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AQA A LEVEL Biology > Section 2 Cells > Flashcards

Section 2 Cells Flashcards

1
Q

What are the 5 kingdoms in biology

A

Animal, plant, bacteria, fungi and protoctista

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2
Q

Eukaryotic and prokaryotic cells

A

Eukaryotic= Animal/plant cell with membrane bound organelles

Prokaryotic= Bacteria has no membrane bound organelles

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3
Q

What are the 2 forms of sexual reproduction?

A

Sexual and asexual

Sexual= In animals and in some plants 2 parents to produce a zygote which develops into an organism.

Asexual= 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 cells are undifferentiated or unspecialised and can form any type of cell.

Zygote divides by mitosis to make many stem cells

These copy to form tissues then organs then organ systems which is then surrounded by a body.

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5
Q

Define tissue, organ and organ system

A

Tissue= is a group of specialised cells

Organ= Formation of tissue

Organ system= organs working together for a bodily function

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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 a 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= Has ribosomes on and makes proteins

Smooth= Has no ribosomes and makes lipids and carbohydrates

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9
Q

Golgi body

A

Modifies and packages proteins

Packs them into vesicles for transport

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10
Q

Mitochondria

A

Site of respiration (produces ATP) power house of the cell

Has a double membrane

Middle portion called matrix

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11
Q

Ribosomes

A

Ribosomes attached to rough endoplasmic reticulum and is the site of protein synthesis.

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12
Q

Plant cells

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 chloroplasts

A

The plant cells site of photosynthesis

Has a double membrane

Contains discs called thykaloids which contain chlorophyll

These stacked are called granum

This then surrounded by a fluid called stroma

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14
Q

What is vacuole?

A

Surrounded by a membrane called a tonoplast, contains Cell sap

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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

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16
Q

What are viruses made of?

A

DNA or RNA

Protein coat called caspid and lipid coat

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17
Q

Chromosome

A

DNA in coiled form

Formed during interphase of cell division

Made of 2 identical sister chromatids joined at the centre by a centromere

Carries 2 copies of the same DNA molecule

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18
Q

What is homologous pair of chromosomes?

A

A pair of chromosomes, 1 maternal and 1 paternal

Carries the same genes but different alleles

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19
Q

What is cell division?

A

Formulation of new cells in multi cellular organisms

2 methods= produces genetically identical

Mitosis produces genetically identical cells for growth and repair of tissues

Meiosis produces genetically different haploid cells as gametes for sexual reproduction (haploid meaning half the genetic information).

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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

What are the benefits of mitosis?

A

Growth and repair of tissues

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22
Q

Stages of mitosis

A

IPMATc

Interphase, prophase, metaphase, anaphase, telophase and cytokenisis (splitting)

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23
Q

What happens during the different stages of mitosis?

A

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

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)

Cytokiensis: Separating cell into into 2

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24
Q

What happens to DNA mass in mitosis?

A

Halves

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25
What happens to the chromosome number in mitosis?
Stays the same (diploid).
26
What is Cancer?
formation of a tumour due to uncontrolled cell division (uncontrolled mitosis)
27
How does uncontrolled cell division occur?
 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)
28
Treatment for Cancer?
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
29
What does meiosis produce ?
4 genetically different cells with half the amount of genetic information (haploid).
30
Benefits of meiosis?
Allows for variation within species by producing gametes with different alleles but the same genes.
31
Stages of meiosis?
Interphase, meiosis 1, meiosis 2, cytokinesis
32
Interphase of meiosis?
Interphase? G1: protein synthesis S: DNA replication (doubles set of DNA) G2: organelle synthesis
33
Meiosis 1 process
Prophase I: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form, crossing over occurs Metaphase I: homologous pair of chromosomes line up in middle 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 (left with 2 nuclei)
34
Meiosis 2 process
Prophase II: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form Metaphase II: chromosomes line up in middle of cell and attach to spindle fibre via centromere by random assortment Anaphase II: spindle fibres pull, centromere splits, sister chromatids move to opposite sides by independent segregation Telophase II: chromatids uncoil, nucleus reforms (left with 4 genetically different nuclei)
35
Cytokinesis of meiosis
separating cell into 4 (each receives a nucleus and organelles/cytoplasm)
36
How does Meiosis produce Variation?
Crossing Over and Independent Segregation
37
What is crossing over?
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
38
What is independent segregation?
- 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
39
What happens to DNA mass in meiosis?
Quarters
40
What happens to Chromosome number in meiosis?
halves (haploid)
41
How do Bacteria do Cell Division?
Binary Fission Copy their DNA (Single Loop and Plasmids) and then separate into 2 new genetically identical bacteria [Asexual Reproduction]
42
2 types of microscopes?
Light and Electron (transmission and scanning)
43
How to judge a microscope?
by Magnification and Resolution
44
Magnification?
how much larger the image size is compared to the actual size
45
Which has higher magnification?
TEM > SEM > LM
46
Formula for magnification?
magnification = image size/actual size
47
Conversion of magnification
1 mm = 1000 micrometre. 1 mm = 1,000,000 nanometre
48
Resolution definition
minimum distance at which 2 very close objects can be distinguished
49
Which has higher resolution?
TEM > SEM > LM
50
Why does electron microscopes have a higher resolution?
Electron microscope uses electrons which have a shorter wavelength (light microscope uses light which has a large wavelength)
51
Difference between TEM and SEM?
Transmission the electrons pass through the specimen, Scanning the electrons bounce off the specimen's surface
52
Advantage and Disadvantage of TEM?
 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
53
Advantage and Disadvantage of SEM?
 Advantage = produces 3D image  Disadvantage = works in a vacuum so can only observe dead specimens, black and white image, artefacts
54
Cell Fractionation?
 Breakdown tissue into cells (cut, pestle & mortar)  add cold/isotonic/buffer solution (cold = reduce enzyme activity, isotonic = same water potential so organelle does not shrink or burst, buffer = maintains constant pH)  homogenate – breaks open cells releasing organelles  filter = removes large debris and intact cells  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)
55
Simple vs Facilitated Diffusion?
 Simple = molecules move directly through the phospholipid bilayer  Facilitated = molecules pass through transport proteins (large use carrier, charged use channel)
56
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)
57
What is Ficks Law?
(Surface Area x Concentration Gradient)/Thickness
58
Define Osmosis
movement of water molecules from an area of high water potential to an area of low water potential through a partially permeable membrane
59
Which liquid has the highest water potential?
Distilled water
60
What happens if you surround animal cells with pure water?
Burst (water enters via osmosis)
61
Surround plant cell with pure water?
 swells but does not burst  cell wall prevents it from bursting  made of cellulose – strong material  the cell is Turgid
62
Surround animal cell with concentrated sugar/salt solution?
shrinks (water leaves by osmosis)
63
Surround plant cell with concentrated sugar/salt solution?
 water leaves by osmosis  cell wall prevents cell from shrinking, keeps it rigid  the protoplast (cell membrane plus contents) shrink  the cell is Plasmolysed
64
Define Active Transport?
? movement of molecules from an area of low concentration to an area of high concentration using ATP and carrier proteins (against concentration gradient)
65
Describe the process of active transport?
 molecules (in area of low concentration) bind to carrier protein  ATP breakdown 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
66
Enzymes of Carbohydrate Digestion?
 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
67
Enzymes of Protein Digestion?
 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
68
Enzymes of Lipid Digestion?
- Lipase in Small Intestine leaves Monoglyceride and 2 Fatty Acids
69
Adaptations of SI for Absorption?
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
70
Absorption of Glucose and Amino Acids in SI?
 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
71
Absorption of Monoglyceride and Fatty Acids?
 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
72
What is Lactose Intolerance?
 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)
73
What is a pathogen?
 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
74
Body's defence against pathogens?
 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)
75
What are the Barriers (I)?
 Skin, an impermeable barrier made of keratin  Cilia & Mucus in Lungs  Stomach Acid (denatures/breaksdown pathogens)
76
Describe the process of Phagocytosis (II)?
 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
77
Describe the Specific Response (III)?
 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
78
What is a antigen?
a protein on the surface of a pathogen that stimulates an immune response
79
How does the immune response lead to production of antibodies?
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
80
w does the immune response lead to production of antibodies?
? 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
What is an antibody's structure
 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
How do Memory cells (B/T) work?
 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
How does a vaccine produce immunity?
involves giving an injection that contains dead/weakened pathogens that carry antigens which stimulates the immune response leading to production of antibodies & memory cells which can kill of the "real" pathogen before it can infect the host.
84
Active vs Passive immunity?
 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.
85
How does activity immunity occur?
naturally = by primary infection, artificially = by vaccination
86
How does passive immunity occur?
naturally = from mother to baby (placenta or breast milk), artificially = by injection
87
Successful Vaccination Programme?
 produce suitable vaccine (effective – make memory cells, does not cause disease, no major side effects, low cost, easily produced/transported/stored/administered)  herd immunity
88
What is herd immunity?
When most of a large population are immune to a specific pathogen it hopefully should kill of the pathogen before it can reach the non immune members of the population.
89
Problems with Vaccination Programmes?
 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- the pathogen mutates and changes shape therefore the sites are no longer complementary and cannot recognise the pathogen.
90
What is HIV/AIDs?
 HIV = Human Immunodeficiency Virus  AIDs = Acquired Immunodeficiency Syndrome  HIV is the Pathogen, AIDs is the Infectious Disease  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

AQA A LEVEL Biology (8 decks)

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