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biology > cell structure and transport-b1 > Flashcards

cell structure and transport-b1 Flashcards

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1
Q

What are light microscopes?

A

Light microscopes use a beam of light to form an image of an object. They were invented in the mid-17th century and can magnify around x2000. They let us see individual cells and subcellular structures like nuclei. Has a resolving power of 200nm

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2
Q

What are electron microscopes?

A

Electron microscopes use electrons instead of light to form an image. They were invented in the 1930s and allow scientists to see and understand more about the cellular structures inside cells. Can magnify around x2000000. Has a resolving power of 10nm

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3
Q

What are the differences between light and electron microscopes?

A

Light microscopes use light and electron microscopes use electrons to form an image.
Light microscopes are relatively cheap, can be used almost anywhere and can magnify live specimens
Electron microscopes are large, very expensive and have to be kept in special temperature, pressure and humidity controlled rooms.
Electron microscopes have a higher magnification that light microscopes. They also have a higher resolution

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4
Q

What is resolution?

A

Resolution is the ability to distinguish between two points, so a higher resolution gives a sharper image.

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5
Q

What is the formula for calculating magnification?

A

magnification=image size/real size

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6
Q

What are the two types of electron microscopes?

A

Scanning electron microscope and a transmission electron microscope.

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7
Q

What is the difference between scanning and transmission electron microscope.

A

Scanning electron microscope creates 3D images(at a slightly lower magnification)
Transmission electron microscope which creates 2D images at a higher magnification.

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8
Q

How do you work out magnification of a light microscope?

A

magnification of an eyepiece lens x magnification of the objective lens

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9
Q

How to prepare a microscope slide?(onion cells)

A

Add a drop of water to the middle of a clean slide
Cut up an onion and seperate it into layers. use tweeezers to peel off some epidermal tissue from the bottom of one of the layers.
Using tweezers, place the epidermal tissue into the water on the slide
Add a drop of iodine solution. Iodine solution is a stain. Stains are sued to highlight objects in a cell by adding colour to them.
Place a cover slip(a square of thin, transparent glass) on top. To do this, stand the cover slip upright on the slide, next to the water droplet. Then carefully tilt and lower it so it covers the specimen. Try not to get any air bubbles under there-they’ll obstruct your view of the specimen.

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10
Q

How to use a light microscope to look at your slide?

A

Clip the slide you have prepared onto the stage
Select the lowest powered objective lens
Use the coarse adjustment knob to move the stage up to just below the objective lens
Look down the eyepiece. Use the coarse adjustment knob to move the stage downwards until the image is roughly in focus.
Adjust the focus with the fine adjustment knob, until you get a clear image of whats on the slide
If you need to see the slide with a greater magnification, swap to a higher powered objective lens and refocus.

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11
Q

What are cells?

A

Building blocks of life

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12
Q

What is the length of an average animal cell?

A

10-30(upside down h)m long

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13
Q

What is the role of the nucleus?

A

The nucleus contains genetic material that controls the activities of the cell. The average diameter is around 10(upside down h)m.

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14
Q

What is the role of the cytoplasm?

A

The cytoplasm is a gel like substance where most of the chemical reactions happen. It contains enzymes that control these reactions.

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15
Q

What is the role of the cell membrane?

A

The cell membrane holds the cell together and controls what goes in and out.

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16
Q

What is the role of mitochondria?

A

Mitochondria is where most of the reactions for aerobic respiration take place. Respiration transfers energy that the cell needs to work.

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17
Q

What is the role of ribosomes?

A

This is where proteins synthesis takes place, making all the proteins needed in the cell.

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18
Q

What is the length of an average plant cell?

A

Bigger than animal cells, they range from 10-100(upside down h)m

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19
Q

What are the differences between animal and plant cells?

A

Animal cells do not have chloroplasts, permanent vacuole or cell wall.

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20
Q

What is the role of chloroplasts?

A

Chloroplasts is where photosynthesis occurs which makes food for the plant. They contain a green substance called chlorophyll which absorbs light needed for photosynthesis.
Chloroplasts are found in the green parts of the plant. They are green because they contain chlorophyll.

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21
Q

What is the role of the permanent vacuole?

A

The permanent vacuole contains cell sap(a weak solution of sugar and salts). It is important for keeping the cells rigid to support the plant.

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22
Q

What is the role of cell wall?

A

The cell wall is rigid and made of cellulose. It supports the cell and strengthens it.

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23
Q

What two types of cells are there?

A

Prokaryotic or eukaryotic

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24
Q

What are eukaryotic cells?

A

Eukaryotic cells are complex and include all animal and plant cells. Eukaryotes are organisms that are made up of eukaryotic cells.

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25
Q

What are prokaryotic cells?

A

Prokaryotic cells are smaller and simpler e.g bacteria

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26
Q

What are bacteria?

A

Bacteria are single celled living organisms. They are examples of prokaryotes.

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27
Q

What features do bacteria have?

A

Bacteria have cytoplasm and a cell membrane surrounded by a cell wall, but the cell wall does not contain the cellulose you see in plant cells. In prokaryotic cells the genetic material is not enclosed in a nucleus. The bacterial chromosome is a single DNA loop found free in the cytoplasm.
Prokaryotic cells may also contain extra small rings of DNA called plasmids. Plasmids code for very specific features such as antibiotic resistance.
Some bacteria have a slime capsule around the outside of the cell wall.
Some types of bacteria have at least one flagellum, that is a long protein strand that lashes about. These bacteria use their flagella to move themselves around.

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28
Q

What are the differences in terms of differentiation of cells in plant cells and animal cells?

A

Most types of animal cells differetiate at and early stage of developemnt, whereas many types of plant cells retain the ability to differentiate throughout life. m

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29
Q

What happens when a cell differentiates?

A

As a cell differentiates, it gets different sub cellular structures that enable it to carry out a particular function.

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30
Q

What is the role of nerve cells?

A

Nerve cells are specialized to carry electrical impulses around the body of an animal. They provide a rapid communication system between the different parts of the body.

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31
Q

What are the adaptations of nerve cells?

A

Lots of dendrites to make connections to other nerve cells.
An axon that carries the nerve impulses from one place to another. They can be very long
The nerve endings or synapses are adapted to pass the impulses to another cell or between a nerve cell and a muscle in the body using special transmitter chemicals. They contain lots of mitochondria to provide the energy needed to make the transmitter chemicals.

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32
Q

What is the role of muscle cells?

A

Muscle cells are specialsied cells that contract and relax. Striated muscle cells work together in tissues called muscles. Muscles contract and relax in pairs to move the bones of the skeleton, so vertebrates can move on land and in water.
Smooth muscle cells form one of the layers of tissue in your digestive system and they contract to squeeze food through your gut.

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33
Q

What adaptations do striated muscle cells have?

A

They contain special proteins that slide over each other making the fibers contract.
They contain many mitochondria to transfer the energy needed for the chemical reactions that take place as the cells contract and relax
They can store glycogen, a chemical that can be broken down and used in cellular respiration by the mitochondria to transfer energy needed for the fibers to contract

34
Q

What is the role of sperm cells?

A

Sperm cells are usually released a long way from the egg they are going to fertilise. They contain the genetic information from the male parent. Depending on the type of animal, sperm cells need to move through water or the female reproductive system to reach the egg. They have to break into the egg.

35
Q

What are the adaptions of sperm cells?

A

A long tail whips from side to side to help move the sperm through water or the female reproductive system
The middle section is full of mitochondria, which transfer the energy needed for the tail to work.
The acrosome stores digestive enzymes for breaking down the outer layers of the egg.
A large nucleus contains the genetic information to be passed on.

36
Q

What is the role of root hair cells?

A

You find out root hair cells close to the tips of growing roots. Plants need to take in lots of water(and dissolved mineral ions). The root hair cells help them to take up water and mineral ions more efficiently. Root hair cells are always relatively close to the xylem tissue. The xylem tissue carries water and mineral ions into the rest of the plant. Mineral ions are moved into the root hair cell by active transport.

37
Q

What are adaptations of root hair cells?

A

They greatly increase surface area available for water to move into the cell
They have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell.
They have many mitochondria that transfer the energy needed for the active transport of mineral ions into the root hair cells.

38
Q

What is the role of photosynthetic cells?

A

One of the main ways animals defer from plants is that plants can make their own food by photosynthesis. These cells carry out photosynthesis

39
Q

What are adaptations of photosynthetic cells?

A

They contain specialized green structures called chloroplasts containing chlorophyll that trap the light needed for photosynthesis.
They are usually positioned in continuous layers in the leaves and outer layers of the stem of a plant so they absorb as much light as possible.

40
Q

What is the role of xylem cells?

A

Xylem is the transport tissue in plants that carries water and mineral ions from the roots to the highest leaves and shoots. The xylem is also important in supporting the plant.

41
Q

What are the adaptions of xylem cells?

A

The xylem cells are alive when they are first formed but a special chemical called lignin builds up in the spirals in the cell walls. The cells die and form long hollow tubes that allow water and mineral ions to move easily through them, from one end of the plant to the other.
The spirals and rings of lignin in the xylem cells make them very strong and help them withstand the pressure of water moving up the plant. They also help support the plant stem.

42
Q

What is the role of phloem cells?

A

Phloem is the specialized transport tissue that carries food made by photosynthesis around the body of the plant. It is made up of phloem cells that form tubes like xylem cells, but phloem cells do not become lignified and die. The dissolved food can move up and down the phloem tubes to where it is needed.
Xylem cells are hollow in the centre so stuff can flow through them

43
Q

What are the adaptations of phloem cells?

A

The cell walls between the cells break down to form special sieve plates. These allow water carrying dissolved food to move freely up and down the tubes to where it is needed.
Phloem cells lose a lot of their internal structures but they are supported by companion cells that help to keep them alive. The mitochondria of the companion cells transfer the energy needed to move dissolved food up and down the plant in the phloem.
Phloem cells have very few sub cellular structures so that stuff can flow through them

44
Q

What is diffusion?

A

Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration.

45
Q

Why does diffusion only happen in solutions and gases?

A

Because the particles in these substances are free to move around randomly.

46
Q

What factors affect diffusion and why?

A

A higher temperature will give a faster diffusion rate because the particles have more energy, so move around faster randomly.
The bigger the concentration gradient, the faster the diffusion rate.

47
Q

If there is a big difference in concentration between two areas will diffusion happen quickly? and how about when there is a small difference?

A

Diffusion will happen quickly, many particles will move randomly towards the area of low concentration. The difference between two areas of concentration is called the concentration gradient. The bigger the difference, the steeper the concentration gradient and the faster the rate of diffusion. Diffusion occurs down a concentration gradient.
However if there is a small difference in concentration between two areas, the net movement by diffusion will be quite slow.

48
Q

What is net movement?

A

net movement=particles moving in-particles moving out

49
Q

How does diffusion across a cell membrane work?

A

Just like with diffusion in the air , particles flow through the cell membrane from where there is a higher concentration to where there is a lower concentration.

50
Q

What dissolved substances can diffuse through the cell membrane?

A

oxygen, glucose, urea

51
Q

How can you increase the rate of diffusion across a cell membrane?

A

Increase the surface area of the cell membrane because the larger the surface area of the membrane, the faster the diffusion rate because more particles can pass through at once.

52
Q

What is osmosis?

A

Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.

53
Q

What does partially permeable mean?

A

Only let some types of particles through, e.g water

54
Q

What does a dilute solution of sugar molecules contain?

A

A dilute solution of sugar molecules contains a high concentration of water and a low concentration of sugar.

55
Q

What does a concentrated solution of sugar molecules contain?

A

A concentrated solution of sugar molecules contains a low concentration of water and a high concentration of sugar.

56
Q

What is isotonic?

A

If the concentration of the solution outside the cell is the same as the internal concentration, the solution is isotonic to the cell.

57
Q

What is hypertonic?

A

If the concentration of the solution outside the cell is higher than the internal concentration, the solution is hypertonic to the cell.
The cell will shrivel up and die

58
Q

What is hypotonic?

A

If the concentration of the solution outside the cell is lower than the internal conditions, the solution is hypotonic to the cell.
The cell will swell and may burst

59
Q

How does osmosis work inside the body?(just read it ig)

A

If a cell uses up water in its chemical reactions, the cytoplasm becomes more concentrated. The surrounding fluid becomes hypotonic to the cell and more water immediately moves in by osmosis.
If the cytoplasm becomes too dilute because more water is made in chemical reactions, the surrounding fluid becomes hypertonic to the cell and water leaves the cell by osmosis. Osmosis restores the balance.

60
Q

Why do plants rely on osmosis?

A

Plants rely on osmosis to support their stems and leaves.

61
Q

What happens when water moves into a plant cell?

A

This causes the vacoule to swell, which presses the cytoplasm against the plant cell wall. The pressure builds up, until no more water can enter the cell- this pressure is turgor. Turgor keeps the cells hard and rigid, which in turn keep the leaves and stems of the plant rigid and firm.

62
Q

What is turgor?

A

The pressure created inside a cell when no more water can enter the cell.

63
Q

What does the turgor pressure cause?

A

Turgor pressure makes the cells hard and rigid, which in turn keeps the leaves and stems of the plant rigid and firm.

64
Q

Why is osmosis so important to plants?

A

Plants need the fluid surrounding the cell to always be hypotonic to the cytoplasm. This keeps water moving by osmosis in the right direction and the cells are turgid.
If the solution surrounding the plant cells is hypertonic to the cell contents, water will leave by osmosis. The cells will no longer be firm and swollen- they become flaccid(soft) as there is no pressure on the cell walls. At this point the plants wilt as turgor no longer supports the plants tissues.

65
Q

What happens when too much water is lost in a plant?

A

The vacuole and cytoplasm shrink and eventually the cell membrane pulls away from the cell wall. This is plasmolysis. Plasmolysed cells die quickly unless the osmotic balance is restored.

66
Q

Osmosis required practical, what is the method?

A

Cut up a potato into identical cylinders, and get some beakers with different sugar solutions in them. One should be pure water and another should be a very concentrated sugar solution(e.g 1mol/dm(cubed). Then you can have a few other with concentrations in between(e.g 0.2mol/dm(cubed), 0.4mol/dm(cubed), 0.6mol/dm(cubed).
You measure the mass of the cylinders, then leave one cylinder in each beaker for a few hours.
Then you take them out, dry them with a paper towel and measure their masses again.
If the cylinders have drawn in water by osmosis, they will have increased in mass. If the water has been drawn out, they will have decreased in mass. You can calculate the percentage change in mass and plot a graph. By calculating percentage change you can compare the effect of sugar solution of the cylinders.

67
Q

What is the independent variable in the osmosis required practical?

A

Concentration of sugar solution

68
Q

What is the dependent variable in the osmosis required practical?

A

Chip mass

69
Q

What are the control variables in the osmosis required practicle?

A

Volume of solution, temperature, time, type of sugar used.

All of these should be kept the same to make sure it is a fair test.

70
Q

Why is active transport needed?

A

Sometimes substances need to be absorbed against a concentration gradient, from a lower to a higher concentration.

71
Q

What is active transport?

A

Active transport allows cells to move substances from an area of low concentration to an area of high concentration. This movement is against the concentration gradient.

72
Q

What can active transport allow a cell to do?

A

Cells can absorb ions from a very dilute solution. It also enables cells to move substances such as sugars and ions, from one place to another through the cell membrane.

73
Q

An example of active transport in the body?

A

Active transport is used in the gut when there is a lower concentration of nutrients in the gut, but a higher concentration of nutrients in the blood. Active transport allows nutrients to be taken into the blood.

74
Q

Why does surface area and volume matter?(read it ig but you always do anyways lol)

A

In single celled organisms, gases and dissolved substances can diffuse directly into the cell across the cell membrane. It is because they have a large surface area compared to their volume, so enough substances can be exchanged across the membrane to supply the volume of the cell.
Multicellular organisms have a smaller surface area compared to their volume, so not enough substances can diffuse from their outside surface to supply their entire volume. This means they need some sort of exchange surface for efficient diffusion.

75
Q

What adaptations do exchange surfaces have to maximize effectiveness?

A

Having a large surface area over which exchange can take place.
Having a thin membrane to provide a short diffusion path
In animals having an efficient blood supply moves the diffusing substances away from the exchange surface and maintains a steep concentration gradient.
In animals being ventilated makes gas exchange more efficient by maintaining steep concentration gradients.

76
Q

What adaptations does the Australian Fitzroy turtle have?

A

Inside the rear opening are two large sacs, lined with finger like folds which provide a large surface area and a rich blood supply for gas exchange.

77
Q

What adaptations do humans have?

A

Air is moved into and out of your lungs when you breathe, ventilating the millions of tiny air sacs called alveoli. The alveoli have an enormous surface area and a very rich blood supply for effective gas exchange.
The villi of the small intestine also provide a large surface area, short diffusion paths and a rich blood supply to make exchange of materials more effective.

78
Q

What adaptations to fish have?

A

Fish need to exchange oxygen and carbon dioxide between their blood and the water they swim in. This happens across the gills, which are made up of stacks of thin filaments, each with a rich blood supply. Fish need a constant flow of water over their gills to maintain concentration gradients needed for exchange. They get this by pumping water over the gills using a flap that covers the gills called the operculum.

79
Q

What adaptations do plant roots have?

A

Plant roots have a large surface area, made even bigger by the root hair cells, to make the uptake of water and mineral ions more efficient. Water constantly moves away from the roots in the transpiration stream, maintaining a steep concentration gradient in the cells.

80
Q

What adaptations do plant leaves have?

A

Flat, thin leaves, the presence of air spaces in the leaf tissue and the stomata all help provide a big surface area and maintain a steep concentration gradient for the diffusion of substances such as water, mineral ions and crabon dioxide.

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