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Stage 2 Biology > CELLS AS THE BASIS OF LIFE > Flashcards

CELLS AS THE BASIS OF LIFE Flashcards

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1
Q

What is a cell?

A
  • The structural and basic functional unit of life (carry out processes to help an organism survive).
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2
Q

Cell theory as a unifying concept

A
  • unifying concept includes the idea that all cells arise from pre-existing cells which contain hereditary information.
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3
Q

What do all living things have in common?

A

All living things have complex and organized structures.

MRS GREN

Movement
Respire
Sensitivity (respond to stimuli)

Grow
Reproduce
Excrete
Nutrition

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4
Q

Why does the cell membrane separate the intracellular and extracellular environment?

A

Because the inside of the cell and outside are chemically different and must remain separated.

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5
Q

Define the Fluid Mosaic Model

A
  • composed of a phospholipid bilayer with protein molecules embedded through the bilayer at various points.
  • It is fluid as the membrane is liquid and constantly moving.
  • It is a mosaic because of the proteins embedded in the layer.
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6
Q

What is the function of the cell membrane?

A
  • Separate contents of the intra and extracellular environment.
  • Regulate the passage of substances in and out of the cell.
  • Enables cells to recognize one another and certain ligands, i.e. hormones.
  • Enables the attachment of the cytoskeleton.
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7
Q

How do cells recognize one another?

A
  • The polysaccharides attached to the proteins embedded in the cell membrane act as receptors.
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8
Q

What are differences between prokaryotic and eukaryotic cells?

A

Prokaryotic:
- Generally smaller than eukaryotic cells (can be as small as 1 micrometer). One tenth of a size of a eukaryotic cell.
- They are relatively unspecialized.
- The cell membrane is contained within a plasma membrane. The plasma membrane is usually surrounded by a cell wall.
- They have short pili on theoutside and a long flagella.
- they DON’T have a nucleus.
- DNA exists within the cytoplasm, as a singular, circular chromosome, and also sometimes in rings called plasmids.
- The have no membrane bound organelles, but do have ribosomes.
- They are single celled organisms.

Eukaryotic:
- More specialised internally
- Larger than prokaryotic cells (10-100 micrometers).
- Contain membrane bound organelles, each with a specific task within the cell.
- They contain a nucleus which stores the DNA of the cell.
- DNA is found in linear chromosomes in the nucleus.
- They have a cell membrane and a cell wall.
- Protists, plants, animals and fungi are eukaryotic.

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9
Q

What is the structure and function of the nucleus?

A

STRUCTURE:
- Has two membrane layers called the nuclear envelope, containing nuclear pores.
- Molecules use these pores to enter and exit the nucleus. But they must pass through the proteins within the pores that act like gates.

FUNCTION:
- Controls cellular activity because DNA is stored in the nucleus.

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10
Q

What is the function of the nucleolus?

A
  • Is in the nucleus
  • Makes ribosomal RNA for the ribosomes.
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11
Q

Describe the structure and function of DNA.

A

STRUCTURE:
- DNA is stored in the nucleus.
- Chromatin (a protein) is associated with nuclear DNA. During cellular respiration chromatin condenses the long strands of DNA into shorter ‘x’ shapes known as chromosomes.

FUNCTION:
- DNA contains hereditary information and information on how the cell functions.

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12
Q

Describe the structure and function of chloroplasts.

A

STRUCTURE:
- Exists from a closely related plant organelles called plastids.
- They have two outer membranes.
- Inside they contain membranous flattened sacs called thylakoids.
- The stacks are called grana, singe stacks called a granum.
- Stroma is the fluid around the sacs
- Thylakoid membranes contain chlorophyll, required for photosynthesis.
- Enzymes required for photosynthesis are made inside the stroma.

FUNCTION:
- provide the site for photosynthesis to occur (converting light energy to chemical energy).

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13
Q

Describe the structure and function of the mitochondria.

A

STRUCTURE:
- They have their own circular DNA (suggesting they were single celled organisms in the past).
- They have two membranes, an outer and an inner.
- The inner membrane is highly folded into critae.

FUNCTION:
- They provide the site for cellular respiration.

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14
Q

Describe the structure and function of the vacuole in plant cells.

A

STRUCTURE:
- It is a fluid filled space bound by a membrane, and is part if the endomembrane system.

FUNCTION:
- A place to store organic compounds such as proteins and sugars. Also stores inorganic molecules such as ions.
- Plant cells also use their vacuole for metabolic waste that would endanger the cell if they remained in the cytoplasm.
- It plays a major role in the growth of the cell as it absorbs water, which elongates the vacuole, and allows the cell to increase in size.

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15
Q

Describe the structure and function of vacuoles in animal cells.

A

STRUCTURE:
- Smaller vacuoles than plant cells, and more of them, called vesicles.
- Two types of vacuoles - food vacuoles (lysosomes), and contractile vacuoles.

FUNCTION:
- Contractile vesicles pump excess water out of the cell.
- Lysosomes contain enzymes which digest macromolecules when a cell engulfs a particle (phagocytosis)

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16
Q

Describe the structure and function of a vacuole in fungi.

A

STURCTURE:
- Similar to plant cell vacuoles in that they are large.

FUNCTION:
- Act as a storage site but also contain enzymes that break down compounds.

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17
Q

Describe the structure and function of the rough endoplasmic reticulum.

A

STURCTURE:
- A system of membranes (endomembrane system) that extends through the cytoplasm.
- Forms a series of ‘passages.’
- Has ribosomes attached.

FUNCTION:
- It’s the site of protein and membrane synthesis due to the attached ribosomes.
- Passages are vital to the transportation of materials around the cell.

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18
Q

Describe the structure and function of the smooth endoplasmic reticulum.

A

STRUCTURE:
- No ribosomes attached.
- Has enzymes embedded in the membrane.

FUNCTION:
- Is involved in lipid synthesis, carbohydrate metabolism, and detoxification of drugs and other poisons.
- Enzymes are vital to the synthesis of fatty acids and, phospholipids, steroids, and other lipids.

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19
Q

Describe the structure and function of the Golgi apparatus.

A

STRUCTURE:
- Stacks of flattened sacs.

FUNCTION:
- Involved in packaging and secreting proteins and carbohydrates.
- Small ‘membrane balls’ called vesicles that contain materials like carbohydrates, bud off from the Golgi body and move to the cell membrane, where they fuse with the cell membrane and expel their contents outside the cell (exocytosis).

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20
Q

Describe the structure and function of the cytoskeleton.

A

STRUCTURE:
- A network of fibers throughout the cytoplasm.
- Made of three main filaments, microtubules, intermediate filaments, microfilaments, made from the proteins actin and tubulin which are classified as globular proteins.

FUNCTION:
- Gives cells their shape, is involved in cell movement, holds organelles in place, and strengthens cells.
- Acts as a skeleton for the cell but can be dismantled and reassembled in a new location (similar to a scaffold).
- Enables the cell to hold specialized shapes of surfaces which mostly increase the SA: V ratio.

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21
Q

Describe the structure and function of microtubules.

A

STRUCTURE:
- Straight hollow rods made from tubulin.
- Microtubules elongate by adding tubulin molecules to its ends, which can be disassembled to build microtubules elsewhere in the cell.

FUNCTION;
- They act as tracks that organelles equipped with motor molecules can move along
- Also involved in chromosome separation during mitosis and can make up centrioles.

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22
Q

Describe the structure and function of intermediate filaments.

A

STRUCTURE:
- Include a diverse range of cytoskeletal elements of the keratin protein family.

FUNCTION:
- They are a more permanent fixture in cells thus are necessary to reinforce the shape and fixture of the organelles.
- They are specialized for bearing tension.

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23
Q

Describe the structure and function of microfillaments.

A

STRUCTURE:
- Made of actin.

FUNCTION:
- Involved in intracellular movement.
- Part of the contractile apparatus in muscle cells, integrates with thicker myosin proteins. The contraction of the muscle results in the actin and myosin sliding past one another.
- Myosin bundles are responsible for the cleaving of the cell during cell division.
- They also act as support structures, such as bundles of microfilaments make up the core of the microvilli.

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24
Q

Describe the structure and function of ribosomes.

A

STRUCTURE:
- Contain a large subunit and a small subunit.

FUNCTION:
- Are involved in protein synthesis.
- Two types of ribosomes - free in cytosol, or bound to the rough endoplasmic reticulum.
- Most proteins produced by free ribosomes function in the cytosol.
- Bound ribosomes produce proteins that are generally destined for inclusion into the membrane or packaging into organelles such as lysosomes.

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25
Q

What organelles do all three types of cells share (from plant, animal and fungi)?

A
  • Nucleus
  • Mitochondria
  • Cytoskeleton
  • Ribosomes
  • Rough and smooth endoplasmic reticulum
  • Golgi body
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26
Q

What organelles do plants and fungi share?

A
  • Cell wall
  • Large vacuole
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27
Q

What organelles are specific to plants?

A
  • Chloroplasts
  • Cell wall - made of cellulose.
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28
Q

What organelles are specific to animal cells?

A
  • Lysosomes
  • Centriole
  • Small vacuoles (vesicles)
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28
Q

What organelles are specific to fungi?

A
  • Cell wall - made of chitin
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29
Q

What is energy and what processes require them?

A
  • Defined as the capacity to do work.
  • Movement, active transport, exocytosis, endocytosis, phagocytosis, and synthesis of macromolecules all require energy.
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30
Q

In what form must energy be obtained in?

A
  • Physical or chemical.
  • In both cases it is transformed so that it is useful.
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31
Q

What does energy allow the cell to do?

A
  • allows the cell to grow, repair, reproduce, and function normally.
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32
Q

How is physical energy obtained?

A
  • Some cells use sunlight as physical energy.
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33
Q

How is chemical energy obtained?

A
  • Cells take in rich energy compounds, rich in the form of chemical energy.
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34
Q

What contributes to a stable intracellular environment?

A
  • Optimum temperature, pH, water and solute balance, oxygen and waste concentration.
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35
Q

Define an autotroph.

A
  • Self feeding.
  • Most autotrophs get their physical form of energy from the sun and convert it to be stored as chemical energy through photosynthesis.
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36
Q

Define a heterotroph.

A
  • Must gain chemical energy from another source.
  • it is eating to create physical energy.
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37
Q

What is the process of photosynthesis, include an equation?

A
  • Converts sunlight to chemical energy.
  • Occurs in the chloroplasts of plant cells.
  • Chlorophyll absorbs light in the granum (stacked thylakoids).
  • Enzymes which catalyze the reaction are found in the granum and stroma.

sunlight, chlorophyll in leaves
6CO2(g) + 6H2O(l) -> C6H12O6(aq) + 602(g)

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38
Q

Describe the process bonds breaking and forming during aerobic respiration - in an energy related context.

A
  • Energy is required to break bonds, and energy is released when new bonds are formed.
  • Respiration is an exothermic reaction because the amount of energy required to break the bonds in the reactants (glucose and oxygen) is less than the energy released when the bonds in CO2 and H2O are formed.
  • Some of this energy is used by the cell to do work, but the rest of it is lost as heat.
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39
Q

Describe ATP - in an energy related context.

A
  • ATP is adenosine triphosphate.
  • ATP stores energy and has adenine bonded with a ribose sugar (like RNA). This is bonded to 3 phosphate groups (triphosphate).
  • The third bond is unstable and can be hydrolyzed (broken with water) to from Adenosine Diphosphate + Pi and energy (ADP).
  • Cells use ATP continuously but also produce it continuously through metabolic processes.
  • The energy required to fuel this process comes from cellular respiration.
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40
Q

Describe the process of aerobic respiration, using equations.

A
  • Occurs in the cytoplasm and mitochondria where chemical energy is transformed into a form stored in ATP molecules.
  • Uses oxygen to break down glucose into carbon dioxide and water.

C6H12O6 + 6O2 -> 6CO2 + H2O.

  • The breakdown of 1 glucose molecule produces 36 ATP molecules when oxygen is used (aerobic respiration).
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41
Q

Describe the process of fermentation in plants, animal, and fungi.

A
  • In plants and yeast, ethanol fermentation occurs.
  • In animals fermentation produces lactic acid.
  • 2 ATP molecules are produced per glucose molecule for both processes.
  • Both processes occur in the cytoplasm

Lactic acid fermentation:
C6H12O6 -> 2C3H6O3

Ethanol fermentation:
C6H12O6 + 6O2 -> 2C2H5OH + 2CO2

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42
Q

What is the reaction pathway for fermentation?

A
  • Both aerobic and anaerobic respiration occur in steps.
  • They both begin with glycolysis but only aerobic respiration continues with the Kreb cycle.
  • This is why fermentation only yields 2 ATP per glucose.
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43
Q

Why do metabolic processes occur in a reaction pathway (i.e., steps)?

A
  • The reaction doesn’t occur too quickly and burn the cell.
  • Maximizes the amount of energy stored in the ATP molecules during the process. BUT some is lost as heat. This is what maintains the optimum temperature for the cellular processes.
  • Intermediate compounds can be produced and used elsewhere by the cell.
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44
Q

Autotrophs inputs

A
  • They MAKE large, energy rich compounds FROM small inorganic compounds.
  • They don’t need to be supplied with large compounds as they produce their own.
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45
Q

Heterotrophs imputs

A
  • They intake a lot of inorganic compounds and large organic compounds because they can’t make it themselves.
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46
Q

How do autotrophs convert inorganic substances to produce organic substances?

A
  • CO2 and H2O are taken in and photosynthesized to make glucose (an organic compound).
  • Fixated nutrients (nitrite ions, nitrate ions, phosphorus ions, and sulfur ions) are take up by plants through their roots from the soil.
  • These fixated nutrients combine with glucose to form lipids, amino acids, bases, and nucleotides.
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47
Q

What are the outputs of fermentation?

A
  • Dependent on the organism
  • Animals: output is lactic acid from glucose
  • Plants and yeast: output is ethanol and carbon dioxide from glucose.
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48
Q

Describe the process of diffusion.

A
  • The movement of a substance from a region of high concentration to a region of low concentration.
  • The movement of substances goes with the concentration gradient.
  • This is a passive process as it doesn’t require energy.
  • The cell membrane is not equally permeable to all substances due to differences in the molecule such as size, charge, and lipid solubility.
  • Diffusion occurs through the membrane bilayer.
  • The diffusion of one molecule is unaffected by the concentration gradient of another molecule.
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49
Q

Describe the point of reaching equilibrium in diffusion.

A
  • Diffusion will continue until equilibrium has been met, however this doesn’t mean the particles stop moving, it just means they stop moving in one direction.
  • The movement of particles in one direction will balance the movement of particles in the opposite direction.
  • Under these conditions the net movement is 0 and there is no concentration gradient.
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50
Q

Describe the process of osmosis.

A
  • The movement of a solvent from a region of low solute concentration to a region of high solute concentration.
  • osmotic pressure is what helps mantain an animal cell’s shape and provides support in plant cells.
  • If osmotic pressure is not correct, the cell may shrivel or burst (but this is less severe in plant cells because of the cell wall).
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51
Q

Describe the three different stages of osmotic pressure in animal cells.

A

Hypertonic - cell is shriveled, meaning more water is leaving, meaning higher solute concentration outside the cell.
Isotonic - completely balanced, equilibrium has been reached, no concentration gradient.
Hypotonic - cell has swollen up, meaning more water is entering the cell, meaning there is higher concentration of solute inside the cell.

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52
Q

Describe the three stages of osmotic pressure in plant cells.

A

Hypotonic - more water entering the cell, higher concentration of solute in the cell. Plant cell becomes turgid.

Hypertonic - They become flaccid.

53
Q

Describe membrane selectivity.

A
  • Not all molecules are able to diffuse through the cell membrane, therefore proteins facilitate diffusion.
  • Therefore, the plasma membrane is not only semi-permeable but also selectively permeable.
54
Q

Describe the process of facilitated diffusion + 2 examples.

A
  • For molecules that aren’t selectively permeable t the plasma membrane.
  • Go through channel proteins which bind to specific ions.
  • Go with the concentration gradient
  • Is a passive process
  • Used for molecules such as glucose and amino acids.
55
Q

Describe the process of active transport.

A
  • Requires energy.
  • Moves substances against the concentration gradient.
  • Done using carrier proteins.
  • Multiple types of active transport including:
    Phagocytosis
    Pinocytosis
    Exocytosis.
56
Q

Define the process of endocytosis.

A
  • The cell engulfs particles with the cell membrane to transport materials into the cell when they are too large to diffuse through the membrane.
  • Two types, phagocytosis and pinocytosis.
57
Q

Describe the process of phagocytosis.

A
  • Engulfs large particles into the cell.
  • Is a specific process

PROCESS:
1. The cytoskeleton moves and shifts to form an invagination in the cell membrane.
2. A large particle enters this invagination and is engulfed into the cell and into a vesicle through the cytoskeleton.
3. The vesicle fuses with a lysosome to transport the material into a lysosome, where enzymes break the large molecule into smaller molecules that can be used by the cell.

58
Q

Describe the process of pinocytosis.

A
  • It is a smaller processes than phagocytosis because it engulfs liquids.
  • Is a non-selective process.

PROCESS:
1. The cytoskeleton shifts to form an invagination in the cell membrane.
2. The liquid content is engulfed by the cell into small vesicles.
3. The vesicle fuses with a lysosome and the liquid is transferred into a lysosome and is broken into smaller pieces to be used by the cell.

59
Q

Describe the process of exocytosis.

A
  • The reverse process of endocytosis.

PROCESS:
1. Vesicles are formed from the Golgi body where they bud off from the Golgi apparatus and into the cytoplasm.
2. Molecules packaged into vesicles fuse with the cell membrane.
2. Contents are expelled into the extracellular environment.

60
Q

Define transport proteins and their role.

A
  • Are involved in transporting materials across the cell membrane.
61
Q

Describe how carrier proteins work.

A
  • Involved in facilitated diffusion and active transport.
  • They transport sugars, amino acids, and nucleosides (components of nucleotides).
  • Whether the carrier the protein is involved in active or passive transport is dependent upon the material being transported in and out of the cell.
  • They differ from channel proteins because they are very selective.
62
Q

Describe a sodium/potassium pump.

A
  • Facilitates the movement of ions across the membrane.
  • Ion’s are moved against the concentration gradient requiring energy in the form of ATP.
63
Q

Describe a glucose/sodium transport protein/pump.

A
  • The pump has a particular shape complementary to the glucose molecule.
  • As more glucose enters the cell, sodium ions outside the cell generate a charge gradient which allows glucose molecules to move against the concentration gradient.
  • This process doesn’t require ATP for this reason.
  • Therefore, as sodium enters the cell, t brings glucose with it.
64
Q

What are the factors that affect exchange across the cell membrane?

A
  • SA: V ratio (explains the size of cells)
  • Concentration gradients (compares the concentration of the intracellular and extracellular space)
  • Nature of exchange materials (determines how easily they can pass through the membrane).
65
Q

Define how SA: V ratio affects exchange across the membrane.

A
  • As the cell increases its size, the SA: V ratio decreases.
  • This means there is less surface area being exposed to the environment compared to the volume of the cell, thus less room for exchange of materials to occur across.
  • As the cell needs to obtain nutrients and excrete waste into the extracellular environment, the SA: V ratio plays a big role because the efficiency of exchange of these materials with the extracellular space decreases.
66
Q

Describe how concentration gradient affects rate of exchange across the cell membrane.

A
  • In diffusion and osmosis particles move with the concentration gradient.
  • The greater the difference in concentration, the faster the movement across the cell membrane.
67
Q

Describe how the nature of exchange of materials affects the rate of exchange across the cell membrane.

A
  • Small uncharged particles such as O2 and CO2 can easily passthrough the membrane via diffusion.
  • Larger or charged particles such as glucose or ions may require assistance from channel proteins, carrier proteins, or exocytosis/endocytosis.
  • Ions will repel either the polar head or the non-polar tail of the phospholipids, therefore require assistance in exchange across the membrane.
68
Q

Define the meaning of cell metabolism + give examples.

A
  • Biochemical processes that occur in the cell.
  • This includes processes such as macromolecule synthesis, and macromolecule breakdown.
  • Occurs in both prokaryotes and eukaryotes.
  • In eukaryotes many of these processes take place in specialized structures that are often bound by membranes, e.g., mitochondria, chloroplasts, rough endoplasmic reticulum, because they provide a greater surface area.
69
Q

What is the importance of membranes?

A
  • Maximizing membranes increases the SA: V ratio, which increases the amount of products you can get for the same amount of time.
  • The larger surface area provides more places for reactions to occur.
70
Q

What are the role of enzymes in metabolism + examples?

A
  • Enzymes involved in metabolic processes are embedded in the membrane.

EXAMPLES:
Examples include:
- ATP synthesize in mitochondria
- Chlorophyll in thylakoids.

71
Q

How is metabolism regulated through glycolysis?

A
  • Glucose is broken down in cellular respiration, occurring in small steps called a metabolic pathway.
  • A specific enzyme catalyzes each reaction.
  • Glycolysis occurs in the cytoplasm, which occurs in both aerobic and anaerobic respiration.
  • Intermediate compounds are created by these enzymes.
  • in the end, glucose is converted to 2 pyruvate, meaning 4 ATP molecules.
  • BUT because 2 ATP molecules are required to facilitate the reaction, it is a net gain of 2 ATP molecules.
72
Q

Why does metabolism occur in steps?

A
  • To make intermediate compounds which can be used for specific purposes.
  • Small steps means we can control and regulate the reaction.
  • Small amounts of energy are being released in each step.
73
Q

How are biochemical processes influenced?

A
  • They’re regulated by enzymes.
  • Enzymes have optimal conditions they work in, therefore if these are changed, the environmental conditions for the biochemical reaction are changed.
  • Thus, biochemical reactions are influenced by environmental factors.
74
Q

What is poison + examples?

A
  • A chemical that interferes with a biochemical process.

EXAMPLES:
- cyanide
- carbon monoxide
- snake venom

75
Q

How does poison interfere with biochemical pathways?

A
  • They disable one or more of the enzymes involved in the reaction pathway.
76
Q

What is the main point in ‘uses of chemicals’

A
  • chemical use must be monitored and assessed over a period of time to ensure there are no detrimental effects.
77
Q

What is an example of a good chemical usage?

A
  • Use of immunosuppressants means that people receiving organ transplants do not reject these.
  • Hormone treatments are used in IVF.
78
Q

Explain an example of chemical usage and its associated advantages and disadvantages.

A

In agriculture:
- Chemicals and hormones are used as pesticides to help plants grow, but it had flow on affects.
- DDT was a chemical used as a pesticide but it also affected pollinators, which lead to unintended consequences of dismantling an entire food web such that predators including eagles died.

79
Q

What is a chemical that inhibits protein synthesis in prokaryotic cells?

A

Tetracycline - Inhibits tRNA binding to ribosomes.

Streptomycin - prevents proper assembly of ribosomes.

Chloramphenicol - stops growing peptide moving from one tRNA to the next.

Erythromycin - strops growing peptide moving to a new codon.

Rifamycin - prevents mRNA synthesis.

80
Q

What is a chemical that inhibits protein synthesis in eukaryotic organisms?

A

cycloheximide - stops growing peptide moving from one tRNA to the next.

Amanitin - stops mRNA synthesis.

81
Q

What is a chemical that inhibits protein synthesis in both prokaryotic and eukaryotic cells?

A

Puromycin - causes incomplete peptides to fall off the ribosome.

Actinomycin - prevents RNA synthesis.

82
Q

What is so important about cell division and how does it occur in both prokaryotic and eukaryotic cells?

A
  • The idea that all cells arise from pre-existing cells.

EUKARYOTIC:
- In multicellular eukaryotes, regular body cells divide by mitosis, whereas sex cells (gametes) are produced by meiosis.

PROKARYOTIC:
- Through binary fission.

  • In each of these cases, the DNA is replicated before division occurs.
  • This means genetic information is carried from one generation of cells to the next.
83
Q

Define the process of asexual reproduction in plant cells.

A

-Is propagation of an organism without fertilization taking place.
- This produces a genetically identical copy of the parent cell, therefore the offspring is a clone.
- This is done through mitosis in eukaryotic organisms.

PLANTS:
- Plants can asexually reproduce by budding, creating bulbs or sending out runners.
- Sea stars, anemones, hydras, and even some seaworms can produce asexually.

84
Q

Describe the process of budding in plants.

A
  • Buds are produced by mitosis.
  • Hydra reproduce in this manner.
  • The bud is genetically identical to the parent (except for the rare occurrence of mutations), therefore the bud is a clone.
  • The bud breaks off, and grows itself, and this can create other smaller buds as well.
85
Q

Describe the different process of vegetative propagation in plants.

A
  • Plants can reproduce using mitosis in different processes.
  • They have a range of undifferentiated cells, therefore they can sustain or renew growth indefinitely. - they can turn from undifferentiated cells to specialized cells under different conditions, which is difficult for humans to do.

PROCESSES:
1. Fragmentation - part of the plat is cut off which grows roots to become a whole new plant (grass).
2. Sprouts from root systems - can produce whole forests.
3. Apomixis - Where a plant produces a flower that does not need fertilization - the ovule becomes a seed which is then windblown for dispersal (like dandelions).

86
Q

Difference between somatic cells and gametes.

A
  • Somatic cells are non-sex cells. They are replicated through mitosis.
  • They have a full complement of chromosomes (in humans it is 46).
  • In gametes, these are sex cells that require fertilization to restore the diploid number of 46 in humans.
87
Q

Describe the process of binary fission.

A
  • It is the replication of prokaryotic organisms.
  1. The chromosomes are duplicated and separated.
  2. The cell elongates to move the duplicated copies further apart.
  3. The cell pinches in the middle of the equator.
  4. The cell splits into the division of two genetically identical daughter cells.
88
Q

What are the phases in mitosis?

A
  • PMAT
  • Prophase, metaphase, anaphase, telophase, and cytokinesis.
89
Q

Describe the process of interphase before mitosis occurs.

A
  • Essentially the normal life of a cell.
  • It lasts 90% of the cell’s life.
  • Cells growth and metabolic activities occur during this time.
  • The chromosomes replicate but DO NOT condense during this time and are still present in loosely packed chromatin.
  • The centrioles duplicate forming two pairs that line up outside the nucleus.
90
Q

Describe what happens during prophase in mitosis.

A

EARLY:
- The chromosomes begin to condense and become visible as loose x-shapes.
- These x shapes are sister chromatids joined by a centromere.
- The centromere begins to move away from each other, retaining connections through microtubules, creating the mitotic spindle.

LATE:
- Nuclear membrane breaks into fragments.
- The chromosomes have become more condensed.
- The microtubules of the mitotic spindle invade the are of the nucleus and connect to the kinetochore on the centromere region.

91
Q

Describe what happens in metaphase during mitosis.

A
  • The centriol pairs are at opposite ends or poles of the cell.
  • The chromosomes line up on the metaphase plate, where the centromeres are aligned.
  • The chromosomes lie with their long axes at roughly right angles to the spindle.
  • The microtubules of the spindle are connected to the centromere.
92
Q

Describe what happens during anaphase of mitosis.

A
  • The pairs of chromatids move apart.
  • Each chromatid is now considered a chromosome.
  • The spindle pulls the chromosomes towards the poles, and at the same time the poles of the cell move further apart.
93
Q

Describe what happens during telophase in mitosis.

A
  • The polar fibers extend even more.
  • The daughter nuclei begin to form from the fragments of the parent nuclear membrane.
  • The cleavage furrow forms.
  • Nucleoli reappear and the chromatin fiber uncoils.
94
Q

Describe what happens during cytokinesis in mitosis.

A
  • The division of the cytoplasm occurs along the cleavage furrow which pinches the cell in two.
95
Q

Define the meaning of meiosis.

A
  • Sexual reproduction.
  • The source of genetic diversity due to the processes that occur in the process.
  • This allows for evolution to occur.
96
Q

Explain what is required for sexual reproduction to occur.

A
  • Sexual reproduction requires genetic information from two cells, called gametes (sperm and ova).
  • Gametes are haploid (they have half the normal chromosome number of somatic cells (23)).
  • Gametes fuse through fertilization and produce a zygote.
  • In order for the life cycle (from adults in one generation to adults in the next generation), gametes must be produced through meiosis.
97
Q

Explain the difference between somatic cells and gametes.

A

Somatic cells - non-sex cells, reproduce through mitosis. Have a full complement of chromosomes (in humans it is 46).
Gametes - sex cells, and reproduce through meiosis.

98
Q

Explain the difference between haploid and diploid.

A
  • Each somatic cell has 2 of the same chromosome types (homologous pair).
  • Cells which contain chromosomes in homologous pairs are DIPLOID.
  • When a cell only has half the number of chromosomes it is HAPLOID.
  • In meiosis, fertilization restores the diploid number.
99
Q

What is the purpose of meiosis, and what is the difference between meiosis 1 and meiosis 2?

A
  • Meiosis has two consecutive divisions, meiosis 1 and miosis 2, resulting in half the chromosome number (haploid).
  • THE PURPOSE OF MEIOSIS IS TO HALF THE CHROMOSOME NUMBER.
  • It also includes genetic variability.
  • Meiosis 1 separates the homologous pairs, and meiosis 2 separates the sister chromatids.
100
Q

State the four sources of genetic variation in reproduction?

A
  • Crossing over of the homologous pairs.
  • Random/independent assortment.
  • Random fertilization
  • Mutations (only way to produce diversity in mitosis)
101
Q

Describe how crossing over of the homologous pairs can result in genetic variation of the offspring.

A
  • This occurs during prophase 1.
  • Sections of non-sister chromatids may touch, break off, rejoin, and therefore transfer genetic information of the same gene.
  • This occurs in chiasma (chiasmata plural).
  • There can also be more than one crossover between a homologous pair.
  • This means each chromosome contains some information from the maternal and paternal parent.
102
Q

Describe how independent assortment leads to genetic variation.

A
  • When the homologous pairs line up in across the metaphase plate and this is random (no particular order).
  • This occurs during metaphase 1.
  • This means in the first meiotic division, you will have a mix of maternal and paternal chromosomes in each daughter cell, contributing to variation.
103
Q

What is important to note about each cell from meiotic division?

A
  • Each cell is haploid.
  • And each cell is unique.
104
Q

Describe how random fertilization contributes to genetic variety.

A
  • Each sperm and ova produced from meiosis are different, therefore there is a lot of genetic diversity between sperm and ova.
  • This means the zygote produced will be genetically unique.
105
Q

What is the product of mitotic division, in comparison to meiotic division?

A
  • Mitosis produces diploid cells.
  • Meiosis produces haploid cells.
106
Q

How does an organism grow?

A
  • Cells reproduce to make new cells, which assist in the growth of an organism.
107
Q

What is apoptosis?

A
  • Ensures that irreparable cells will not divide.
  • Therefore, the cell self destructs.
108
Q

What is cancer?

A
  • A change in DNA sequence that makes a cell divide uncontrollably.
109
Q

What is the purpose of cell division?

A
  • To replace lost cells from general living or during injury.
110
Q

What are stem cells and state the difference between undifferentiated and differentiated cells?

A
  • Undifferentiated cells.
  • Therefore, they have the capability to differentiate into any type of cell.
  • A differentiated cell has specialized structure and function.
111
Q

What does one daughter cell remain after cell division?

A
  • One daughter cell remains differentiated (stem cell).
  • The other continues to change and differentiate to undertake specialized functions.
112
Q

State the different stages in the cell cycle?

A
  • Interphase (90% of cells life)
  • M phase (mitosis)

DURING INTERPHASE:
- G0
- G1
- S phase
- G2

113
Q

State where the checkpoints are in the cell cycle?

A
  • At the end of G1
  • End of G2
  • Middle of M phase (during metaphase)
114
Q

What happens to a cell when it reaches a checkpoint?

A
  • The cell halts all activity and the cell does not proceed through the rest of the cell cycle until a signal has been received.
115
Q

What are the key signals for a stem cell to begin dividing in G1?

A
  • The size of the cell
  • Signals received from the environment (growth factors) which trigger relay proteins.
  • Then the cell commits to DNA replication in S phase.
  • The decision to divide or not happens at the end of G1 at the ‘R’ (restriction) checkpoint.
  • Receiving these growth factor signals allows the cell to continue past checkpoint ‘R’.
116
Q

What happens during G1 and the checkpoint?

A
  • The cell accumulates ATP, glucose, and oil droplets (for energy).
  • DNA replication must be complete before the cell commits to nuclear division.
  • DNA is copied once per cycle.
  • At the end of G1, restriction point R is where the cell ‘decides’ whether it can continue or not.
117
Q

What happens during G2 and what is checked for at the checkpoint?

A
  • The regulation point of G2 is related to the presence of two types of proteins.
  • One is an enzyme, CdK (cyclin-dependent kinase).
  • The other is the regulatory protein cyclin, which activates the enzyme.
  • When these react (enzyme and substrate) they form a mitosis promoting factor (MPF).

CdK + Cyclin —> MPF

  • An increase of cyclin stimulates mitosis as an increase of MPF is produced in prophase and metaphase.
  • Anaphase requires the presence of MPF to decrease.
118
Q

What two things can inhibit cell division?

A
  • Physical signals such as cells touching each other in tissue culturing can inhibit cell division.
  • Chemical signals also influence cell division, from external sources.
119
Q

What are examples of chemical signals that inhibit cell division?

A
  • Growth factors constitute more than 50 kinds of growth hormones.
  • Hormones are present in low concentrations so cells compete for them, but if we introduced more hormones, then the cell would divide more quickly.

MORE HORMONES = MORE GROWTH.

120
Q

Explain how an external factor increases cell division.

A
  • Hormones - a chemical factor.
  • They have receptors on them and when they find a match outside the cell they bind.
  • This interaction allows the cell to increase production of a protein that increases cell division.
121
Q

What are internal and external gene products that inhibit cell division?

A

Internal:
- Cyclin
- CdK
- MPF

External:
- Hormones

122
Q

Explain how hormones inhibit cell division.

A
  • The idea of contact inhibition.
  • They grow over the top of each other which reduces cell division.
123
Q

What is cell culturing and what are the advantages?

A

Culturing cells to make them for a specific use.

ADVANTAGE:
- Millions of cells can be growth in a small space and hundreds of generations can be studied in a short time-span.
- This means that mutations can be detected and the organisms carrying them isolated.
- Studying mutant cells lacking one enzyme has led to huge advancements in our understanding of biochemistry
- Individual cell types can be grown to study their properties.
- Ethical testing of therapies is enabled by cell culturing.

124
Q

What is required for animal cell culturing?

A
  • A matrix for the cells to grow, i.e., petri dish or a culture flask.
  • A nutrient medium. Could be a solution that contains vitamins and other organic compounds.
  • Appropriate pHs and temperatures to encourage growth of these cells due to the enzymes involved. - they can’t denature.
125
Q

Describe the process of plant cell culturing.

A
  • Plant cells are able to more readily divide after they have differentiated (after the G0 phase).

PROCESS:
1. A small group of cells (tissue sample) are removed from the donor and washed with alcohol to remove contaminating microbes.
2. These cells are placed in a nutrient medium that contains hormones and glucose.
3. The cells can divide into an undifferentiated callus.
4. This is broken up by enzymes into individual cells.
5. Further culturing of these cells produces a cloned plant.

ADVANTAGES:
- Simple technique without the hassle of harvesting and planting seeds, and keeping birds away from the seeds.

126
Q

Describe the process of animal cell culturing.

A
  1. Tissue is minced for clustering.
  2. Disaggregation by use of enzyme (tissue is split into individual cells).
  3. Cells inoculated in a fresh culture medium (to grow).
  4. Confluent culture cell separation using enzymatic disaggregation (placed in a happy environment for the cells to grow).

THEN EITHER:
5. Subculturing or passaging (taking cells out of culture medium and freezing them for further use)

OR
5. Cryopreservation (use enzymes to break them up)
6. Cryopreservation of cells for further use (separate them).

127
Q

What is an application of metabolite production using plant cell culturing?

A

AAT (metabolite or protein produce):
- The matric is the membrane
- The plant cell is Oryza sativa
- Application is to prevent emphysema, hepatitis, and skin disorders.

128
Q

What is an application of spray on skin and what are its associated advantages and disadvantages?

A
  • Used to prevent traditional method of treating server burns which includes scraping existing skin and stitching it directly on the wound.

ADVANATAGES:
- Spray on skin is better because the skin cells can lay in the order they want, and fill smaller gaps of unusual shapes.
- There is less scarring

DISADVANTAGES:
- Still requires painful method of scraping skin donor.
- Is a costly process
- Requires sterile conditions.

129
Q

What is the process of spray on skin?

A
  1. A sample of donor skin is obtained.
  2. Skin cells are released by trypsin digestion and scraping.
  3. A suspension made of varying skin cells is sprayed onto the would.
  4. Spray on skin cells proliferate and bind together, forming a new layer of skin.
130
Q

Why does cell culturing require sterile conditions?

A
  • Cell culturing is usually performed in a laminar flow cabinet (only clean air passing through sample, no microbes).
  • This cabinet is exposed to UV light (ionizing radiation) to cause mutations and kill unwanted things, when not in use and wiped down in 70% ethanol before and after use.
  • Lids from flasks and plates are removed for the shortest time possible (limiting airflow in that might be containing microbes).
  • Tools used are sterilized with Ethylene Oxide (more common than steam and used for items that might melt at high temperatures).
131
Q

What are the limitations of cell culturing?

A
  • The culture medium must have all the correct ingredients to promote cell growth.
  • Water availability, pH, and temperature need to be maintained.
  • The medium should be well aerated (oxygen is available to all the cells).
  • Sterile conditions are required, otherwise opportunistic microorganisms will grow instead of the wanted cells.
  • Cost - of materials, and paying scientists.

Stage 2 Biology (3 decks)

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