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B2 Flashcards

1
Q

What is an integral protein?

A

A protein embedded throughout the entire membrane. Able to do so as they are amphipathic, have a hydrophobic region in the middle where the fatty acid tails are, and ends are hydrophilic where the aqueous environments are. Allow larger or polar molecules to move through membrane, most are specific.

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2
Q

What is a peripheral protein?

A

Proteins that are bound to the surface of the membrane, so do not need to be amphipathic. Can be found on the inner or outer surface of a cell, and can be attached to the phospholipids or to an integral protein.

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3
Q

What is cholesterol?

A

A chain of steroid lipids that are in the hydrophobic region of the membrane of animal cells. They allow for fluidity by preventing the over expanding or condensing of the membrane in extreme temperatures.

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4
Q

How does the phrase “fluid mosaic model” explain the structure of the phospholipid bilayer?

A

Fluid= made of closely associated but not bound phospholipids which provides fluidity to allow mobement and facilitate transport (vesicles, endo/exo cytosis)
Mosaic= the presence of different proteins in a non-consistent pattern

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5
Q

Why are phospholipids amphipathic?

A

Tails: non-polar and hydrophobic- fatty acid tails
Heads: contains a phosphate group and a glycerol. phosphate= negative charge, glycerol- positive charge. This makes it polar, thus hydrophilic

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6
Q

What is meant by partially or selectively permeable?

In terms of the phospholipid bilayer

A

Some substances move easily through the cell membrane, while others do not.

Small, non-polar molecules diffuse through membrane non-selectively
Larger or polar molecules cannot, so they require integral proteins to move through.

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7
Q

What are some functions of membrane proteins?

A
  • J: Junctions- joins two cells together
  • E: Enzymes- catalyse metabolic reactions e.g ATP synthase
  • T: Transport- facilitated diffusion, osmosis, active transport
  • R: Recognition- glycoproteins markers for cell identification (antigens)
  • A: Anchoring- attachment site for cytoskeleton
  • T: Transduction- Receptor for hormones (and other signalling hormones)
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8
Q

Describe the differences between active and passive transport

A

Active- moves particles from area of low concentration to high concentration, against the concentration gradient. Requires energy, usually as ATP to move against gradient. Through integral proteins.

Passive- natural flow of particles from an area of high concentration to low concentration with the concentration gradient. Does not require energy. Can be through bilayer or integral protein.

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9
Q

Explain the structure and function of glycoproteins and glycolipids

A

Both are carbohydrate chains that attach to the outer surface of the cell membrane for cell identification and adhesion.

Glycolipid- attach directly to phospholipids
Glycoprotein- attach to a peripheral protein

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10
Q

What is the role of saturated fatty acids in the membrane?

A

Saturated fatty acids are straighter and have a higher melting point, creating a dense bilayer which limits expansion at warmer temperatures

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11
Q

What is the role of unsaturated fatty acids in the membrane?

A

The presence of double bonds that makes the phospholipids less straight, preventing them from packing tightly, especially at higher temperatures.

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12
Q

How does cholesterol aid in membrane fluidity in animal cells?

A

At high temps: adds stability to the membrane and prevents overexpansion of the phospholipids
At low temps- their presence prevents the phospholipids from packing so tightly and reducing fluidity.

Note: organelle membranes often have much less cholesterol as they are exposed to less temperature fluctuations.

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13
Q

Define simple diffusion

A

When particles move from an area of high concentration to low concentration (with the concentration gradient) through the phospholipid bilayer. Does not require proteins to move.

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14
Q

Define facilitated diffusion

A

When particles require a protein to be transported in or out of the cell as they are too large, charged or polar to travel through the bilayer. Moves with the concentration gradient.

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15
Q

Define osmosis

A

The movement of water through a semi-permeable membrane via passive transport, from dilute to concentrated. Water is polar and thus takes a long time to move through simple diffusion, so often moves through proteins called aquaporins.

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16
Q

What are aquaporins?

A

Protein channels dedicated to the movement of water in and out of the cell. Water is polar, so aquaporins have a polar core to facilitata rapid water movement.

Note: having aquaporins is an adaptation for water movement, thus concentration can vary.

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17
Q

Define hypertonic

A

A solution with a higher concentration of solutes is hypertonic to the other. If the extracellular environment is higher in solutes than the cell, then it is hypertonic. Water will be drawn out of the cell.

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18
Q

Define hypotonic

A

A solution with a lower concentration of solutes is hypotonic to the other. If the extracellular environment is lower in solutes than the cell, then it is hypotonic. Water will be drawn into the cell.

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19
Q

Define isotonic

A

When the solution inside and outside the cell have the same concentration of solutes. No net movement of water in or out of the cell.

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20
Q

What types of molecules can move through the cell membrane by simple diffusion?

A
  • Small enough to fit through phospholipid heads
  • Non-polar to move through the tails
  • Examples: CO2, O2

Note: polar particles can move through, but very slowly

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21
Q

What are the differences between carrier proteins and protein channels?

A
  • Channel proteins: have a polar core that creates a space for polar and charged particles to move through
  • Carrier proteins: changes shape as the molecules move through it
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22
Q

How does the sodium and potassium pump demonstrate active transport?

A

Active transport is used to move particles against concentration gradient. Done by protein pumps which use energy and only move in one direction.

Example: the sodium-potassium pump moves 2 ions, is crucial for neural signalling

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23
Q

Define endocytosis

A

Materials entering the cell by pushing through the cell membrane and creating a vesicle. The pinching of the membrane requires energy, thus is active transport. Can be regulated by receptors

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24
Q

What are the types of endocytosis?

A

Phagocytosis: endocytosis of large, solid particles
Pinocytosis: endocytosis of liquids and solutes

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25
Define exocytosis
When materials are removed from the cell. Materials are inside a vesicle which merges with the cell membrane to expell the contents. The vacuole is made by the golgi apparatus.
26
What are the uses of exocytosis
* Used by unicellular organisms to expel water in a contractile vacuole to maintain osmotic balance * Used to export proteins
27
What are gated ion channels?
Channel proteins that can be opened at specific times for diffusion to be turned on. This allows for an regulation or more dramatic influxes (useful for action potential)
28
What is indirect active transport?
When ATP is used to move a substance, but another substance can move as a result of the active transport of the first.
29
What is Cell Adhesion Molecules (CAM)
Cells in multicellular organism tissue are connected by cell to cell junctions. CAM are proteins embedded in the cell membranes. They protrude towards other cells and create junctions between cells, allowing more complex cellular arrangements in tissues.
30
Explain the role of the golgi apparatus in exocytosis of proteins
Proteins made at the Rough ER are packaged and moved to the Golgi for synthesis. The membrane of the Golgi pushes through to create vesicles that transport protein products to the membrane. At the membrane, the vesicle fuses with the membrane and the protein is expelled.
31
What is the difference between a neurotransmitter and a voltage gated ion?
Neurotransmitter/ ligand gated channels: a chemical messenger facilitates the opening of the channel Voltage gated channels: gates open/ close based on changes to internal/ external environments. A change in the charge (from action potential) causes the channel to open.
32
How is the sodium- potassium pump an example of an exchange transporter?
The same protein moves sodium in one direction, and potassium in the other direction. When the pump changes shape to release the sodium ions, the potassium ions enter at the same time. When it changes shape again to release the potassium, the sodium can be collected again.
33
What is the role of ATP in the functioning of the Sodium-Potassium pump?
ATP creates the shape change that closes the pump on the inside and facilitates its reopening on the outside. When ATP is 1x phosphate group binds to the outside of the pump and breaks off the ATP. When potassium enters the pump, the sodium is expelled and the phosphate gets detached, which triggers the next shape change.
34
How are sodium-dependent glucose cotransporters an example of indirect active transport? | in the intestines and kidneys
The sodium-potassium pump uses active transport to move sodium into the extracellular space where glucose resides. Once a high sodium concentration is established, the sodium will move via a channel protein that moves glucose and sodium. No ATP is used to move the glucose, but was used to move the sodium, so moving the glucose is indirectly energy consuming.
35
What are some of the uses of cell adhesium molecules in living organisms?
* To prevent movement * To facilitate movement * To protect against the spread of tumors by preventing cells from breaking away (metasis)
36
What are some examples of endocytosis?
* Immune system- phagocytosis by white blood cells * Unicellular feeding * Endosymbiotic theory
37
What are some examples of exocytosis?
* Protein transport * Waste removal via vesicles * Expulsion of water in unicellular organisms
38
What is an example of a neurotransmitter gated ion channel?
Nicotenic acytocholine receptor
39
How has ultracentrifugion aided in cell fractionation? | Inc. what is ultracentrifugion
Ultracentrifugion= seperation of particles by size Cell fractionation= the seperation of cells into types of organelles. The cells are mixed with cold buffer solution and blended to break cell membranes. It is then centrifuged to sink heavier organelles. This is repeated until organelles are sorted by size.
40
Which cellular structures are considered organelles and which are not?
Organelles: * Discrete subunit of a cell that is adapted to perform one or more functions. * Plasma membrane * Ribosomes * Rough ER * Golgi apparatus * etc Not organelles: * Cell wall (extracellular) * Cytoskeleton (not discrete) * Cytoplasm (too many functions)
41
Why is it beneficial for eukaryotes to have seperation between the nucleus and the cytoplasm?
* Protection of DNA from enzymes in the cytoplasm * Translation does not begin until after transcription is completed, allowing for mRNA modifications
42
What are the benefits of compartmentalisation for eukaryotic cells?
* Enzymes can be concentrated to areas where they will be used * Digestive enzymes in lysosomes can be kept seperate * Specific pH's can be maintained in different areas for certain functions * Easier transport of materials * Increased membrane areas for reactions to occur across
43
How is the cell protected from harm during phagocytosis by lysosomes?
Lysosomes contain hydrolytic enzymes that break things down. Instead of being free in the cytoplasm, they are contained in a vesicle. When something requiring digestion enters by phagocytosis, lysosomes merge with the vesicle and release enzymes into the vesicle, keeping hydrolysis inside to protect other cellular structures.
44
Why is it beneficial for the nucleus to have a double membrane?
Having a double membrane means that nuclear processes (replication and transcription of DNA) can occur without being impacted by other cellular processes. The membrane has pores (membrane proteins) to allow materials to move metween nucleoplasm and cytoplasm. Materials that need to move between: mRNA and ribosome subunits move out, regulatory proteins move in
45
How does chromatin interact with the nuclear membrane?
The inner of the two nuclear membranes interact with DNA chromatin to keep the membrane spread out (almost like a cytoskeleton)
46
What happens to the nuclear membrane during cell division?
The nuclear membrane breaks down so DNA can spread out and align to help division of the genetic material. The membrane breaks down into smaller vesicles which can rejoin to form new membrane- phospholipids naturally seperate and merge.
47
What is the matrix?
A cytoplasm like fluid with enzymes inside the highly folded inner membrane of the mitochondria. Where the krebs cycle occurs for cellular respiration.
48
What are cristae?
Tubular regions created by deep folds of the inner membrane. Increases the surface amount of membrane and intermembrane space for the electron transport chain of aerobic cellular respiration.
49
What are thylakoids?
Disks of membrane with a thin thylakoid space inside. Located in chloroplasts. Create stacks called granum and are joined by lamella.
50
What are stroma?
Stroma is the aqueous cytoplasm-like fluid area surrounding the thylakoid in the chloroplast. Contains important enzymes for the second stage of photosynthesis, the calvin cycle.
51
What are cisternae?
Stacked, flattened sacs in the golgi apparatus. Can both expand to accept new vesicles, or bud off to make exporting vesicles.
52
What are clathrins?
Proteins in the cell membrane that anchor specific proteins to the membrane. Can be for anchoring receptor proteins involved in receptor mediated endocytosis. When the vesicle forms, the clathrins join together to create a coated vesicle. Creates a highly specific, efficient and regulated form of endocytosis.
53
What is the purpose of the inner membrane of the mitochondria?
Highly folded to increase surface area. The membrane is lined with enzymes that carry out cellular respiration. More membrane= more enzymes.
54
What is the purpose of the outer membrane of the mitochondria?
It is thought to have arisen through endosymbiosis. The purpose is to create a space between the two membranes where a proton gradient can build, which is neccessary for reactions in aerobic cellular respiration.
55
What are the benefits of having cristae and a small intermembrane space for mitochondria?
The last part of cellular respiration relies on a build up of H+ ions in the intermembrane space. A very thin membrane allows the gradient to fill quickly. Cristae produce extra intermembrane space throughout the mitochondria for these reactions.
56
What is the benefit of localising enzymes to the matrix (mitochondria) or stroma (chloroplast)?
In cellular respiration and photosynthesis, important metabolic processes occur in the matrix (krebs cycle) and stroma (calvin cycle). They are enzyme catalysed so by localising the enzymes, these pathways can be more efficient than if they were diffused throughout.
57
Why is it beneficial for the thylakoids to have a large surface area and small volume?
Light-dependent photosynthesis reactions rely on pigments and enzymes in thylakoid membranes. An increase in thylakoid membranes (by adding more to the granum) increases the amount of pigment and enzymes, increasing photosynthesis. Having thin thylakoids allows for proton gradients to form quickly.
58
What is the difference in function between free ribosomes and ribosomes attached to the rough ER?
Free: make proteins to be used within the cell e.g cytoskeleton, nucleus, mitochondria Attached: create proteins that are transported (via ER) usually for export out of the cell.
59
What is the difference between the cis and trans side of the golgi apparatus?
Cis side: side that faces the ER. Accepts vesicles produced by the ER that then merge with the golgi. Trans side: side that faces the cell membrane. Vesicles bud off the golgi towards the plasma membrane for exocytosis.
60
Explain the process of receptor mediated endocytosis with clathrins
1. Particles to be moved into the cell bind to receptors- the receptors are anchored through the cell membrane by clathrins 2. Particles and receptors are engulfed in a vesicle. 3. Clathrins are on the outside of the vesicle and help speed up vesicle formation 4. Particles are released into the cytoplasm and the receptors and clathrins are recycled
61
What is a morphogen?
Morphogens are signalling molecules that control early cell differentiation. Builds different concentrations in different areas of the embryo to determine what the cells differentiate into. Highest concentration= differentiate into epiphiel cells Medium concentration= differentiate into muscle cells Lowest concentration= differentiate into nervous system
62
What are stem cells?
Undifferentiated cells that can become multiple different types of specialised cells. Early in embryonic development, all cells are stem cells, but we retain some stem cells as adults.
63
What is a stem cell niche?
A stem cell niche is a location in adults where lots of stem cells are present. This is done through cell division where one daughter cell stays as a stem cell and the other permanently differentiates.
64
What are the steps between gametes and an infant?
1. Gametes (fertilisation) 2. Zygote (5 days) 3. Embryo (4-8 weeks) 4. Foetus (birth) 5. Infant
65
How does cell signalling impact cell differentiation during embryonic development?
Cell differentiation= the process of delivering information to the cell surface that impacts its actions e.g gene expression During embryonic development, cell differentiation directs which cells to be expressed for the stem cells to become differentiated.
66
What are unique properties of stem cells?
1. Can self renew- both can self renew, both can differentiate or one can self-renew and the other differentiate 2. Can recreate a functional tissue by differentiating into specialised cells that carry out important functions.
67
What are two examples of locations of human stem cell niches?
1. Bone marrow- contains haemopoetic stem cells which can differentiate into white blood cells, red blood cells etc 2. Hair follicles- epithiel stem cells can differentiate into skin cells, hair cells, oil production cells etc.
68
What are totipotent stem cells?
Totipotent stem cells are capable of producing any tissue type in the organism through continued division. Could produce a whole organism. Only found in the early stages of embryo development.
69
What are pluripotent stem cells?
Pluripotent stem cells are cells that have begun specialising within the embyro. Can differentiate into most cell types but not all- cannot make a full organism. Pluripotent stem cells can be harvested as embryonic stem cells from embryos or cord blood.
70
What are multipotent stem cells?
Multipotent stem cells are able to differentiate into several related or similar cell types. Distinct from specialised cells but are much more limited than pluripotent stem cells. e.g haemopoetic stem cells
71
Explain the cell size and benefits of an egg cell
Size: 110μm in diameter Benefits: increased surface area for food storage in cytoplasm
72
Explain the cell size and benefits of a sperm cell
Size: 50μm in length Benefits: narrow with small volume to aid in movement and increase its SA:V
73
Explain the cell size and benefits of red blood cells
Size: 6-8μm in diameter but only 1μm thick Benefit: has a biconcave shape to move throug vessels and increase SA:V to allow O2 to bond to haemoglobin
74
Explain the cell size and benefits of white blood cells
Size: inactive- 10μm, active- 30μm Benefits: when active, expands to fit extra ER and Golgi to produce and pack antibodies
75
Explain the cell size and benefits of a neuron
Size: Soma (cell body)- 20μm, axon- 350μm Benefits: long axon to reduce synapses to increase neural transmission
76
Explain the cell size and benefits of striated muscle fibres
Size: 20-100 μm in diameter and up to 100mm in length Benefit: flexibility and force for movement
77
What is surface area-to-volume ratio?
Surface area= perimeter (cell membrane) Volume= internal (cytoplasm) SA:V is an indicator of the amount of membrane relative to cell size.
78
What is a nephron?
The nephron is a functioning filtering loop in the kidney. Adapted to have an increased surface area to allow movement of substances between the blood and the urine.
79
What is an alveoli?
Alveoli are individual air sacs at the end of lung branches that facilitate gas exchange between the lungs and the bloodstream. Having alveoli increases the surface area of lung tissue to increase the rate of gas diffusion
80
What are the challenges of a larger cell?
* More volume is further away from the cell membrane * It takes longer for needed materials to get to there they are needed in the cell * It is harder for wastes to exit which could lead to toxic levels of waste
81
How do you calculate SA:V ratio?
1. Calculate surface area using the formula for the shape 2. Calculate volume using the formula for the shape 3. Divide surface area by volume to get a ratio
82
What is the relationship between cell size and SA:V?
Small cells= LARGER SA:V ratio (more membrane per cytoplasm) As cells get larger, the volume increases rapidly which DECREASES the SA:V ratio
83
What are the formulas for surface area and volume of a sphere?
Surface area: 4πr^2 Volume: 4/3πr^3
84
What are some of the modifications cells can have to increase the SA:V?
* Change shape (long and thin) * Projections made of membrane * Localise functions requiring transport close to the membrane * Cell junctions to aid in material transport
85
What are the adaptations of erythrocytes/ RBC's to increase SA?
* Biconcave disc shape to reduce volume * Cytoplasm with haemoglobin is close to the membrane to facilitate oxygen transport
86
What are the adaptations of proximal convoluted tubule cells to increase SA?
* Cube shape for packing * Microvilli inside kidney create a 'brush border' * Lots of mitochondria for active transport * Invaginations- folds in the opposite side of the cell to increase SA
87
What are the adaptations of Type 1 Pneumocytes for SA?
* Thin and flat * Contains minimal organelles * Surrounded by a one cell thick capillary for efficient exchange * Tight junctions between cells prevents fluid entry
88
What are the adaptations of Type 2 Pnuemocytes?
* Cube shape for more volume for organelles (secretory vesicles for surfactant) * Microvilli facing alveolus * Often irregular shape due to regular exocytosis
89
Explain the adaptations of cardiac muscle cells
* Branching to connect multiple cells (Y shape) * Intercalculated discs as junctions between cells for signal transmission
90
Explain the adaptations of striated skeletal muscle cells
* Each muscle fibre is a single long cell with multiple nuclei * Has visible bands called striations related to lengthening and shortening * Large SA:V
91
Explain the adaptations of sperm cells
* Flagella for swimming * Midpiece with mitochondria (provide ATP for swimming) * Acrosome with enzymes to break down zona pellucida
92

IB Biology (12 decks)

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