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CELLS Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is the magnification equation?

A

magnification = image size / actual size

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2
Q

What are the conditions for cell fractionation and why are these needed

A

COLD - prevents enzymes from breaking down the cell organelles

ISOTONIC SOLUTION - so that the water potential of the solution surrounding the organelles is the same as the water potential of the solution inside the cell organelles to prevent any water from moving in or out of the organelle

BUFFERED SOLUTION - maintains a constant pH so that enzymes and other proteins are not denatured.

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3
Q

Describe the stages of cell fractionation - homogenisation

A

Homogenisation = describes the breaking up of cells
1. The sample of tissue (containing the cells to be broken up) must first be placed in a cold, isotonic buffer solution
2. The tissue-containing solution is then homogenised using a homogeniser which breaks the plasma membrane of the cells and releases the organelles into a solution called the homogenate.

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4
Q

Describe the stages of cell fractionation - filtration and ultracentrifugation

A
  1. The homogenate is filtered to separate out any large cell debris.
    The organelles are all much smaller than the debris and are not filtered out which leaves a filtrate.
  2. The filtrate is placed into a tube and the tube is placed in a centrifuge which spins and separate the materials
    - spun on a low speed which causes the densest to form a pellet first (like nuclei) bu the rest of the organelles stay suspended in the supernatant
  3. The supernatant is drained off and placed into another tube, which is spun at a higher spee leaving a new supernatant
    -This process is repeated at increasing speeds until all the different types of organelle present are separated out
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5
Q

Define magnification

A

the ability to make objects appear larger

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6
Q

Define resolution

A

the minimum distance that two objects can be in order for them to appear as two separate items

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7
Q

Light (optical) microscopes

A

Can’t resolve structures closer than 200nm
- low magnification and resolution
- Specimens can be alive
- Specimen can be coloured
- Can be seen with the eye
- Focused by glass lenses

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8
Q

Transmission electron microscopes (TEM)

A

HOW = beam of electrons passes through the specimen and parts absorb the electrons and appear dark

ADVANTAGES:
- small objects can be seen
- high resolution - 0.1nm

DISADVANTAGES:
- in a vacuum
- no living specimens
- extremely thin specimen
- complex staining technique
- 2D image

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9
Q

Scanning electron microscope (SEM)

A

HOW = beam of electrons are directed on the surface of the specimen in a regular pattern

ADVANTAGES:
- surface of specimen
- higher resolution than LM - 20nm
- 3D image produced

DISADVANTAGES:
- in a vacuum
- lower resolution than TEM
- no living specimens
- complex staining technique

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10
Q

Why does the electron microscope have a better resolving power than an optical microscope?

A

Electrons have a shorter wavelength than light in a optical microscope

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11
Q

Eukaryotic : Nucleus

A

Structure:
Nuclear envelope is a double membrane that surrounds the nucleus
Nuclear pores allows the passage of large molecules like RNA
Nucleoplasm is jelly-like material that makes up the bulk
Nucleolus manufactures ribosomal RNA

Function:
Control centre of cell through production of mRNA and tRNA
Retains genetic material of the cell in form of DNA and chromosomes
Manufacture ribosomes

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12
Q

Eukaryotic : Mitochondria

A

Structure and function:
1-10 micrometers long
Double membrane around it and the inner of the two membranes is folded to form cristae (they provide a large surface area)
Matrix makes up the rest and contains proteins, lipids, ribosomes and DNA.
Site of aerobic respiration and release energy

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13
Q

Eukaryotic : Chloroplast

A

Structure:
2-10 micrometers long
Granum - stack of thylakoid membranes that gives a large surface area
Starch grains - Insoluble so doesn’t alter water potential inside the chloroplast
Stroma - fluid compartment thats the site of the light independent reaction
Thylakoid - houses chlorophyll and site of LDR
Double membrane - permeable to oxygen, co2, glucose and some ions

Function :
- Granal membrane provide a large surface area for attachements that carry out first stage of photosynthesis
- Fluid of the stroma has all enzymes needed to make sugars
- Chloroplasts have DNA and ribosomes so can manufacture some proteins needed for photosynthesis

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14
Q

Eukaryotic : Endoplasmic reticulum

A

Rough ER - has ribosomes present on outer surfaces of membranes
- Folds and processes proteins made on the ribosomes

Smooth ER - lacks ribosomes and has a tubular appearance
- synthesis, store and transport lipids and carbohydrates

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15
Q

Eukaryotic : Golgi body

A

Structure:
- Stack of membranes that make up cisternae with small rounded hollow structure called vesicles.

Function:
- Adds carbs to proteins to form glycoproteins
- Produce secretory enzymes
- Secrete carbs
- Transport, modify and store lipids

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16
Q

Eukaryotic : Lysosomes

A

Structure:
- vesicles containing digestive enzymes bound by a single membrane.

Function:
- Hydrolyse material ingested by phagocytic cells
- Release enzymes to the outside of the cell to destroy material around the cell
- Digest worn out organelles
- Completely break down cells after they have died (autolysis)

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17
Q

Ribosomes

A

Two subunits made of ribosomal RNA and proteins
80S - eukaryotic cells, 25nm in diameter
70S - prokaryotic cells, mitochondria and chloroplasts, smaller
Function = site of protein synthesis

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18
Q

Eukaryotic : Cell wall

A

Structure:
- Consists of microfibrils of the polysaccharide cellulose. Microfibrils have considerable strength and contribute to overall strength
- Middle lamella = thin layer that marks boundary between adjacent cell wall

Functions:
- Provides mechanical strength
- Gives each cell its own shape
- Middle lamella helps cement one cell to the next

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19
Q

Eukaryotic : Vacuole

A

Structure:
Single membrane (tonoplasts)
Solution of dissolved mineral

Function:
Contribute to turgidity of cell by pushing cytoplasm against cell membrane

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20
Q

Prokaryotic: Cell wall

A

Rigid outer covering
contains murein

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21
Q

Prokaryotic: Capsule

A

Protective slimy layer
which helps the cell to retain
moisture and adhere to surfaces.

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22
Q

Prokaryotic: Plasmid

A

Circular piece of DNA

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23
Q

Prokaryotic: Flagellum

A

a tail like structure
which rotates to move the cell.

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24
Q

Prokaryotic: Pili

A

Hair-like structures which
attach to other bacterial cells.

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25
Q

Prokaryotic: Mesosomes

A

Infoldings of the inner membrane which contain enzymes required for
respiration

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26
Q

What is mitosis?

A

Division of a cell that results in each of the daughter cells having an exact copy of the DNA of the parent cell. Doesn’t give rise to genetic variation

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27
Q

Describe interphase

A

Stage between one cell division and the next
90% of the time cells are in interphase
DNA is spread out as chromatin and chromosomes aren’t visible

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28
Q

Describe prophase

A

Chromosomes condense and become visible
Centrioles move to two poles of the cell from which spindle fibres develop
Nucleolus disappears and nuclear envelope breaks down so the chromosomes are free in the cytoplasm of the cell

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29
Q

Describe metaphase

A

Chromosomes are now seen to be made up of two chromatids which are joined by the centrometre
Chromosomes line up on the equator
Spindle fully forms

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30
Q

Describe anaphase

A

Centrometres split into trow and chromatids are pulled apart to opposite ends of the cell
Energy for this process is provided by mitochondria which gather around the spindle fibre cells

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31
Q

Describe telophase and cytokinesis

A

Nuclear membrane forms
Cytoplasm divides

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32
Q

What is the importance of mitosis? (3)

A
  1. GROWTH = all cells produced are identical so organisms can grow using mitosis.
  2. REPRODUCTION = single celled organisms divide by mitosis
  3. REPAIR = all cells produced are identical so organisms can replace dead tissues using mitosis.
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33
Q

What is the process and purpose of binary fission?

A

Used by prokaryotic cells to divide
* replication of the circular DNA and of plasmids
* division of the cytoplasm to produce two daughter cells, each
with a single copy of the circular DNA and a variable number
of copies of plasmids.

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34
Q

What is the cell cycle?

A

When some cells don’t divide continuously but still undergo a regular cycle of division separated by periods of cell growth it is known as the cell cycle

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35
Q

What are the 3 stages of the cell cycle?

A

Interphase
Nuclear division
Cytokinesis

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36
Q

Describe interphase (cell cycle)

A

Occupies most of the cell cycle no division takes place

37
Q

Describe nuclear division (cell cycle)

A

Nucleus divides into either 2 (mitosis) or 4 (meiosis)

38
Q

Describe cytokinesis (cell cycle)

A

Cytoplasm divides to produce 2 (mitosis) or 4 (meiosis) new cells.

39
Q

What is cancer?

A

A group of diseases caused by a growth disorder of cells
It is the result of damage to the genes that regulate mitosis and the cell cycle. leads to an uncontrolled growth and division of cells and a tumour develops

40
Q

Control of mitosis in terms of cancer

A

the rate of mitosis can be controlled by two types of genes. A mutation to one of these results in uncontrolled mitosis which forms tumours.

41
Q

Treatment of cancer

A

Involves killing cells by blocking a part of the cell cycle.
Drugs to do this prevent the cell cycle by:
1. preventing DNA from replicating
2. inhibiting the metaphase stage of mitosis by interfering with spindle formation
PROBLEMS: disrupt cell cycle of normal cells but the drugs are more effective against rapidly dividing cells.

42
Q

Define a cell membrane

A

organelle controls what substances enter and leave the cell

43
Q

Describe the structure of membranes

A

PHOSPHOLIPIDS : All membranes are made up of a phospholipid bilayer with the hydrophilic heads pointing outwards and the hydrophobic tails pointing inwards
PROTEINS : 2 types of proteins in a membrane
1. Extrinsic - lie on one side of membrane only
2. Intrinsic - span the membrane from one side to the other

44
Q

Function of membranes

A

-only allow small molecules through (selectively permeable)
- Small molecules can diffuse through the phospholipid bilayer
- Large molecules can only diffuse if they are lipid soluble

45
Q

What is the fluid mosaic model? Describe

A

how scientists describe what the cell membrane looks and functions like
Fluid : Phospholipid molecule move relative to each other giving the molecule a flexible structure
Mosaic : Proteins vary in size
Glycoprotein = Branching carbohydrate portion of a protein that acts as a recognition site

46
Q

Function of proteins

A

Mechanical support to membrane
Protein channeled that transport water-soluble ions across the membrane
Allow active transport across the membrane via carrier proteins
Conjunction with glycolipids as cell receptors for molecules such as hormones

47
Q

Extra molecules in membranes

A

CHOLESTEROL - makes the membrane more rigid and
reduces the lateral movement of the phospholipids. It also prevents the leakage
of water and dissolved ions from the cell as it is very hydrophobic.
PHOSPHOLIPIDS - made up of a phospholipid with carbohydrate attached, extend from the surface of the cell and acts as a cell surface receptors for certain molecules. Also allows cells to adhere to one another to form tissues.
GLYCOLIPIDS - carbohydrates
that attach to extrinsic proteins and acts as
a cell surface receptors and
neurotransmitters. They help cells to attach and form tissues

48
Q

Define diffusion

A

The net movement o particle from a region of relatively high concentration to a region of lower concentration

49
Q

Factors affecting diffusion across membrane

A

Temperature : warm molecules have more kinetic energy
Size of molecule - small molecules have more kinetic energy
Concentration gradient - steeper gradient the faster the diffusion
Nature of molecule - lipid soluble gets across membrane faster, non polar diffuse faster than polar
Thickness of membrane - thicker membrane, greater diffusion distance
Surface area of membrane - greater surface are = faster diffusion
Number of specific carrier/channel proteins - more proteins, the faster diffusion will happen

50
Q

Define facilitated diffusion

A

The net movement of particle down a concentration gradient that only happens with the help of carrier or channel proteins

51
Q

What are transporter proteins?

A

They can be carrier or channel and are:
- Intrinsic
- Specific to one type of molecule
- Have binding sights for that molecule

52
Q

What do channel proteins do (facilitated diffusion)

A

Form hydrophyllic channels across membranes
Transport water soluble ions
Can be gated

53
Q

What do carrier proteins do (facilitated diffusion)

A

Molecule attaches to the binding site which causes the protein to change shape
Molecule is then deposited on the other side of the membrane
No energy is needed and they only transport molecules down a concentration gradient.

54
Q

How do channel and carrier proteins aid facilitated diffusion?

A

They give the cell the ability to control what enters and leaves the cell or the internal organelles

55
Q

Define osmosis

A

Movement of water from a higher water potential to a lower water potential across a partially permeable membrane

56
Q

What is water potential?

A

A measure of the pressure created by water molecules
Measured in kilopascals
Pure water has the highest water potential (0KPa)
- All solutions are compared to pure water and so have negative water potentials

57
Q

Describe osmosis in animal and plant cells

A

HYPOTONIC:
- Water potential in surrounding solution: Less negative
- Water movement between cell and solution: Moves into cell
Effect on cell: Swells and bursts (animal). Plants become turgid
ISOTONIC:
- Water potential in surrounding solution: Same
- Water movement between cell and solution: No movement
Effect on cell: No change in animals. Plants = incipient plasmolysis
HYPERTONIC:
- Water potential in surrounding solution: More negative
- Water movement between cell and solution: Moves out of cell
Effect on cell: Shrinks in animals. Plants = plasmolysed.

58
Q

Define active transport

A

Movement of molecules from a region of their lower concentration to a region of their higher concentration using carrier proteins and energy

59
Q

Features of active transport

A
  • Substances move against their concentration gradient
  • Require specific carrier proteins which need energy in the form of ATP to change shape and deposit the molecules on the other side of the membrane
  • ATP is needed to change to the shape of the protein
60
Q

Why does active transport require oxygen?

A

Because it requires energy
- If respiration stops active transport stops so cells only use active transport to move important molecules

61
Q

describe co transport

A
  1. Na+ ions are actively transported out of the epithelial cells in the ileum by a sodium - potassium pump into the blood this takes place in a specific carrier protein
  2. Higher concentration of sodium in the lumen of small intestine than epithelial cells
  3. Na+ ions diffuse into the epithelial cells down this concentration gradient and bring amino acids along with them
  4. Amino acids then pass into the blood plasma via facilitated diffusion
62
Q

name three physical barriers to infection

A
  1. SKIN = tough physical barrier consisting of keratin
  2. STOMACH ACID = HCL kills bacteria
  3. GUT AND SKIN FLORA = natural bacterial flora competes with pathogens for food and space
63
Q

what are non specific defence mechanisms

A

= responses is immediate and the the same for all pathogens
1. physical barriers
2. phagocytosis

64
Q

what are specific defence mechanisms

A

= response is slower and specific to each pathogen
1. cell mediated response
2. humoral response

65
Q

What is phagocytosis

A

Phagocytes (type of white blood cell) - ingest and destroy the pathogen before it can cause harm

66
Q

Stage of phagocytosis

A
  1. Chemical products of pathogens act as attractants causing phagocytes to move towards the pathogen
  2. Phagocytes have several receptors on their cell-surface membrane that recognise and attach to chemicals on the surface of the pathogen
  3. Engulf the pathogen to form a vesicle known as a phagosome
  4. Lysosomes move towards the vesicle and fuse with it
  5. Enzymes calls lysozomes are present within the lysosome. These enzymes destroy ingested bacteria by hydrolysis of their cell walls
  6. The soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagocyte
67
Q

What are APC’s

A

cells that display foreign antigens on their surface are called antigen-presenting cells
- as they present antigens of other cells on their own cell surface membrane

68
Q

What do T cell lymphocytes respond to

A

Antigens that are presented on a body cell rather than to antigens within the body fluids - receptors on each T cell respond to a single antigen

69
Q

Stage of cell-mediated immunity

A
  1. Pathogens invade body cells or are taken in by phagocytes
  2. The phagocyte places antigens from the pathogen on its cell surface membrane
  3. Receptors on a specific helper T cell fit exactly onto these antigens
  4. This attachment activated the T cell to divide rapidly by mitosis and form a clone of genetically identical cells
  5. The cloned T cells:
    a) develop into memory cells
    b) stimulate phagocytes to engulf pathogens by phagocytosis
    c) stimulate B cells to divide and secrete their antibody
    d) activate cytotoxic T cells
70
Q

role of cytotoxic t cells

A

kill abnormal cells and body cells that are infected by pathogen by producing a protein that makes hole in the cell surface membrane ( becomes permeable to everything and so the cell dies)

71
Q

What is humoral immunity

A

Involves antibodies
- there are many diff types of B cell and each B cell produces a specific antibody that responds to one specific antigen

72
Q

Stage of humoral immunity

A
  1. Surface antigens of an invading pathogen are taken up by a B cell
  2. The B cell processes the antigens and presents them on its surface
  3. Helper t cell (cell mediated activated ones) attach to the processed antigen on the B cell = activates the B cell
  4. B cell divides by mitosis to give a clone of plasma cells
  5. Cloned plasma cells produce and secrete the specific antibody that exactly fits the antigen on the pathogen surface
  6. Antibody attached to antigens on the pathogen and destroys them
  7. Some B cells develop into memory cells. Respond to future infections by dividing rapidly and developing into plasma cells that produce antibodies
73
Q

What is the primary response

A

Plasma cells secrete antibodies into blood plasma - these antibodies lead to the destruction of the antigen.
Production of antibodies and memory cells is known as the primary immune response

74
Q

What is the secondary response

A

Memory cells = secondary response
- Live longer than plasma cells and don’t produce antibodies but circulate in the blood and tissue fluid
Divide rapidly into plasma cells and more memory cells when antigen is encountered again ( provides long term immunity)

75
Q

define antibody

A

antibodies are proteins with specific binding sites synthesised by B cells.
- binding sites are specific to a complementary antigen and variety of antibodies is possible because they are made of many proteins

76
Q

structure of an antibody

A

-four polypeptide chains = long heavy chains and shorter light chains
- specific binding site that fits very precisely onto a specific antigen to form an antigen-antibody complex

77
Q

what is a variable region

A

binding site is different on different antibodies and this is called the variable region
- rest of antibody is the constant region

78
Q

what is agglutination

A

clumps of bacterial cells are formed making it easier for the phagocytes to locate them as they are less spread out within body
- possible due to each antibody having two antigen binding sites
- serve as markers that stimulate phagocytes to engulf the bacterial cells to which they are attracted

79
Q

what is a monoclonal antibody

A

antibodies which are produced by a single clone of a specific white blood cell. they are specific to one binding site on one protein antigen so they are able to target specific cells

80
Q

what is direct monoclonal antibody therapy

A
  1. monoclonal antibodies are produced that are specific to antigens on cancer cells
  2. these antibodies are given to a patient and attach themselves to the receptors on their cancer cells
  3. They attach to the surface of their cancer cells and block the chemical signals that stimulate their uncontrolled growth
    - example is herceptin
    + since antibodies aren’t toxic and are highly specific they lead to fewer side effects than other forms of therapy
81
Q

what is indirect monoclonal antibody therapy

A

Involves attaching a radioactive or cytotoxic drug to the monoclonal antibody
- when the antibody attaches to the cancer cells it kills them

82
Q

why are monoclonal antibodies important

A

important in diagnosis of certain cancer.

83
Q

what is passive immunity

A

produced by the introduction of antibodies into individuals from an outside source
- no direct contact with the pathogen is necessary to induce immunity = immunity is acquired immunity
- no memory cells as antibodies aren’t replaced when broken down = no lasting immunity

84
Q

what is active immunity

A

produced by stimulating the production of antibodies by the individuals own immune system
- direct contact with pathogen is necessary
- long lasting and there are two types
1. Natural =individual is infected with a disease under normal factors
2. Artificial = inducing an immune response in an individual (no sypmtoms) = vaccine

85
Q

Features of a successful vaccine

A
  1. Economically available in sufficient quantities to immunise most of the vulnerable population
  2. Few side effects
  3. Means for production, storing and transportation must be available
  4. Appropriate means of administration
86
Q

What is herd immunity

A

When a sufficiently large proportion of the population has been vaccinated making it difficult for a pathogen spread within a population

87
Q

Why is herd immunity important

A

Its impossible for a whole population to be vaccinated e.g. provides protection for babies and the elderly

88
Q

Why may vaccine not eliminate a disease

A
  1. Vaccination facts to induce immunity in certain individuals e.g. people with defective immune systems
  2. Pathogen may frequently mutate so its antigen change suddenly. Vaccines become ineffective as the new antigens aren’t recognised by the immune system
    3.May be loads of variety of a particular pathogen that its impossible to vaccinate against them all e.g. the cold
  3. Individuals may have objection to vaccines due to religion, ethical or medical reasons

biology (4 decks)

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