topic 11 Flashcards
1
Q
A
2
Q
every organism has —– ——– on the surface of their cells
A
unique molecules
3
Q
antigens on the surface of red blood cells
A
stimulate antibody production in a person with a different blood group
4
Q
describe the presence and absence of antigens on the surface of blood cells from different blood groups
A
- all three alleles involve a basic antigen sequence called antigen H
A: this is modified by the addition of molecule N-acetylgalactosamine
B: additional molecule is galactose
AB: both types of antigen
O: neither surface glycoprotein
5
Q
what happens if a recipient is given a transfusion involving the wrong type of blood?
A
an immune response occurs. antibodies are produced, agglutination (clumping) occurs, followed by hemolysis where red blood cells are destroyed and blood may coagulate in vessels
6
Q
describe an immune response
A
- macrophage ingests pathogen and displays antigens on it
- helper T cell specific to the antigen is activated by the macrophage
- B cell specific to the antigen is activated by proteins from the helper T cell
- B cell divides repeatedly to produce antibody-secreting plasma cells
- B cell also divides to produce memory cells
- antibodies produced by the clone of plasma cells are specific to antigens on the pathogen and help destroy it
7
Q
how does activation of helper T cells work?
A
they have an antibody-like receptor protein in their plasma membranes, which can bind to antigens displayed by macrophages
8
Q
how does the structure of plasma cells relate to their function?
A
- the cytoplasm contains an extensive network of rough endoplasmic reticulum (rER), which manufactures, modifies, and transports proteins (antibodies).
- The range of genes expressed is lower than a typical cell as the cell produces a lot of the same protein
9
Q
define clonal selection
A
the generation of large numbers of plasma cells that produce one specific antibody type
10
Q
give and explain 4 ways in which antibodies aid the destruction of pathogens
A
- opsonisation- make the pathogen more recognisable to phagocytes so they are more readily engulfed. also, once bound, they can link the pathogen to phagocytes
- neutralisation of viruses and bacteria: antibodies prevent viruses from docking to / entering host cells
- neutralisation of toxins- bind to the toxins produced by pathogens, preventing them from affecting susceptible cells
- activation of complement- antibodies activate a complement cascade which leads to the formation of a membrane attack complex that forms a pore in the membrane of the pathogen allowing water and ions to enter the cell and causing lysis
- agglutination of pathogens, preventing cell entry and aiding ingestion by pathogens
11
Q
what is the complement system?
A
a collection of proteins which ultimately lead to the perforation of the membranes of pathogens
12
Q
what does immunity depend upon?
A
the persistence of memory cells
13
Q
describe how vaccines lead to immunity
A
they contain antigens that trigger immunity by causing a primary immune response but do not cause the disease
if the actual pathogen enters the body, it will be destroyed by the antibodies in a secondary immune response
14
Q
what was the first infectious disease of humans to have been eradicated by vaccination?
A
smallpox
15
Q
give 3 reasons why the smallpox eradication campaign was successful
A
- only humans can catch and transmit smallpox. there is no reservoir where the disease could be maintained and re-emerged
- symptoms of infection emerge quickly and are readily visible allowing teams to ‘ring vaccinate’ all of the people who might have come into contact with the afflicted person
- immunity is long-lasting
16
Q
pathogens can either be
A
species-specific or able to cross species barriers
17
Q
define a zoonosis
A
a pathogen which can cross a species barrier
these are a growing health concern
18
Q
when and how are histamines released?
A
- by mast cells (immune cells found in connective tissue) secrete histamine in response to infection
- by basophils which circulate in the blood
19
Q
state the effect of histamine on blood vessels
A
causes the dilation of the small blood vessels in the infected area causing the vessels to become leaky. This increases the flow of fluid containing immune components to the infected area and allows for some of the immune components to leave the blood vessel resulting in both specific and non-specific responses.
20
Q
Sensitization: Initial exposure to allergen and
Allergic Reaction: Secondary exposure to same allergen
A
- when a specific B cell first encounters the allergen, it differentiates into plasma cells and makes large quantities of antibody (IgE)
- the IgE antibodies attach to mast cells, effectively ‘priming’ them towards the allergen
- upon re-exposure to the allergen, the IgE-primed mast cells release large amounts of histamine which causes inflammation
21
Q
symptoms of an allergic reaction
A
nose: itching, fluid build-up, sneezing, mucus secretion and inflammation
allergic rashes and dangerous swelling (anaphylaxis)
22
Q
define monoclonal antibodies
A
highly specific, purified antibodies that are produced by a clone of cells derived from a single cell. they recognise only one antigen
23
Q
what is the use of monoclonal antibodies?
A
the treatment and diagnosis of diseases; eg the test for malaria or the creation of antibodies for injection into rabies victims
24
Q
define a hybridoma cell
A
the cells formed by fusion of antibody-producing plasma B cells and myeloma (tumour) cells, which produce monoclonal antibodies
25
describe how hybridoma cells are created
1. antigen recognised by the antibody is injected into a mouse or other mammal
2. the mouse's immune system makes plasma B cells that are capable of producing the desired antibody
3. plasma cells are removed from the spleen of the mouse and fused with cancer cells called myeloma cells
26
describe how pregnancy tests work with a diagram
kits use monoclonal antibodies to detect hCG, which is produced during pregnancy by the developing embryo and the placenta. the urine of pregnant women contains detectable levels of hCG
1. free monoclonal antibodies specific to hCG are conjugated to an enzyme that changes the colour of a dye
2. a second set of monoclonal antibodies specific to hCG are immobilised to the dye substrate
3. if hCG is present in urine, it will interact with both sets of monoclonal antibody (forming an antibody ‘sandwich’)
4. when both sets of antibody are bound to hCG, the enzyme is brought into physical proximity with the dye, changing its colour
5. a third set of monoclonal antibodies will bind any unattached enzyme-linked antibodies, functioning as a control
27
28
29
function of bones and exoskeletons
provide anchorage for muscles and act as levers
30
define exoskeletons
external skeletons that surround and protect most of the body surface of animals such as crustaceans and insects
31
describe a first class lever and give an example
E (down), F, R (up)
Example - when a person nods their head backwards
32
describe a second class lever and give an example
F, R, E (down)
Example - someone walking, the moment where they stand on their tiptoes.
33
describe a third class lever and give an example
F, E (up), R (down)
Example - flexing forearm down
34
skeletal muscles are
antagonistic
35
define antagonistic muscles
when one muscle contracts, the other relaxes - they thus produce opposite movements at a joint
36
give a example of an antagonistic muscle pair
in the elbow, the triceps extends the forearm while the biceps flex the forearm
37
give an example of antagonistic pairs of muscles in an insect
in the leg of a grasshopper, which is specialised for jumping.
1. when the grasshopper prepares to jump, the flexor muscles will contract
2. this will bring the tibia and tarsus into a position where they resemble the letter Z and the femur and tibia are brought closer together (flexing). extensor muscles relax during this phase
3. extensor muscles contract extending the tibia and producing a powerful propelling force.
38
draw a diagram of insect legs and their antagonistic muscle pairs
478
39
draw a diagram of a human flow as an example of a synovial joint
40
define a synovial joint
a freely moveable joint that allows a wide range of movement (articulation)
41
cartilage
- tough, smooth tissue that covers the regions of bone in the joint
- prevents contact between regions of bone that might otherwise rub together, helping prevent friction
- absorbs shocks that might cause bones to fracture
42
synovial fluid
- fills a cavity in the joint between the cartilages on the ends of the bones
- lubricates the joint so helps to prevent the friction that would occur if the cartilages were dry and touching
43
joint capsule
- tough ligamentous covering to the joint
- seals the joint and holds in the synovial fluid
- helps prevent dislocation
44
radius bone
to which the biceps is attached
45
biceps
flexes the joint
46
humerus bone
to which the biceps and triceps are attached
47
triceps
extends the joint
48
ulna bone
to which the triceps is attached
49
synovial joints allow
certain movements but not others
50
what determines the movements that are possible in a body part?
the structure of a joint, including the joint capsule and the ligaments
51
the knee joint can act as
a hinge joint, which allows only flexion (bending) and extension (straightening). It can also act as a pivot joint when flexed, which is when it has a greater range of movement
52
the hip joint can act as
a ball and socket joint that can flex and extend, rotate, and move sideways (abduction) and back (adduction).
53
state the three types of muscle
- striated (skeletal muscle)
- smooth muscle
- cardiac muscle
54
function of striated/skeletal muscle
muscles attached to bones that are used to move the body
55
what is striated muscle composed of?
bundles of muscle cells known as muscle fibres
56
state the main features of muscle fibres
- sarcolemma
- many nuclei
- sarcoplasmic reticulum
- mitochondria
- myofibrils
57
sarcolemma
single plasma membrane that surrounds each muscle fibre
58
why are muscle fibres much longer than typical cells and contain many nuclei?
embryonic muscle cells fuse together to form muscle fibres
59
what is the sarcoplasmic reticulum and what does it do?
it is a modified version of the endoplasmic reticulum and wraps around every myofibril, conveying the signal to contract to all parts of the muscle fibre at once. It also stores calcium.
60
where are mitochondria stored?
between the myofibrils
61
muscle fibres contain many...
myofibrils
62
describe a myofibril
- alternating light and dark bands, which give striated muscle its stripes
- in the centre of each light band is a disc-shaped structure (Z-line)
63
each myofibril is made up of...
contractile sarcomeres.
64
define a sarcomere
the functional unit of a myofibril, located between one Z-line and the next.
65
what is the pattern of light and dark bands in sarcomeres due to?
a precise and regular arrangement of two types of protein filament - thin actin filaments and thick myosin filaments
66
location of actin filaments
attached to a Z line at one end
67
location of myosin filaments
interdigitated with actin filaments at both ends and occupy the centre of the sarcomere
68
describe the ratio of actin to myosin filaments and their function
each myosin filament is surrounded by six actin filaments and forms cross-bridges with them during muscle contraction.
69
draw a labelled diagram of the structure of a sarcomere
p481
70
how is the contraction the skeletal muscle achieved?
by the sliding of actin and myosin filaments; the myosin filaments pull the actin filaments inwards during the centre of the sarcomere. this shortens each sarcomere and therefore the overall length of the muscle fibre
71
what causes the sliding motion of actin and myosin filaments?
myosin filaments: they have heads that can bind to special sites on actin filaments, creating cross-bridges, through which they can exert a force, using energy from ATP
72
how is it that many cross-bridges can form at once?
the myosin heads are regularly spaced along the actin filaments
73
what is the M-line?
another line in the centre of the sarcomere
74
what is the visible difference between a relaxed and a contracted sarcomere?
in a relaxed sarcomere, there is a more visible light band on either side of the M-line
75
what controls muscle contractions?
calcium ions and the proteins tropomyosin and troponin
76
describe how calcium ions, tropomyosin and troponin work to control muscle contractions
- in a relaxed muscle, tropomyosin (a regulatory protein) blocks the binding sites on actin
- when a motor neuron sends a signal to a muscle fibre to make it contract, the sarcoplasmic reticulum releases calcium ions
- Ca ions bind to troponin which causes tropomyosin to move, exposing actin's binding sites.
77
describe the process of muscle contraction
1. myosin filaments have heads which form cross-bridges when they are attached to binding sites on actin filaments
2. ATP binds to the myosin heads and causes them to break the cross-bridges by detaching from the binding sites
3. ATP is hydrolysed to ADP and phosphate, causing the myosin heads to change their angle. The heads are said to be cocked in their new position as they are storing potential energy from ATP
4. the heads attach to binding sites on actin that are further from the centre of the sarcomere than the previous sites
5. the ADP and phosphate are released and the heads push the actin filament inwards towards the centre of the sarcomere (called the power stroke)
78
79
what to spermatogenesis and oogenesis both involve?
mitosis, cell growth, two divisions of meiosis and differentiation
80
define oogenesis
the production of egg cells in the ovaries
81
describe the pre-puberty stage of oogenesis
1. starts in the ovaries of a female fetus
2. germ cells in the fetal ovary divide by mitosis and the cells formed move to distribute themselves through the cortex of the ovary
3. when the foetus is four or five months old, these cells grow and start to divide by meiosis
4. by the seventh month, they are still in the first division of meiosis and a single layer of cells (follicle cells) has formed around them.
no further development takes place until after puberty
82
define a primary follicle
the cell that has started to divide by meiosis, together with the surrounding follicle cells
83
describe the post-puberty stage of oogenesis
no more primary follicles are produced, but at the start of each menstrual cycle a small batch are stimulated to develop by FSH. Usually only one goes on to become a mature follicle, containing a secondary oocyte.
84
difference between a mature ovarian follicle and a primary follicle
a mature ovarian follicle has many more follicle cells, outer and inner follicle cells and cavities, and the oocyte is more fully developed
85
define spermatogenesis
the production of sperm in the testes
86
describe the testes
composed of a mass of narrow tubes, called seminiferous tubules
87
describe the germinal epithelium
- outer layer of cells of seminiferous tubules.
- where process of sperm production begins
- contains cells in various stages of sperm production, with the most mature stages closest to the fluid-filled centre of the ST
88
Sertoli cells
large nurse cells in the wall of the tubule
89
spermatozoa
cells that have developed tails
90
draw a diagram and describe the stages of spermatogenesis
1. an outer layer called germinal epithelium cells (2n) divide endlessly by mitosis to produce more diploid cells
2. diploid cells grow larger and are then called primary spermatocytes (2n)
3. each primary spermatocyte carries out the first division of meiosis to produce two secondary spermatocytes (n)
4. each secondary spermatocyte carries out the second division of meiosis to produce two spermatids (n)
5. spermatids become associated with nurse cells (Sertoli cells) which help the spermatids to develop into spermatozoa (cell differentiation)
6. sperm detach from Sertoli cells and are eventually carried out of the testis by the fluid in the centre of the seminiferous tubule
91
draw a diagram and describe the stages of oogenesis
1. The process begins during foetal development, when a large number of cells (oogonia) are formed by mitosis before undergoing a period of growth
2. These cells begin meiosis but are arrested in prophase I until puberty
3. At puberty, some follicles continue to develop each month is response to FSH secretion
4. These follicles complete the first meiotic division to form two cells of unequal size
The cell with less cytoplasm is a polar body (which degenerates), while the larger cell forms a secondary oocyte
5. The secondary oocyte begins the second meiotic division but is arrested in prophase II (until fertilisation)
6. It is released from the ovary (ruptured follicle develops into corpus luteum) and, if fertilisation occurs, will complete meiosis
7. The second meiotic division will produce an ovum and a second polar body
92
draw and annotate an egg
- two centrioles
- haploid nucleus
- cytoplasm (or yolk) containing droplets of fat
- cortical granules
- layer of gel composed of glycoproteins (zona pellucida)
- layer of follicle cells (corona radiata)
- plasma membrane
- first polar cell
93
draw and annotate a sperm
- acrosome
- plasma membrane
- haploid nucleus
- centriole
- helical mitochondria
- mid-piece
- tail
- microtubules in a 9+2 arrangement
- protein fibres to strengthen the tail
94
differences between oogenesis and spermatogenesis:
Location
Number of gametes produced
Gametes per germ cell
Beginning of process
Timing of gamete formation
End of process
Timing of gamete release
Meiotic divisions
Germ line epithelium
Testis
Life long production (millions)
Four
Begins at puberty
Continuous (any time)
Fertility is life long but reduces
Any time
Uninterrupted
Involved in gamete production
Oogenesis
Ovary
Fixed amount (only - 400 mature)
One
Begins during fetal development
Once a month (menstrual cycle)
Fertility stops at menopause
Monthly cycle
Arrested
Not involved in gamete production
95
define polyspermy
when multiple sperm enter the egg
96
state the 3 mechanisms that occur after sex
1. the acrosome reaction
2. penetration of the egg membrane
3. the cortical reaction
97
the acrosome reaction
when the sperm binds to the zona pellucid and the contents of the acrosome are related, the enzymes from it digest the zona pellucida.
98
describe the acrosome
a large membrane-bound sac of enzymes in the head of the sperm
99
penetration of the egg membrane
- acrosome reaction exposes an area of the membrane on the tip of the sperm that has proteins that can bind to the egg membrane.
- the first sperm that gets through the zona pellucid therefore binds and the membranes of sperm and egg fuse together
- the sperm nucleus enters the egg cell (fertilisation)
100
cortical reaction
- sperm causes activation of the egg
- the cortical granules (vesicles located near the egg membrane) release their contents from the egg by exocytosis
- cortical vesicle enzymes result in the digestion of binding proteins so that no further sperm can bind, as well as a general hardening of the zona pellucida
101
fertilisation in animals can be
internal or external
102
internal fertilisation
- terrestrial animals
+ ensures gametes do not dry out and sperm and ova are placed in prolonged close proximity to each other,
+ developing embryo is protected inside female
103
external fertilisation
- aquatic animals
+ animals have behaviours that bring eggs into proximity with sperm
- risks including predation and susceptibility to environmental variation such as temperature and pH fluctuations and pollution
104
fertilisation -> implantation
1. fertilised ovum divides by mitosis to become an embryo
2. there is migration of cells, giving the embryo the shape of a hollow ball (blastocyst)
3. at 7 days old, the blastocyst reaches the uterus, having been moved down the oxidant by the cilia of cells in the oviduct wall
4. at this age the zona pellucida (surrounded + protected embryo) breaks down
5. obtains needed supply of food by sinking into endometrium/uterus wall (implantation)
105
implantation onwards
1. outer layer of blastocyst develops finger-like projects allowing it to penetrate uterus lining and exchange materials with mother's blood
2. embryo grows and develops
3. by 8 weeks, it has started to form bone tissue and is considered a foetus rather than embryo
106
role of hCG in early pregnancy
early in pregnancy the embryo produces human chorionic gonadotropin, which stimulates the corpus lute in the ovary to continue to secrete progesterone and oestrogen, which stimulate the continued development of uterus wall, which supplies the embryo with everything that it needs
107
two main roles of placenta
- facilitate exchange of materials between mother and embryo
- secrete estrogen and progesterone
108
why is the placenta needed?
because the body surface area to volume ratio becomes smaller as the foetus grows larger
109
describe the structure of the placenta
- chorionic villi extend into the intervillous space (lacuna) and exchange materials between mother and fetus
- villi are lined by microvilli to increase SA for material exchange
- fetal capillaries within the villi lie close to the surface to minimise diffusion distance from blood in the lacunae
- materials such as oxygen, nutrients, vitamins, antibodies and water diffuse from the lacunae into fetal capillaries
- fetal waste diffuses from the lacunae into the maternal blood vessels
110
amniotic sacs
series of membranes developed by the foetus, which contain amniotic fluid which supports and protects the developing fetus
111
what is the basic functional unit of the placenta?
a finger-like piece of fetal tissue (placental villus)
112
why do these villi increase in number during pregnancy?
to cope with the increasing demands of the foetus for the exchange of materials with the mother
113
where does maternal blood flow in the placenta?
in the intervillous spaces around the villi
114
where does foetal blood flow in the placenta?
in blood capillaries, close to the surface of each villus
115
placental barrier
cells that separate maternal and fetal blood (selectively permeable)
116
draw a diagram of placenta
p507
117
describe exchange of materials between mother and foetus
mother -> foetus:
- oxygen (diffusion)
- glucose (facilitated diffusion)
- antibodies (endocytosis)
- water (osmosis)
foetus -> mother:
- urea
- carbon dioxide (diffusion)
- water (osmosis)
118
role of placenta in oestrogen and progesterone production
by about the 9th week of pregnancy, the placenta secretes these hormones in large enough quantities to sustain the pregnancy so the corpus luteum is no longer needed
119
what is birth mediated by?
positive feedback involving oestrogen and oxytocin
120
role of progesterone in parturition
during pregnancy, progesterone inhibits secretion of oxytocin by the pituitary gland and contractions of myometrium (contractions of the muscular outer wall of the uterus).
at the end of pregnancy, hormones produced by the foetus signal to the placenta to stop secreting progesterone, and oxytocin is therefore secreted
121
role of oxytocin in parturition
positive feedback system:
- oxytocin stimulates contractions of the muscle fibres in the myometrium
- these contractions are detected by stretch receptors, which signal to the pituitary gland to increase oxytocin secretion
- this makes contractions more frequent and vigorous
122
what is the advantage of this positive feedback system?
causes a gradual increase in the myometrial contractions, allowing the baby to be born with the minimum intensity of contraction
123
describe parturition
1. relaxation of muscle fibres in the cervix causes it to dilate
2. uterine contraction bursts amniotic sac and amniotic fluid passes out
3. further uterine contractions push the baby out through the cervix and the vagina
4. placenta and umbilical cord expelled rom body
124
precocial state
hatched or born in an advanced state and able to feed itself and move independently almost immediately.
125
mammals with a large body size are more likely to be
precocial - this is correlated with a long gestation period
126
altricial state
relatively helpless, incompletely developed offspring
127
