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A Level Biology (SNAB) > Topic 3 > Flashcards

Topic 3 Flashcards

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1
Q

What are the structures within animal cells?

A
  • Mitochondria
  • Lysosome
  • SER / RER
  • Cell membrane
  • Golgi complex
  • Nucleus
  • Centrioles
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2
Q

What are the structures within plant cells?

A
  • Mitochondria
  • Lysosome
  • SER/RER
  • Golgi complex
  • Nucleus
  • Cell wall
  • Chloroplasts
  • Vacuole
  • Amyloplasts / Tonoplasts
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3
Q

What is the structure of Prokaryotic cells (unicellular)?

A
  • Do not have any membrane bound organelles
  • Ribosomes are smaller (70S)
  • Cell wall consists of proteins and carbohydrates
  • Water borne bacteria have flagellum which consists of protein fibres
  • Mesosome increases SA and holds ET chain enzymes for aerobic respiration and helps with cell division
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4
Q

What is the structure of Eukaryotic cells (multicellular)?

A
  • DNA is a double helix and in a chromosome
  • DNA is enclosed in a nuclear membrane
  • Have a similar structure and function of cell membranes and cytoplasm
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5
Q

What is the structure and function of the Mitochondria?

A

Structure
- Double bilayer membrane
- Inner folded to form cristae
- Contains electron transport chain enzymes
- Matrix contains enzymes
- Contains DNA inherited only from the
mother

Function
- Carries out aerobic respiration = releasing energy from glucose
- Energy is used to drive cell metabolism, eg. protein synthesis and mitosis

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6
Q

What is the structure and function of the Cytoplasm?

A

Structure
- Cytosol (liquid)
- Cytoskeleton (microfilaments)

Function
- Cytosol contains enzymes, eg. glycolysis or anaerobic respiration
- Cytoskeleton provides structure and allows movement of organelles

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7
Q

What is the structure and function of Lysosomes?

A

Structure
- Surrounded by a single bilayer (a membrane bound bag basically)

Function
- Contains enzyme Lysozyme, released when cells are damaged
- Causes cell death: apoptosis or cell lysis (cell breakdown)

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8
Q

What is the structure and function of the SER?

A

Structure
- Sequence of tubes that run continuous w/ outer nuclear membrane

Function
- Inv. in the synthesis of carbs and lipids

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9
Q

What is the structure and function of the RER?

A

Structure
- Like SER but w/ membranes

Function
- Inv. in the synthesis of proteins to be exocytosed

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10
Q

What is the structure and function of free ribosomes?

A

Structure
- Larger in Eukaryotic cells (is 2 sub units) than in Prokaryotic cells

Function
- Reads codons on a mRNA molecule
- Translates them into a primary protein sequence
- Produces proteins for inside the cell

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11
Q

What is the structure and function of centrioles?

A

Structure
- Microtubules (absent in prokaryotic and higher plants)

Function
- Produces microfibres to separate chromatids in the anaphase stage

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12
Q

What is the structure and function of the Golgi Apparatus?

A

Structure
- Flattened sacs, often seen w/ vesicles moving or fusing w/ the sacs

Function
- Inv. w/ the modification, repackaging and redistribution of substances, eg. enzymes that are to leave the cell

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13
Q

What is the structure and function of the Nuclear Membrane?

A

Structure
- Double bilayer membrane, containing channel proteins and nuclear pores

Function
- Allows mRNA to leave the nucleus and move to the ribosome

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14
Q

What is the structure and function of the Nucleolus?

A

Structure
- Small spherical structure that appears dense w/n the nucleus, contains rRNA

Function
- Inv. in the synthesis of ribosomes

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15
Q

What is the structure and function of the Nucelus?

A

Structure
- Surrounded by a double bilayer membrane, contains channel proteins/ pores

Function
- Contains chromosomes and is the site of transcription

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16
Q

What is the structure and function of the Plasma Membrane?

A

Structure
- Bilayer of phospholipids: Fluid Mosaic Model

Function
- Controls entry and exit of substances, through facilitated + simple diffusion, channel proteins + active transport, carrier proteins + endo/exo/pinocytosis

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17
Q

What is the structure and function of Chloroplasts?

A

Structure
-Double bilayer membrane
- Inner liquid part = stroma, contains calvin cycle enzymes
- Stack of flattened sacs = grana, contain electron transport chain
- One is called a Thylakoid

Function
- Inv. in the capture of light, used by organelle to synthesise glucose

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18
Q

Describe intracellular transport?

A
  1. MRNA attaches to a ribosome on the RER
  2. A primary protein is made
  3. A signal recognition particle attaches to the start of the primary protein and then moves the primary protein to a regular molecule on the pore of the RER. This allows the primary protein to be transported inside the RER
  4. Inside the RER, the primary proteins modified into a secondary protein (a helix or b pleated sheet - H bonds)
  5. A vesicle ‘buds’ off the RER membrane and transports to the Golgi
  6. The secondary protein is modified (tertiary protein), repackaged (into a new vesicle), and redistributed (travels to inside of cell membrane)
  7. Vesicle binds to glycoproteins on the inside of the cell membrane which allows the vesicle to fuse with the cell membrane (causes cell growth as membrane gets larger)
  8. The vesicles contents are exocytosed
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19
Q

What is variation?

A

Variation = crossing and random assortment since haploid gametes that meet at fertilisation which produce offspring that are all different from each other

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20
Q

Describe Meiosis?

A
  1. Chromosome replicate (DNA replication)
  2. Cell division occurs (meiosis I)
  3. Chromosomes line up in pairs again, crossing over occurs
  4. Genes from male chromosomes swap places w/ genes from the female chromosomes
  5. Random assortment occurs and chromosomes are placed in gametes
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21
Q

Describe fertilisation?

A
  1. Hundreds of sperm attracted to the corona radiata begin to break through the barrier of granulosa cells and approach the zona pellucida
  2. Contact w/ the zona pellucida triggers acrosome reaction in sperm
  3. When the membrane fuses to form holes so the digestive enzymes are released
  4. The enzymes released break down the glycoprotein membrane of the zona pellucida, exposing oocytes plasma membrane
  5. One sperm will succeed in reaching the membrane
  6. The sperms plasma membrane fuses with that of the oocytes
  7. The sperm then releases its nucleus into the cytoplasm
  8. Once it enters, vesicles w/n oocyte moves to the membrane and fuse
  9. They then release their contents (chemical) via exocytosis
  10. The chemicals bind to the sperm receptors preventing no other sperm from binding
  11. This is called the fertilisation membrane
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22
Q

Mitosis - Interphase

A

Interphase - double up
- The tangled, uncoiled mass of chromosomes fills the nucleus
- DNA is beginning to be replicated + protein synthesis occurs
- Cell growth occurs as new vesicles fuse w/ cell membrane

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23
Q

Mitosis - Prophase

A

Prophase - double up
- The chromosomes coil and condense, each one appearing as two chromatids (that’s why they appear thicker)
- The nucleolus breaks down and the centrioles begin to separate and start to form the spindle

24
Q

Mitosis - Metaphase

A

Metaphase - line up
- The nuclear membrane breaks down
- Spindles made of microtubules have been formed by centrioles
- The chromatids line up on the equator

25
Q

Mitosis - Anaphase

A

Anaphase - split up
- the centromeres separate and each chromatid is pulled along a spindle tubule towards one of the poles centromere first

26
Q

Mitosis - Telophase

A

Early Telophase
- The chromatids reach the poles of the cell where they are now known as chromosomes
- The membrane begins to reform and cytoplasm divides

Late Telophase
- Chromosomes begin to decondense
- Nuclear membranes + nucleoli are fully reformed + centrioles are present again
- Division of cytoplasm continues until two identical cells are formed
- The two new cells then begin interphase

27
Q

Chromosomes - Mitosis

A
  • Will consist of 2 chromatids during path of the cell cycle
  • Double helix of DNA, super coiled around histone proteins/ chromatin
  • Also 1 chromatid is a chromosome
28
Q

DNA - Mitosis

A
  • Polymer which forms a double helix

Chromatid
- Identical sister pairs (2 chromatids = 1 chromosome)
- On its own it is still a chromosome

29
Q

Describe the root tip experiment?

A
  1. Cut 5mm of a root tip from a plant such as an onion →this is where mitosis occurs in the root →take care when cutting
  2. Soak the root tip in HCL in a water bath of 60°C →to soften the root tip →in the eyes
  3. Add a few drops of orcein stain →stain to show chromosomes→eyes and skin covered, orcein is toxic to blood
  4. Gently break root tip apart on a microscope slide and gently flatten →spread out the cells to one layer to see it clearer →glass slides can break
  5. Add more stain, warm it and then place under a microscope →warming intensifies the stain, and microscope to see the chromosomes →stain and potential burning
30
Q

Stem cell, Pluripotency, and Totipotency

A

Stem cell = undifferentiated cells that has the potential to develop into any cell (embryonic)

Totipotency =can become all cell types inc. embryonic cells (from early embryos)

Pluripotency = has the potential to become most cell types but not embryonic cells (from older embryos)

Multipotency = adult stem cells that have the ability to form a variety of different cell types

31
Q

What are the advantages with Embryonic Stem Cells?

A
  • Easy to extract and grow
  • more likely to be totipotent
32
Q

What are the disadvantages with Embryonic Stem cells?

A
  • ethical issues
  • possible rejection by body
  • risk of infection w/ insertion
  • can become cancerous
33
Q

What are the advantages with Adult Stem Cells?

A
  • fewer ethical issues
  • no rejection risk of patients’
34
Q

What are the disadvantages with Adult Stem Cells?

A
  • difficult to extract
  • only pluripotent
  • risk of infection
35
Q

What are the advantages with Fused Cells?

A
  • no rejection risk if nucleus is from the patient
  • can treat genetic disorders
36
Q

What are the disadvantages with Fused Cells

A
  • ethical issues w/ source of embryonic nuclei
  • risk of infection w/ insertion
  • can become cancerous
37
Q

Using Stem Cells

A
  • Potentially they can treat medical conditions where there is a loss, shortage or reduced functioning of certain cell types

Parkinson’s = a progressive loss of nerve cells in the brain that are inv. in muscle control

Multiple Sclerosis = the electrical insulating layer surrounding nerve cells breaks down (the myelin sheath - see Topic 7)

Burns = skin cells damaged so can’t be replaced

Leukemia = My Sister’s Keeper, where a second child was created to use their bone marrow to save their sister

38
Q

Using certain stem cells

A

Embryonic cells = have the potential to become life so can be seen as immoral to use (totipotent)

Umbilical cord cells = it would take a lot of storage space and money to do for everyone (pluripotent)

Somatic cells = need to be taken from family or matching immune systems (multipotent)

39
Q

Issues with the use of stem cells

A
  • When does an embryo become a human w/ human rights?
  • Is it acceptable to use human embryos specially created for research?
  • Is it acceptable to remove the chance of life from the embryo in fused cells?
40
Q

What is gene expression?

A

Gene expression = the process by which information from a gene is used in the synthesis of a functional gene product

41
Q

What is differential gene expression?

A

Differential gene expression = gene expression that responds to signals or triggers

42
Q

What is the process of differential gene expression?

A
  • A means of gene regulation
    1. Correct stimulus is given to unspecialised cells
    2. Some genes are switched on and become active, others switched off
    3. mRNA is made from the active genes only
    4. mRNA goes to the ribosome to be read and protein is made
    5. The protein can permanently alter the structure and function of the cells
43
Q

What is epigenetics?

A

Epigenetics = the study of changes in organisms caused by modification of gene expression

44
Q

What is an epigenome?

A

Epigenome = a mixture of chemical markers that ‘instruct’ genes/ are attached to histone proteins
- It affects the phenotype w/o affecting genotype

45
Q

What is cellular differentiation?

A

Cellular differentiation = the process by which a less specialised cell becomes a more specialised cell type

46
Q

How do you turn genes on?

A
  • Acetyl or methyl groups attach to DNA histones
  • This prevents the DNA from coiling around the histone proteins
  • Uncoiled DNA can be read and transcripted since transcription factors can bind
47
Q

How do you turn genes off?

A
  • Methyl groups attach to DNA
  • This stops transcription factors from binding
  • The DNA can’t be read and transcripted
  • E.g alcohol causes collagen production, a connective tissue for hair and nails
48
Q

What happens when epigenetics goes wrong?

A
  • The gene for the protein isn’t turned off in - - - WBCs when it’s only suppose to be on in bone cells
  • When a tissue becomes damaged the WBCs go to the area releasing the proteins
  • This turns tissue cells into bone cells
49
Q

What is a cell?

A

Cell = specialised for a particular function

50
Q

What is a tissue?

A

Tissues = one or a few different types of cell that work together to perform a function

51
Q

What is an organ?

A

Organs = various tissues grouped together and perform their function efficiently

52
Q

What is a system?

A

Systems = various organs that work together to perform a large scale function

53
Q

Polygenetic Inheritance?

A
  • Variation in phenotype can be continuous (height) or discontinuous (blood group)
    I- s caused by variation in genotype
  • Monogenic = controlled by one gene, at one loci (generally discontinuous)
  • Polygenic = controlled by a number of genes, at different loci (generally continuous)
54
Q

What is a phenotype?

A

Phenotype = outward expression of a cell or organism due to the interaction of:

Genotype
- Genetic differences leading to outward differences

Environment
- Environmental differences leading to outward differences

55
Q

What is a genotype?

A
  • Genotype = the combination of two alleles for that gene

Eg. Siamese cat hair colour
- Genotype = codes for the enzyme for dark fur
- Environment = enzyme only active when temp below 31°C
- Phenotype = generally only ears, paws, and tail turn black as the rest of the body stays above 31°C

56
Q

Epigenetics through cell division

A

Mutations = the changing of a structure of a gene

Mutagen = factor which causes a mutation

Carcinogen = any agent that causes cancer

  • When a cell divides and replicates, epigenetic changes can be passed onto daughter cells
  • Methyl groups are normally removed during gamete production but some aren’t
  • Meaning the genes de/activated in the original will also be de/activated in the daughter
  • If the change was due to a change in the environment the daughter cell will be adapted to it like the original cell was

A Level Biology (SNAB) (4 decks)

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