Topic 1: Cell Biology Flashcards
1
Q
What are chromosomes?
A
Thread-like structures in the nucleus made of DNA.
2
Q
What are chromosomes made of?
A
Highly coiled strands of long DNA molecules.
3
Q
How are chromosomes found in diploid organisms?
A
They are normally found in pairs, one from each parent.
4
Q
How many chromosomes do humans have?
A
Humans have 46 chromosomes in 23 pairs.
5
Q
Which human cells do not have chromosomes?
A
Red blood cells, as they lose their nuclei.
6
Q
What happens to chromosomes before cell division?
A
They double and form X-shaped structures.
7
Q
What is mitosis?
A
A stage in the cell cycle when the nucleus divides to produce two identical daughter cells.
8
Q
What happens during the growth phase of the cell cycle?
A
The genetic material doubles, and subcellular structures increase.
9
Q
What happens during mitosis?
A
Chromosomes replicate, align, separate, and a new nucleus forms.
10
Q
What is cytokinesis?
A
The process where the cytoplasm and membrane divide, forming two identical daughter cells.
11
Q
Why is mitosis important?
A
It enables growth, repair, and the formation of new cells in multicellular organisms.
12
Q
What happens when a human cell with 46 chromosomes divides?
A
The chromosomes double to 92 chromatids, then split into two cells with 46 chromosomes each.
13
Q
What are the three stages of the cell cycle?
A
Growth phase, mitosis, and cytokinesis.
14
Q
What are stem cells?
A
Undifferentiated cells capable of dividing and specializing into different cell types.
15
Q
How many specialized cell types are there in the human body?
A
Around 250, including red blood cells and motor neurons.
16
Q
What are embryonic stem cells?
A
Cells that can differentiate into almost any type of human cell.
17
Q
Where are stem cells found in plants?
A
In the meristems, where they can differentiate into various plant cells.
18
Q
What is therapeutic cloning?
A
A process where an embryo is created with the same genes as a patient to produce stem cells.
19
Q
Why is therapeutic cloning beneficial?
A
It prevents immune rejection and helps in treating diseases.
20
Q
What is one benefit of plant stem cells?
A
They allow rapid cloning of plants, including rare or disease-resistant species.
21
Q
Why is plant cloning useful?
A
It helps preserve biodiversity and reduces the need for pesticides.
22
Q
What is the function of the cell membrane?
A
Holds the cell together, separating the inside of the cell from the environment outside, controlling what can and cannot enter or leave the cell
23
Q
What is the function of the cytoplasm?
A
A jelly-like substance where many chemical reactions inside the cell happen. Surrounds sub-cellular structures
24
Q
What is the function of ribosomes?
A
Site of protein synthesis in the cell
25
What are the two distinct types of cell?
- Eukaryotic
- Prokaryotic
26
What are eukaryotic cells?
- Plant + Animal Cells
- DNA is enclosed in nucleus
- 10 to 100 µm (micrometre)
27
What are prokaryotic cells?
- Bacteria Cells
- Genetic material found in a single loop of DNA within cytoplasm
- Other circular pieces of DNA (plasmids)
- Cell Wall (Made from peptidoglycan)
- Smaller than eukaryotic, 1µm in size
28
What are organelles?
Subcellular ‘compartments’ where specific processes take place within the cell
29
What are the main subcellular structures in an animal cell?
- Nucleus
- Cell Membrane
- Mitochondria
- Ribosomes
- Cytoplasm
30
What is the function of the mitochondria?
- Site of aerobic respiration
31
What kind of cells have higher number of mitochondria?
- High Rates of Metabolism (carry out cell reactions)
32
What is the function of the nucleus?
Contains genetic material (DNA) which controls activities in cell
33
What subcellular are plant cell specific?
Cell Wall
Permanent Vacuole
Chloroplasts
34
What is the function of the cell wall?
- Made of cellulose
- Gives cell extra support, defining its shape
35
What is the function of the chloroplast?
Contain green chlorophyll pigments to absorb light energy and the enzymes needed for photosynthesis
36
What is the function of the permanent vacuole?
- Consists of cell sap; solution of sugar and salts dissolved in water
- Used for storage of certain materials
- Help support shape of cell
37
What is a specialised cell?
Cell that has a structure that aids its specific function (e.g cell shape, combination of structures)
38
What is the process in which cells specialise?
Differentiation
39
What is the function of the nerve cell?
- Conduction of electrical impulses
40
What are the special features which aid the nerve cell?
- Long, can conduct nerve impulses between areas of body
- Extension of cytoplasm known as dendrites, allow communication of other nerve cells, muscles and glands
- Axon covered with fatty sheath which speeds up nerve impulse transmission
41
What is the function of the muscle cell?
Contraction for movement
42
What are the special features which aid the muscle cell?
- Have many mitochondria to release energy for contraction
- Contain protein filaments that slide over each other
43
What is the function of the sperm cell?
Transfer of genetic material to an egg cell for fertilisation
44
What are the special features which aid the sperm cell?
- Mid-piece packed with mitochondria to release energy for tail
- Tail rotates, to propel cell forward
- Acrosome in head contain digestive enxymes which break down outer layer
- Half no. of chromosome which allows restoration to normal no. during fertilisation
45
What is the function of the root hair cell?
Absorption of water and mineral ions from soil
46
What are the special features which aid root hair cell?
- Hairs increase SA so rate of water uptake by osmosis is greater
- Thin walls, short diffusion distance
- Mitochondria release energy for active transport
47
What is the function of the xylem vessels?
Transport of water and dissolved ions
48
What are the special features which aid the xylem vessel?
- No walls between cells to allow continuous hollow tubes
- No organelles or cytoplasm
- Thickened with lignin for support and strengthening
49
What is the function of the phloem cell?
Transport of dissolved sugars and amino acids
50
What are the special features which aid the phloem cells?
- Cells joined end-to-end and contain holes in end walls to allow sugar and amino acid to flow easily
- Few subcellular structures
51
What is cell differentiation?
Cell differentiation is the process by which a cell changes to become specialized, enabling it to perform specific functions within an organism.
52
What are unspecialized cells?
Unspecialized cells are cells that have not yet differentiated and do not have a specific function.
53
Do all cells in a multicellular organism contain the same genetic information?
Yes, almost all cells in a multicellular organism contain the same genetic information (the same genes or alleles), but only some genes are used to control the development of a particular cell based on its role.
54
How does a cell's structure change during differentiation?
During differentiation, a cell develops a specific structure and composition of subcellular structures that enable it to carry out a certain function.
55
What changes occur in an undifferentiated cell to form a nerve cell?
The cytoplasm and cell membrane of an undifferentiated cell elongate to form connections over large distances, enabling it to function as a nerve cell.
56
When do most animal cells differentiate?
In animals, most cells differentiate at an early stage of development.
57
What is the main role of cell division in mature animals?
In mature animals, cell division is mainly restricted to repair and replacement of cells.
58
Can animal cells differentiate after they become specialized?
No, animal cells generally lose their ability to differentiate after they become specialized early in the life of the animal.
59
What are adult stem cells, and what is their role?
Adult stem cells are cells that retain the ability to differentiate throughout the life of an animal. They are mainly involved in replacing and repairing cells, such as blood or skin cells.
60
How do plant cells differ from animal cells in terms of differentiation?
Unlike animal cells, many types of plant cells retain the ability to fully differentiate throughout the life of a plant, not just in the early stages of development.
61
What are light microscopes?
Use light and lenses to magnify specimens, allowing visualisation of cells and large subcellular structures like nuclei and vacuoles, often with the aid of stains
62
What are electron microscopes?
Use electron beams instead of light, providing much higher resolution and magnification due to the smaller wavelength of electron beams
63
Why are electron microscopes better than light microscopes?
- Higher magnification and resolving power
- Study cells in finer detail
- Develop better understanding of structure of nucleus and cell membrane
64
What is the magnification equation?
Magnification = Drawing Size ÷ Actual Size
65
How do bacteria multiply?
Bacteria multiply by a type of simple cell division known as binary fission.
66
What happens during binary fission in bacteria?
The bacterial cell replicates its genetic material, increases in size, and then the cytoplasm divides. A copy of each piece of circular DNA moves to each end of the cell, and new cell walls form around each daughter cell.
67
How does the number of bacterial cells increase during binary fission?
Each division of one cell produces two cells, so the number of cells increases by a power of 2 each time binary fission occurs.
68
What conditions are required for bacteria to multiply quickly?
Bacteria require an adequate supply of nutrients (carbohydrates, proteins, minerals, and vitamins) and an appropriate temperature (which varies depending on the species being grown).
69
What is the maximum allowed temperature for bacterial growth in a school lab?
25°C
70
Why is it important to grow uncontaminated cultures of microorganisms in the lab?
Uncontaminated cultures are vital because the presence of competing species can affect the growth of cultures and the validity of any study performed on them.
71
What are aseptic techniques, and why are they important?
Aseptic techniques are methods used to prevent contamination of cultures by other microorganisms. They are important to ensure the validity and reliability of experiments.
72
How can the effectiveness of antibiotics, antiseptics, or disinfectants be determined?
The effectiveness can be determined by calculating the area of an inhibition zone around a disc of the substance being tested.
73
What is the formula to calculate the area of an inhibition zone?
The area of an inhibition zone can be calculated using the formula:
Area=πr²
where r is the radius of the inhibition zone.
74
Why is it more accurate to measure the diameter of an inhibition zone than the radius?
It is more accurate to measure the diameter because it is easier to measure directly. However, remember to halve the diameter to get the radius before using the area formula.
75
What is the mean division time of bacteria?
Average amount of time it takes for a bacterial cell in a population to divide.
76
How can you calculate the number of bacteria in a population over time?
You can calculate the number of bacteria by knowing the mean division time and the total time division has been occurring. The number of cells produced is 2n , where n is the number of divisions.
77
Why might you need to express the number of bacteria in standard form?
Because bacteria can multiply very quickly, resulting in very large numbers. Standard form makes it easier to handle and express these large numbers.
78
What is the purpose of lifting the lid of a petri dish only slightly?
Lifting the lid only slightly reduces the risk of contamination by other microorganisms while still allowing air to enter, which is required by bacteria grown in school labs.
79
What is the significance of calculating the area of an inhibition zone?
Calculating the area of an inhibition zone provides a more accurate way of comparing the effect of different substances on bacterial growth than judging by sight alone.
80
What are the three transport processes that living organism use for exchange?
- Diffusion
- Osmosis
- Active Transport
81
Why is transport necessary for an organism to function properly?
Needs to exchange substances such as food molecules and waste products between itself and its environment
82
Where does the exchange of substances occur?
Across the cell membrane
83
What is diffusion?
Spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement of particles from an area of higher concentration to an area of lower concentration
84
What type of process is diffusion?
Passive, movement of particles in fluid dependent on how much kinetic energy they have
85
How does temperature affect diffusion?
Higher temp. , higher kinetic energy, faster movement by diffusion
86
What are examples of substances that enter cells by diffusion?
- Oxygen (must diffuse into cells for aerobic respiration)
- Carbon Dioxide (must diffuse into photosynthesising plant cells to be available for photosynthesis)
87
What are examples of substances that leave cells by diffusion?
- Urea (broken down excess amino acids which is highly toxic and must diffuse out of cells to be excreted by kidneys)
- Carbon Dioxide (produced by aerobic respiration)
88
How is the movement driven when substances are transported in and out of cell?
Concentration Gradient
89
What can cause movement of a substance by diffusion to change?
Change in direction of concentration gradient
90
What are the factors which affect rate of diffusion?
- Difference in Concentration Gradient (greater difference, faster overall rate0
- Temperature (More kinetic energy, move faster)
- Surface Area of Membrane (greater surface area has greater rate of diffusion)
91
What is the surface area to volume ratio of large multicellular organisms?
Small surface area to volume ratios compared to single-celled organisms, creating longer diffusion distances from surface to centre that limit efficient exchange of materials
92
What is an adaptation to exchange in large organisms because of low SA : volume ratio?
Evolved specialized exchange surfaces and transport systems (like circulatory systems) because diffusion, osmosis, and active transport alone cannot meet their metabolic needs
93
What is the role of the small intestine and how is it adapted?
- Absorption of digested food molecules into bloodstream occurs across wall of intestine
- Foldable surface with specialised epithelial cells (which also has foldable cell membrane) to increase SA
- Only one layer of cells cover surface of villus to decrease diffusion distance
- Villus has good blood supply - maintain conc. gradient
94
What is the role of the lungs and how is it adapted?
- Gas exchange between air in alveoli and blood
- Supply cells with O₂ for aerobic respiration and removing CO₂
- Millions of alveoli to increase SA
- One cell thick, moist lining
- Excellent blood supply - maintain conc. gradient
95
What is the role of the gills and how is it adapted?
- Gas exchange between war through gills and blood
- Supply cells with O₂ for aerobic respiration and removing CO₂
- Gill made of smaller plates called filaments which are covered in lamellae, increase SA
- Dense capillary network to ensure good blood supply - maintain conc. gradient
96
What is the role of leaves and how is it adapted?
- Contain photosynthetic cells
- Efficient gas exchange with minimal water loss
- Stomata to cover lower side of leaf, allowing air circulation inside leaf - decreases diffusion distance for CO₂ and O₂
- Spongy mesophyll cells allowing air circulation
96
What is the role of roots and how is it adapted?
- Absorb water and mineral ions from soil
- Anchor plant
- Root network highly branched to increase SA
- Roots covered with root hair cells, specialised structure with projections , increase SA
97
How do exchange surfaces maximise material transfer?
- Large SA to increase transport rate
- Thin barrier for short diffusion distance
- Extensive blood vessel networks to reduce exchange distance and maximise conc. gradient
- Well-ventilated gas exchange surface to preserve conc. gradient for efficient diffusion
98
What is osmosis?
Diffusion of water molecules from a dilute solution to a concentrated solution through a partially permeable membrane
99
What is meant by a dilute solution?
- High conc. of water molecules
- Low conc. of solute molecules
100
What is meant by a concentrated solution?
- Low conc. of water molecules
- High conc. of solute molecules
101
What is active transport?
Moves substances against concentration gradients (from dilute to concentrated solutions), requiring energy from cellular respiration
102
What does active transport rely on?
Specialized protein carrier molecules embedded in the cell membrane that use energy to transport substances into or out of cells.
103
What is an example of active transport in plants?
- Root hair cells use active transport to move essential minerals (Mg²⁺, NO₃⁻) from dilute soil solution into concentrated cytoplasm against concentration gradients
- Magnesium enables chlorophyll production; nitrates support protein synthesis and growth.
104
What is an example of active transport in animals?
- Moves molecules like glucose from the intestinal lumen into bloodstream even against concentration gradients, ensuring nutrient absorption continues regardless of existing blood concentration levels.
105
What is diffusion?
Movement of substances in fluid down a concentration gradient.
106
Does diffusion require energy from respiration?
No
107
Name three substances that move by diffusion in organisms.
Oxygen, carbon dioxide, glucose, amino acids, urea
108
Where does diffusion occur in the human body?
In the lungs (gas exchange), in the digestive system (absorption), in the lumen of the small intestine and intestinal cells.
109
What is osmosis?
Special type of diffusion of water that occurs between two solutions separated by a partially permeable membrane where water potential gradient exists.
110
What substance moves during osmosis?
Water
111
Does osmosis require energy from respiration?
No
112
Where does osmosis occur in organisms?
Between all cells and their immediate environment (particularly between cells and the bloodstream).
113
What is active transport?
Movement of substances across a membrane against a concentration gradient.
114
Does active transport require energy from respiration?
Yes
115
What substances are commonly moved by active transport?
Glucose, mineral ions (sodium, potassium, magnesium, nitrates)
116
Where does active transport occur in animals?
Between the lumen of the small intestine and intestinal cells, into the soil.
117
Where does active transport occur in plants?
In root hair cells absorbing minerals from soil
118
Why do large multicellular organisms need specialized exchange surfaces?
Because they have small surface area to volume ratios, making diffusion alone insufficient to meet their metabolic needs.
119
What are two ways exchange surfaces maximize material transport?
Having a large surface area and providing a thin barrier between regions (short diffusion path)
120
How do blood vessels enhance exchange in animals?
By reducing distance between cells and bloodstream, and maintaining concentration gradients by moving substances toward/away from exchange surfaces.
121
What happens to cells if blood ion concentration is too high?
Cells lose too much water by osmosis and shrink/dehydrate
122
What happens to cells if blood ion concentration is too low?
Cells absorb too much water, swell, and possibly burst
123
What are isotonic sports drinks?
Drinks with similar concentrations of salt and sugar as human blood, primarily used for hydration
124
What are hypertonic sports drinks?
Drinks with higher concentrations of salt and sugar than blood, used for supplying glucose during intense exercise
125
What are hypotonic sports drinks?
Drinks with lower concentrations of salt and sugar than blood, used for rapid rehydration
126
Why do plants need active transport in root hair cells?
To move minerals from the dilute soil solution to the more concentrated cytoplasm
127
What mineral ion is needed to make chlorophyll in plants?
Magnesium ions
128
What mineral ions are needed for protein synthesis in plants?
Nitrate ions
129
Why do athletes choose sports drinks over water after exercise?
To replace not just water but also salts (electrolytes) and glucose lost during exercise
130
What are three things lost from the body during exercise?
Water, salts (ions/electrolytes), and glucose
