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Cells Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Eukaryotic vs prokaryotic cells

A
  • eukaryotic, animal/plant cell has membrane bound organelles
  • prokaryotic, bacteria has no membrane bound organelles
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2
Q

2 forms of reproduction

A
  • sexual reproduction, uses 2 parents, gametes combine to form zygote
  • asexual reproduction, 1 parent to produce genetically identical offspring
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3
Q

Define stem cell

A

an unspecialised cell which can form into any other type of cell

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4
Q

How does a zygote develop into an organism

A
  • zygotes are stem cells
  • zygotes divide 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 organs
  • different organs join to form organ system
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5
Q

Define tissue, organ and organ system

A
  • tissue = a group of specialised cells
  • organ = made up of different tissues
  • organ system = different organs working together
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6
Q

Structure of nucleus

A
  • contains DNA
  • ## DNA wrapped around histones to form chromatin
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7
Q

Difference between smooth and rough endoplasmic reticulums

A
  • rough has ribosomes, makes proteins
  • smooth has no ribosomes, makes lipids/carbohydrates
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8
Q

Role of golgi

A

modifies and packages proteins, packs them into vesicles for transport

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9
Q

Role of mitochondria

A

site of aerobic respiration, produces ATP

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10
Q

Structure of mitochondria

A

-double membrane, inner membrane folded into cristae (increases SA for enzymes of respiration)
- middle portion called matrix

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11
Q

Role of ribosomes

A

protein synthesis, attached to RER

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12
Q

Structure of chloroplast

A
  • double membrane
  • contains discs called thylakoids
  • thylakoids contain chlorophyll
  • stack of thylakoids called granum
  • thylakoids surrounded by fluid called stroma
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13
Q

Features of bacteria

A
  • no nucleus, loose DNA in single loops and plasmids
  • no membrane bound organelles, smaller ribosomes
  • contains cytoplasm
  • contains cell membrane and cell wall
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14
Q

What is a virus made of

A
  • DNA or RNA (if RNA, also has enzyme called reverse transcriptase which converts RNA into DNA)
  • protein coat called capsid
  • attachment proteins on outside
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15
Q

What is a chromosome

A
  • DNA in coiled form
  • formed during interphase of cell division
  • made of 2 identical sister chromatids joined by centromere
  • carries 2 copies of same DNA molecule
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16
Q

Define homogolous pair of chromosomes

A

a pair of chromosomes, 1 from mother, 1 from father, which carry same genes but different alleles

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17
Q

2 types of cell division

A
  • mitosis; produces genetically identical cells for growth and repair of tissues
  • meosis; produces genetically different haploid cells as gametes for sexual reproduction
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18
Q

What does mitosis produce

A

2 genetically identical diploid cells

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19
Q

Benefit of mitosis

A

growth and repair of tissues

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20
Q

Name the 3 stages of cell division

A
  • interphase
  • mitosis
  • cytokinesis
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21
Q

What happens during interphase

A
  • protein synthesis
  • DNA replication
  • organelle synthesis
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22
Q

Name the 4 stages of mitosis

A
  • prophase
  • metaphase
  • anaphase
  • telophase
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23
Q

Describe the process of mitosis

A
  • Prophase; DNA coils to form chromosomes, nucleus breaks down, 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 poles
  • Telophase; chromatids uncoil, nucleus reforms (left with 2 genetically identical nuclei
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24
Q

What happens in cytokinesis

A

cell separates into two, each receives a nucleus and organelles/cytoplasm

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25
Q

What happens to DNA in mitosis

A

it halves

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26
Q

What happens to chromosome number in mitosis

A

stays the same (diploid)

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27
Q

What is cancer

A

formation of a tumour due to uncontrolled cell division/mitosis

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28
Q

How does uncontrolled cell division occur

A
  • due to mutation of DNA
  • mutation can only occur randomly or due to mutagens
  • cancer cells are rapidly dividing cells
  • so they have less time in interphase and more time in mitosis
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29
Q

Treatments for cancer

A
  • surgery, aims to remove tumour
  • radiotherapy, radiation used to destroy cancer cells
  • chemotherapy, uses drugs which inhibit mitosis in rapidly dividing cells
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30
Q

What does meiosis produce

A

4 genetically different cells (haploid), half the amount of chromosomes

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31
Q

Benefit of meiosis

A

produces gametes which will be used in sexual reproduction in animals and plants

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32
Q

What are the stages of meiosis

A
  • interphase
  • meiosis I
  • meiosis II
  • cytokinesis
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33
Q

What happens in interphase

A
  • protein synthesis
  • DNA replication
  • organelle synthesis
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34
Q

What happens in meiosis I

A
  • prophase I, DNA coils to form chromosomes, nucleus breaks down, spindle fibres form, crossing over occurs
  • metaphase I, homologous pair of chromosomes line up at centre of cell and attach to spindle fibre via centromere by random assortment
  • anaphase I, spindle fibres pull, homologous pair of chromosomes separate to opposite sides by independent segregation
  • telophase I, chromosomes uncoil, nucleus reforms
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35
Q

What happens in meiosis II

A
  • prophase II, DNA coils to form chromosomes, nucleus breaks down, spindle fibres form
  • metaphase II, chromosomes line up at centre of cell and attach to spindle fibres via centromere by random assortment
  • anaphase II, spindle fibres pull, sister chromatids move to opposite sides by independent segregation
  • telophase II, chromatids uncoil, nucleus reforms, left with 4 genetically different nuclei
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36
Q

What happens in cytokinesis (meiosis)

A

cell separates into 4, each receives a nucleus and organelles/cytoplasm

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37
Q

How does meiosis create variation

A

crossing over and independent segregation

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38
Q

What is crossing over

A
  • occurs in prophase I of meiosis I
  • homologous pair of chromosomes wrap around each other and swap equivalent sections of chromatids; produces new combination alleles
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39
Q

What is independent segregation

A
  • occurs in anaphase I of meiosis I
  • occurs in anaphase II of meiosis II
  • produces a mix of alleles from paternal and maternal chromosomes in a gamete
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40
Q

What happens to DNA in meiosis

A

quarters

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41
Q

What happens to chromosomes in meiosis

A

number halves (haploid)

42
Q

How do bacteria do cell division

A
  • binary fission
  • copy their DNA
  • then separate into 2 new genetically identical bacteria (asexual reproduction)
43
Q

Name 2 types of microscope

A
  • light
  • electron (TEM and SEM)
44
Q

How do you judge a microscope

A

by magnification and resolution

45
Q

What is magnification

A

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

46
Q

Which has higher magnification

A

TEM>SEM>light

47
Q

Formula for magnification

A

magnification= image size/actual size

48
Q

Conversions

A
  • 1mm= 1000 micrometres (pm)
  • 1mm= 1000000 nanometres (nm)
49
Q

Why can organelles appear different in images

A

viewed from different angles and at different levels

50
Q

What is resolution

A

minimum distance at which two very close objects can be distinguished

51
Q

Which has the highest resolution

A

TEM>SEM>light

52
Q

Why do electron microscopes have a higher resolution

A

they use electrons which have a shorter wavelength

53
Q

Advantages and disadvantages of TEM

A
  • advantage; highest magnification and resolution
  • disadvantages; can only observe dead specimens, specimen needs to be thin, black and white image, 2D image
54
Q

Advantages and disadvantages of SEM

A
  • advantage; produces 3D image
  • disadvantages; can only observe dead specimens, black and white image
55
Q

Describe cell fractionation

A
  • break down tissue into cells by cutting a small sample and using a pestle and mortar
  • add cold, isotonic, buffer solution to the sample
  • homogenate the sample to break open cells releasing organelles
  • filter the solution to remove large debris and inact cells
  • add solution to a centrifuge, spin at low speed, heaviest pellet present at the bottom
56
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)
57
Q

Factors that affect rate of diffusion

A
  • surface area; increase= increase in ROD
  • concentration gradient; increase= increase in ROD
  • thickness
  • temperature; increase means more kinetic energy, molecules move faster, faster ROD
  • size of molecules; smaller = increased ROD
58
Q

What is Fick’s law

A

(surface area x concentration)/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 water

61
Q

What happens if you surround an animal cell with pure water

A

cell swells and bursts due to osmosis

62
Q

What happens if you surround a plant cell with pure water

A

swells but doesn’t burst, becomes turgid, cell wall prevents it from bursting since cellulose is a strong material

63
Q

What happens if you surround an animal cell with concentrated sugar/salt solution

A

cell shrinks, water leaves by osmosis

64
Q

What happens if you surround a plant cell with concentrated sugar/solution

A

water leaves by osmosis, cell wall prevents cell from shrinking, keeps it rigid, cell is plasmolysed

65
Q

Define active transport

A

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

66
Q

Describe the process of active transport

A
  • molecules in area of low concentration bind to carrier protein
  • ATP breaks down to ADP and Pi and energy
  • the Pi and energy cause carrier protein to change shape
  • carrier protein releases molecules on opposite side in area of high concentration
  • carrier protein releases the attached Pi to return to its original shape
67
Q

Enzymes of carbohydrate digestion

A
  • amylase; converts starch/glycogen into maltose
  • maltase on lining of small intestine; converts maltose into glucose
  • lactase on lining of small intestine; converts lactose into glucose and galactose
  • sucrase on lining of small intestine; converts sucrose into glucose and fructose
68
Q

Where can amylase be found

A

salivary gland and pancreas

69
Q

Enzymes of protein digestion

A
  • endopeptidase in stomach; hydrolyses peptide bonds in middle of polypeptide chain into smaller chains
  • exopeptidase in small intestine; hydrolyses peptide bonds at end of chains to leave dipeptides
  • dipeptidase on lining of small intestine; hydrolyse dipeptides into amino acids
70
Q

Enzymes of lipid digestion

A

lipase in small intestine leaves monoglyceride and 2 fatty acids

71
Q

Adaptations of small intestine for absorption

A
  • cells lining SI have microvilli which increase surface area
  • wall of SI is thin, short diffusion distance
  • rich blood supply, maintains concentration gradient
  • cells lining SI have transport proteins, enzymes and many mitochondria
72
Q

Describe the absorption of glucose and amino acids in the SI

A
  • sodium ions are actively transported from cells lining SI into the blood
  • this lowers the sodium ion concentration in the cell
  • therefore sodium ions move from lumen of SI to the cell
  • this pulls in glucose and amino acids via a cotransport protein
  • therefore glucose and amino acids build up in the cell and move into blood via diffusion
73
Q

Describe the absorption of monoglyceride and fatty acids

A
  • lipids emulsified by bile into micelles
  • micelles digested by lipase into monoglyceride and 2 fatty acids
  • monoglyercide and fatty acids absorbed by cells lining SI by simple diffusion
  • this forms a chylomicron which enters the blood
74
Q

What is lactose intolerance

A
  • person doesn’t produce lactase enzyme
  • lactose remains undigested
  • leads to diarrhoea and flatulence
75
Q

What is a pathogen

A

a microorganism which causes disease

76
Q

Examples of pathogens

A

virus, bacteria, fungi

77
Q

How do bacteria cause disease

A

by producing toxins

78
Q

How do viruses cause disease

A

by dividing inside cells causing them to burst

79
Q

Name the body’s 3 forms of defence against pathogens

A
  • barriers
  • phagocytes
  • specific response
80
Q

Name examples of a barrier

A
  • skin, an impermeable barrier
  • mucus and cilia in lungs
  • stomach acid denatures pathogens
81
Q

Describe the process of phagocytosis

A
  • pathogen releases chemicals
  • this attracts the phagocyte
  • phagocyte binds to the pathogen
  • phagocyte englufs the pathogen
  • this forms a phagosome around the pathogen
  • lysosomes inside the phagocyte release digestive enzymes into the phagosome
  • this breaks down the pathogen by hydrolysis
82
Q

Describe the cell-mediated response

A
  • phagocytes perform phagocytosis without destroying the antigen, they place antigens on their surface
  • t cells bind to the antigen and become stimulated
  • they divide by mitosis to form 3 types of cells, t helper, t killer and t memory
  • t helper cells stimulate b cells
  • t killer cells kill infected cells
  • t memory cells provide long term immunity
83
Q

Role of t helper cells

A

stimulate b cells

84
Q

Role of t killer cells

A

kill infected cells

85
Q

Role of t memory cells

A

provide long term immunity

86
Q

Describe the humoral response

A
  • b cells engulf and present antigens on their surface
  • t helper cells bind to this
  • b cells become stimulated and divide by mitosis to form plasma cells and b memory cells
  • plasma cells produce antibodies
  • b memory cells provide long term immunity
87
Q

Role of plasma cells

A

produce antibodies

88
Q

Role of b memory cells

A

provide long term immunity

89
Q

What is an antigen

A

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

90
Q

How does the immune response lead to the production of antibodies

A
  • phagocytes stimulate t cells
  • t cells form t helper cells
  • t helper cells stimulate b cells
  • b cells form plasma cells
  • plasma cells make antibodies
91
Q

What is an antibody

A

a protein specific to an antigen secreted by plasma cells

92
Q

How do memory cells work

A

if a person is reinfected with the same pathogen, memory cells recognise the pathogen, produce antibodies rapidly and to a large amount

93
Q

How does a vaccine provide immunity

A

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

94
Q

Active vs passive immunity

A
  • active; person has memory cells, makes their own antibodies and provides long term immunity
  • passive; person given antibodies, these work then die, no long term immunity, no memory cells
95
Q

How does active immunity occur

A
  • naturally; by primary infection
  • artificially; vaccination
96
Q

How does passive immunity occur

A
  • naturally; from mother to baby
  • artificially; by injection
97
Q

Features of a successful vaccination programme

A
  • produce effective vaccine, makes memory cells without major side effects
  • low cost
  • easily produced
  • herd immunity
98
Q

What is herd immunity

A

when a large proportion of the population is vaccinated so most people will be immune, increases chance of non-immune person coming into contact with immune, so pathogen won’t spread

99
Q

What is antigenic variability

A

pathogen mutates, antigen changes shape so memory cells no longer complementary, so pathogen can reharm

100
Q

Describe how HIV is replicated

A
  • attachment protein attaches to receptors on t helper cell
  • RNA enters cell
  • reverse transcriptase converts RNA into DNA
  • enzymes are produced
  • virus particles are assembled then released
101
Q

Describe how HIV is replicated once inside a T helper cell

A
  • RNA is converted into DNA using reverse transcriptase
  • DNA is inserted into t helper cell’s nucleus
  • DNA is transcribed into HIV mRNA
  • HIV mRNA is translated into new HIV

Biology (5 decks)

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