Cell Biology Flashcards
1
Q
What are the two types of cells?
A
Eukaryotic (plant and animal)
Prokaryotic (bacteria)
2
Q
What are the differences between eukaryotic and prokaryotic cells?
A
Prokaryotic cells are much smaller than eukaryotic cells.
Eukaryotic cells contain membrane bound-organelles and a nucleus containing genetic material, while prokaryotes do not
3
Q
What is the prokaryotic cell wall composed of?
A
Peptidoglycan
4
Q
How is genetic information stored in a prokaryotic cell?
A
Found free within the cytoplasm as:
Chromosomal DNA (single large loop of circular DNA)
Plasmid DNA
5
Q
What are plasmids?
A
Small, circular loops of DNA founf free in the cytoplasm and separate from the main DNA.
Carry genes that provide genetic advantages e.g. antibiotic resistance
6
Q
What is order of magnitude?
A
A power to the base 10 used to quantify and compare size
7
Q
What is a centimetre in metres? Give answer in standard form
A
1 x 10^-2 metres
8
Q
What is a millimetre in metres? Give answer in standard form
A
1 x 10^-3 metres
9
Q
What is a micrometre (μm) in metres? Give answer in standard form
A
1 x 10^-6 metres
10
Q
What is a nanometre (nm) in metres? Give answer in standard form
A
1 x 10^-9 metres
11
Q
What is the difference in order of magnitude between a human hair (length = 100 μm) and the HIV virus (length = 100 nm)?
A
100 μm = 10^-4 m
100 nm = 10^-7 m
-4-(-7) = -4 + 7 = 3
12
Q
List the components of both plant and animal cells (5)
A
Nucleus
Cytoplasm
Cell membrane
Mitochondria
Ribosomes
13
Q
List the additional cell components found in plant cells (3)
A
Chloroplasts
Permanent vacuole
Cell wall
14
Q
Other than storing genetic information, what is the function of the nucleus?
A
Controls cellular activities
15
Q
Describe the structure of the cytoplasm
A
Fluid component of the cell
Contains organelles, enzymes and dissolved ions and nutrients
16
Q
What is the function of the cytoplasm?
A
Site of cellular reactions e.g. first stage of respiration.
Transport medium
17
Q
What is the function of the cell membrane?
A
Controls the entry and exit of materials into and out of the cell
18
Q
What is the function of the mitochondria?
A
Site of later stages of aerobic respiration in which ATP is produced
19
Q
What is the function of the ribosomes?
A
Joins amino acids in a specific order during translation for the synthesis of proteins
20
Q
What is the plant cell wall made of?
A
Cellulose
21
Q
What is the function of the plant cell wall
A
Provides strength.
Prevents the cell bursting when water enters by osmosis
22
Q
What does the permanent vacuole contain?
A
Cell sap (a solution of salts, sugars and organic acids)
23
Q
What is the function of the permanent vacuole?
A
Supports the cell, maintaining its turgidity
24
Q
What is the function of chloroplasts?
A
Site of photosynthesis
25
Describe how sperm cells in animals are adapted to their function
Haploid Nucleus - contains genetic information
Tail - enables movement
Mitochondria - provide energy for tail movement
Acrosome - contains enzymes that digest the egg cell membrane
26
Describe how nerve cells in animals are adapted to their function
Long axon - allows electrical impulses to be transmitted all over the body from the central nervous system
Dendrites - from the cell body connect to and receive impulses from other nerve cells, muscles and glands
Myelin sheath - insulates the axon and speeds up the transmission of impulses along the nerve cell
27
Describe how muscle cells are adapted to their function
Arrangement of protein filaments - allows them to slide over each other to produce muscle contraction
Mitochondria - to provide energy for muscle contraction
Merged cells in skeletal muscle - allow muscle fibre contraction in unison
28
Describe how root hair cells in plants are adapted to their function
Large surface area - to absorb nutrients and water from surrounding soil
Thin walls - that do not restrict water absorption
29
Describe how xylem cells in plants are adapted to their function
No upper or lower margins between cells - to provide a continuous route for water flow
Thick, woody side walls - strengthen their structure and prevent collapse
30
Describe how phloem cells in plants are adapted to their function
Sieve plates - let dissolved amino acids and sugars be transported up and down the stem
Companion cells - provide energy needed for active transport of substances along the phloem
31
What is cell differentiation?
The process by which cells become specialised
32
Why is cell differentiation important?
Allows production of different tissues and organs that perform various vital functions in the human body
33
At what point in their life cycle do most animal cells differentiate?
Early in their life cycle
34
For how long do plant cells retain the ability to differentiate?
Throughout their entire life cycle
35
What is the purpose of cell division in mature animals?
Repair and replacement of cells
36
What changes does a cell go through as it differentiates?
Becomes specialised through acquisition of different sub-cellular structures to enable a specific function to be performed by the cell
37
Define magnification
The number of times bigger an image appears compared to the size of the real object
38
Define resolution
The smallest distance between two objects that can be distinguished
39
How does a light microscope work?
Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed
40
What are the advantages of light microscopes? (4)
Inexpensive
Easy to use
Portable
Observe both dead and living specimens
41
What is the disadvantage of light microscopes?
Limited resolution
41
How does an electron microscope work?
It uses a beam of electrons which are focused using magnets. The electrons hit a flourescent screen which emits visible light, producing an image
41
Name the two types of electron microscope
transmission electron microscope (TEM)
Scanning electron microscope (SEM)
42
What is the advantage of electron microscopes?
Greater magnification and resolution
43
Why do electron microscopes have a greater magnification and resolution?
They use a beam of electrons which has a shorter wavelength than photons of light
44
How have electron microscopes enabled scientists to develop their understanding of cells?
Allow small sub-cellular structures (e.g. mitochondria, ribosomes) to be observed in detail
Enable scientists to develop more accurate explanations about how cell structure relates to function
45
What are the disadvantages of electron microscopes? (4)
Expensive
Large so less portable
Require training to use
Only dead specimens can be observed
46
How can the magnification of an image be calculated?
magnification = size of image / size of real object
47
What is standard form?
A way of expressing numbers - written as a figure between 1 and 10 multiplied by a positive or negative power of 10
48
Write 0.005 in standard form
0.005 = 5 x 10^-3
49
How do bacteria multiply?
Binary fission (simple cell division)
50
How often do bacteria multiply?
Once every 20 minutes if enough nutrients are available and the temperature is suitable
51
State 2 ways in which bacteria can be grown
Nutrient broth solution
Colonies on an agar gel plate
52
What nutrients make up a nutrient broth solution?
All nutrients required for bacteria to grow including nitrogen for protein synthesis, carbohydrates for energy and other minerals
53
What are uncontaminated cultures of microorganisms needed for?
Investigating disinfectant and antibiotic action
54
Describe the preparation of an uncontaminated culture using aseptic technique
1. Use pre-sterilised plastic Petri dishes or sterilis glass Petri dishes and agar gell before using with an autoclave
2. Pour the sterile agar gel into the Petri dish and allow time to set.
3. Sterilise the inoculating loop by passing it through a Bunsen burner flame
4. Dip the inoculating loop into the solution of microorganisms and make streaks with the loop on the surface of the agar
5. Put the lid on the Petri dish and secure it with tape. Label accordingly then turn and store upside down.
6. Incubate the culture at 25°C in school laboratories
(I'm losing my mind.)
55
Why must Petri dishes and culture media be sterilised before use?
To kill any bacteria already present
56
Why must inoculating loops be sterilised by passing them through Bunsen burner flame?
To kill any bacteria present on the inoculating loop
57
Why must the Petri dish lid be secured with adhesive tape and the whole dish stored upside down?
Stops bacteria in the air contaminating the culture.
The lid is not fully sealed to prevent the growth of anaerobic bacteria in a lack of oxygen.
Upside down to prevent condensation from forming and dripping down onto the colonies
58
Why are cultures incubated at 25°C in school laboratories?
Harmful pathogens are less likely to grow at this temperature
59
What is the formula used to calculate cross-sectional area of bacterial colony or clear area around a bacterial colony?
Pi x r^2 (I cba to find the symbol)
60
How is the number of bacteria in a population after a certain time calculated from the mean division time?
1. Calculate the number of times the bacteria will divide in the given time period from the mean division time.
2. Use the following equation to calculate the number of bacteria:
Number of bacteria in population at end of time period = number of bacteria at the beginning of the time period x 2^(number of divisions in the time period)
Express the answer in standard form if possible
61
What are chormosomes made up of?
Chromosomes consist of DNA molecules combined with proteins. They contain genes which provide the instructions for protein synthesis
62
What is a gene?
A section of DNA which codes for a protein
63
How many chromosomes are found in the nucleus of human body cells?
46
64
How many chromosomes are found in the nucleus of gametes?
23
65
How are chromosomes arranged in the nucleus of a body cell?
arranged in pairs - 46 chromosomes form 23 pairs
66
What are the three main stages of the cell cycle?
1. Replication of DNA and synthesis of organelles
2. Mitosis
3. Division of cell
67
Why is mitosis important?
Produces identical cells which all have the same genetic information.
Produces additional cells for growth and replair
68
Describe the first stage of the cell cycle
Longest stage - cells grow and increase in mass, replicate DNA and synthesise more organelles (eg. mitochondria, ribosomes)
69
Describe the second stage of the cell cycle
Each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides
70
Describe the third stage of the cell cycle
The cytoplasm and cell membrane divide - two identical daughter cells are produced
71
What is a stem cell?
An unspecialised cell which is capable fo differentiating into other cell types and of self-renewal
72
What is the function of stem cells in embryos?
Embryonic stem cells can replicate themselves and differentiate into many other types of cells.
Embryonic stem cells may be able to treat conditions such as paralysis and diabetes by dividing to replace damaged cells
73
What is the function of stem cells in adult bone marrow?
Adult stem cells can differentiate into several cell types to replace dead or damaged tissues. For example, bone marrow stem cells can form many different types of blood cell
74
What is the function of stem cells in plant meristems?
Meristem stem cells retain the ability to differentiate into any type of plant cell throughout their lifespan - they can differentiate into any cell which is required by the plant
75
What is therapeutic cloning?
A cloning method where an embryo is produced wich the same genetic makeup as the patient. The stem cells which originate from the embryo will not be rejected by the patient's immune system, so can be used to treat certain medical conditions
76
What are the advantages of cloning plants using meristem stem cells?
Can prevent rare plants from becoming extinct
Can produce large numers of plants with a favourable characteristic
Can produce identical plants for research
77
What are issues that are associated with the use of stem cells?
Many embryonic stem cells are sourced from aborted embryos - some people have an ethical/religious objection.
Development of stem cell therapies is slow, expensive and difficult.
Adult stem cells injected with viruses could transfer infections to patients.
If donor stem cells do not have a similar genetic makeup to the patient, an immune response could be triggered.
78
What is diffusion?
The net movement of particles from an area of higher concentration to an area of lower concentration
79
What three main factors affect the rate of diffusion?
Concentration gradient - larger gradient, faster diffusion
Temperature - higher temperature, faster diffusion
Surface area - larger surface area, faster diffusion
80
Give examples of substances transported by diffusion in the lungs and the kidney
lungs: oxygen diffusees into the blood from the lungs and carbon diozide diffuses into the lungs from the blood, both down their concentration gradient
kidney: urea diffuses from cells into blood plasma so it can be excreted in urine
81
How are single-celled organisms adapted for diffusion?
They have a large surface area to volume ratio - maximises the rate of diffusion of molecules to meet the organisms's needs
82
How is surface area to volume ratio calculated?
Surface area = number of sides x (side length x side width)
volume = length x width x depth
ratio = surgace area:volume
83
What four factors increase the effectiveness of a gas exchange surface?
Large surface area
Thin membrane (short diffusion path)
Efficient blood supply (animals)
Ventilation (animals)
84
What is osmosis?
The movement of water from a dilute solution to a concentrated solution through a partially permeable membrane
85
What is meant when a solution is isotonic to a cell?
The concentrations of the external and internal (inside cell) solutions are the same
86
What is meant when a solution is hypertonic to a cell?
The concentration of the external solution is higher than that of the internal solution (inside cell)
87
What is meant when a solution is hypotonic to a cell?
The concentration of the external solution is lower than that of internal solution (inside cell)
88
What may happen when an animal cell is placed in a very hypotonic solution?
Water moves into the cell, causing it to burst
89
What may happen when an animal cell is placed in a very hypertonic solution?
Water moves out of the cell, causing it to shrivel up
90
How do plant leaves and stems remain rigid?
Turgor pressure - water moves in by osmosis, causing the vacuole to swell and the cytoplasm to press against the cell wall
91
What may happen when a plant cell is plaved in a very hypertonic solution?
Water moves out of the cell by osmosis and the vacuole and cytoplasm decrease in size. The cell membrane may pull away from the cell wall, causing the cell to become plasmolysed
92
What is active transport?
The movement of molecules from a more dilute solution to a more concentrated solution against a concentration gradient, using energy from respiration
93
How do plant root hair cells use active transport?
Root hair cells use active transport to take up mineral ions from a more dilute solution in soils. Ions such as magnesium and nitrates are required for healthy growth
94
How is active transport used to absorb the products of digestion?
Active transport is used to transport glucose from a lower concentration in the gut to a higher concentration in the blood. Glucose is then transported to the tissues where it can be used in respiration
