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Cell Biology Flashcards

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1
Q

What are the three laws of Cell Theory

A

Living organisms are all composed of cells
Cells are the smallest unit of life
All cells come from preexisting cells

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2
Q

What are some exceptions to Cell Theory (3)

A

Striated Muscle Cell
• Challenges the idea that cells always function as autonomous, independent units
• Much larger than most cells (300mm) and are multi-nucleated (they have multiple nuclei)

Giant Algae
• Challenges the idea that larger organisms are always made of many microscopic cells
• Giant Algae can grow up to 100mm in length, yet are unicellular and contain only one nucleus

Aseptate Fungal Hyphae
• Challenges the idea that living structures are composed of discrete cells
• Aseptate hyphae are not divided up into sub-units because they don’t have septa. Therefore, they have long undivided sections of hypha which will have a continuous cytoplasm with no end wall or membrane and contain many nuclei

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3
Q

What are the 6 functions of life?

A

Metabolism - living things undertake essential chemical reactions
Reproduction - produce offspring
Sensitivity - respond to internal and external stimuli
Homeostasis - maintenance and regulation of internal cell conditions
Excretion - the removal of waste
Nutrition - synthesis of organic molecules or absorption of organic matter
Growth - increase in size and volume

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4
Q

Outline the functions of life in a paramecium (7)

A
  1. Reactions in the cytoplasm are catalyzed by enzymes
  2. Reacts to stimuli: Reveres direction of movement when it touches a solid object
  3. Keeps internal conditions within limits
  4. Increases in size and dry mass by accumulating organic matter and minerals from its food
  5. Expels waste products of metabolism: CO2 from respiration diffuses out of the cell
  6. Reproduces asexually or sexually
  7. Feeds on smaller organisms by ingesting and digesting them in vesicles
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5
Q

Outline the functions of life in a Chlamydomonas (7)

A
  1. Reactions in the cytoplasm catalyzed by enzymes
  2. Reacts to stimuli: Senses where the brightest light is with its eyespot and swims towards it
  3. Keeps internal conditions within limits
  4. Increases in size and dry mass due to photosynthesis and absorption of minerals
  5. Excepts waste products of metabolism: Oxygen from photosynthesis diffuses out of the cell
  6. Reproduces asexually or sexually
  7. Produces its own food by photosynthesis using a chloroplast that occupies much of the cell
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6
Q

What is the importance of the SA: volume ratio?

4

A
  1. The surface area affects the rate at which particles can enter and exit the cell while the volume affects the rate at which materials are made or used within the cell
  2. As the volume of the cell increases so does the surface area however not to the same extent. As the cell gets larger its surface area to volume ratio gets smaller
  3. A cell that becomes too large may not be able to take in essential materials or excrete waste substances quickly enough
  4. However, if the cell is too small it might overheat
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7
Q

How can some cells increase their SA? (2)

A

Special cells can increase their surface area by:
o Changing their shape to be long and thin
o Halving folds in the cell membrane

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8
Q

Why do cells reproduce? (3)

A

o For growth in multicellular organisms
o For reproduction in single-cell organisms
o To replace dead/damaged cells

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9
Q

What are emergent properties?

A

Emergent properties are properties of a group that are not possible when any of the individual elements of that group act alone. (cells-> tissues - > organs)

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10
Q

What are stem cells?

A

Cells with the potential to develop into many different types of specialized cells in the body

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11
Q

How do stem cells differ from other cells? (2)

A

o Self-Renewal: Stem cells can continually divide (self-sustaining)
o Potency: Stem cells are undifferentiated (unspecialized) and can differentiate in different ways to produce different cell types

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12
Q

Outline the role of stem cells in embryonic development (6)

A
  1. After fertilization, a zygote is formed in all multicellular organisms
  2. After the formation of a zygote, there is a large increase in the number of cells. This relies on the ability of stem cells to continually divide
  3. Early embryonic stem cells are capable of becoming any type of specialized cell (pluripotent stem cells)
  4. Subsequently, cells of the embryo start to commit to different pathways of cell differentiation and become limited in the types of specialized cells they can form
  5. Embryonic development results in a unique body pattern with organs and tissues comprising of specialized cells
  6. Fully specialized cells are no longer flexible to form other types of specialized cells
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13
Q

Where can stem cells be found? (3)

A
  • Embryonic stem cells: Cells from the embryo that are undifferentiated can become any time of cell. These are found in the inner cell mass of blastocysts
  • Adult stem cells: Cells found in certain adult tissues that can become a limited number of types of cell. Adult tissues include the bone marrow or liver
  • Blastocysts are a thin-walled hollowed structure in early embryonic development that contains a cluster of cells called the inner cell mass from which the embryo arises)
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14
Q

Outline two therapeutic uses of stem cells

A

Stargardt’s Disease
• Stargardt’s disease: A genetic disease that can cause blindness in children
• Stargardt’s disease affects a membrane protein in the retina causing photoreceptor cells in the retina to become degenerative
• Stargardt’s disease is treated by injecting embryonic stem cells that can develop into retina cells into the back of the eyeball

Parkinson’s Diseases
• Parkinson’s disease: A degenerative disorder of the central nervous system caused by the gradual loss of dopamine-producing cells in the brain
• Dopamine is a neurotransmitter responsible for transmitting signals involved in the production of smooth, purposeful movements. Those with Parkinson’s disease typically exhibit tremors, rigidity, slowness of movement and postural instability
• Parkinson’s Disease is treated by replacing dead nerve cells with living, dopamine-producing ones

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15
Q

Outline the main ethical concerns regarding stem cells

A

For
o The health and quality of life of patients suffering from otherwise incurable conditions may be greatly improved
o Early stage embryos lack a nervous system so do not feel pain or suffer in other ways during stem cell procedures
o If embryos are produced deliberately, no individual that would otherwise have had the chance of living is denied the chance of life
o Larger numbers of embryos by IVF are never implanted and do not get the chance of life

Against
The use of stem cells involves the creation and death of an embryo that has not yet differentiated in order to obtain embryonic stem cells. Thus, is it ethically acceptable to create a human embryo even if it could save human lives?

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16
Q

Outline the structure of prokaryotes (6)

A
  • Prokaryotes are unicellular organisms that lack membrane-bound structure
  • Hence, prokaryotes do not have a nucleus and instead generally have a single chromosome
  • Prokaryotic chromosomes have a single, circular double stranded DNA located in an area of the cell called the nucleoid
  • Most prokaryotes have a cell wall outside the plasma membrane
  • Two of the three major domains are prokaryotes: Bacteria and Archean
  • Prokaryotes are also small (between 1-10μm)
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17
Q

Outline the structure of eukaryotes (4)

A
  • Eukaryotes have membrane bound organelles despite having a cytoplasm like prokaryotes
  • Furthermore, eukaryotes compartmentalized their organelles.
  • Eukaryotic cells are larger (5-100μm) than prokaryotic cells
  • Eukaryotes consist of both animal and plant cells:
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18
Q

What are the advantages of compartmentalization? (4)

A

Compartmentalization allows for different chemical reactions to be separated from other organelles and allows for an increase in efficiency
o Efficiency of metabolism: Enzymes and substrates can become localized and much more concentrated
o Localized conditions: Different pH and other factors can be kept at optimal levels
o Toxic/damaging substances can be isolated: E.g. digestive enzymes can be isolated
o Numbers of organelles can be changed depending on the cell’s requirements

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19
Q

Outline the process of binary fission (3)

A

• For unicellular organisms, cell division is the only method used to produce new individuals. Prokaryotes reproduce asexually using the process of binary fission

  1. The chromosome is replicated and each identical copy is moved to either end of the cell
  2. The cell elongates. New cell wall forms and plasma membrane pinches in
  3. Cross walls form two separate cells. The two new cells separate
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20
Q

Plants Vs Animal Cell (7)

A 
Plant
Cell wall
Chloroplasts present
Large central vacuole
Store excess glucose as starch
No centrioles within the centrosome area
Generally have a fixed regular shape
Do not have cholesterol in cell membrane
Animal
No cell wall
No chloroplasts
Vacuoles absent or small
Stores excess glucose as glycogen
Has centrioles within the centrosome area
Generally have an amorphous (flexible) shape
Have cholesterol in membrane
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21
Q

Prokaryote vs Eukaryote

A 
Prokaryotic
DNA in a loop form, with no proteins
DNA free in the cytoplasm
No membrane-bound organelles
70s ribosomes
Size less than 10μm
Eukaryotic
DNA wrapped around proteins
DNA enclosed within nucleus
Has membrane-bound organelles
80s ribosomes
Size more than 10μm
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22
Q

Light Microscope vs Electron microscope

A 
Light microscope
Light rays
x2000
Living or dead can be viewed
Small & portable
Easy to use
Relatively cheap
Electron microscope
Electron beams
x500 000
Has to be dead
Large
Time consuming to set up
Very expensive
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23
Q

What is resolution?

A

Resolution: The shortest distance between two points that can be distinguished

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24
Q

List the organelles within prokaryotes (8)

A

Plasma membrane - allows certain substances through and in charge of homeostasis
Cell Wall - provides the cell with a strong shape and makes it rigid
Nucleoid - stores genes and site of DNA replication
Ribosome - synthesises proteins
Cytoplasm - jelly like fluid where chemical reactions take place
Pili - enable adhesion to substances and sexual conjugation
Flagella - allows cell movement
Plasmid - aids DNA exchange

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25
Q

List the organelles with eukaryotes (6)

A

Vacuoles - contains cell sap and used for storage of water to increase cell turgor
Mitochondria - provides the cell with ATP energy
Lysosomes - Membrane-bound vesicles that contain enzymes for intracellular digestion. It is important for cell defence, digesting harmful organisms and chemicals.
Smooth/Rough Endoplasmic Reticulum - folded membranes that modify proteins
Cell membrane - lipid bilayer that acts as a protective barrier
Golgi Apparatus - marks and secretes proteins

26
Q

What is a phospholipid? (3)

A

• Phospholipids: A lipid consisting of a glycerol, bound to two fatty acids and a phosphate group
• Phospholipids are made up of two parts, a phosphate head and a fatty acid tail
• Lipids are amphipathic as:
o The head is hydrophilic (water-loving) and is attracted to water
o The tail is hydrophobic (water-hating) and is repelled by water

27
Q

Describe the characteristics of a membrane (4)

A

• Characteristic of membranes include:
o Flexible: Move and form a variety of shapes
o Strong: The hydrophobic region hates water so much that the repelling nature keeps the membrane together
o Self-healing: A hole in the membrane will self-heal due to the hydrophobic region’s hatred of water
o Semipermeable: Only some solutes may pass through the membrane

28
Q

What is the difference between integral and peripheral proteins?

A

o Integral proteins: Permanently embedded

o Peripheral proteins: Temporary embedded

29
Q

What are the functions of proteins in the membrane? (J.E.T.R.A.T)

A

o Junctions: Connects cells together
o Enzymes: Can act as enzymes
o Transport: Responsible for facilitated diffusion and protein pumps
o Recognition: For cells to identify each other
o Anchorage: Attachment points for the cytoskeleton
o Transduction: Receptors for hormones

30
Q

What is the role of cholesterol in membranes (3)

A
  • Membranes need to be fluid enough so the cell can move and necessary substances can move across the membrane
  • However, if too fluid the membrane could not effectively restrict the movement of certain substances across itself
  • Cholesterol controls membrane fluidity by making the phospholipids pack more tightly and regulates the fluidity and flexibility of the membrane by preventing tails from touching and crystallizing the membrane
31
Q

Evolution of the Fluid Mosaic Model (4)

A
  1. Danielli and Davson Model - a model that proposed the lipid bilayer was covered on both sides by a thin layer of protein.
  2. As electron microscopy emerged, there were some inconsistencies between new observations:
    o Not all membranes were symmetrical
    o Membranes with different functions also have a different composition, which the model did not allow for
    o A protein layer is not likely because it is non-polar and doesn’t interact well with water
  3. Due to freeze fracture electron micrographs (outer phospholipid layer removed, globular proteins present) and protein extraction (proteins were globular and varied in size), model was rejected
  4. Replaced by Singer and Nicolson’s Fluid Mosaic Model
32
Q

What is passive transport? (3)

A
  • Particles move from areas of higher concentration to areas of lower concentration (along a concentration gradient)
  • Hence, passive transport does not require chemical energy as it is driven through by kinetic and natural energy
  • There are four major types of passive transport: simple diffusion, facilitated diffusion, filtration and osmosis
33
Q

What is active transport? (3)

A
  • Particles move from areas of lower concentration to areas of higher concentration (against a concentration gradient)
  • Hence, active transport requires energy through ATP and the assistance of a type of protein called a carrier protein
  • There are three major types of active transport: protein pumps, endocytosis, exocytosis
34
Q

What is the definition of osmosis?

A

Osmosis: The passive movement of water between a semi-permeable membrane

35
Q

What are the three categories of osmolality?

A
  1. Solutions with a relatively higher osmolarity are categorised as hypertonic (high solute concentration) (causes cell to shrivel)
  2. Solutions with a relatively lower osmolarity are categorised as hypotonic (low solute concentration) (Causes cell to swell/burst)
  3. Solutions that have the same osmolarity are categorised as isotonic (same solute concentration ⇒ no net water flow)
36
Q

How does size and charge affect transport?

A
  1. Small & non-polar molecules easily move across membranes e.g. Oxygen, carbon dioxide
  2. Large & polar molecules find it more difficult e.g. ions, glucose
37
Q

Describe how a sodium potassium pump works

A
  1. 3 Na+ ions located inside the cell bind to the carrier protein
  2. A phosphate group is removed from ATP and binds to the carrier protein
  3. The carrier protein changes shape and transports Na+ ions outside of the cell
  4. 2 K+ located outside of the cell bind to the carrier protein
  5. The phosphate group is released, restoring the protein to its original shape
  6. The 2 K+ ions released into the cell
38
Q

What is endocytosis?

A 
The taking in of external substances by an inward pouching of the plasma membrane, forming a vesicle
o	Pinocytosis (cell-drinking): Intake of extracellular fluids
o	Phagocytosis (cell-eating): Intake of large particles (like pathogens)
39
Q

What is exocytosis?

A

The release of substances from a cell (secretion) when a vesicle joins with the cell plasma membrane
• The Golgi wraps large molecules in a vesicle, then that vesicle fuses with the membrane which pushes the material to the outside of the cell

40
Q

What were Pasteur’s discoveries? (3)

A

• Pasteur’s experiment disproved spontaneous generation (living things can arise from non-living things)
• In order to do this Pasteur:
1. Boil nutrient broth and place it in two flasks
2. One flasks had access to open air, other did not
3. A sample from each flask was incubated to check for the presence of live bacteria
• Only the one with the open neck grew bacterial cells. This supported Cell Theory #3: Cells only arise from pre-existing cells

41
Q

What is the process of the Endosymbiotic Theory?

A
  1. About 2 billion years ago, a host cell engulfed a prokaryotic cell (bacteria) capable of photosynthesis or cell respiration
  2. The bacterial cell and prokaryote formed a symbiotic relationship
  3. Over time, that bacteria cell underwent changes to eventually become a mitochondria
  4. The same could be said for photosynthetic bacteria and chloroplasts
42
Q

Evidence for the Endosymbiotic Theory

A

Mitochondria and Chloroplasts :

  1. They are about the same size as prokaryotes
  2. Divide by binary fission, like prokaryotes
  3. Have their own DNA in a circular loop, like prokaryotes
  4. Have 70s ribosomes, like prokaryotes
  5. Have a double membrane (from when they were engulfed)
  6. Genes in the DNA of mitochondria and chloroplasts are more similar to prokaryotes than the cell in which they are found
43
Q

What is mitosis needed for?

A

o Growth: Multicellular organisms increase their size by increasing their number of cells through mitosis
o Asexual Reproduction: Certain eukaryotic organisms may reproduce asexually by mitosis
o Tissue Repair: Damaged tissue can recover by replacing dead or damaged cells
o Embryonic development: A fertilized egg (zygote) will undergo mitosis and differentiation in order to become an embryo

44
Q

What is mitosis?

A

Mitosis is division of the nucleus into two genetically identical daughter nuclei.

45
Q

What is interphase?

A

Interphase - an active phase which involves multiple metabolic reactions occurring in the nucleus and cytoplasm.
G1 – First intermediate gap stage in which the cell grows and prepares for DNA replication
S – Synthesis stage in which DNA is replicated
G2 – Second intermediate gap stage in which the cell finishes growing and prepares for cell division

46
Q

What is supercoiling?

A

Supercoiling - DNA is initially loosely packed in chromatins and its info can be translated by the cell (interphase). The DNA is then condensed into chromosomes by supercoiling so it can be easily separated during mitosis

47
Q

Outline prophase (4)

A
  1. DNA Supercoil: chromatin condenses and becomes sister chromatids, which are visible under the light microscope
  2. Nuclear membrane is broken down and disappeared
  3. Centrosomes move to the opposite poles of the cell
  4. Spindle fibres begin to form
48
Q

Outline metaphase (2)

A
  1. Chromatids line up in the equator

2. Spindle fibres (microtubules) attach to the centromere of sister chromatids

49
Q

Outline anaphase (3)

A
  1. Contraction of the spindle fibres cause the separation of the sister chromatids
  2. The chromatids are now considered as chromosomes
  3. Chromosomes move to opposite poles of the cell
50
Q

Outline telophase (3)

A
  1. Chromosomes uncoil to become chromatin
  2. Spindle fibres break down
  3. New nuclear membrane reforms at opposite pole
51
Q

What is cytokinesis? (3)

A
  1. The splitting/separation of the cell immediately following mitosis.
  2. In animal cells, a cleavage furrow forms around the middle and the ring contracts pinching the cell in two
  3. In plant cells, a cell plate forms in the middle and it grows until the two cells separate
52
Q

What are cyclins? (4)

A
  1. Cyclins activate cyclin dependent kinases (CDKs), which control cell cycle processes through phosphorylation
  2. When a cyclin and CDK form a complex, the complex will bind to a target protein and modify it via phosphorylation
  3. The phosphorylated target protein will trigger some specific event within the cell cycle (e.g. centrosome duplication, etc.)
  4. After the event has occurred, the cyclin is degraded and the CDK is rendered inactive again
53
Q

Define mutagens

A

Agents that can cause mutations in one’s DNA which can lead to cancer

54
Q

Define cancer

A

The disease that results when the primary tumour spreads to other parts of the body

55
Q

Define metastasis

A

The spreading of cancerous/tumour cells through the body via the blood or other mechanisms

56
Q

Define oncogenes

A

Genes that have turn “on” to start division and a turn “off” when cell division is complete

57
Q

Define carcinogens

A

Agents that can cause cancer, such as viruses, X-rays, UV radiation

58
Q

What is the difference between a primary and a secondary tumour?

A
  • Primary tumour: A mass of cells that are dividing at abnormally fast rates for no apparent reason
  • Secondary tumour: The tumour that forms in other parts of the body after metastasis of the primary tumour
59
Q

Why do primary tumours form?

A
  1. Carcinogens or genetic mutations cause a change to the oncogene of a cell
  2. The malfunctioning oncogene causes the cell to continuously replicate
  3. The mass of defective cells forms a primary tumour
60
Q

What is the mitotic index?

A
  1. A measure of the proliferation status of a cell population (i.e. the proportion of dividing cells)
  2. The mitotic index may be elevated during processes that promote division, such as normal growth or cellular repair
  3. It also functions as an important prognostic tool for predicting the response of cancer cells to chemotherapy
  4. Mitotic index= cells in mitosis/ total number of cells

IB Biology SL (7 decks)

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