Cell Biology Flashcards
(91 cards)
1
Q
What are the sub-cellular structures inside an animal cell?
A
Cell membrane, mitochondria, nucleus, ribosomes, cytoplasm
2
Q
What does the nucleus do?
A
Controls the activities of the cell and contain genetic materials
3
Q
What does the cytoplasm do?
A
It’s a jelly like substance in which most of the chemical reactions happen
4
Q
What does the cell membrane do?
A
Controls the passage of substances in and out of the cell.
5
Q
What do mitochondria do?
A
Where aerobic respiration takes place.
6
Q
What do the ribosomes do?
A
Where proteins are synthesised (made)
7
Q
What extra features does a plant cell have?
A
A cell wall
A permanent vacuole
Chloroplasts
8
Q
What does the cell wall do?
A
Made of cellulose, which strengthens the cell.
9
Q
What does the permanent vacuole do?
A
Filled with sap, supports the plant
10
Q
What do chloroplasts do?
A
Absorb light to make food (glucose) by photosynthesis.
11
Q
What are the two main types of cell?
A
Prokaryotic and eukaryotic
12
Q
What are some examples of eukaryotic cells?
A
Plant, animal and fugal cells
13
Q
What is an example of a prokaryotic cell?
A
Bacterial cells
14
Q
What is the structure of a eukaryotic cell like?
A
Eukaryotic cells have a cell membrane, cytoplasm and genetic material enclosed in a nucleus
15
Q
What is the structure of a prokaryotic cell like?
A
They have cytoplasm and a cell membrane surrounded by a cell wall.
16
Q
What are the differences between prokaryotic and eukaryotic cells?
A
- Prokaryotic cells are much smaller inside.
- The genetic material in prokaryotic cells is not enclosed by a nucleus.
- The genetic material in prokaryotic cells is a single DNA loop and there may be one or more loops of DNA called plasmids.
- Prokaryotic cells don’t contain mitochondria or chloroplasts.
17
Q
What is the shape of bacterial cells like?
A
Bacterial cells have many different shapes (some round, rod shaped, spiral)
18
Q
In bacterial cells, what roles does the cytoplasm take over?
A
It takes over the roles of the mitochondria and chloroplasts.
19
Q
What are plasmids and what do they allow bacterial cells to do?
A
They are small circles of DNA that can be transferred from one cell to another. Plasmids allow bacterial cells to move genes from one cell to another.
20
Q
How are bacterial cells adapted to their function?
A
- They have plasmid DNA which can replicate independently of chromosomal DNA, DNA is not found within a nucleus and is usually found as one circular chromosome.
- They have a cell wall (not made of cellulose) which provides structural support for the bacteria.
- They have a flagella which are tail like structures that rotate to help some bacteria move.
21
Q
What do cells in an organism do as the organism develops?
A
Cells differentiate to form different types of cells- they become specialised.
22
Q
When do animal cells differentiate?
A
Most types differentiate at an early age.
23
Q
What do plant cells differentiate?
A
Many types of plant cell retain the ability to differentiate throughout life.
24
Q
How is cells division restricted in mature animals?
A
It is mainly restricted to repair and replacement.
25
What does a cell acquire during differentiation?
It acquired different sub-cellular structures to enable it to carry out a certain function.
26
What is differentiation?
The process whereby a cell changes to become more specialised for its job.
27
Where is the sperm cell located?
In the reproductive system.
28
How is the sperm cell adapted to its functions?
Acrosome- Contains enzymes to allow the sperm to penetrate the outer layer of egg.
Mitochondria- Sperm may have many of these cell components with are the major site of respiration to provide energy for their journey.
Tail- Propel the sperm to fertilise the egg.
Nucleus- Contains only one set of genetic information
29
What is the function of the nerve cell?
To carry electrical signals from one part of the body to another. They are specialised for rapid signalling.
30
How are nerve cells adapted to their function?
These cells are long (to cover more distance) and have branched connections to connect to other nerve cells and form a network throughout the body.
31
How are muscle cells specialised for their function?
They are specialised for contraction, these cells are long (so that they have space to contract) and contain lots of mitochondria to generate the energy needed for contraction.
32
How are root hair cells adapted for their functions?
They are specialised for absorbing water and minerals. They are on the surface of the plant roots which grow into long hairs, that stick out into the soil. This gives the plant a big surface area for absorbing water and mineral ions from the soil. They have lots of mitochondria for active transport of minerals.
33
How are phloem cells adapted to their function?
They are arranged end to end into tubes, they have very few sub cellular structures, so stuff can flow through them. The end walls of the cells allow sugar through but support the tubes.
34
What are xylem and phloem cells adapted for?
For transporting substances.
35
How are xylem cells adapted to their functions?
They are arranged end to end but the end walls break down to form hollow tubes. The cell was is strengthened by a substance called lignin.
36
What is the typical diameter of an animal cell?
0.2mm
37
What is the typical diameter of a prokaryotic cell?
0.002mm
38
What is resolution?
The ability to see two or more objects as separate objects.
39
When was the light microscope invented and what does it do?
The late 16th century and gave a greater resolution that the human eye.
40
When did scientists first use the electron microscope?
1933
41
How does an electron microscope work?
It passes electrons rather than light through the specimen and can give much better resolution.
42
What does an electron microscope allow you to see?
Cells can be seen in much finer detail:
- The structures inside mitochondria and chloroplasts can be studied and this has helped scientists to find out how they work.
- Ribosomes can be seen and their role in making proteins can be studied.
43
Why would you need to calculate magnification?
When a microscope is used to look at cells, scientists will often take photographs or produce drawings. These images are many times larger than the real cell/ structure.
44
What is magnification?
How many times larger the image is than the object.
45
How do you calculate magnification?
Size of image/ size of real object
46
What type of cell division do bacteria use?
Binary fission (an example of asexual reproduction)
47
How fast can bacteria multiply?
As frequently as every 20 minutes if the have enough nutrients and suitable temperature.
48
How does binary fission work?
1) Single bacteria
2) Replicates chromosomes and cell elongates.
3) Chromosomes separate and cell wall starts to form.
4) Cell wall forms completely.
5) Two daughter cells.
49
How do you calculate how many times the bacteria will duplicate?
Bacteria at the end = bacteria at the start x 2^number of divisions.
50
What is a culture?
Bacteria can be grown in a nutrient broth solution or as colonies on a type of jelly called agar. This bacteria is called a culture.
51
Why do cultures of microorganisms need to be uncontaminated?
So that specific strains can be used to test the effects of antibiotics or disinfectants.
52
How can uncontaminated cultures be produced?
1) The petri dishes and the agar must be sterilised before to kill any unwanted organisms.
2) An inoculating Koop is sterilised by passing it through a flame.
3) The cooled inoculating loop is used to transfer the bacteria to agar.
4) The lid of the Petri dish must be quickly removed and replaced when transferring bacteria and secured with tape to stop it coming off (otherwise microorganisms from the air may contaminate the culture).
5) The dish is stored upside down to stop condensation dripping into the agar surface.
53
What sort of technique is the production of uncontaminated cultures?
An aseptic technique and ensures that only the required microorganisms are grown.
54
What temperature should cultures be incubated at in school labs and how does this differ in industry?
A max of 25 degrees Celsius, to reduce the likelihood of the growth of harmful bacteria. In industry higher temperatures can be used for more rapid growth.
55
How do you calculate the area of a colony of bacteria?
Area of a circle:
Pi r squared
56
Where a chromosomes located?
Nucleus
57
What are chromosomes made of?
DNA
58
How do genes control the development of different characteristics?
Different genes contain the code to make different proteins and so control the development of different characteristics.
59
How many chromosomes does a human have?
23 pairs or 46 individual
60
Why are chromosomes found in pairs?
You get one from each parent.
61
What is the cell cycle?
When cells go through a series of changes involving growth and division.
62
What is mitosis?
One of the stages of the cell cycle- when the cell divides into two identical cells.
63
What does a cell need to do before it can divide?
To grow and increase the number of sun-cellular structures e.g. ribosomes and mitochondria. This DNA then replicated to form two copies of each chromosome, in this way the genetic material doubles.
64
What happens during mitosis?
- One set of chromosomes is pulled to each end of the cell.
- The nucleus divides.
- The cytoplasm and cell membrane divide to form two identical cells.
65
What are the stages in the cell cycle?
1) Each cell grows and makes new sub-cellular structures.
2) DNA is copied and new chromosomes are made.
3) Mitosis
66
Why is cell division by mitosis important?
Because it makes new cells for:
- Growth and development of multicellular organisms
- Repairing damaged tissues
- Asexual reproduction
67
What is a stem cell?
An undifferentiated cell which is capable of giving rise to many more cells of the same type, and from which other cells can arise from differentiation.
68
Where a stem cells found?
In human embryos, in the umbilical cord of a new born baby and in some organs and tissues.
69
What are stem cells from embryos called?
Embryonic stem cells and these can make all different types of cell.
70
Where are adult stem cells found?
In some organs and tissue e.g. bone marrow. They can only make some types of cells and their capacity to divide is limited.
71
How are stem cells used?
They are very useful in testing conditions where cells are damaged or not working properly e.g. diabetes or paralysis. They can also be used to replace damaged cells.
72
What is therapeutic cloning?
When a clone embryo of a patient may be used as a source of stem cells.
73
Why is therapeutic cloning very useful for treating a patient?
Stem cells from the cloned embryo will not be rejected by the body.
74
What are some concerns about using stem cells cloned from embryos?
- There may be risks e.g. transfer of viral infection.
| - They may have ethical/ religious objections.
75
Where are stem cells found in plants?
In special areas called meristems.
76
What do meristems allow plants to do?
Make new cells for growth. The stem cells can also be used to produce cloned for plants.
77
Why do we need to produce clones of plants?
- Rare species can be protected from extinction.
| - Large numbers of identical crop plants with identical features e.g. disease resistant can be made.
78
How are substances transported in and out of a cell via diffusion?
Diffusion is the spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of high concentration to an area of lower concentration until they are evenly spread out.
79
Why does diffusion happen?
Because the particles move randomly and spread out.
80
What are some examples of substances transported by diffusion?
- Oxygen and carbon dioxide diffuse during gas exchange in the lungs, hills and plant leaves.
- Urea diffuses from cells into the blood plasma for excretion by the kidney.
- Digested food molecules diffuse from the small intestine to the blood.
81
What are the factors that affect the rate of diffusion?
- Difference in concentration (concentration gradient)
- Temperature
- Surface area of membrane
82
Why can a single-called organism sufficiently transport molecules in and out of a cell?
A single-celled organism has a relatively large surface area to volume ratio. This allows sufficient transport of molecules in and out of the cell to meet the needs of the organism.
83
How do you calculate surface area to volume ratio?
Surface area / volume
84
What is the surface area to volume ratio in a multicellular organism like?
It is smaller than in a single-celled organism but the organ systems are specialised for exchanging materials.
85
How are different multicellular organisms specialised for exchanging materials?
The small intestine, gills in fish and the roots and leaves in plants are specialised for exchanging materials, this is to allow sufficient molecules to be transported into and out of cells for the organism’s needs.
86
How is the effectiveness of an exchange surface increased?
- Large surface area.
- Thin membrane to provides a short diffusion path.
- Surfaces usually kept moist do that substances can dissolve and diffuse across cell membranes faster.
- (in animals) a rich blood supply maintains the concentration gradient.
- (in animals) ventilation occurs to speed up gaseous exchange.
87
How does water move across a cell?
Via osmosis
88
What is osmosis?
The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
89
What does active transport do?
Moves substance from a more dilute solution to a more concentrated solution (against a concentration gradient).
90
What does active transport require?
Energy from respiration.
91
What does active transport allow things to do?
- Allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil.
- Allows sugar to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. Sugar molecules are used for cell respiration.
