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Wills AQA Biology > Module 2 > Flashcards

Module 2 Flashcards

1
Q

Virus alive or not?

A

Viruses are not defined as
living organisms because they do not have the standard components of a cell – acellular, and cannot perform MRS GREN without a host

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2
Q

Eukaryotic vs Prokaryotic Cells?

A

− Eukaryotic = animal/plant cell, has membrane bound organelles (nucleus, endoplasmic reticulum, golgi body, lysosome, mitochondra)
− Prokaryotic = bacteria, has no membrane bound organelles

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3
Q

What are the 2 forms of Reproduction?

A

Sexual & Asexual
− Sexual Reproduction in Animals & Some Plants
− Asexual Reproduction in Microorganisms & Some Plants
− Sexual Reproduction uses 2 parents (each provides a gamete which fuse to form a zygote, zygote develops into organism)
− Asexual Reproduction uses 1 parent to produce genetically identical offspring

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4
Q

How does a Zygote develop into an Organism?

A

Zygote is a stem cell
− stem cell = undifferentiated/unspecialised cell, can form any type of cell
− zygote divides by mitosis to make many stem cells
− each stem cell differentiates into specialised cell
− each specialised cell divides by mitosis to make many copies and form a tissue
− different tissues join to form an organ
− different organs join to form an organ system
− this is surrounded by the Body

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5
Q

Define a tissue, organ and organ system?

​

A

tissue = a group of specialised cells
​organ = made of different tissues
​organ system = different organs working together

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6
Q

What is an Animal Cell made of?

A

Organelles (nucleus, endoplasmic reticulum, golgi body, lysosomes, mitochondria, ribosomes) – all have membrane except the ribosomes
− Cytoplasm (site of chemical reaction)
− Cell Membrane (holds cell contents together, controls what enters/leaves cell, cell signalling)

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7
Q

Structure of Nucleus?

A

contains DNA (made of genes, genes code for making proteins)
− DNA wrapped around histones to form Chromatin
− nucleus has a double membrane, called Nuclear Envelope, which contains pores
− at centre of nucleus is Nucleolus – produces mRNA (copy of a gene)
− rest of nucleus made of Nucleoplasm (contains the DNA/chromatin)

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8
Q

Endoplasmic Reticulum?

A

2 types = Rough and Smooth
− Rough Endoplasmic Reticulum has ribosomes on it, makes proteins
− Smooth Endoplasmic Reticulum has no ribosomes on it, makes lipids/carbohydrates

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9
Q

Golgi body?

A

modifies and packages proteins
− packages them into vesicles for transport
− digestive enzymes are placed into lysosomes (vesicles with membranes around them)

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10
Q

Mitochondria?

A

site of respiration, releases energy, produces ATP (energy carrier molecule)
− has a double membrane, inner membrane folded into Cristae (increases surface area for enzymes of respiration)
− middle portion called Matrix

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11
Q

Ribosomes?

A

attached to RER
− site of protein synthesis

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12
Q

What is a Plant Cell made of?

A

Organelles (nucleus, endoplasmic reticulum, golgi body, lysosomes, mitochondria, chloroplast, vacuole, ribosomes) – all have membrane except the ribosomes
− Cytoplasm (site of chemical reaction)
− Cell Membrane (holds cell contents together, controls what enters/leaves cell, cell signalling)
− Cell Wall (made of cellulose, prevents cell from bursting or shrinking)

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13
Q

Structure of chloroplast?

A

organelle for photosynthesis
− has double membrane
− contains discs called thylakoids
− thylakoids contain chlorophyll
− stack of thylakoids called granum
− thylakoids surrounded by a fluid called stroma

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14
Q

Vacuole?

​

A

Surrounded by a membrane called a tonoplast, contains Cell Sap (water, sugar, minerals)

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15
Q

What is Bacteria made of?

A

No nucleus – loose DNA in the form of a single loop and plasmid
− No membrane bound organelles: smaller ribosomes, mesosomes – infolding of cell membrane for respiration
− Cytoplasm
− Cell Membrane & Cell Wall (made of peptidoglycan/murein)
− some have a Capsule (reduce water loss, protect from phagocytosis) and Flagella (movement)

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16
Q

What is Virus made of?

A

DNA or RNA (if RNA, also has a enzyme called reverse transcriptase to turn RNA into DNA)
− Protein Coat called Capsid and Lipid Coat
− Attachment proteins on outside
− (infects host cells by attaching using their attachment protein, send in their DNA which uses the cell to make the viruses components and uses the cell membrane to make the viruses lipid coat, hence, producing copies of the virus and destroying the host cell)

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17
Q

What is a Chromosome?

A

DNA in coiled form
− formed during interphase of cell division (mitosis/meiosis) in Animals/Plants
− made of 2 identical/sister chromatids joined by a centromere
− carries 2 copies of the same DNA molecule

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18
Q

What is a homologous pair of chromosomes?

A

​a pair of chromosomes: 1 maternal (from mother)/1 paternal (from father)
​carries same genes but different alleles – there are 23 pairs in humans

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19
Q

What is Cell Division?

A

formation of new cells in multicellular organisms (animals & plants)
− 2 methods = mitosis & meiosis
− mitosis = produces genetically identical cells for growth & repair of tissues
− meiosis = produces genetically different haploid cells as gametes for sexual reproduction

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20
Q

What does Mitosis (cell cycle) produce?

​

A

2 genetically identical cells, diploid (have full set of chromosomes/DNA)

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21
Q

Benefit of Mitosis?

A

growth and repair of tissues

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22
Q

Stages of Mitosis?

A

Interphase/Mitosis/Cytokinesis

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23
Q

Mitosis?

​

A

Prophase: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form
​Metaphase: chromosomes line up in middle of cell and attach to spindle fibre via centromere
​Anaphase: spindle fibres pull, centromere splits, sister chromatids move to opposite sides
​Telophase: chromatids uncoil, nucleus reforms (left with 2 genetically identical nuclei)

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24
Q

What happens to DNA mass in mitosis?

What happens to Chromosome number in mitosis?

A

halves

stays the same (diploid)

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25
Q

What is Cancer?

A

formation of a tumour due to uncontrolled cell division (uncontrolled mitosis)

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26
Q

How does uncontrolled cell division occur? ​

A

due to mutation of DNA/cells forming cancer cells
− mutation can occur randomly or due to mutagens (chemicals/radiation)
− cancer cells are rapidly dividing cells (like hair cells, skin cells, red blood cells), they spend less time in interphase and more time in the other stages (mitosis)

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27
Q

Treatment for Cancer?

​

A

Surgery = aim is to remove tumour

​Chemotherapy = - using drugs that inhibit mitosis in rapidly dividing cancer cells
​ - problem, also affect normal healthy cells (hair cell, skin cells, rbcs) ​ ​ causing side effects (hair loss, dry skin, tiredness)
​ - treatment given as regular doses to allow time for normal healthy ​ ​ cells to recover in number

​Radiotherapy = radiation used to destroy cancer cells

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28
Q

What does Meiosis produce?

A

​4 genetically different cells, haploid (half the amount of chromosome/DNA)

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29
Q

Benefits of Meiosis?

​

A

produces gametes which will be used in sexual reproduction in animals & plants
​(2 gametes fuse to form a zygote, zygote develops into organisms)

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30
Q

Stages of Meiosis?

A

Interphase
Meiosis I
Meiosis II
Cytokinesis

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31
Q

​Metaphase I:

A

homologous pair of chromosomes line up in middle of cell and attach to ​spindle fibre via centromere by random assortment

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32
Q

What is HIV/AIDs?

A

− HIV is spread by fluid to fluid contact (unprotected sexual intercourse, sharing needles, mother to child via placenta or breast feeding)

− HIV damages and destroys T Helper Cells, therefore person no longer produces Immune Response and has no defence to against pathogens/infections = AIDs

− With AIDs, individual at risk from all sorts of pathogens/infections called Opportunistic Infections

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33
Q

What is antigenic variability?

A

the pathogen mutates, the antigen changes shape, so the memory cells no longer complementary – do not recognise the pathogen, therefore the pathogen can reharm

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34
Q

Problems with Vaccination Programmes?

A

− vaccine does not work (dead form ineffective, pathogen hides from immune system)
− vaccine not safe (no weak/inactive form, causes major side effects)
− many strains of pathogen
− cannot achieve herd immunity (logistic of vaccinating large proportion)
− antigenic variability

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35
Q

What is herd immunity?

A

when a large proportion of the population is vaccinated, therefore most people will be immune, only a few will not be a immune, increases chance of non-immune person coming into contact with immune person, so the pathogen has no where to go, so it dies out

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36
Q

Successful Vaccination Programme?

−

A

produce suitable vaccine (effective – make memory cells, does not cause disease, no major side effects, low cost, easily produced/transported/stored/administered)
− herd immunity

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37
Q

How does passive immunity occur?

A

naturally = from mother to baby (placenta or breast milk),

artificially = by injection

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38
Q

How does activity immunity occur?

A

naturally = by primary infection, artificially = by vaccination

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39
Q

What is crossing over?

​

A

occurs in Prophase I of Meiosis I

​homologous pairs of chromosomes wrap around each other and swap equivalent sections of ​chromatids – produces new combination of alleles

40
Q

What is independent segregation?

A

​- in Anaphase I of Meiosis I – the homologous pairs of chromosomes separate

​- in Anaphase II of Meiosis II – the chromatids separate

​- independent segregation produces a mix of alleles from paternal and maternal ​chromosomes in gamete

41
Q

What happens to DNA mass in meiosis?

What happens to Chromosome number in meiosis?

A

quarters

halves (haploid)

42
Q

How do Bacteria do Cell Division?

A

Binary Fission

− Copy their DNA (Single Loop and Plasmids)

and then separate into 2 new genetically identical bacteria

[Asexual Reproduction]

43
Q

2 types of microscopes?

A

Light and Electron (transmission and scanning)

44
Q

How to judge a microscope?

A

by Magnification and Resolution

45
Q

Magnification?

A

how much larger the image size is compared to the actual size

46
Q

Which has higher magnification?

A

TEM > SEM > LM

47
Q

Formula for magnification?

A

magnification = image size/actual size

48
Q

Why can organelles appear different in images?

A

viewed from different angles and at different ​levels/depth

49
Q

Conversion?

A

1 mm = 1000 micrometre.
1 mm = 1,000,000 nanometre

50
Q

Resolution?

A

minimum distance at which 2 very close objects can be distinguished

51
Q

Which has higher resolution?

A

TEM > SEM > LM

52
Q

Why does electron microscopes have a higher resolution?

A

Electron microscope uses electrons ​which have a shorter wavelength (light microscope uses light which has a large wavelength)

53
Q

Difference between TEM and SEM?

A

in Transmission the electrons pass through the specimen, ​ in Scanning the electrons bounce off the specimen’s surface

54
Q

Advantage and Disadvantage of TEM?

A

Advantage = highest magnification and highest resolution

Disadvantage = works in a vacuum so can only observe dead specimens, specimen needs to be thin, black and white image, 2D image, artefacts

55
Q

Advantage and Disadvantage of SEM?

A

Advantage = produces 3D image

Disadvantage = works in a vacuum so can only observe dead specimens, black and white image, artefacts

56
Q

Cell Fractionation?

A

1 Breakdown tissue into cells (cut, pestle & mortar)
2 add cold/isotonic/buffer solution (cold = reduce enzyme activity, isotonic = same water potential so organelle does not shrink or burst, buffer = maintains constant pH)
3 homogenate – breaks open cells releasing organelles
4 filter = removes large debris and intact cells
5 centrifuge – spin at low speed, largest organelle builds at bottom (nucleus), leaves supernatant, spin at higher speed, next heaviest organelle forms at bottom (chloroplast or mitochondria)

6 (organelle by size: nucleus, chloroplast, mitochondria, endoplasmic reticulum/golgi body/lysosomes, ribosomes)

57
Q

Simple vs Facilitated Diffusion?

A

Simple = molecules move directly through the phospholipid bilayer
− Facilitated = molecules pass through transport proteins (large use carrier, charged use ​ channel)
Factors that affect rate of diffusion?

− surface area (increase = increase rate of diffusion)
− concentration gradient (increase = increase rate of diffusion)
− thickness (decrease = decrease diffusion distance = increase rate of diffusion)
− temperature (increase = increase kinetic energy = molecules move faster = increase rate ​ of diffusion)
− size of molecules (smaller molecules = increase rate of diffusion)

58
Q

What is Ficks Law?

A

(Surface Area x Concentration Gradient)/Thickness

59
Q

Define Osmosis?

A

movement of water molecules from an area of high water potential to an area of ​ low water potential through a partially permeable membrane

60
Q

Which liquid has the highest water potential?

A

distilled/pure water
− has a value of 0kPa
− lower water potential by adding solutes (makes water potential negative)
− water moves from less negative water potential (e.g. -35 kPa) to more negative water potential (e.g. -75 kPa)

61
Q

Surround animal cell with pure water?

A

swells and burst (water enters by osmosis)

62
Q

Surround plant cell with pure water?

A
  • swells but does not burst
    − cell wall prevents it from bursting
    − made of cellulose – strong material
    − the cell is Turgid
63
Q

Surround animal cell with concentrated sugar/salt solution?

A

shrinks (water leaves by osmosis)

64
Q

Surround plant cell with concentrated sugar/salt solution?

A
  • water leaves by osmosis
    − cell wall prevents cell from shrinking, keeps it rigid
    − the protoplast (cell membrane plus contents) shrink
    − the cell is Plasmolysed
65
Q

Define Active Transport?

A

movement of molecules from an area of low concentration to an area of ​high concentration using ATP and carrier proteins (against concentration ​ gradient)

66
Q

Describe the process of active transport?

A

− molecules (in area of low concentration) bind to carrier protein
− ATP breaksdown to ADP, Pi and Energy
− the Pi and Energy cause the carrier protein to change shape
− carrier protein releases molecules on opposite side (in area of high concentration)
− the carrier protein releases the attached Pi to return to its original shape

67
Q

Enzymes of Carbohydrate Digestion?

A

− Starch/Glycogen (Salivary Amylase in Mouth, Pancreatic Amylase in Small Intestine) into Maltose
− Maltose (Maltase on lining of Small Intestine) into Glucose
− Lactose (Lactase on lining of Small Intestine) into Glucose and Galactose
− Sucrose (Sucrase on lining of Small Intestine) into Glucose and Fructose

68
Q

Enzymes of Protein Digestion?

A

− Endopeptidase (in stomach), hydrolyses peptide bonds in middle of polypeptide chain into many smaller chains
− Exopeptidase (in small intestine), hydrolyses peptide bonds at end of chains to leave dipeptides
− Deipeptidase (on lining of small intestine), hydrolyse dipeptides into amino acids

69
Q

Enzymes of Lipid Digestion?

A

​- Lipase in Small Intestine leaves Monoglyceride and 2 Fatty Acids

70
Q

Adaptations of SI for Absorption?

A

− folded to form Villus (large surface area)
− cells lining SI have Microvilli (large surface area)
− wall of SI is thin (short diffusion distance)
− rich blood supply (maintains concentration gradient)
− cells lining SI have transport proteins, enzymes (maltase, lactase, sucrase, didpeptidase) and many mitochondria

71
Q

Absorption of Glucose and Amino Acids in SI?

A

− sodium ions are actively transported from the cells lining the SI into the blood
− lowers the sodium ion concentration in the cell
− therefore sodium ions move from the lumen of the SI into the cell
− this pulls in glucose and amino acids via a cotransport protein
− therefore glucose and amino acids builds up in the cell and moves into the blood by diffusion

72
Q

Absorption of Monoglyceride and Fatty Acids?

A

− Lipids initially emulsified by Bile into Micelles (smaller droplets)
− Micelles digested by Lipase into Monoglyceride and 2 Fatty Acids
− Monoglyceride and Fatty Acids absorbed by Cells lining SI by simple diffusion
− Form a Chylomicron (lipid + cholesterol + lipoprotein)
− Enters Lymph as Lacteal, then enters Blood

73
Q

What is Lactose Intolerance

A

− Person does not make Lactase Enzyme
− Lactose remains Undigested
− Leads to Diarrhoea and Flatulence
− Undigested Lactose in Lumen of Intestine lowers it’s water potential, so water enters the lumen by osmosis leading to water faeces (Diarrhoea)
− Undigested Lactose brokendown by micro-organisms in Large Intestine, giving off gas (Flatulence)

74
Q

What is a pathogen?

A

− a disease causing micro-organism
− e.g. bacteria, virus, fungi
− bacteria cause disease by producing toxins
− virus cause disease by dividing in cells causing them to burst

75
Q

Body’s defence against pathogens?

A

− I, Barriers (prevents pathogens entering the body)
− II, Phagocytes (perform phagocytosis and stimulate specific response)
− III, Specific Response (uses lymphocytes to produce memory cells and antibodies)

76
Q

What are the Barriers (I)?

A

− Skin, an impermeable barrier made of keratin
− Cilia & Mucus in Lungs
− Stomach Acid (denatures/breaksdown pathogens)

77
Q

Describe the process of Phagocytosis (II)?

A

− pathogen releases chemicals
− this attracts the phagocyte
− the phagocyte binds to the pathogen
− the phagocyte engulfs the pathogen
− forms a phagosome around the pathogen
− lysosomes inside the phagocyte release digestive enzymes into the phagosome
− breaking down the pathogen by hydrolysis

78
Q

Describe the Specific Response (III)?

A

− phagocytes perform phagocytosis (engulf and destroy pathogen) without destroying the antigen, they place antigens on their surface, they present antigens
− t lymphocytes (t cells) bind to the antigen and become stimulated
− they divide by mitosis to form 3 types of cells: t helper, t killer, t memory
− t helper cells stimulate b lymphocytes (b cells)
− t killer cells kill infected cells (infected by virus)
− t memory cells provide long term immunity
− b lymphocytes (b cells) engulf and present antigens on their surface, the t helper cells bind to this
− the b cells become stimulated and divide by mitosis to make 2 types of cells: Plasma ​Cells & B Memory Cells
− Plasma cells make antibodies
− B memory cells provide long term immunity

79
Q

What is a antigen?

A

a protein on the surface of a pathogen that stimulates an immune response

80
Q

How does the immune response lead to production of antibodies?

A

the phagocytes stimulate the t cells, the t cells form t helper cells, the t helper cells stimulate the b cells, the b cells form plasma cells, the plasma cells make antibodies

81
Q

What is an antibody?

A

− a globular protein
− made by plasma cells
− has 3 regions: variable region, hinge region, constant region
− variable region has a different shape in each antibody, contains the antigen binding sites, these bind to complementary antigens (on a pathogen) to form an antigen-antibody complex, destroying the pathogen
− hinge region gives the antibody flexibility
− constant region the same shape in all antibodies, binds to phagocytes to help with phagocytosis

82
Q

How do Memory cells (B/T) work?

A

− made during the specific immune response after a new infection by a pathogen (called a primary infection)
− B and T memory cells remain in the blood
− if person is reinfected by the same pathogen (called a secondary infection) the memory cells will recognise the pathogen and produce antibodies RAPIDLY and to a LARGE amount
− therefore the pathogen is killed before it can cause harm = immunity

83
Q

Active vs Passive immunity?

A

− Active = individual has memory cells – can make their own antibodies & provides long term immunity
− Passive = person given antibodies, these work then die, no long term immunity, no memory cells.

84
Q

How does a vaccine produce immunity?

A

involves giving an injection that contains dead/weakened pathogens that carry antigens which stimulates the immune response leading to production of antibodies & memory cells

85
Q

Interphase? ​

A

G1: protein synthesis
​S: DNA replication (doubles set of DNA)
​G2: organelle synthesis

86
Q

Cytokinesis?

A

separating cell into 2 (each receives a nucleus and organelles/cytoplasm)

87
Q

Interphase? ​

A

G1: protein synthesis
​S: DNA replication (doubles set of DNA)
​G2: organelle synthesis

88
Q

Prophase I:

A

DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form, ​crossing over occurs

89
Q

Anaphase I:

A

spindle fibres pull, homologous pair of chromosomes separate to opposite sides ​by independent segregation

90
Q

Telophase I:

A

chromosomes uncoil, nucleus reforms (left with 2 nuclei)

91
Q

Prophase II:

A

DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form

92
Q

How does Meiosis produce Variation?

A

Crossing Over and Independent Segregation

93
Q

Cytokinesis?

A

separating cell into 4 (each receives a nucleus and organelles/cytoplasm)

94
Q

Telophase II:

A

chromatids uncoil, nucleus reforms, left with 4 genetically different nuclei

95
Q

​ Anaphase II:

A

spindle fibres pull, centromere splits, sister chromatids move to opposite sides ​by independent segregation
​

96
Q

Metaphase II:

A

chromosomes line up in middle of cell and attach to spindle fibre via ​centromere by random assortment

Wills AQA Biology (28 decks)

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