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HL Biology - topical sets > Topic 1 > Flashcards

Topic 1 Flashcards

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1
Q

Explain how properties of phospholipids help to maintain the structure of cell membranes

A
  • hydrophobic and hydrophilic regions/amphipathic;
  • hydrophobic phosphate ‘heads’ attracted to water and hydrophilic fatty acid ‘tails’ repel water;
  • form a bilayer in water with heads in contact with the water on both sides of the membrane/ in contact with the cytoplasm and the environment;
  • structure held together by attraction between hypho tails/attraction between heads and water
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2
Q

Explain how the cell cycle is controlled [6]

A
  • cell cycle consists of different phases - G1, S, G2
  • cyclins control the cycle
  • levels of cyclins rise and fall at different points of the cycle
  • regulated by internal and external factors
  • different cyclins/four cyclins required to enter different stages of the cell cycle
  • cyclins activate cyclin-dependent kinases
  • kinases phosphorylate proteins
  • phosphorylated proteins perform different functions in cell cycle
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3
Q

Explain the different processes in interphase in a cell [3] (mix of bioninja and MS info)

A
  • G1: synthesis of organelles/protein/cell growth
  • S: Replication of DNA
  • G2: continued growth of cytoplasm/organelle duplication

According to bioninja the processes occurring in interphase:
DNA replication
Organelle replication
Cytoplasmic volume increase
Transcription/translation - for synthesis of required proteins/enzymes
Obtain nutrients
Respiration - ATP production for mitosis

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4
Q

Processes of cytokinesis in plant and animal cells [4+4]
(bioninja)

A

Animal:
- after anaphase, microtubule filaments form a concentric ring around the centre of the cell
- filaments constrict so a cleavage furrow forms
- furrow deepens till 2 ends meet -> cells pinched off
- centripetal

Plant:
- centrifugal
- carbohydrate rich vesicles align at centre of cell
- fuse to form early cell plate
- builds outwards and fuses with the cell walls –> separates the 2 cells

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5
Q

Exceptions to cell theory

A
  • Striated muscle cell: multinucleated, very large (‘refutes’ - cells always function as autonomous units)
  • giant algae: very large, complex
  • aseptate fungal hyphae: multinucleated, complex, large
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6
Q

Life processes

A

Metabolism: the web of all enzyme catalysed reactions in a cell
Response: the organism’s response to internal and external stimuli
Homeostasis: maintenance of a constant internal environment
Growth: a permanent increase in physical size due to an increase in cell size, cell number or both
Reproduction: the production of offspring from a parent organism
Excretion: the removal of the waste products of metabolism from the organism’s body
Nutrition: the consumption and use of nutrients for energy and growth

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7
Q

Paramecium life processes

A

M: enzyme catalysed reactions within the cytoplasm
R: moves using its cilia
H: osmoregulation. controls the cytoplasm’s osmolarity by collecting excess water in contractile vacuoles then expelling it through PM
G: grows by consuming organic molecules until it reaches critical ratio then divides asexually
R: sexual and asexual. asexual - 2 daughter cells via binary fission
E: waste products of respiration are removed through whole membrane surface
N: microorganisms/food particles are engulfed via feeding groove - digested and absorbed in cytoplasm

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8
Q

chlamydomonas life processes

A

M: enzyme catalysed reactions in the cytoplasm
R: uses eyespot to sense light changes -> move there for photosynthesis
H: osmoregulation. collect excess water in contractile vacuoles and expels it through PM
G: produce organic molecules till reach a critical ratio, then divide via binary fission
R: sexually or asexually
E: excretes using whole body surface (PM)
N: generates own organic molecules via photosynthesis using large chloroplast

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9
Q

Why do cells need to divide after reaching a certain size

A
  • the rate of material exchange is a function of surface area
  • the rate of metabolism is a function of volume
  • unicellular organisms require a high SA:V -> molecules for life processes diffuse in and out of the cell through the PM
  • as cell size increases the surface area to volume ratio decreases -> rate of material exchange compared to rate of metabolism isn’t enough to sustain life processes
  • if the rate of metabolism exceeds the rate at which material is transported in and out of the cell, the cell will die
  • excess heat not lost efficiently
  • increased V = increased diffusion time, increased V = increased metabolism -> need more resources
  • ## after a CRITICAL RATIO IS REACHED, cell divides (critical ratio stimulates mitosis)
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9
Q

Why do cells need to divide after reaching a certain size? [5]

A
  • the rate of material exchange is a function of surface area
  • the rate of metabolism is a function of volume
  • as cell size increases the surface area to volume ratio decreases -> volume increases faster than surface area
  • if the rate of metabolism exceeds the rate at which material is transported in and waste is transported out of the cell, the cell will die
  • cell divides to ensure the SA:V is low
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10
Q

what are emergent properties [1]

A

when individual components interact to carry out specialised functions that the parts couldn’t carry out individually

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11
Q

Define cell differentiation [2]

Also, describe the packaging of DNA in the cells [1]

A

The expression of certain genes but not others in cells. The cells have specialised structure and functions as a result

  • Active genes -> euchromatin -> expanded form -> accessible to transcriptional machinery
  • Inactive genes -> heterochromatin -> condensed form -> saves space -> not accessible to transcriptional machinery
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12
Q

2 main qualities of stem cells that make them useful [2]

Types of stem cells [4]

A
  • capable of self renewal
  • can differentiate into any specialised cell
  • Totipotent -> can differentiate into any cell type + extra-embryonic/placental tissue (eg - zygote)
  • Pluripotent -> can differentiate into any cell type in an organism (eg ESCs)
  • Multipotent -> can diff into certain types of similar cells (hematopoietic SCs)
  • Unipotent -> can’t differentiate, but capable of self-renewal (eg - muscle stem cells)
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13
Q

Explain the use of HSCs for leukemia

A
  • haematopoietic cells from bone marrow/peripheral/cord blood extracted
  • damaged WBC in the body are killed via radio and chemo
  • the HSCs are re-inserted into bone marrow where they differentiate –> healthy cells replaced
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14
Q

Explain the use of ESCs for Stargardt’s

A
  • disease: macular degeneration of receptor cells in the retina –> loss of central vision
  • ESCs treated to make retinal photoreceptor cells
  • reinserted into the retina, attach and become functional
  • central vision returns
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15
Q

Process of stem cell diff [3]

A
  • treatment with biochemical solutions to trigger differentiation
  • reinsertion into the patient
  • suppression of host immune system if cells are foreign
  • monitoring -> ensure not cancerous
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16
Q

Ethical/DA and A discussion of each type of SC (3 points per A/DA per type)

A

ESCs -
A: - can differentiate into almost any cell type
- many escs from IVF/abortions and things go waste anyway
- lower chance of genetic damage
- may provide relief to existing patients
- have been successfully used before

DA:
- lack of consent of ESCs -> are killed
- increased risk of rejection -> foreign
- increased risk of tumours
- religious/political groups may be against the whole killing the embryo vibe
- invasive surgery/potential exploitation (not the best point but in case)

ASC-
A: - adults can give informed consent
- involves no killing
- if sc from the patient, lowered rejection chance
- most adult tissues have some stem cells

DA: - smaller number of cell types it can differentiate into
- only certain/limited sources it can be derived from
- certain adult cells have no SCs

CBC:
A: - the umbilical blood is discarded anyway, so would go to waste otherwise
- little to no rejection chance
- infrastructure in place to store and collect it
- easy to obtain

DA:
- very little cord blood
- can’t differentiate into many cell types

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17
Q

4 kingdoms of eukaryotes

A
  • Protista - unicellular/multicellular without specialised tissue
  • fungi - cell wall of chitin -> obtain nutrients heterotrophically
  • plantae - cell wall of cellulose, obtain nutrients autotrophically
  • animalia - no cell wall, obtain nutrients via heterotrophic ingestion
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18
Q

organelles of cells

A

All cells:
- cytoplasm: fluid inside the cell containing all the organelles + where most metabolic rxns occur. jelly-like, mainly water + dissolved substances.
- cytoskeleton: inner scaffolding. provides structure and aids in material transport.
- centrioles + MT: c: anchor points for microtubules in processes. mt: small, cylindrical fibres -> moves chromosomes in cell division
- free ribo: synth polypeptides
(via translation fo mrna) for use in cell. has larger and smaller binding sites for tRNA and mRNA respectively

Eukaryotic
- rER: made of flattened sacs called cisternae + studded w ribosomes. synthesis of proteins for secretion
- sER: made of cisternae. lipid production
- golgi: flattened membrane sacs. processes, modifies and packages proteins for secretion.
- vesicle: single membrane org used to transport material in cell
- mitchon: has 2x-mem, inner foldings called cristae, matrix (enzymes) and mem proteins.
- PM: made of PBL w mem proteins. allows the entry of some materials but not others into the cell -> selectively permeable
- lysosome: contains enzymes. dogests damaged parts of the cell or the whole cell itself
- nucleus: double membrane structure with pores. has the genetic info of the cell. site of DNA replication, transcription and

Plant only:
- cell wall: made of cellulose,e rigid, high tensile strength, permeable -> to give structural support, ensure plant turgid, doesn’t lyse with excess water uptake
- chloro: 2x membrane structure, chlrorphyll, thylakoids, grana, stroma. site of photosynthesis.
- Vacuole: single cell membrane -> holds waste, fluids, excess water, nutrients. maintains hydrostatic pressure

19
Q

define resolution

A

the smallest distance that can be clearly seen on an electron microscope

20
Q

LM v EM

A
  • LM shines visible light through sample, EM firing electrons at sample
  • LM samples can be live, EM must be chemically treated
  • EM has greater magnification (250,000x/LM has 2,000x) and resolution (1 nm/LM has 200 nm)
  • LM: samples take a few minutes to prepare, EM can take hours
  • LM: colour images, EM: black and white
21
Q

SEM v TEM

A

SEM: high resolution image of the surface of a 3D object
TEM: High res image of a cross section of an object

22
Q

Properties of the bilayer (acc to bioninja)

A
  • Fluid -> as individual PL can move around within the layer -> hence can exo and endocytosis
  • selectively permeable: some substances cannot pass through the hydrophilic or hypho layers
23
Q

2 types of membrane protein and how they attach to membrane [2]

A
  • Peripheral: temporary proteins, attach via non-covalent attractions to one surface of the membrane
  • Integral: permanently attached, span across the membrane (associate with both surfaces)
24
Q

Membrane protein functions [6]

A
  • Junctions: serve to connect/join 2 cells
  • Enzymes: fixing to membrane -> metabolic pathways localised
  • Transport: carrier or channel proteins
  • Recognition: markers of cell identification
  • Anchorage: extracellular matrix and cytoskeleton attachment points
  • Transduction: receptor proteins for various hormones
25
Q

Describe how and why binary fission occurs in cell [5]

A
  • critical SA:V ratio reached
  • chemical signal for DNA and sometimes plasmid to replicate
  • copies of DNA move to opposite ends of the cell and attach to the PM
  • cell PM and CW grows/enlarges, then starts to form a furrow
  • furrows deepen until they meet and pinch off
  • 2 identical daughter cells
26
Q

The impact of cholesterol on PBL [3]

effect of FA chain lengths and kinks on the fluidity

A
  • cholesterol controls fluidity -> impacts which materials can pass through
  • at low temp -> cholesterol forces the PLs apart -> maintain fluidity
  • high temp, bonds between PL and cholesterol reduce fluidity (keep it from breaking apart)
  • associates with heads -> increased rigidity
  • separates tails -> lower crystallisation
  • shorter fA chain-> more fluid, susceptible to KE changes
  • more kinks, more fluid -> hard to pack
27
Q

Cholesterol structure and associations with the PLs

A
  • Contain OH group (hyphil)
  • contain steroid + HC tail (hypho)
  • associate with both parts of the membrane accordingly
28
Q

Davson and Danielli model

A

what:
- trilaminar: 2 protein layers, one lipid layer in between

issues:
- all membranes would have to have an even thickness and a constant lipid: protein ratio
- symmetrical internal and external surfaces expected
- doesn’t account for the transport of materials across the membrane
- solidification temperature data didn’t match the observations

falsification:
- fluorescent antibody tagging -> one cell with red stage, one with green -> cells fused –> red and green evenly distributed
- freeze-fracturing -> rough texture of the PM -> embedded proteins
- mem proteins were insoluble + different sizes -> don’t form this

29
Q

What are the 2 types of active transport

A
  • primary: use of energy from atp hydrolysis to transport a molecule across a membrane, against [] grad.
  • secondary: coupling the molecule with one moving down an electrochemical gradient
    - symport: same direction as
    diffusing molecule
    - antiport: opp direction to diffusing
    molecule
30
Q

what is osmolarity

A

the measure of the solute concentration in osmoles of a solute per litre of water

relative osmolarity -> hyper, hypo or isotonic in comparison to other solutions

31
Q

Uses of isotonic solutions

A
  • IV/saline drips
  • eyedrops
  • to store organs before transplantation
  • to keep areas of damaged skin moist before applying skin grafts
  • to clean wounds
32
Q

Carrier vs channel proteins

A

Carrier:
- molecule binds to a site on the integral glycoprotein (specific site -> like E-S specificity)
- conformational change that translocates the molecule to other end
- can also be used for AT if molecule is going against [] grad -> but here ATP is hydrolysed
- slower

Channel:
- integral lipoprotein provides an opening through which ions can pass
- ion-selective and may be voltage-gated to ensure passage of certain types only
- faster
- can’t be used for AT

33
Q

Na+/K+ pump

A
  • 3 Na+ bind to the intracellular site son the pump
  • ATP binds -> hydrolysis, transfers a phosphate group to the pump
  • conformational change trnslocating the Na to the other site
  • 2 K+ binding sites exposed
  • k+ bind
  • phosphate group released -> return to OG conformation, moving the K+ to the other side
34
Q

Materials stored in the vesicle may either

A
  • be secreted into the extracellular matrix by vesicle fusing with the pM
  • be stored in a vesicle for delayed release upon a chemical signal
35
Q

endocytosis defintion

A

the process by which molecules enter the cell in bulk, without crossing the membrane

36
Q

endocytosis process

A
  • the PM invaginates, forming a flask-like depression
  • the substances enter the depression, which becomes larger
  • the 2 ends of the depression meet, and the vesicle pinches off
  • the phospholipids that faced the extracellular material now form the inner layer of the vesicle
37
Q

exocytosis process (these points aren’t mark scheme points they’re kind of from the MS I rmb -> try to find better solid MS - same for endo)

A
  • vesicle fuses with the plasma membrane
  • forms a depression containing the material
  • depression flattens, and material is pushed out into the extracellular matrix
  • the PLs of the vesicle become part of the membrane
38
Q

describe the speculated theory of abiogenesis

A
  • simple organic molecules existed
    • generated from conditions on the
      earth. monomers such as nitrogen,
      methane, ammonia, etc. mixed in
      shallow oceans to make the
      ‘primeval soup’
    • exposed to energy from lightning, at
      high temp -> form organic
      molecules
  • organic molecules arranged themselves into more complex polymers
    • deep sea fissure allow geothermal
      energy to escape into the water
    • reducing inorganic compounds
      supply -> helps allow polymerisation
      of OM to occur
  • some polymers were able to self replicate
    • Likely to be RNA -> self rep
    • DNA is stable and good for storing
      genetic info, but can’t self replicate
  • these then became enclosed in a membrane -> different internal chemistry
    • phospholipids automatically form bilayers in aq
39
Q

Describe the Miller-Urey experiment

A

aim: to show that organic molecules can be synthesised from inorganic molecules

  • conditions: anoxic conditions (little oxygen) created by mixing water vapour with various gases (CH4, NH3, H2)
  • electrical discharge –> mimic lightning as an energy source
  • the mixture was cooled to concentrate components
  • found traces of simple organic molecules
40
Q

Pasteur and what his experiments proved

A
  • biogenesis: all life arises from pre-existing life
  • boiled 2 nutrient broths
  • one with a swan neck to allow air but not microbes, one with a snapped neck
  • snapped -> growth, swan -> no growth
41
Q

evidence for the endosymbiotic theory

A
  • Antibiotics have an impact on the chloroplast and mito
  • DNA - have their own, resembles that of prokary
  • replication: divide on their own, in a way similar to binary fission
  • double membrane
  • 70s ribosomes, like prokary
  • ## They transcribe their DNA and use the mRNA to synthesize some of their own proteins.
42
Q

describe the process of endosymbiosis

A
  • larger prokaryote engulfs smaller cyanobacterium or proteobacterium
  • smaller bac not fully digested
  • proves to be a good source of atp or organic molecule, providing an advantage to this bacteria
  • increased reproduction, the endosymbionts also reproduce
  • future generations contain them as organelles
  • lose some of their autonomy as a result over time

Nucleus formation:
- the prokaryote grows in size
- membrane infolds to increase sa:v
- pinches off -> forming the nuclear
envelope
- encloses the nucleoid region

43
Q

4 pieces of ‘evidence’ supporting the cell theory

A
  • cells are highly complex ->
    cells haven’t been found to form from smaller subunits
  • genetic code is universal
  • viruses produced from smaller subunits but viruses not made of cells (viruses not living and require a host organism to reproduce)
  • all known examples of growth are from cell division
44
Q

Define mutagen and describe the 3 different types

A

Mutagen: an agent that changes the genetic material of an organism (acts on DNA or in the replication machinery)

  • Physical: sources of radiation (ionising) or UV or radioactive decay
  • chemical: DNA interacting substances like reactive oxygen species or metals
  • biological: viruses like HPV, certain bacteria, etc.
45
Q

two types of oncogenes

A
  • proto-oncogene: it promotes cell growth and proliferation -> increased expression -> cancer/tumour formation
  • tumour suppressor gene: promotes apoptosis and represses the cell cycle progression -> if doesn’t function normally -> cancer formation
46
Q

describe metastasis

A
  • spread of tumour from the first location (primary tumour) to form a secondary tumour else wehre
  • if the tumour stays where it is - benign
  • if it travels - malignant
  • sec. tumour will be of the same cells as primary

HL Biology - topical sets (11 decks)

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