Cell Theory (SCR) Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What is cell theory?

A

Living organisms are composed of cells. cells are the smallest unit of life. cells can only arise from pre-existing cells. organisms that are only one cell carry out all functions of life in that cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why is DNA as a genetic component required in cells?

A

for protein synthesis. (contain information needed for a cell to carry out its functions. it can be copied and passed on to other cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

why is cytoplasm that is made out of mainly water and cells enzymes required in cells?

A
  • water allows for substances to be dissolved
  • enzymes catalyse different reactions- metabolism of the cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

why is a plasma membrane which is mainly made out of lipids required in cells?

A

controls entry and exit of substances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what makes a living thing living?

A

1) living things use energy in order to keep themselves in a highly ordered state

2) living things can pass on the ability to maintain a highly ordered state to their offspring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How did Pasteur disprove the theory of spontaneous generation?

A

Scientists believed in ‘spontaneous generation’ of the formation of living organisms; this was the case because there was no knowledge of microbes or cells.
- made nutrient broth by boiling water containing yeast and sugar. ( to kill any existing micro-organisms)
- poured into swan necked flasks
- due to the swan neck, very little air was able to reach the nutrient broth and so very little bacteria grew

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What makes something living?

A

movement- the ability to go from A to B

reproduction- the ability to procreate and increase the number of your species

sensitivity/stimuli- the ability to react to changes in the environment
control (homeostasis)- the ability to maintain their internal environment

growth- an irreversible increase in size

respiration- to get energy for use in cells

excretion- to be able to remove toxic metabolic waste

Nutrition- obtaining food, to provide energy and the materials needed for growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what was the pre-biotic atmosphere like?

A
  • only traces of O2 as it reacted with other elements
  • methane concentration was very high due to intense volcanic activity and many meteors
  • Carbon dioxide concentrations were also higher due to volcanic activity
    (temperature was also higher due to CO2 and CH4 trapping Greenhouse Gasses; this happened even though the sun was emitting 20% less energy
    The ozone layer (in the stratosphere) that absorbs UV, protecting us from skin cancer, would not have existed. UV is high energy, so without the ozone there would have been more chemical reactions.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Evidence for the origin of carbon compounds

A
  • this was tested in 1950 by Stanley Miller and Harold Urey
  • they mixed CO2, NH3, CH4 and H2O then used electrical discharges to stimulate lightning
  • after the experiment had been running for a day, the water turned pink; after a week it turned dark red. Analysis showed that a variety of carbon compounds had been produced including more than 20 different amino acids. —> this showed that it was possible for carbon compounds to form spontaneously on earth before life had evolved
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Spontaneous formation of vesicles by coalescence of fatty acids into spherical bilayers

A

Membranes play an important role in cells because they separate the genetic material and biochemical processes inside the cell from its outside environment; this is known as compartmentalisation
Membrane formation would have been a crucial step in the origin of cells
It is likely that the membranes of the first cells were composed of fatty acids because of the amphipathic nature of these molecules
Fatty acids are major components of lipids
When a few lipid molecules are placed in water, they will naturally form a monolayer on the surface; the polar parts of the lipid will be in water, while the non-polar parts will stick out of the water surface
If more lipid molecules are added, they form bilayers with the polar parts facing outward towards the watery environment while the non-polar parts will point towards each other
These bilayers will spontaneously form microspheres, or small vesicles, which could possibly have formed the membranes of early cells

These early membranes would have separated the internal chemistry of the cells from their outside environment
It is theorised that the fatty acids could have combined with glycerol during condensation reactions to form triglycerides as membranes evolved
Finally, these triglycerides could have undergone phosphorylation to form simple phospholipids which make up the main component of modern cell membranes
Eukaryotic cells evolved to contain multiple internal compartments, allowing further division of activity within cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

RNA as presumed first genetic material

A
  • to replicate DNA and pass genes to offspring, living organisms need enzymes
  • to make enzymes they need genes. at an earlier phase of evolution, RNA may have been the genetic material: RNA can store information in the same way as DNA but it is self replicating and it can act as a catalyst
  • some viruses use RNA as their genetic material, supporting the theory that RNA could have been used before genes made of DNA evolved
  • viruses with RNA involved tend to have a high mutation rate—> because the polymerase enzyme that is used to copy RNA is much less accurate than the one used for DNA
  • a small number of reactions are catalysed by RNA (even though it does not have a complex three dimensional structure). RNA can catalyse the formation of peptide bonds.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Evidence for a last universal common ancestor

A

There are many different possible genetic codes a species can use; however upon investigation the genetic code was found to be universal. the meanings of the 64 different codons could be assigned in a limitless number of ways, having different meanings for different species—> making it highly unlikely that two species would use the same genetic code by chance. Instead, the obvious explanation would be that they inherited it from a common ancestor (LUCA))

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Approaches used to estimate the dates of the first living cells and the last universal common ancestor

A
  • we can deduce that the earliest cells must have existed before 3.42 Gya (as stromatolites came into existence at around 3.42 Gya)
  • the oldest rocks on earth have all been metamorphosed by heat and pressure, so they do not contain clearly recognisable fossils; therefore the only evidence of life is from isotope rations. carbon originating from living organisms has a low 13C/12C ratio
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Evidence for the evolution of the evolution of the last common ancestor in the vicinity of hydrothermal vents.

A
  • researchers have identified genes that occur widely among groups of organisms that originated early in life- bacteria and archea- and if LUCA was a common ancestor it probably had the gene.
  • researchers have identified 355 protein families that are likely to have been in LUCAs genome. These are genes required for anaerobic metabolism and for fixing CO2 and N2 —> from this we can deduce LUCA lived in an environment rich on H2, CO2 and Fe (hydrothermal vents)
  • hydrothermal vents are cracks in the earths surface
    • they have high temps 60-90 degrees celsius
    • H2, CH4, NH3, S2 (readily accesable sources of energy)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Features in Eukaryotic Cells (Plastids)

A

A family of organelles with two outer membranes and internal membrane sacs
Animals- none
Fungi- none
Plants- chloroplasts for photosynthesis and amylopasts to store starch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Features in Eukaryotic Cells (Cell Wall)

A

Animals- none
Fungi- yes; made of chitin
Plants- yes; made of cellulose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Features in Eukaryotic cells (vacuole)

A

Animal- Small temporary vacuole to expel water or digest food or pathogen taken in by phagocytes
Fungi and Plants- Large permanent vacuole used for storage of substances and pressuring cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Features in Eukaryotic cells (centrioles)

A

Cylindrical organelles that organise the assembly of structures that are composed of microtubules
Animal- used to construct the spindle that moves chromosomes in mitosis and the microtubules in cilia and flagella
Fungi and Plants- Absent. Only exception is in those that have swimming male gametes with flagella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Features in Eukaryotic Cells (Undulipodia)

A

Cilia and flagella used to generate movement of cell of the fluid adjacent to a cell
Animal- Present in many e.g. the tails of male gametes (sperm)
Fungi and Plants- Absent. Only exception is in those that have swimming male gametes with flagella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Eukaryotic vs Prokaryotic cells

A

Eukaryotes have a distinct nucleus divided into compartments and has membrane bound organelles with 80s ribosomes (e.g. plant, animal and fungi cells)

Prokaryotes don’t have a distinct nucleus divided into compartments and they don’t have membrane bound organelles. they have 70s ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the advantage of having compartmentalised nucleus and cytoplasm separately?

A

In protein synthesis- the mRNA can be modified in the nucleus before being attached to the ribosome in the cytoplasm during the translation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Eukaryotic Cell components (Nucleus)

A

Function
this is where DNA is replicated and transcribed to form mRNA. the nuclear membrane has pores through it and the mRNA is transported out through these. Contains chromosomes made up of DNA which is coiled around histone proteins. This is called chromatin when the chromosomes uncoil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Eukaryotic Cell components (Rough endoplasmic reticulum)

A

Sheets of membranes called cisternea which have 80s ribosomes attached onto the outside. The ribosomes synthesise protein which is then transported out through the cisternea in vesicles and then move to the Golgi apparatus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Eukaryotic Cell components (Golgi apparatus)

A

Made up of shorter curved cisternea. it processes the proteins made by the rough endoplasmic reticulum and then these are carried to the membrane in vesicles to be secreted.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Eukaryotic Cell components (Lysosomes)

A

These are spherical and formed from the Golgi vesicles. they contain high levels of proteins including enzymes which can break down organelles, food or whole cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Eukaryotic Cell components (Mitochondria)

A

Site of respiration to release energy in the form of ATP. Has a double membrane with invaginations called cristae and a fluid inside called the matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Eukaryotic Cell components (Free ribosomes

A

These are formed in the nucleolus part of the nucleus and are known as 80s ribosomes. they synthesise proteins to work in the cytoplasm.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Eukaryotic Cell components(Chloroplasts)

A

Produce glucose and other compounds via the process of photosynthesis. they have stacks of thylakoids inside (flattened stacks of membrane) and sometimes contain starch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Eukaryotic Cell components (vacuoles and vesicles)

A

Have a single membrane and fluid inside. can be large in plants and animal cells can use them to:
- absorb and digest food inside
-used to expel excess water
vesicles are used to transport material inside cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Eukaryotic Cell components (Microtubules and centrioles)

A

Microtubules are small cylindrical fibres around the cytoplasm of cells. centrioles consist of two groups of nine microtubules. both are involved in the process of cell division

31
Q

Eukaryotic Cell components (Cilia and flagella)

A

These are whip like structures which project from the surface and are used in locomotion. Flagella are large and usually only one is present whereas cilia are smaller and normally there are many

32
Q

Atypical cell structures (challenging cell theory) Striated muscle fibres

A
  • Tissue used to change the position of body
  • building blocks are muscle fibres
  • surrounded by a membrane
  • have own genetic material
  • have an energy release system
  • much larger than most animal cells
  • have many nuclei
33
Q

Atypical cell structures (challenging cell theory) Fungal Hyphae

A
  • Fungi consists of narrow thread like structures called hyphae (many hyphae= mycelium)
  • they have a cell membrane and a cell wall
  • in some the hyphae are divided up into smaller cell-like sections by cross-walls called septa
  • But, in aseptate fungi there are no septa and each hyphae is an uninterrupted tube like structure with many nuclei
  • ## challenges the idea that organisms are made up by discrete cells
34
Q

Atypical cell structures (challenging cell theory) Algae (protoctists)

A
  • an organsim which feeds itself by photosynthesis but more simple than plants
  • store genetic information in a nucleus
  • many consist of one microscopic cell
  • some grow to be much larger (up to 100 nm) but still seem to be one single cell (giant algae) and only have one nucleus
  • chlorophyll and chloroplasts
35
Q

Endosymbiosis theory

A

Evidence suggests that all eukaryotes evolved from a common unicellular ancestor that had a nucleus and reproduced sexually. The theory that mitochondria and then chloroplasts may have then evolved from free-living prokaryotes that used to live inside host cells by the process of endosymbiosis.

36
Q

the theory that mitochondria and chloroplasts may have evolved from free- living prokaryotes that used to live inside host cells by the process of endosymbiosis. what is the evidence for this?

A
  • they have a double membrane- this may have formed when engulfed
  • they replicate by binary fission on their own like free living prokaryotes (separate from their host cell)
  • they have their own circular DNA
  • they have 70s ribosomes and so can manufacture their own proteins
  • they have organelles similar to free- living prokaryotes
  • they have their own circular DNA
  • they have organelles similar to free-living prokaryotes
  • they are similar in size to free-living prokaryotes
  • the mitochondrial inner membranes manufacture ATP like bacterial membranes
  • there is currently no free living prokaryote like a mitochondrion
37
Q

What is the advantage of being multicellular?

A
  • more cells to grow bigger
  • specialise for specific functions
  • cells can interact to perform more complex functions
38
Q

Multicellular beings have properties that emerge from the interaction of cellular components

A
  1. individual specialised cells
  2. tissues (a group of cells in the same specialised cell type joined together)
  3. organs (multiple tissues- organ properties emerge as a result of tissues working together)
  4. organ system- organs working together
  5. organism- properties of the organism emerge due to the interaction of organ systems
39
Q

Emergent properties in cells

A

emergent properties result from the interaction between different groups of specialised cells (and the organs they form) to perform more complex functions.

The brain of an organism does not control this, the properties of the cell themselves do as a result of co-operation between cells.

40
Q

why do cell look different?

A

they perform different specialised functions and so have different structures.

why can a sperm cell (haploid) can make different proteins to a phagocyte (diploid) despite being genetically identical?

not all of the genes are expressed resulting in different proteins being made in different cells (combination of proteins determines characteristic)

41
Q

how does the surface area to volume ratio increase cell sizes?

A
  • small cells have a larger ratio
  • SA must be large enough to absorb nutrients/oxygen/substances needed
  • and to excrete waste products
  • need for minerals is determined by cell volume
  • by diffusion
42
Q

Stem Cells

A
  • stem cells are undifferentiated cells which have the ability to differentiate to produce many different cell types
  • the ability to differentiate into other cells is called ‘potency’
  • they also have the ability to divide rapidly and indefinitely, this is called ‘self renewal’
43
Q

Adult Stem Cells (from tissues such as bone marrow)

A

difficult to obtain and very few cells, deep within tissues. less growth potential than embryonic cells. limited capacity to differentiate. rejection problems do not occur as compatible with adult tissues

44
Q

Cord blood stem cells (from blood in umbilical cord)

A

limited capacity to develop into different cell types- only naturally develop into blood cells. easily obtained and stored. compatible with the adult tissues that grow from the same baby

45
Q

embryonic stem cells (from embryo)

A

can differentiate into any type of cell in the body. almost unlimited growth potential. greater risk of developing into tumour cells. less chance of damage due to the accumulation of mutations

46
Q

specialisation in Embryonic Stem cells

A

the fertilised egg (zygote) divides into two cells by mitosis then four then eight and so on from the blastocyst- a mass of genetically identical cells.

  • cells in the blastocyst are unspecialised and have the ability to differentiate into many different cell types and are said to be pluripotent. these cells are known as embryonic stem cells
  • they can also self renew dividing rapidly and indefinitely until differentiation occurs
  • they have a large nucleus relative to the size of their cytoplasm (which is still diploid)
  • only some genes are expressed in daughter cells, leading to different specialisation
47
Q

What characteristics would make stem cells useful in medicine?

A
  • undifferentiated
  • are pluripotent- cab specialise to produce many different cell types
  • can be used to form a variety of different tissue due to pluripotency
  • can self renew and retain capacity to divide
  • can replace lost or damaged tissues due to their ability to differentiate
  • used in medical research
  • used to treat diseases such as leukaemia and stargardts disease
  • can produce large cultures of identical cells
48
Q

Magnification

A

how many times bigger the image is when compared to the object (increased magnification does not always mean increased resolution)

49
Q

Resolution

A

the ability to distinguish between separate points (each microscope has a limit based on radiation wavelength)

50
Q

Light microscopes

A

uses light beam to view specimens, light has relatively long wavelength, therefore poor resolution.

pros and cons of light microscope

  • does not need to be in a vaccum
  • can be used to view live specimens
  • can use thicker specimens
  • give a colour image
  • can’t see very small specimens
51
Q

Electron microscopes

A

uses beam of electrons. electrons have a short wavelength. therefore a higher resolution.

Transmission electron microscope pros and cons

2D image of electrons from above:

  • onto thin specimen
  • vaccum (non living)
  • staining needed (artefacts)
  • not colour image

Scanning electron microscopes pros and cons

3D image from electrons from below

  • not as thin specimen
  • vaccum (non living)
  • staining needed (artefacts)
  • not colour image
52
Q

Freeze fracture microscopy

A

Freeze fracture microscopyinvolves freezing a sample and then using a specialised tool to break the sample into small pieces. These small pieces are then observed using an electron microscope to see the internal structure. This is a particularly useful technique for being able to visualise structures that are not normally visible, such as the internal plasma membrane.

53
Q

Cryogenic electron microscopy

A

Cryogenic electron microscopyinvolves freezing a sample to cryogenic temperaturesto fix the molecules, making them more firm or stable. The specimen is then viewed using electron microscopy. Freezing the sample improves the resolution of the image formed and reduces damage that may occur from the electron beam.

54
Q

Immunofluorescence in microscopy

A

Immunofluorescenceis a technique used in light microscopy to better visualise certain structures. A, flourescent tag called a fluorophore, is attached to antibodies specific for antigens on a structure or cell being viewed. When the antibody binds to the antigen, the structure is then ‘tagged’ with immunofluorescence. When a certain wavelength of light is shone onto the fluorescence tag, the tag will emit light of a different wavelength that can then appear as brightly coloured spots, allowing the visualisation of the location of these target molecules.

55
Q

Fluorescent dyes in light microscopy

A

Fluorescent dyescan be used in light microscopy. When the dye is added to the sample it will preferentially attach to certain structures. As in immunofluorescence, the labelled areas will appear as brightly coloured spots, allowing visualisation of the target molecule throughout the specimen.

56
Q

units

A

m=1
dm= 1x10-1
cm= 1x10-2
mm= 1x10-3
μm= 1x10-6
nm= 1x10-9

57
Q

Viruses

A

Viruses are highly diverse in structure. all viruses have a structure called a capsid, a protein sheath that surrounds and protects the genetic material. some viral capsids are simple and spherical, like the capsid of the influenza virus, and some are much more complex such as the multilayered complex-shaped capsid of the bacteriophage (transfer of genes into bacteria)

57
Q

Actual image formula

A

Actual= Image/ magnification

58
Q

Viruses with single stranded RNA

A

HIV, influenza, coronaviruses

59
Q

Double stranded RNA

A

Rotaviruses

60
Q

single stranded DNA

A

Parvovirus

61
Q

double stranded DNA

A

Bacteriophage lambda, variola virus, herpes viruses

62
Q

RNA vs DNA

A

RNA- ribose sugar, single stranded, shorter in length

DNA- deoxyribose sugar, double helix/ double stranded

63
Q

why do some viruses have an envelope?

A

this helps to protect the capsid and viral genome. it also helps to disguise the virus from the immune system of the host cell. it also helps the virus to attach and enter new host cells.

64
Q

what is the downside to not having an envelope as a virus?

A

other viruses, such as nanovirus and adenovirus are not enveloped. viruses without an envelope may be more stable and less resistant to environmental factors than enveloped viruses, as lipid envelopes may become damaged by heat light and chemicals.

65
Q

Bacteriophage lambda

A

type of virus: bacteriophage (a DNA virus that uses a bacterium as its host)
NOT ENVELOPED
genetic material: one double stranded DNA molecule
features: can follow lytic or lysogenic cycle
Host: E-coli bacteria

66
Q

Covid 19

A

type of virus: coronavirus (an RNA virus with a crown like shape that uses an animal as its host)
IT IS ENVELOPED
genetic material: one single stranded RNA molecule
features: caused a pandemic in 2020. example of zoonosis as it was passed to humans from a bat
host: human cells and possibly other mammals

67
Q

HIV

A

type of virus: retrovirus (a virus that converts its RNA genome to DNA after infecting a host)
IT IS ENVELOPED
genetic material: two copies of a single stranded RNA molecule
features: contains the enzyme reverse transcriptase which makes DNA from the viral RNA
host: T-helper cells in the human immune system

68
Q

are viruses alive?

A

M- cannot move themselves- use the hosts transport machinery to move/spread

R- do not respire or have their own source of energy- host cell energy required to replicate

S- no

G- no, they stay the same size

R- use the hosts machinery such as enzymes and ribosomes to translate their genetic material into viral proteins

E- no

N- no

69
Q

virus entry into cells (receptor mediated fusion)

A

virus binds to the receptors on host plasma membrane. Fuse with the membrane. injects genetic material into the cell

70
Q

virus entry into cells (endocytotic pathway) (endocytosis)

A

virus is taken up by the host cell endosome (an invagination if the host cell membrane)
the plasma membrane opens up and starts to change state. it is then put in a vesicle and fuses at low pH (done due to presence of H+ ions)

71
Q

Lytic cycle

A
  1. the bacteriophage attaches to the host cell and inserts its genetic material into the host cell.
  2. the bacteriophage DNA circularises and enters the lytic cycle
  3. bacteriophages are assembled inside the host cell
  4. bacteriophages cause the host cell to lyse, causing the new viral particles to be released from the cell
72
Q

Lysogenic cycle

A
  1. occasionally the viral genome is excised from the cell genome
  2. the infected host cell divides producing daughter cells which also contain the bacteriophage DNA integrated into their genome
  3. the bacteriophage DNA integrates with the host cell genome
  4. the viral DNA is inside the host cell
73
Q

ways of viral genome reproduction

A

the lytic cycle and the lysogenic cycle.

some viruses use only the lytic or lysogenic cycle, and some virus switch between the lytic and lysogenic cycles, when exposed to certain environmental conditions such as UV light or chemical stressors. an example of a virus that can utilise both lytic and lysogenic cycles is bacteriophage lambda, a virus that infects bacterium E-coli