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A-Level Biology > Module 2: Cells > Flashcards

Module 2: Cells Flashcards

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1
Q

explain kingdoms

A

5 kingdoms
animal and plant are multicellular
bacteria, fungi and protoctista are microorganisms
all made from cells

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2
Q

properties of all cells

A

DNA, ribosomes, cytoplasm, cell membrane

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3
Q

what are the 5 kingdoms?

A 
animal
plant
bacteria
fungi
protoctista
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4
Q

why are viruses not defined as living organisms?

A

don’t have standard cell components

can’t perform living processes without a host cell

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5
Q

eukaryotic cells

A

animal/plant cell that has a membrane bound nucleus and membrane bound organelles

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6
Q

examples of membrane bound organelles

A 
nucleus
endoplasmic reticulum
golgi 
lysosome 
mitochondria
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7
Q

prokaryotic cells

A

bacteria, has no membrane bound nucleus or membrane bound organelles

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8
Q

2 forms of reproduction

A

sexual

asexual

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9
Q

sexual reproduction

A

animals and some plants
uses 2 parents
each parent provides a gamete which fuses to form a zygote, zygote develops into an organism

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10
Q

asexual reproduction

A

microorganisms and some plants
uses 1 parent
genetically identical offspring

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11
Q

how does a zygote develop into an organism

A

zygote is a stem cell
divides by mitosis to make several stem cells
all stem cells differentiates into specialised cells
specialised cell divides by mitosis
different tissues form organs
organs form organ systems
surrounded by the body

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12
Q

define a tissue

A

a group of specialised cells

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13
Q

define an organ

A

made of different tissues working together

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14
Q

define an organ system

A

different organs working together

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15
Q

Organelles in an animal cell

A 
Nucleus
Endoplasmic reticulum 
Golgi
Lysosomes 
Mitochondria
Ribosomes
Cytoplasm
Cell membrane
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16
Q

Cytoplasm

A

Site of chemical reactions

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17
Q

Cell membrane

A

Controls what enters/leaves the cell
Holds cell contents together
Cell signalling

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18
Q

Structure of nucleus

A

Contains DNA
DNA wrapped around histones to form Chromatin
Nucleus has double membrane called nuclear envelope which contains nuclear pores
Centre is nucleolus which produces mRNA
Nucleoplasm which contains DNA/chromatin

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19
Q

2 types of Endoplasmic reticulum

A

Rough

Smooth

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20
Q

Rough endoplasmic reticulum

A

Ribosomes on surface

Makes proteins

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21
Q

Smooth endoplasmic reticulum

A

No ribosomes

Makes lipids/ carbohydrates

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22
Q

Golgi

A

Modifies and packages proteins
Packages into vesicles for transport
Digestive enzymes placed into lysosomes (vesicles with membranes around them)

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23
Q

Mitochondria

A 
Site of aerobic respiration 
Releases energy 
Produces ATP
Double membrane:
-inner membrane=cristae (increases SA for enzymes of respiration)
-middle section is matrix
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24
Q

Ribosomes

A

Attacted to RER
Site of protein synthesis
70S- smaller, found in bacteria
80s- bigger, found in eukaryotes

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25
Q

What’s a plant cell made of

A 
Nucleus
Endoplasmic reticulum 
Golgi 
Lysosomes
Mitochondria
Chloroplast
Vacuole
Ribosomes
Cytoplasm
Cell membrane
Cell wall
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26
Q

Cell wall

A

Made of cellulose

Prevents cell from bursting or shrinking

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27
Q

Structure of chloroplast

A 
Organelle for photosynthesis
Double membrane
Discs called thylakoid
Which contain chlorophyll 
Stacks of thylakoid called granum 
Fluid called stroma
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28
Q

Vacuole

A

Surrounded by tonoplast membrane

Contains cell sap

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29
Q

What is bacteria made of

A

No nucleus- loose DNA in form of single loop and plasmid
No membrane bound organelles- smaller ribosomes, mesosomes
Cytosol
Cell membrane/cell wall (made of glycoprotein murein)
Some have a capsule and flagella

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30
Q

Capsule

A

Protect

Water loss prevention

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31
Q

Flagella

A

Movement

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32
Q

What is a virus made up of?

A

DNA or RNA (if RNA then will have RNA transcriptase to convert)
Capsid (protein coat)
Attachment proteins
Viral enzymes

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33
Q

Attachment proteins

A

Infects host cells by attaching using attachment protein
Send in DNA which uses cell to make viruses components and uses the cell membrane to make viral lipid coat
Produces copies of the virus and destroys host cell

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34
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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35
Q

Homologous pair of chromosomes

A

A pair of chromosomes
1 maternal
1 paternal
Same genes but different alleles

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36
Q

Cell division

A

Formation of new cells in multicellular organisms

Mitosis and meiosis

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37
Q

Mitosis

A

Produces genetically identical cells for growth and repair of tissues

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38
Q

Meiosis

A

Produces genetically different haploid cells as gametes for sexual reproduction

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39
Q

What does mitosis produce

A

2 genetically identical cells
Diploid
Full set of chromosomes/DNA

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40
Q

Benefits of mitosis

A

Growth and repair of tissues

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41
Q

Stages of mitosis

A

Interphase
Mitosis
Cytokinesis

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42
Q

Three phases of interphase

A

G1: protein synthesis
S: DNA replication
G2: organelle synthesis

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43
Q

Mitosis process

A

Prophase: DNA coils to form chromosomes, nucleus breaks down, spindle fibres form
Metaphase: chromosomes line up in the middle of the cell, attach to spindle fibre via centromere
Anaphase: spindle fibres pull, centromere splits, sister chromatids move to opposite sides
Telophase: chromatids uncoil, nucleus reforms, leaves 2 genetically identical nuclei

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44
Q

Cytokinesis

A

Separates cell into 2

Each receives a nucleus and organelles/cytoplasm

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45
Q

What happens to DNA mass in mitosis

A

Halves

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46
Q

What happens to number of chromosomes in mitosis

A

Stays same

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47
Q

What is cancer

A

Formation of tumour due to uncontrolled cell division

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48
Q

How does uncontrolled cell division occur

A

Mutation of DNA/cells forming cancer cells
Mutation can occur randomly or due to mutagens
Cancer cells are rapidly dividing cells that spend less time in interphase and more time in other stages (mitosis)

49
Q

Treatments for cancer

A

Surgery
Chemotherapy
Radiotherapy

50
Q

Surgery

A

Aim is to remove tumour

51
Q

Chemotherapy

A

Uses drugs that inhibit mitosis
But can also affect normal healthy cells causing side effects
Treatment given as regular doses to allow time for normal healthy cells to recover in number

52
Q

Radiotherapy

A

Radiation used to destroy cancer cells

53
Q

What does meiosis produce

A

4 genetically different cells
Haploid
Half amount of chromosome DNA

54
Q

Benefits of meiosis

A

Produces gametes which will be used in sexual reproduction in animals and plants
2 gametes fuse to form a zygote, zygote develops into organisms

55
Q

Stages of meiosis

A

Interphase
Meiosis 1
Meiosis 2
Cytokinesis

56
Q

Meiosis 1

A

Prophase 1: DNA coils forming chromosomes, nucleus breaks down, spindle fibres form, crossing over occurs
Metaphase 1: homologous pairs of chromosomes line up at equator and attach to spindle fibre via centromere by random assortment
Anaphase 1: spindle fibres pull, homolgous pairs of chromosomes separate to opposite sides by independent segregation
Telophase 1: chromosomes uncoil, nucleus reforms (2 nuclei)

57
Q

Meiosis 2

A

Prophase 2: DNA coils to form chromosomes, nucleus breaks down, spindle fibres form
Metaphase 2: chromosomes line up at equator, attach to spindle fibres via centromere randomly
Anaphase 2: spindle fibres pull, centromere splits, sister chromatids move to opposite ends by independent segregation
Telophase 2: chromatids uncoil, nucleus reforms (4 genetically different nuclei)

58
Q

Cytokinesis in meiosis

A

Each cell into 4

59
Q

How does meiosis produce variation

A

Crossing over

Independent segregation

60
Q

Crossing over

A

Occurs in prophase 1 of meiosis 1
Homologous pairs of chromosomes wrap around each other and swap equivalent sections of chromatids
Produces new combination of alleles

61
Q

Independent segregation

A

Anaphase 1 of meiosis 1- homologous pairs of chromosomes separate
Anaphase 2 of meiosis 2- chromatids separate
Independent segregation produces a mix of alleles from paternal and maternal chromosomes in gamete

62
Q

What happens to DNA mass in meiosis

A

Quarters

63
Q

What happens to chromosome number in meiosis

A

Halves

Haploid

64
Q

Bacteria cell division

A 
Binary fission 
Copy DNA (single loop and plasmid) and separate into 2 new genetically identical bacteria (asexual reproduction)
65
Q

3 types of microscopes

A

Light
Transmission electron
Scanning electron

66
Q

Magnification

A

Englarging the physical appearance of an object

67
Q

Highest magnification microscopes

A

TEM
SEM
LM

68
Q

How to calculate magnification

A

Image= actual x magnification

69
Q

1mm to micrometer

A

1000

70
Q

1mm to nanometre

A

1,000,000

71
Q

Why can organelles appear different in images

A

Viewed from different angles and different depths

72
Q

Definition of resolution

A

Minimum distance apart two objects can be so they are still distinguished separately

73
Q

Which microscope has highest resolution

A

TEM
SEM
LM

74
Q

Why do electron microscopes have a higher resolution

A

Electrons have a shorter wavelength than light

75
Q

Difference between TEM and SEM

A

TEM the electrons pass through the specimen

SEM the electrons bounce off the surface of the specimen

76
Q

Advantage and disadvantage of TEM

A

+highest magnification and resolution

- works in a vacuum so can only observe dead specimen, specimen must be thin, 2d black and white image is produced

77
Q

Advantage and disadvantage of SEM

A

+produces 3D image

- works in a vacuum so can only observe dead specimen, black and white image

78
Q

Process of cell fractionation

A

breakdown tissues into cells using pestle and mortar
Add cold isotonic buffer solution
Homogenize using a blender to release organelles
Centrifuges and increasing speeds, intensities and time
Supernatant respan
Pellets are formed (nucleus, chloroplast,mitochondria, endoplasmic reticulum golgi and lysosomes, ribosomes

79
Q

Reason for conditions of buffer solution

A

Cold- reduce enzyme activity
Isotonic-sane water potential so organelle doesn’t shrink or burst
Buffer- maintains constant ph Incase lysosomes burst and release enzymes

80
Q

Order of pellet formation in cell fractionation

A 
Nucleus
Chloroplasts 
Mitochondria
Endoplasmic reticulum, golgi, lysosomes
Ribosomes
81
Q

Simple vs facilitated diffusion

A

Simple- molecules move directly through the phospholipid bilayer
Facilitated-molecules pass through transport proteins (large use carrier and charged use channel)

82
Q

Factors affecting the rate of diffusion

A 
Surface area (increase=increase the rat3 o& diffusion)
Concentration gradient (increase= increase rate)
Thickness( decrease=decrease diffusion distance=increased rate of diffusion)
Temperature(increase=increase kinetic energy= molecules move faster= increased rate of diffusion)
Size of molecules (smaller molecules=increased rate of diffusion)
83
Q

Ficks law

A

Rate of diffusion is proportional to (surface area x concentration gradient)/ thickness

84
Q

Osmosis definition

A

Movement of water molecules from an area of high water potential to an area of lower water potential across a partially permeable membrane

85
Q

Which liquid has the highest water potential

A

Distilled/pure water
Value of 0kPa
Lower water potential by adding solutes
Water moves from less negative water potential to more negative water potential

86
Q

Surround animal cell with pure water?

A

Swells and bursts

Osmotic lysis

87
Q

Surround plant cell with pure water?

A

Swells but doesn’t burst
Cell wall prevents it from bursting
Made of cellulose
Cell is turgid

88
Q

Surround animal cell with conc sugar/salt solution

A

Shrinks

Water leaves by osmosis

89
Q

Surround plant cell with conc salt/sugar solution

A

Water leaves by osmosis
Cell wall prevents shrinkage so cell stays rigid
Protoplast shrinks
Cell is plasmolysed

90
Q

Active transport definition

A

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

91
Q

Process of active transport

A

Molecules in an area of low concentration bind to carrier protein
ATP breaks down to ADP and Pi and energy
Pi and energy cause the carrier protein to change shape when Pi binds to it
Carrier protein releases molecules on opposite side in the area of high concentration
Carrier proteins releases attached Pi to return to its original shape

92
Q

Enzymes of carbohydrate digestion and their products

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 (sucrose on lining of small intestine) into glucose and fructose
93
Q

Enzymes of protein digestion

A

Endopeptidase (in stomach) hydrolysis peptide bonds in the middle of the polypeptide chain into many smaller chains
Exopeptidase (in small intestine) hydrolysis peptide bonds at the end of the chain into dipeptides
Dipeptidase (lining of the small intestine) hydrolyses dipeptides into amino acids

94
Q

Enzymes of lipid digestion

A

Lipase in small intestine leaves monoglyceride and two fatty acids

95
Q

Adaptations of the small intestine for absorption

A

Folded to form villus for increased surface area
Cells lining the small intestine have microvilli to increase surface area
Walls of small intestine is thin for short diffusion distance
Rich blood supply to maintain the concentration gradient
Cells lining the small intestine have transport proteins, enzymes (Maltase,lactase,sucrase,dipeptidase) and many mitochondria

96
Q

Absorption of glucose and amino acids in small intestine

A

Sodium ions are actively transported from the cells lining the small intestine into the blood
Lowers the sodium ion concentration in the cell
Sodium ions move from lumen of small intestine into the cell
Pulls in glucose and amino acids via a co transport protein
Glucose and Amino acids build up in the cell and move into the blood via diffusion

97
Q

Absorption of monglycerides and fatty acids

A

Lipids initially emulsified by bile into micelles
Micelles digested by lipase into monglycerides and two fatty acids
Monoglycerides and fatty acids absorbed by cells lining small intestine by simple diffusion
Form a chylomicron (lipid+cholesterol+lipoprotein)
Enters lymph as lacteal then enters blood

98
Q

What is lactose intolerance

A

Person doesn’t make lactase
Lactose remains undigested
Undigested lactose in lumen of intestine lowers its water potential so water enters the lumen by osmosis leading to water faeces
Undigested lactose breakdown by microorganisms in large intestine giving off gas

99
Q

Pathogen definition

A

Microorganism that causes disease

100
Q

Body’s three defenses against pathogens

A

Barriers (prevent pathogens entering the body)
Phagocytes (phagocytosis and stimulate specific response)
Specific response (uses lymphocytes to produce memory cells and antibodies)

101
Q

What are the barriers in pathogen defense

A

Skin-impermeable barrier of keratin
Cilia and mucus in the lungs
Stomach acid-denatures and breaks down pathogens

102
Q

Process of phagocytosis

A

Pathogen releases chemoattractants
Attracts the phagocyte
Phagocyte binds to the pathogens cell surface proteins non specifically
Phagocyte engulfs the pathogen
Forms a phagosome around the pathogen
Lysosomes inside the phagocyte release lysozymes into the phagosome
Breaks down the pathogen by hydrolysis
Phagocyte presents antigens on its own cell surface membrane

103
Q

Process of the specific immune response

A

Phagocytes perform phagocytosis and present antigens on their own cell surface membrane
T cells bind to the antigens and become stimulated
They divide by mitosis to form: t helper cells, cytotoxic T cells and memory T cells
T helper cells stimulate B cells
Cytotoxic T cells destroy cells infected by virus as they release performing to make holes in the membrane
T memory cells provide long term immunity
B cells engulf and present antigens on their surface and the t helper cells bind to this
Stimulates B cells to divide by mitosis to form plasma cells and memory cells
Plasma cells make antibodies and memory cells provide long term immunity

104
Q

Antigen definition

A

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

105
Q

How does the immune response lead to production of antibodies

A 
Phagocytes stimulate T cells 
T cell form t helper cells
T helper cells stimulate B cells 
B cells form plasma cells 
Plasma cells make antibodies
106
Q

What is an antibody

A

Globular protein
Made by plasma cells
Has 3 regions: variable region, hinge region, constant region

107
Q

What are the three regions of an antibody

A

Variable
Hinge
Constant

108
Q

What do the three regions of an antibody do?

A

Variable- different shape in each antibody, contains antigen binding sites, Bind to complementary antigens on a pathogen to form an antigen antibody complex to destroy the pathogen
Hinge-give antibody flexibility
Constant- same shape in all antibodies, binds to phagocytes to help with phagocytosis

109
Q

How do memory cells work

A

Made during the specific immune response after a new infection by a pathogen (primary infection)
B and T cells remain in the blood
Upon secondary infection the memory cells will recognize the pathogen and produce antibodies rapidly to a large amount
Pathogen is killed before it can harm
Immunity

110
Q

How does a vaccine programmer produce immunity

A

Involves giving an injection that contains dead/weakened form of a pathogen that carry antigens which stimulates the immune response leading to the production of antibodies and memory cells

111
Q

Active immunity

A

Individual has memory cells
Make their own antibodies
Provides long term immunity

112
Q

Passive immunity

A

Person given antibodies
These work then die
No long term immunity
No memory cells

113
Q

How does active immunity occur

A

Naturally-primary infection

Artificially-vaccination

114
Q

How does passive immunity occur

A

Naturally-mother to baby via placenta or breast milk

Artificially- by injection

115
Q

Successful vaccination programme

A

Produce suitable vaccine (effective by making memory cells, doesn’t cause disease, no major side effects, low cost, easy administration)
Herd immunity

116
Q

What is herd immunity

A

When a large population of the population is vaccinated therefore most people will be immune, increases chances of a non-immune person coming into contact with immune person so the pathogen has no where to go and will die out

117
Q

Problems with vaccination programmes

A 
Vaccine doesn’t work 
Vaccine isn’t safe 
Many strains of a pathogen 
Can’t achieve herd immunity 
Antigenic variability
118
Q

Antigenic variability

A 
The pathogen mutates 
Antigen changes shape 
Memory cells no longer complementary 
Doesn’t recognize the pathogen 
Therefore the pathogen can re harm
119
Q

What is HIV/AIDS

A

HIV is pathogen
AIDS is infectious disease
HIV spreads by fluid
Damages t helper cells so person has no defense against pathogens leading to aids

A-Level Biology (14 decks)

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