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Science - Biology - GCSE > P1 - Cells > Flashcards

P1 - Cells Flashcards

Revise cells and cell processes

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1
Q

What are eukaryotic cells ?

A

Eukaryotic cells are complex, all animal and plant cells are eukaryotic.

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2
Q

What are prokaryotic cells ?

A

Prokaryotic cells are smaller and simpler, bacteria are prokaryotic cells.

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3
Q

What sub-cellular structures are in an animal cell ?

A

The nucleus, cytoplasm, cell membrane, mitochondria and ribosomes.

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4
Q

what sub-cellular structures do plant cells have that animal cells don’t ?

A

The cell wall, permanent vacuole and chloroplasts.

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5
Q

What sub-cellular structures do bacteria have ?

A

The cell wall, cell membrane, cytoplasm, a single loop of DNA (bacteria don’t have a true nucleus) and plasmids.

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6
Q

What are the two kinds of microscope ?

A

Light microscope and electron microscope.

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7
Q

What is the difference between light and electron microscopes ?

A

Electron microscopes have a higher resolution and magnification.

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8
Q

What is the formula to work out magnification ?

A

magnification = image size ÷ real size

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9
Q

How do you prepare a slide for a microscope ?

A

Add drop of water to the middle, use tweezers to place object into the water, add a drop of iodine solution to stain it and place a cover slip on top.

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10
Q

How do you use a light microscope ?

A

Clip the slide onto the stage, select objective lens with lowest magnification, use coarse adjustment knob to move stage up to just below objective lens, look through eyepiece and move stage downwards until roughly in focus, move fine adjustment knob until you get a clear image. For a bigger image use an objective lens with a higher magnification.

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11
Q

What are specialised cells ?

A

Cells in an organism that carry out a specific function.

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12
Q

What happens when cells differentiate ?

A

They develop different sub-cellular structures, they turn into different types of cells allowing them to carry out specific functions.

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13
Q

When can cells differentiate in animals ?

A

Only in the early stages of an animals life.

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14
Q

When can cells differentiate in plants ?

A

Lots of plants cells can for the whole of the plants life.

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15
Q

How are sperm cells specialised ?

A

They have tails and streamlined head to help them swim to the egg and has lots of mitochondria to provide energy for swimming. Also has enzymes in head to digest through egg cell membrane.

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16
Q

How are nerve cells specialised ?

A

They are long to cover more distance in the body and have branches at the end to connect to other nerve cells.

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17
Q

How are muscle cells specialised ?

A

They are long so they have space to contract and they have lots of mitochondria to provide energy for contracting.

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18
Q

How are root hair cells specialised ?

A

They grow long to stick into the ground, giving the plant a big surface area for absorbing water and mineral ions.

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19
Q

What does a phloem cell do ?

A

Transport food in a plant.

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20
Q

What does a xylem cell do ?

A

Transport water in a plant.

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21
Q

How are phloem and xylem cells specialised ?

A

The cells form tubes and are very long and joined end to end. Xylem cells are hollow and phloem cells have very few sub-cellular structures to allow lots of space inside for stuff to flow through them.

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22
Q

Where a chromosomes found ?

A

In the nucleus of a cell.

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23
Q

What are chromosomes ?

A

Coiled up lengths of DNA molecules, each one carries a large number of genes and different genes control the development of different characteristics.

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24
Q

What is the cell cycle ?

A

Where body cells in multi-cellular organisms divide to make new cells.

25
Q

What happens in the Growth and DNA Replication stage of the cell cycle ?

A

The cells grows and increases number of sub-cellular structures, the DNA is replicated and forms X-shaped chromosomes where each arm is an exact copy of the other.

26
Q

What happens in the Mitosis stage of the cell cycle ?

A

The chromosomes line up at the centre of the cell, and the two arms of the chromosomes are pulled apart to opposite ends of the cell by cell fibres, dividing the nucleus. Each set of chromosomes becomes the nucleus of a new cell and the cytoplasm and cell membrane divide leaving two exact copies or daughter cells of the original cell.

27
Q

What are stem cells ?

A

They are undifferentiated cells, and they can produce lots more undifferentiated cells and differentiate into different types of specialised cell.

28
Q

Where can stem cells be found ?

A

In early human embryos, called embryonic stem cells, and in adults - in the bone marrow, called adult stem cells.

29
Q

What is the difference between adult and embryonic stem cells ?

A

Embryonic stem cells can differentiate into any kind of cell, whereas adult stem cells can only produce certain types of cell (i.e blood cells). They can both be cloned in a lab and these can be used in medicine or research.

30
Q

How might stem cells be able to cure some diseases ?

A

Embryonic stem cells can be used to replace faulty cells in sick people, you could make nerve cells for people with paralysis, or insulin producing cells for people with diabetes.

31
Q

What is therapeutic cloning ?

A

The making of an embryo that has the same genes as the patient, meaning the stem cells won’t be rejected by the patients body.

32
Q

What is a risk involved in using stem cells in medicine ?

A

The particular stem cells used could be infected with a virus, which could be passed on to the patient making them sicker.

33
Q

Why are some people against stem cell research ?

A

They argue that embryos shouldn’t be used in research as each one could be a human life, and that scientists can and should be using other sources of stem cells.

34
Q

Why do people argue for the use of stem cell research ?

A

They say that curing patients who are suffering is more important than the rights of embryos, and that embryos used in research are usually unwanted ones from fertility clinics and would otherwise be destroyed.

35
Q

What are meristems ?

A

Meristems are tissues that plants have in the tips of its roots and shoots - where growth occurs. They contain stem cells that can differentiate into any type of plant cell and this can happen throughout the plants entire life.

36
Q

How can meristems be used ?

A

To makes clones of plants quickly and cheaply, for the preservation of rare species or crop plants with desirable features.

37
Q

What is diffusion ?

A

The movement of particles from an area of high concentration to an area of low concentration.

38
Q

What is the difference in concentration called ?

A

The concentration gradient - the bigger this difference, the faster the diffusion rate.

39
Q

What affects diffusion rate ?

A

A higher temperature will increase the diffusion rate, as particles have more energy to move around faster. And also, in cells, the surface area of the membrane increases it as more particles can pass through it at the same time.

40
Q

What’s special about cell membranes ?

A

The let stuff diffuse in and out of the cell, from where there’s a high concentration to where there’s a lower concentration.

41
Q

What is osmosis ?

A

The movement of water molecules across a partially permeable membrane from a less concentrated solution to a more concentrated solution.

42
Q

What is a partially permeable membrane ?

A

One with very small holes in it so tiny molecules like water can pass through but larger molecules like sucrose can’t.

43
Q

What happens in osmosis ?

A

Water molecules move from the less concentrated solution to the more concentrated solution, meaning the more concentrated solution becomes more dilute.

44
Q

What experiment can you do to observe the effects of sugar solutions on plant tissue ?

A

First cut a piece of potato into two cylinders of the same proportions, and get two beakers - one with pure water an the other with concentrated sugar solution. Measure mass of each potato cylinder and put one in each beaker and leave for twenty-four hours. Then take them out and dry with a paper towel, and measure their masses again. If mass has increased, water moved into the potato cells, however if it decreased water moved out. You can then calculate the percentage change in mass.

45
Q

What are root hairs ?

A

They cover plant roots, there are millions of them, and they stick out into the soil to increase surface area. This is for absorbing water and mineral ions to grow healthily.

46
Q

What is active transport ?

A

When substances are absorbed from a lower concentration to a higher concentration, against the concentration gradient. Requires energy from respiration.

47
Q

How do root hair cells take in minerals ?

A

Using active transport, from a low concentration in the soil to a high one in the root hair cells.

48
Q

Where in the body is active transport used ?

A

To move nutrients from the gut into the blood, to allow glucose to be taken into the blood and transported to cells for respiration.

49
Q

How do organisms exchange substances ?

A

Cells use diffusion to take in substances from the environment, and also to get rid of waste products: carbon dioxide and urea.

50
Q

What determines the ease through which organisms can exchange substances ?

A

Their surface area to volume ratio, the smaller the surface area compared to volume the harder it is.

51
Q

How do prokaryotic cells replicate ?

A

By binary fission - meaning it splits in two.

52
Q

What happens in binary fission ?

A

Circular DNA and plasmids replicate, as cell gets bigger these move to opposite poles, cytoplasm divides and new cell walls form to produce two daughter cells - each with one copy of the circular DNA but variable number of plasmids.

53
Q

What affects how quickly bacteria divide ?

A

Divide quicker in warmer conditions and with lots of nutrients, if there’re unfavourable conditions cells stop dividing and die.

54
Q

How can you calculate the number of bacteria in a population ?

A

You can use a cells mean division time to work out how many times it has divided in a certain amount of time, and so the number of cells produced.
2^n where n is number of divisions in the time.

55
Q

Where are bacteria grown ?

A

In a culture medium.

56
Q

What is a culture medium ?

A

Contains carbohydrates, minerals, proteins and vitamins bacteria need to grow.

57
Q

How do you make an agar plate ?

A

Hot agar jelly is poured into a shallow petri dish, when it’s cooled and set microorganisms can be transferred to the culture medium (agar) with an inoculating loop or sterile dropping pipette and spreader.

58
Q

How can you make sure your cultures aren’t contaminated ?

A

Petri dishes and culture mediums must be sterilised before use to kill unwanted microorganisms, if inoculating loop is used - should be sterilised over a hot flame. After transferring bacteria lid of petri dish should be taped on, and petri dish should be stored upside down.

59
Q

P

A

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Science - Biology - GCSE (7 decks)

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