctions and give their main function.
1. Tight junctions: seal 2. Adherens junctions: attachments 3. Gap junctions: communications
40
What are the similarities and differences between a desmosome and a hemidesmosome?
41
What are the nuclear pores for?
To move ions, proteins and nucleotides from nucleus to cytoplasm and the other way.
42
What is the nucleolus?
A space in the nucleus where rRNA is synthesied.
43
What are ribosomes made of?
rRNA and small proteins
44
What are euchromatins?
Loose DNA for expression of DNA (DNA replication)
45
What is heterochromatin?
Tightly packed DNA
46
Is it the rough or the smooth endoplamic reticulum that has ribosomes on the outer membrane?
Rough ER
47
What do the ribosomes do?
Synthesise proteins from mRNA | To release protein it buds off and goes to Golgi
48
Does the smooth ER have ribosomes?
No
49
What is the function of the smooth ER?
Lipid synthesis (fatty acids, phospholipids, cholesterol) Bud off vesicles that go to Golgi
50
What is glycogen?
A big polymer of glucose.
51
What is the function of the Golgi apparatus?
``` Receives vesicles on cis-phase and they bud off on trans-phase. Modifies proteins - glycosylation -phosphorylation Packages molecules in own vesicles ```
52
What is the main function of the lysosome?
Breaking down macromolecules Autophagy of organelles Autolysis of damaged cells
53
What is the functions of peroxisomes?
Deal with ROS using its enzymes: catalase and oxidase. Breaks down fatty acids. Make lipids for white matter in brain Break down ethanol
54
What happens in mitochondria?
``` ATP synthesis Oxidative phosphorylation Electron transport chain Krebs cycle Heme synthesis ```
55
What is the cytoskelleton?
It is scattered all around the cell and makes up the structure. Consists of micro filaments, intermediate filaments and microtubules.
56
What are microfilaments?
Actin. Used in muscle contraction with myosin. Used in cytokinesis. Used in phagocytosis of white blood cells.
57
What are intermediate filaments?
Tough and connect cell to extracellular matrix and to other cells. Anchors organelles.
58
What are microtubules?
Two different protein units alfa and betaa tubulin. Provides intracellular transport. Requires ATP. Separates chromatids in cell division. Important for cell extensions: cilia (in lungs, uterus) and flagella (moves sperm cells)
59
What is the basal lamina?
Connective tissue, a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits
60
What are tight junctions and where can they be found?
Hold cells together so that nothing can pass. Acts as a diffusion barrier for ions and large molecules. Connected at apical surface. Found in BBB, G.I. tract, stomach and respiratory tract.
61
What are adherens junctions and where can they be found?
For keeping cells together from abrasive forces. | Found in G.I. tract, epithelial tissue, lungs, respiratory tract, bladder, blood vessels, skin
62
What are desmosomes and where are they found?
Keeping cells together stronger than adherens junctions. Very good for high tensile stretch. Found in cardiac tissue (called intercalated disc) and epidermis.
63
What are hemidesmosomes?
Connections between cell and basal laminar, not cell to cell.
64
What are gap junctions? Where are they found?
Connections between cells for cell to cell communication. Made up of two proteins connexons (made up of 6 connexins each). Found in cardiac tissue, smooth muscle tissue and neurons.
65
What is moved by simple diffusion?
Small and non-charged molecules such as CO2 and O2, steroid hormones. Molecules move from high to low concentration.
66
What is moved by facilitated diffusion?
Large and charged molecules. Requires a channel or carrier.
67
What is osmosis?
The movement of water from high to low concentration and also depends on solute concentration (low to high). Flow through proteins called aquapourins.
68
What is primary active transport?
Moving substances against concentration gradient from areas of low to high concentration using ATP
69
Secondary active transport uses ATP...
indirectly.
70
In secondary active transport Na+ moves from high to low concentration and brings with it...
glucose, protons and amino acids that move against concentration gradient.
71
What is symport?
When two molecules move in same direction.
72
What is antiport?
When two molecules move in opposite direction.
73
Which types of endocytosis exist?
Pinocytosis (cellular drinking) Phagocytosis (cellular eating) Receptor mediated endocytosis
74
What is endocytosis?
When the cell engulfs molecules into the cell membrane and a small part of the cell membrane becomes a vesicle for it
75
What is exocytosis?
A way for the cell to excrete molecules, waste, neurotransmitters, hormones. Also moves mRNA from ribosome to Golgi apparatus. Dynein and kinesin moves vesicles along microtubules using ATP.
76
What is receptor mediated endocytosis?
Receptors called LDL bind molecule LDL. Clathrins come to inner surface and starts pulling to form vesicle. LDL receptors are sent back to the membrane when a vesicle with LDL molecules has been created.
77
What are microtubuli?
• Stiff hollow tubes formed by polymerisation of tubulin dimer subunits, polarized (+ and -) • Centrosome = dynamic microtubule-organising centre near the nucleus • Maintain spatial organisation of the organelles –motor proteins (dyneins and kinesins) • Motility (cilia and flagella)
78
What are motor proteins?
Dynein and kinesin • Drive intracellular transport • Move in opposite directions • Play an important role in movement and positioning of organelles within eukaryotic cell –e.g. during cell division and nerve cells
79
Where are cell membranes synthesised?
Synthesis of phospholipids by enzymes on ER

Cell biology (11 decks)

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