Cell Biology Flashcards
1
Q
what is a eukaryote?
A
organism with cells that have a nucleus and membrane-bound organelles
2
Q
is a prokaryotic or eukaryotic cell bigger?
A
eukaryotic - measured in micrometres (prokaryotic 1/10 smaller, nanometres)
3
Q
what is the structure of a prokaryotic cell?
A
cytoplasm, cell membrane, cell wall, genetic material in a single DNA loop in cytoplasm, may be smaller rings of DNA in cytoplasm (plasmids)
4
Q
what is a prokaryotic cell?
A
simple cell without a nucleus
5
Q
what is a pathogen?
A
microorganism which can cause disease
6
Q
what are the 6 groups of microorganism?
A
bacteria, fungi, protozoa, algae, archaea, viruses
7
Q
describe the structure of an animal cell.
A
- eukaryotic
- nucleus, mitochondria, ribosomes, cytoplasm, cell membrane
8
Q
describe the structure of a plant cell.
A
- eukaryotic
- nucleus, mitochondria, ribosomes, cytoplasm, cell membrane, permanent vacuole, cell wall
9
Q
what is the function of the nucleus?
A
contains genetic material
10
Q
what is the function of the mitochrondria?
A
releases energy via respiration
11
Q
what is the function of ribosomes?
A
carry out protein synthesis
12
Q
what is the function of the cytoplasm?
A
most chemical reactions occur here
13
Q
what is the function of the cell membrane?
A
controls movement of substances in and out of cell
14
Q
what is the function of the cell wall?
A
gives strength to the cell and supports the plant
15
Q
what is the function of chloroplasts?
A
absorb light for photosynthesis
16
Q
what is the function of the permanent vacuole?
A
filled with cell sap to help keep cell turgid
17
Q
what is specialisation?
A
adaptation of an organ or part to serve a special function
18
Q
give an example of a specialised cell [6].
A
sperm cells, nerve cells, muscle cells, root hair cells, xylem cells, phloem cells
19
Q
how are sperm cells specialised?
A
- have a tail for swimming
- full of mitochondria to provide energy
- acrosome contains enzymes to help break into ovum
20
Q
how are muscle cells specialised?
A
- full of mitochondria to provide energy
- contain filaments of protein that slide over each other to cause muscle contraction
21
Q
what is differentiation?
A
the process by which cells become specialized to perform specific functions in an organism
22
Q
what is a stem cell?
A
an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type and from which certain other cells can arise from differentiation
23
Q
how do light microscopes work?
A
use light to view specimens
24
Q
what is the magnification of a light microscope?
A
low magnification - x1500
25
what is the resolution of a light microscope?
low resolution - 200nm
26
what is a limitation of a light microscope?
details in sub-cellular structures cannot be easily seen
27
how do electron microscopes work?
use electrons to see surface of cells, or inside of cells; sub-cellular structures can be seen in detail
28
what is the magnification of a electron microscope?
very high magnification - x500,000
29
what is the resolution of a electron microscope?
very high resolution - 0.1nm
30
what is the calculation for magnification?
size of image divided by size of real object
31
How would onion cells look different if they were seen using an electron microscope rather than a light microscope?
The cells would look larger and would show more internal structures.
32
how do you set up a light microscope?
1. place specimen on stage
2. switch microscope on so that light passes through the specimen
3. make sure the x4 objective lens is clicked into place above the specimen
4. bring specimen into focus by looking down eyepiece lens and moving into coarse focus
5. when specimen is in focus, move objective lenses so that the x10 objective lens is clicked into place above specimen
6. if specimen is out of focus, bring it into focus using small movements of the fine focus
-7.repeat 5 & 6 with x40 objective lens
33
Plan an investigation to test effect of antibiotics on growth of bacteria.
1. use aseptic techniques to spread bacteria onto agar plate
2. grow at 25 degrees for several days, until bacterial colonies can be clearly seen
3. place drop of antibiotic solution onto different areas of agar plate and leave for 24 hours
4. observe and measure any zones of inhibition
34
give an example of an aseptic technique [4].
- sterilising all petri dishes and culture media
- sterilising inoculation loops by passing them through a flame
- securing the lid of the petri dish with tape and storing it upside down
- not incubating bacterial cultures about 25 degrees centigrade
35
what is the purpose of aseptic techniques?
to prevent contamination to test effectiveness of disinfectants and antibiotics
36
what are 3 types of stem cell?
adult, embryonic, meristem
37
where are embryonic stem cells found?
embryos (IVF, abortion), umbilical cord
38
what is a positive of using embryonic stem cells? [2]
can differentiate into any type of human cell to make different organs needed in humans - pluripotent
- create large numbers as easily grown in culture
39
where are adult stem cells found?
bone marrow
40
what is a limitation of using adult stem cells? [3]
- limited as to what they can become - rbc (rbc cant be made via mitosis), wbc (in case of infection)
- rare in mature tissues
- methods for expansion not yet worked out
41
What is meristem tissue?
plant stem cells found at ends of roots and shoots
42
why do plants have meristem?
stem cells are kept forever because plants dont have all their organs at the start of their life
43
what are some risks of using stem cells in treatments?
- rejection - immunosuppressants
- infection and anaesthesia
44
what is a con of using embryonic stem cells? [2]
- probably rejection as not patient's own dna
- ethical issues as from aborted embryos or spare IVF
45
what is a pro of using adult stem cells? [2]
- no risk of rejection as dna from patients own body
- no ethical issues
46
describe the process of therapeutic cloning
1. nucleus is removed from human egg cell from donor
2. nucleus is removed from patient's cell and transferred to donor egg cell
3. cell is stimulated to divide
4. cell develops into embryo
5. after 4-5 days stem cells are removed
6. stem cells are cultured for therapeutic uses (eg grow organs for transplant)
47
describe the process of growing plantlets from plant stem cells.
1. scrape tissue sample from plant
2. tissue sample placed in agar growth medium containing nutrients and auxins
3. samples develop into tiny plantlets
4. plantlets planted into compost
48
why are plants are cloned using meristem cells?
- to produce identical plants quickly and economically
- faster than allowing plants to reproduce naturally
- can cultivate desired characteristics ie disease resistance, large and lots of fruit
49
what is mitosis?
process of cell division were one cell divides into 2 identical daughter cells
50
what is interphase?
the phase of the cell cycle in which a typical cell spends most of its life-metabolic phase of the cell
- the cell obtains nutrients and metabolizes them, grows, replicates its DNA in preparation for mitosis, and conducts other "normal" cell functions
51
what happens in Gap 1 Interphase?
- cell makes a new set of organelles & proteins for daughter cells
- new set of organelles: cytoplasm, ribosomes, mitochondria, cell membrane
52
what happens in synthesis interphase?
DNA synthesis; cell perfectly replicates 46 new chromosomes
53
what happens in Gap 2 interphase?
cell growth continues and there is synthesis of special proteins in preparation for mitosis
54
what happens in cytokinesis? [3]
- mitotic spindle is broken down
- 2 new nuclei form, one for each set of chromosomes. Nuclear membranes reappear.
- The chromosomes begin to decondense and return to their “stringy” form.
- cell divides into 2 new daughter cells
55
list the parts of the cell cycle. [5]
- G1 (Gap 1 interphase)
- S (synthesis interphase)
- G2 (Gap 2 interphase)
- M (mitosis)
- Cytokinesis
56
why do cells need to divide? [3]
- growth of new tissue
- repair of damaged tissue
- asexual reproduction
57
why is mitosis important?
- to make new cells
- to make cells consistently the same size and shape
58
describe the process of mitosis.
- DNA replicates to form 2 copies of each chromosome (interphase)
- chromosomes start to condense to make them easier to pull apart. mitotic spindle begins to form, nucleolus disappears (prophase)
- chromosomes become even more condensed, nuclear membrane breaks down, releasing the chromosomes, mitotic spindle grows more, and some of the microtubules start to “capture” chromosomes. (prometaphase)
- spindle has captured all the chromosomes and lined them up at the equator, ready to divide (metaphase)
- protein “glue” that holds the sister chromatids together is broken down as the sister chromatids separate from each other and are pulled towards opposite ends of the cell, Microtubules not attached to chromosomes elongate and push apart, separating the poles and making the cell longer.(anaphase)
-cell starts to re-establish its normal structures as cytokinesis takes place (telophase)
- cytoplasm and cell membranes divide to form identical daughter cells (cytokinesis)
59
what is the mitotic spindle?
a structure made of microtubules, strong fibres that are part of the cell’s “skeleton.” It organises the chromosomes and moves them around during mitosis
60
what is the nucleolus?
part of the nucleus where ribosomes are made; when it disappears, this is a sign that the nucleus is getting ready to break down
61
describe the structure of a chromosome
made from highly coiled strands of relatively long DNA that is too thin to see under microscope. Each arm is a chromatid
62
how many chromosomes are in a normal human cell?
there are 46 chromosomes, and 23 pairs of chromosomes, in each human cell
63
does every species have the same number of chromosomes?
different number of chromosomes for every species - depends on how molecules the cells need to make
64
why do cells need 2 copies of the same DNA when they are dividing?
if they didn't, each cell would only have 23 chromosomes - each cell needs all chromosomes (46)
65
what is the number of chromatids in a cell getting ready to divide, after replicating its DNA?
92
66
what is the number of genes on 1 chromosome?
~500
67
what are the female sex chromosomes?
XX
68
what are the male sex chromosomes?
XY
69
why are there 2 versions of each chromosome?
1 from each parent
70
what is the composition of DNA?
deoxyribose (sugar), phosphate, base
71
what are the 4 bases in DNA?
A (adenine), T (thymine), C (cytosine), G (guanine)
72
How do the bases in DNA fit together?
C + G, A + T - complimentary base pairing
73
what is diffusion?
movement of particles from a place of high concentration to a place of low
74
what is concentration?
number of particles in a fixed area/volume
75
why is it important that oxygen moves from alveolus to capillary?
it must be carried in bloodstream to all body cells for aerobic respiration to release energy
76
what are adaptations of alveoli for gas exchange?
- alveoli and capillary wall are only 1 cell thick - easier diffusion, short diffusion path
- large surface area - many rounded alveoli
- steep concentration gradient - blood is constantly moving and we are constantly breathing
- lots of capillaries nearby
- moist
77
why must carbon dioxide be removed from body?
it is toxic so when it builds up it can make the body too acidic and will affect enzymes
78
how and why does carbon dioxide move from the air into palisade cells?
- high concentration outside leaf in atmosphere - low inside - steep concentration gradient
- diffusion into leaf through stoma, through air spaces between spomgy mesophyll
- even lower concentration inside palisade cells, as the cells use it in photosynthesis, so will diffuse in as it tries to reach equilibrium
- photosynthesis occurs in chloroplasts in palisade cells - creates glucose as energy for plant
79
what is diffusion like, at night, for plants?
- cannot photosynthesise as no light so no concentration gradient
- no diffusion at night so stomata close so that the plant doesn't lose water
80
what is urea?
toxic chemical dissolved in urine
81
why is urea found in the liver?
extra sugar and carbs are stored in liver however extra protein can't be stored so liver breaks it down
82
how is urea formed?
- enzymes in liver split up amino acid molecules
- the part which contains carbon is turned into glycogen and stored
- the part which contains nitrogen is turned into ammonia which is highly toxic
- ammonia is immediately converted into urea which is less toxic
83
what are the 3 stages in processing urea?
filtration, selective reabsorption, formation of urine
84
what happens in filtration, when processing urea?
- blood passes through a nephron
- there are many capillaries and blood is under high pressure at the start of the nephron which aids filtration
- small molecules are filtered and pass into nephron tubule but the large molecules (water, ions, and glucose) are too big
85
what happens in selective reabsorption, when processing urea?
reabsorbs all glucose originally filtered out, as much water as the body needs to maintain a constant water level in the blood plasma, as many ions as the body needs to maintain constant balance of mineral ions in blood plasma
86
what happens in forming urine, when processing urea?
molecules not selectively reabsorbed (urea, excess water, ions) continue along nephron tubule as urine and eventually pass down to bladder
87
describe how urea moves from the liver to the bladder.
- high conc in liver, low in blood plasma as blood is sconstantly moving and takes it wat
- diffuses from liver to blood as tries to reach equilibrium
- higher conc in blood plasma, low in kidneys so diffuses
- filtered in kidneys and moves to bladder
88
what are the factors which affect the rate of diffusion? [4]
temperature, surface area, concentration gradient, length of diffusion pathway
89
how does temperature affect diffusion?
higher temperature means particles have more kinetic energy so increased motion means they move and mix quicker
90
how does surface area affect diffusion?
larger surface area means there is more space for particles to diffuse across - diffusion will be faster
91
how does the concentration gradient affect diffusion?
greater difference in concentration means a steeper gradient - faster diffusion as trying to move from a place of high concentration to a place of low
92
what is an adaptation of amoeba?
lots of pseudopods - increases sa for higher rate of diffusion
93
what are the human adaptations to overcome low sa:v ratio?
transport systems and specialised exchange surfaces
94
what is ventilation?
movement of air in and out of an animal
95
what is exchanged in the small intestines?
fats, carbs, proteins
96
how is the small intestine adapted for exchange of materials?
- surface area: millions of villi, very long, highly folded
- diffusion distance: walls are 1 cell thick, nearby capillaries and blood vessels
- conc gradient: constantly moving blood, lymph vessel runs through centre to transport fatty acids and glycerol
97
how are fish gills adapted for exchange of materials?
- surface area: lamellae, filaments
- diffusion distance: thin walls, rich blood supply
- conc gradient: counter current flow principle, ventilation
98
what is exchanged in fish gills?
water - o2, co2
99
what is exchanged in roots?
water and minerals
100
what is exchanged in leaves?
co2, o2
101
how are roots adapted for exchange of materials?
- surface area: long root hair
- diffusion distance: thin cell walls
- conc gradient: lots of water outside plant, not in, xylem and phloem, transpiration
102
how are leaves adapted for exchange of materials?
- surface area: large leaves
- diffusion distance: thin leaves and thin cell walls, stomata, air spaces
- conc gradient: ventilation, photosynthesis
103
what is osmosis?
net movement of water from a dilute solution to a concentrated solution across a SPM
104
what factors affect osmosis?
sa, temperature, length of osmosis pathway
105
what does hypertonic mean?
water leaves cell via osmosis as the concentration of solution is high
105
what does isotonic mean?
water does not enter or leave the cell - equilibrium
106
what does hypotonic mean?
water enters cell via osmosis as the concentration of solution is low
107
why is osmosis important in animal cells?
controls chemical reactions, makes cytoplasm, keeps cell hydrated and full of moisture, to make blood
108
what happens to an animal cell in a hypertonic solution?
the cell loses water and shrinks and loses its shape - crenation.
109
what happens to an animal cell in a hypotonic solution?
the cell takes in too much water and swells and may burst - lysis
110
what happens to an animal cell in a isotonic solution?
equilibrium - cell is in normal state
111
what happens to a plant cell in a hypotonic solution?
the cell takes in water and swells - turgid
112
what happens to a plant cell in a hypertonic solution?
the cell loses water and shrinks and loses its shape - plasmolysis.
113
what happens to a plant cell in a isotonic solution?
equilibrium - flaccid (cell wall will always stay the same)
114
why is osmosis important in animal cells?
controls chemical reactions, needed for cytoplasm and vacuoles
115
what is active transport?
movement of substances (usually charged particles or larger molecules that would struggle to move by diffusion) from one cell to another against the concentration gradient using transport/carrier proteins
116
why is active transport necessary for plant roots absorbing minerals?
minerals are in roots and need to get to leaves; minerals are dilute in soil and concentrated in leaves as they build up there
117
describe the process of active transport.
- transport protein on semi-permeable membrane
- transport protein recognises solute in dilute solution and grabs it
- protein rotates in membrane and releases solute inside cell (high concentration) using energy
- protein rotates back again (often using energy)
118
why are air pockets are important in soil for active transport?
oxygen is required for respiration - release energy - to do active transport
119
why does a large SA help active transport?
there is more space for transport proteins to be present
120
what is Mg in plants used for?
chlorphyll
121
what is N in plants sued for?
to make proteins (enzymes)
122
what is P in plants used for?
for fruits and flowers
123
What is K in plants used for?
for opening and closing stomata
124
how is the epithelium adapted for exchange of materials?
- lots of mitochondria
- large sa
- active transport proteins
125
why is active transport required to bring glucose into the body?
- starts with diffusion of glucose from lumen to epithelial cell
- reaches equilibrium - diffusion stops
- active transport starts to move remaining glucose (50%) into blood
