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Biology Paper 1 > Cells > Flashcards

Cells Flashcards

1
Q

What are the two types of cell?

A

Eukaryotic (with a nucleus, e.g., animal, plant, and yeast cells) and prokaryotic (no nucleus - bacterial cells only).

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2
Q

Which cells are biggest/smallest?

A

Plant cells are the largest, followed by animal cells, yeast cells, and finally bacterial cells are the smallest.

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3
Q

Where is the DNA in a eukaryotic cell?

A

Eukaryotic cells have their DNA inside a nucleus, coiled up into structures called chromosomes.

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4
Q

Where is the DNA in a prokaryotic cell?

A

Prokaryotic cells have their DNA in the cytoplasm, in a single DNA loop, and may also have small rings of DNA called plasmids.

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5
Q

What cell structures are in all eukaryotic cells?

A

Cell membrane, cytoplasm, nucleus, mitochondria, and ribosomes.

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6
Q

What is the function of a cell membrane?

A

Controls entry and exit of substances (cell transport).

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7
Q

What is the function of mitochondria?

A

To carry out aerobic respiration and release energy (in the form of ATP) for cell activities. The more mitochondria, the more energy the cell needs.

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8
Q

What is the function of a ribosome?

A

To carry out protein synthesis (making proteins). The more ribosomes, the more proteins the cell needs.

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9
Q

What structures are only found in plant/algal cells?

A

Chloroplasts, large vacuole, and cell wall made of cellulose.

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10
Q

What is the function of chloroplasts?

A

Chloroplasts absorb light energy to carry out photosynthesis and produce glucose for the plant. The more chloroplasts, the more glucose a cell can make.

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11
Q

What is the function of a large vacuole?

A

To store water and solutes and help keep the cell upright.

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12
Q

What is the function of the cell wall?

A

Cellulose is strong and rigid. It strengthens the cell, which is important as plants do not have a skeleton to give them support.

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13
Q

What are the only cell structures in a prokaryotic cell?

A

DNA and ribosomes are the only cell structures in a prokaryotic (bacterial) cell.

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14
Q

Why don’t prokaryotic cells have mitochondria?

A

Mitochondria are bigger than prokaryotic cells, so they don’t fit inside.

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15
Q

What is a specialised cell?

A

A cell that has a certain structure to help it carry out a particular function.

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16
Q

What examples are there of specialised animal cells?

A

Sperm cells, nerve cells (neurones), muscle cells, glandular cells, epithelial cells.

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17
Q

What examples are there of specialised plant cells?

A

Root hair cells, xylem cells, phloem cells, palisade, and spongy mesophyll cells.

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18
Q

What is a stem cell?

A

A cell that has not become specialised yet.

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19
Q

What is cell differentiation?

A

The process during development where a stem cell develops to form a specialised cell.

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20
Q

When does differentiation happen?

A

In animal cells, differentiation happens at an early stage (when the animal is an embryo), but in plants, some cells can differentiate throughout the life of the plant.

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21
Q

Where can stem cells be found in an animal?

A

Early stage embryos are completely made of stem cells, but in adults, the only place stem cells exist is in our bone marrow (inside large hollow bones, eg. Thigh bone)

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22
Q

Where can stem cells be found in a plant?

A

Meristem tissue is made of stem cells. It is found near the xylem and phloem, and also in the root and shoot tips.

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23
Q

Why do scientists think animal stem cells are so useful?

A

Stem cells can be made to differentiate into different types of cell. We can use them to treat diabetes and paralysis as well as use them for research into other disorders.

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24
Q

What is therapeutic cloning?

A

Producing an embryo with the same DNA as a patient, so that stem cells can be used for medical treatment. The stem cells will not be rejected by the patient’s body.

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25
What are the risks of using animal stem cells?
Infections caused by viruses could be transferred. Also, some people have ethical objections for religious reasons (as embryos are destroyed during treatments and research).
26
Why do scientists think plant stem cells are so useful?
Stem cells can be used to clone plants quickly and cheaply. This can save rare species from extinction, or produce crop plants with resistance to disease.
27
What is a microscope?
A piece of equipment that uses lenses to magnify cells so that we can see some of their structures.
28
What types of microscope are there?
Light microscope (uses light to make an image) and electron microscope (uses electrons to make an image).
29
How have microscopes developed over the years?
Lenses have improved now glass can be made without cracks or bubbles showing up. Also, the electron microscope shows more detail than the light microscope.
30
Why is an electron microscope better?
Electron beams rather than light means resolution is better. So, more detail can be seen as we can get clearer images of sub-cellular structures at higher magnifications.
31
What is the equation for magnification?
Magnification = image size / actual size (Remember this as 1 / AM).
32
What are chromosomes?
Structures in the nucleus, made of a chemical called DNA. They are normally found in pairs in body cells (one of each pair from Mum, and one from Dad).
33
What are genes?
A small section of DNA (in a chromosome) that is the code for one whole protein. Ribosomes read the code and then make a protein by joining lots of amino acids together.
34
What is the cell cycle?
The life of a cell, including it growing and carrying out its functions and then replicating its DNA before getting ready to divide by mitosis to form new cells.
35
When does mitosis take place?
When cells need to divide to grow or repair an organism. Adults do less mitosis as they are no longer growing, and only repairing tissues/replacing old cells.
36
What are the new cells from mitosis like?
Two genetically identical cells (identical to each other and to the parent cell that they came from).
37
What are the three types of cell transport?
Diffusion, osmosis and active transport all move molecules in and out of cells.
38
What is the definition of diffusion?
The spreading out of particles (molecules) in a solution or a gas, from an area of high concentration to an area of lower concentration. It is passive as it requires no energy.
39
What factors affect the rate of diffusion?
Concentration gradient, temperature, and surface area of the membrane.
40
What molecules move into cells by diffusion?
Oxygen and glucose are the two most important molecules that enter cells by diffusion. They are both needed for aerobic respiration.
41
What molecules move out of cells by diffusion?
Carbon dioxide and urea are both removed as wastes from cells by diffusion.
42
What is surface area to volume ratio? (SA: Vol)
The larger the surface area compared to the volume of a cell or organism, the faster the rate of diffusion.
43
What are the features of efficient exchange surfaces?
Large surface area and thin membrane, plus, in animals, efficient blood supply and ventilation.
44
Which mammal surfaces are efficient?
Small intestine and lungs.
45
Which fish surfaces are efficient?
Gills.
46
Which plant surfaces are efficient?
Roots and leaves.
47
What is the definition of osmosis?
The diffusion of water molecules from a dilute solution to a more concentrated solution across/through a partially permeable membrane.
48
What is the definition of active transport?
The movement of substances (solutes) against their concentration gradient (from dilute to more concentrated). This requires energy from respiration, so it is active not passive.
49
Why is active transport needed?
When a cell needs molecules that it can't get by diffusion, as there are more of the molecules in the cell than there are outside it.
50
Plant example of active transport?
Allows mineral ions to be absorbed into root hair cells from very dilute solutions in the soil.
51
Animal example of active transport?
Glucose molecules in the small intestine need to be absorbed into the blood.
52
How do bacteria reproduce?
They reproduce by BINARY FISSION.
53
How often can bacteria reproduce?
As often as every 20 minutes.
54
What can slow the rate of bacteria reproducing?
Unsuitable temperature and not enough nutrients.
55
How can we grow bacteria in the laboratory?
They are grown on a nutrient gel called AGAR or in a solution called a NUTRIENT BROTH.
56
What is the 'aseptic technique' we use to grow bacteria?
It's a method of growing uncontaminated cultures of bacteria for study.
57
What is a Petri dish?
A plastic or glass dish with a lid, filled with agar and used to grow bacteria.
58
Why does the agar and the Petri dish have to be sterilised?
When we sterilise the agar and dish, all other bacteria are killed. This reduces contamination
59
How do we transfer bacteria to the Petri dish?
We use an inoculating loop.
60
How do we sterilise the inoculating loop?
We pass the inoculating loop through a Bunsen flame.
61
Once inoculated, the Petri dishes are stored upside down. Why?
To prevent condensation forming on the agar surface and disturbing the bacteria.
62
What temperature should bacteria be grown at in a school?
25°C.
63
Why are bacteria grown at 25°C in a school and not at 37°C?
Bacteria which are dangerous to humans could grow at 37°C.
64
What is a bacterial colony?
A group of bacteria which have all grown from one original bacteria.
65
Bacterial colonies are often circular in shape. How would you find out its area?
Use the formula mr?

Biology Paper 1 (5 decks)

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