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Biology > A2.1 Origins of cells, A2.2, A2.3 > Flashcards

A2.1 Origins of cells, A2.2, A2.3 Flashcards

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1
Q

Conditions of early earth (6)

A

Surface Temp: 75-95 C

single global ocean (no land masses)

bombarded by asteroids/comets

no ozone layer

hotter liquid inner core –> weaker magnetic field –> high levels of cosmic + solar (UV) radiation

extreme weather - electric storms

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2
Q

Asteroids/Comets in influencing early earth conditions (3)

A

asteroid/comets brought water + other compounds

collisions + volcanoes released methane + ammonia gas

earth’s early atmosphere - methane, ammonia, water vapour, CO2

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3
Q

How were carbon compounds formed from early earth (4)

A

reducing atmosphere due to reducing gases (ammonia + methane)

able to donate electrons to other molecules –> enables chemical reactions

reactions formed more complex carbon compounds (amino acids + hydrocarbons)

carbon compounds could be joined to form building blocks of cells (proteins, nucleic acids, lipids)

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4
Q

Define metabolism (2)

A

chemical reactions that take place in the cells of an organism

enzymes speed up these chemical reactions

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5
Q

Define response to stimuli/sensitivity (2)

A

responding to changes/external stimuli in environment

e.g detecting chemicals in environment –> moving towards or away from area

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6
Q

Define homeostasis (2)

A

maintenance of constant internal conditions

e.g active transport to control concentration of ions

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7
Q

Define movement

A

organisms having control over their position and location

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8
Q

Define growth (2)

A

increase in cell size + number or dry mass over period of time

e.g cell division

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9
Q

Define reproduction

A

production of offspring + passing down of genes

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10
Q

Define excretion

A

removal of metabolic waste

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11
Q

Define nutrition (2)

A

intake/production of nutrients

nutrients obtained through external environment or produced from inorganic material

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12
Q

Necessary steps for the spontaneous origin of cells to be brought about by evolution (5)

A

formation of simple organic compounds (amino acids + hydrocarbons)

catalysis - control over chemical reactions

larger organic molecules formed from simpler ones

self-replication of molecules

compartmentalisation - membrane to enclose cell contents

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13
Q

Aim of Miller and Urey’s experiment (2)

A

proving spontaneous origin of cells

simulate earth’s prebiotic conditions

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14
Q

Miller and Urey’s closed system (3)

A

water - simulated ocean

gas inlet - to add reducing gases (methane, ammonia, hydrogen)

electrical sparks - simulate electric storms

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15
Q

Procedure of Miller and Urey (4)

A

water vaporised –> run through gases + electric sparks

cooling jacket to condense water

water droplets represented primordial soup

water droplets collected + analysed

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16
Q

Results of Miller and Urey (3)

A

water droplets contained basic organic monomers (amino acids)

proved that non-living synthesis of organic compounds was possible

could have been how carbon compounds originated

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17
Q

Explain the spontaneous formation of vesicles (2)

A

fatty acids spontaneously coalesce due to hydrophobic/hydrophillic traits

formed spherical bilayer - curved to reduce hydrophobic tail exposure

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18
Q

Function of spontaneous formation of vesicles (2)

A

interior provides different chemical environment to outside

allows cell to control/maintain conditions (e.g pH level, solute concentration)

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19
Q

RNA first genetic material hypothesis (2)

A

basis for formation of first cell-structure

acts as genetic material + catalyst

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20
Q

What is suggested if the hypothesis that RNA was the first genetic material is true (5)

A

RNA formed from inorganic sources

able to replicate using ribozymes (RNA molecules with enzymatic activity)

able to catalyse protein synthesis

RNA able to produce DNA + protein

DNA became main genetic material due to being more stable

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21
Q

Evidence to support RNA first hypothesis (3)

A

RNA can self-replicate - short RNA sequences can duplicate other RNA molecules

RNA has some catalytic activity - could have initially acted as genetic material + enzymes

ribozymes still catalyse peptide bond formation in protein synthesis

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22
Q

Miller-Urey hypothesis

A

spontaneous generation of simple organic molecules in pre-earth conditions (amino acids, carbohydrates, lipids)

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23
Q

Metabolism first hypothesis (4)

A

simple metabolic reactions –>

simple metabolic pathways –>

formed more complex molecules –>

formed basis of cells

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24
Q

“Sulfur world” hypothesis

A

forms of life based on ion-sulfur chemistry

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25
"Lipid world" hypothesis (2)
lipid bilayers evolved before RNA provide protective layer for RNA
26
Define LUCA (3)
last universal common ancestor original life forms that gave rise to all species existing today likely that there was more than one life form --> may have gone extinct through competition from LUCA
27
Features of LUCA (4)
single-celled autotrophic microbe possible RNA genome anaerobic existed in hydrothermal vents in ocean - hydrogen, methane, sulfur used as an energy source
28
Evidence for LUCA
universal genetic code across all living organisms may have originated from LUCA
29
Why the universal genetic code was preserved (3)
genetic code has been conserved essential for the transmission of genetic information any change to this genetic code could be detrimental to organism
30
Relationship between LUCA, bacteria, archaea, eukaryotes (2)
bacteria + archaea arose from LUCA eukaryotes - endosymbiosis of bacteria + archaea
31
Define a specimen
object being viewed under a microscope
32
Using a microscope (6)
start with lowest magnification + stage at the highest position. adjust coarse + fine focus to get clear image of specimen look through eyepiece anticlockwise to move specimen further from lens, and clockwise to move it closer use fine focus knob/wheel to image clearer adjust magnification - rotating nosepiece to use different objective lens
33
Define cell theory (3)
all organisms made up of one or more cells cells = smallest unit of life all cells come from pre-existing cells
34
Making temporary mounts of cells/tissues (onion) (5)
scapel to cut piece off (onion) tweezers to place onto glass slide add drop of iodine lower cover slip over specimen gently press cover slip to push out bubbles
35
Define stains (3)
distinguish between parts of cells due to them usually being transparent bind to particular structures - making it easier to identify e.g iodine for plants
36
Define cover slips/slides (4)
small thin pieces of glass hold specimen in place prevent specimen from drying out prevent specimen from touching lens of microscope
37
Define deductive reasoning (2)
starting with a rule/hypothesis testing the rule through experiments
38
Define inductive reasoning (2)
starting with examples attempting to form rule/hypothesis
39
Inductive reasoning in cell theory (2)
observation - parts of diverse organisms consist of cells hypothesis - all organisms consist of ells
40
Define magnification
number of times larger an image is than an object image size/actual size
41
Define resolution (2)
ability to distinguish 2 close points as separate rather than one clarity of image
42
micrometers to millimitres (2)
1 micrometer = 0.001millimitres 1 millimeter = 1000 micrometers
43
micrometers to nanometers
1 micrometer = 1000 nanometers
44
Quantitative vs Qualitative data (2)
quantitative - numerical + objective qualitative - observations/descriptions that are more subjective
45
Define transmission electron microscopes (3)
beam of electrons passed through specimen electrons absorbed by denser parts of sample + scattered/pass through less dense areas picked up by electron detector ---> forms image
46
Advantages of electron microscopes (2)
shorter wavelengths than light --> higher resolution magnification of 500,000x
47
Disadvantages of electron microscopes (2)
only give black and white images electron beams kill specimen
48
Define freeze-fracture in microscopy (5)
sample frozen then physically broken apart vapour of carbon/platinum fired onto fracture --> replica of fracture electron microscopy used to observe replica gives image of cell's internal structure
49
Define cryogenic electron microscopy (4)
flash-freezing sample to cryogenic temperatures (placed in liquid ethane) - makes molecules more firm/stable specimen then viewed using electron microscopy computer algorithms - create 3D image of protein molecules primarily used for structure of proteins
50
Advantages of cryogenic electron microscopy (2)
freezing sample improves resolution + reduces damage that may occur from the electron beam captures protein at instant time
51
Define immunofluorescence light microscopy (4)
fluorescent tag (fluorophore) - attached to antibodies specific for specimen antibody binds to the antigen --> structure ‘tagged’ with immunofluorescence certain wavelength of light shone onto fluorescence tag --> emits light of different colour appear as brightly coloured spots --> can locate target molecules
52
Define fluorescent dye light microscopy (3)
dye added to sample --> attach to certain structures. dye absorbs light at one wavelength --> re-emits fluorescence labelled areas become brightly coloured spots --> can locate target molecules in specimen
53
Structures of typical cells (3)
plasma membrane cytoplasm DNA
54
Features of plasma membrane (2)
separates cell from external environment controls what exits/enters cell
55
Features of cytoplasm (3)
water-based jelly-like fluid suspends organelles of cell site of enzymes that carry out metabolic reactions
56
Features of DNA (2)
contain information for cell to carry out its functions hold instructions for making proteins
57
Define prokaryotes (3)
unicellular organisms that lack membrane bound organelles no nucleus e.g bacteria, archaea
58
Features of prokaryotes (6)
cell wall plasma membrane cytoplasm naked DNA in a loop 70s Ribosomes plasmid
59
Naked DNA as a component of prokaryotes (3)
single molecule of DNA as a loop not associated with histone proteins found in region called nucleoid
60
70S ribosomes as a component of prokaryotes (2)
protein synthesis smaller mass than eukaryotic ribosomes
61
Plasmids as components of prokaryotes
small/circular pieces of DNA that can be transferred from one prokaryotic cell to another (horizontal gene transfer)
62
Define eukaryotes (4)
cells with a nucleus and membrane bound organelles usually larger than prokaryotes some are multicellular (organism consists of more than one cell) e.g animal cells, plant cells, fungi cells
63
Advantages of compartmentalisation (3)
ability to create higher concentrations of certain substances within organelles ability to separate toxins + potentially damaging substances from cell control conditions in organelle (pH for enzymes)
64
Features of eukaryotes (11)
plasma membrane cytoplasm mitochondria 80S ribosomes nucleus smooth endoplasmic reticulum rough endoplasmic reticulum golgi apparatus vesicle vacuole cytoskeleton
65
Define mitochondria (2)
double membrane bound organelle converts glucose into ATP in respiration
66
Define nucleus (3)
contains DNA associated with histone proteins and organised into chromosomes nucleus contains the nucleolus --> involved in production of ribosomes double membrane which contains pores through which certain molecules can pass (e.g glucose, RNA, ions)
67
Define the smooth endoplasmic reticulum (2)
produces + stores lipids (including steroids) detoxification
68
Define the rough endoplasmic reticulum (3)
has ribosomes attached to surface ribosomes produce proteins usually used outside of cell attached to nuclear envelope
69
Define the golgi apparatus (2)
processes/packages proteins released in golgi vesicles
70
Define a vesicle (2)
small sac that transports and releases substances produced in cell by fusing with cell membrane
71
Define a vacuole (2)
maintains osmotic balance of cell may also be used to store substances
72
Define the cytoskeleton (3)
system of protein fibres called microtubules and microfilaments holds organelles in place maintains structure of cell
73
Define paramecium (3)
unicellular protozoa heterotrophs located in aquatic environments
74
Movement of paramecium
whip-like cilia propel paramecium
75
Growth of paramecium (2)
consumes food --> enlarges certain size reached --> divides into 2 daughter cell
76
Response to stimuli of paramecium (2)
detect changes in water temp. move to warmer waters
77
Homeostasis of paramecium/chlamydomonas
constant internal environment maintained by collecting excess water in contractile vacuoles + expelling it through plasma membrane (osmoregulation)
78
Nutrition of paramecium (3)
engulfs food particles in vacuoles where digestion takes place nutrients then absorbed into cytoplasm of the cell feeds on microorganisms (e.g bacteria, algae and yeast)
79
Reproduction of paramecium/chlamydomonas (2)
sexual + asexual (more common) reproduction cell divides into 2 daughter cells
80
Excretion of paramecium (4)
metabolic waste collects in vacuoles vacuole moves to anal pore vacuole ruptures - expels waste contents into environment contractile vacuoles pump excess water
81
Metabolism of paramecium (2)
breaking down nutrients obtained from environment rely on external organic sources for energy
82
Chlamydomonas (3)
genus of unicellular green algae located all over the world (e.g soil, fresh water, oceans, snow on mountain tops) autotrophs
83
Growth of chlamydomonas (4)
produces organic molecules in photosynthesis absorbs minerals causes increase in size it reaches certain size --> divide into two daughter cells
84
Movement of chlamydomonas (2)
flagella of chlamydomonas rotates moves organism towards more favourable conditions e.g(higher light intensity)
85
Response to stimuli of chlamydomonas (2)
senses light changes using its "eye spot" (photoreceptor) moves towards brighter region to increase photosynthesis rate
86
Nutrition of chlamydomonas (2)
autotroph uses large cup-shaped chloroplast to photosynthesize
87
Excretion of chlamydomonas
whole surface of plasma membrane excretes waste products (diffusion)
88
Metabolism of chlamydomonas (2)
grows heterotrophically (photosynthesis) mixotrophically - absorb organic molecules
89
Features of animal cells (4)
centrioles - cylindrical organelles that establish/organise microtubules during cell division/metaphase lysosomes some contain cillia/flagella small temporary vacuole
90
Define lysosomes (4)
sacs surrounded by membrane containing hydrolytic enzymes (break down things using water) break down (destroy) biological molecules + old cellular organelles high concentrations found in phagocytes (white blood cells)
91
Cillia (2)
hair-like structures made of microtubules used for movement of substances past the cell
92
Vacuole in animal cells (2)
expels excess water digest food/pathogens taken by endocytosis
93
Features of plant cell (3)
cell wall chloroplasts vacuole
94
Cell wall of plant cells (2)
made of polysaccharide cellulose maintains shape of cell/protects it
95
Chloroplasts of plant cells (4)
double membrane bound organelle converts light energy into chemical energy through photosynthesis type of plastid contains pigment chlorophyll - makes it green
96
Define plastid (2)
small organelle responsible for manufacturing/storing chemical energy plant cell specific
97
Vacuoles in plant cells (2)
regulate osmotic potential of cells - stores excess water away from cytoplasm supports structure of cell through turgor pressure
98
Features of fungal cells (3)
cell wall (made of chitin) large vacuoles centrioles
99
Vacuoles of fungal cells (2)
break down molecules in cell act as storage site for small molecules (e.g ions)
100
Centrioles of fungal cells (3)
producing/organising cytoskeleton significant in cell division not present in most fungi (except male gametes of some fungi)
101
Reproduction of fungi cells (2)
budding - daughter cell (copy) buds/separates from parent cell form ring of tissue called budding scars
102
Define atypical cells (2)
contain abnormal numbers of organelles in eukaryotes do not contain some of organelles in eukaryotes
103
Skeletal muscles as atypical cells (2)
multinucleated - one single cell has multiple nuclei muscle cell formed from fusion of smaller myocytes
104
Mature red blood cells as atypical cells (2)
anucleate – no nucleus (cannot repair themselves when damaged) cell has greater haemoglobin capacity + transport more oxygen
105
Aseptate fungal hyphae as atypical cells (2)
long tube structures without septa (internal walls dividing cells) multinucleated - many nuclei in a singular cellular unit
106
Phloem sieve tube elements as atypical cells (3)
phloem hollow tube has sieve-like gaps anucleate = nucleus + other components broken down sieve elements connected to other cells with nuclei + mitochondria
107
Theory of endosymbiosis (2)
eukaryotic organisms engulfed prokaryotic cell capable of generating energy from oxygen cells remained inside host cell --> carried out aerobic respiration + providing energy to host cells (mitochondria)
108
Evolution of chloroplasts (3)
endocytosis of a prokaryotic cell prokaryotic cell could convert light energy to chemical energy eventually evolved into chloroplast
109
Evidence for the endosymbiotic theory (6)
mitochondria + chloroplast measure 8 micrometers, same length as other prokaryotes both have double membranes - inner membrane could be plasma membrane of prokaryote, outer membrane could be vesicle both have circular naked DNA both have 70S ribosomes both divide by binary fission susceptible to some antibiotics (that target prokaryotic structures)
110
Define specialised cells (2)
specific cells having different roles in a multicellular organism these cells work together to form tissues + muscles of organisms
111
Define cell differentiation (3)
involves turning on of genes necessary for function of the specialised cell and turning off of genes unecessary for function of the specialised cell regulation of gene expression can be controlled by changes in environment of the cell
112
Define cell aggregation (2)
individual cells cluster together --> more efficient to obtain + share nutrients, benefiting from group protection from predators cells in cluster evolved to become differentiated to have specialised roles

Biology (14 decks)

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