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Biology GCSE > Help > Flashcards

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1
Q

Why is starch a good way for plants to store carbs?

A

It is not soluble, it ao compact and can be broken down easily.

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2
Q

How to test leaves for starch:

A

Remove leaf put in boiling water for 30 seconds TURN OFF BUNSEN BURNER Put in test tube with ethanol and remove colour by boiling it wash with cold water Add iodine solution which should turn blue/black if starch present

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3
Q

How can you prove starch is only made in plants that are green?

A

Test a variegated leaf for starch Green areas should be blue

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4
Q

How to prevent a plant from making starch (2)

A

Put it in a box with no light for 2/3 days Put it in a box with soda like to absorb CO2

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5
Q

What do leaves need to make starch? (3)

A

Carbon dioxide Sunlight Chlorophyll

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6
Q

Function of epidermi?

A

They have few chloroplasts and are covered in a thin waxy cuticle which reduces water loss by evaporation and acts as a barrier to the entry of pathogens.

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7
Q

Function of the stoma?

A

Allows CO2 to diffuse into the leaf, to reach the photosynthetic tissues. Allow oxygen and water wa pour to diffuse out. Each stoma is formed as a gap between two specialised guard cells which can alter their shape to open or close the stoma.

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8
Q

Function of mesophyll?

A

Palisade layers made of elongated cells containing hundreds of chloroplasts each, the main site of photosynthesis. The palisade cells are close to the source of light and the upper epidermis is really transparent allowing light to pass through to the chloroplasts.

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9
Q

Why does light intensity level off?

A

Usually because another factor needed for photosynthesis is in short supply, usually carbon dioxide.

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10
Q

How to measure effect of light intensity on elodea?

A

Measure how many bubbles per minute Keep temp of water the same Increase distance of the lamp from the beaker

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11
Q

How does concentration of carbon dioxide in the air change during the day?

A

Concentration is highest at midnight, it falls and then rises again as during the day there is most sun and it is in the best position for photosynthesis at noon.

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12
Q

Function of spongy mesophyll?

A

Made from round loosely packed cells with air spaces between them. They absorb CO2 and release oxygen.

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13
Q

What happens in the xylem?

A

Water and mineral ions are supplied to the leaf by vessels in a tissue called the xylem, forming a continuous transport system in the plant. Water absorbed by roots and passed through stem and veins in the transpiration system in the leaves, water leaves xylem and supplies mesophyll cells.

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14
Q

What’s the phloem?

A

Products of photosynthesis such as sugars are carried away from the mesophyll layer by the phloem. Supplies tissues and organs that can’t make their own food.

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15
Q

What is hydrocarbon ate indicator?

A

Sensitive to changes in carbon dioxide concentration, changes colour depending.

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16
Q

Hydrocarbonate indicator high conc. of CO2 colour

A

Yellow

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17
Q

Hydrocarbonate indicator low conc. of CO2 colour

A

Purple

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18
Q

Hydrocarbonate indicator regular air conc. of CO2 colour

A

Orange

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19
Q

What is osmosis?

A

The net movement of water across a partially permeable membrane from an area of high to low water potential.

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20
Q

What is an artificially partially permeable membrane called?

A

A Visking tube

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21
Q

Uses of artificially partially permeable membrane?

A

Kidney dialysis

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22
Q

How does Visking tubing work?

A

It has microscopic holes in it letting small molecules like water pass through but not permeable to larger molecules like starch sucrose.

23
Q

How can you show the effects of osmosis? Why does this happen?

A

Put a capillary tube with Visking tubing on the end with sucrose solution inside in a beaker full of water. The liquid will rise up the capillary tube. This happens because the larger sucrose molecules cannot pass through the membrane but the water molecules can and are attracted to the sucrose molecules causing a net movement.

24
Q

What is water potential?

A

How free the water molecules are to move.

25
Q

What has the highest water potential?

A

Pure water.

26
Q

Describe the process of a turgid cell?

A

If a cell is out into pure water or dilute solution the contents of the cell have a lower water potential that the external solution to the cell will absorb water by osmosis. Then the cell swells up and the cytoplasm pushes against the cell wall. This internal pressure is called turgidity.

27
Q

What is a tropism?

A

The growth response of a plant to a directional stimulus.

28
Q

Describe the process of a flaccid cell?

A

Cell gets out in a more concentrated solution, it will lose water by osmosis and become flaccid as the cell contents shrink so much.

29
Q

What is a plasmolysed cell?

A

When the membrane and cytoplasm split away from the cell wall and gaps appear in the membrane.

30
Q

How to investigate the effects of osmosis on a potato tuner tissue

A

Three test tubes, one with sucrose solution, one with tap water and one with just air. Cut potato into 5x1x1 dimensions, same size chips. Remove excess water on chip and weigh them. Put them in tubes for 30 minutes, blot them, reweigh. Find percentage change off mass and put results in a table.

31
Q

How does water enter the roots?

A

Osmosis, soil has a higher water potential than the inside of the cell. Water potential inside cells is set up so it will move up by osmosis towards the xylem.

32
Q

Describe the process of transpiration?

A

Water leaves the cells of the leaf mesophyll and evaporates into the air spaces between the spongy mesophyll cells. The water vapour diffuses out through the stomatal pores.

33
Q

What is the transpiration stream?

A

When water vapour is lost through the leaves it sets up a water potential gradient in the mesophyll cells which draws more water for. The cells. The xylem vessels supple the mesophyll with more water.

34
Q

Function of the transpiration stream?

A

Supplies water for the leaf cells to carry out photosynthesis. Carries mineral ions dissolved in the water. Provides water to keep cells turgid. Allows evaporation or the lead surface which cools the leaf.

35
Q

How are xylem vessels filled?

A

Xylem contain dead cells forming continuous vessels. When they are mature the vessels contain no cytoplasm just a hollow lumen through which water passes.

36
Q

What are the walls of the xylem made for? Why?

A

The walls of the xylem are surrounded by a woody material called lignin. The lignin makes them die, becoming hollow tubes. They become stronger and more able to carry water up tall plants without collapsing. It is also impermeable to water.

37
Q

What’s special about the phloem tubes?

A

They have no nucleus, they are controlled by other cells that lie alongside the sieve cells called companion cells.

38
Q

What are vascular bundles and where would you find them on a leaf diagram?

A

Xylem and phloem tubes grouped together. In a cross section of a leaf they and around the outside, phloem further out than xylem.

39
Q

How do guard cells open and close?

A

When they become turgid the stoma opens, when they become flaccid it closes.

40
Q

Factors that effect the rate of transpiration

A

Light intensity - opening of stomata Temperature - increase the rate of evaporation and thus transpiration Humidity - decreases diffusion gradient between air and leaf, slows Wind speed - increases with more wind.

41
Q

How do plants respond to stimuli during germination?

A

Gravity is pulling down on the root so auxin gathers on the lower sides of the shoot and root causing the shoot to grow on the side with the most hormone, growing upwards and the root to grow more on the side with the least hormone, bending downwards.

42
Q

How is auxin distributed when there is unidirectional light?

A

Auxin is distributed to the side with less light causing it to grow more thus bending towards the light stimulus.

43
Q

An obvious example of mechanical digestion?

A

Where teeth bite and chew food, cutting it into smaller pieces that have a large surface area so enzymes can act on food more quickly.

44
Q

What are the two layers or the gut?

A

The circular muscle layer which has fibres running in rings around the gut and the longitudinal muscle layer which has fibre running in rings down the length of the gut.

45
Q

Describe the process of peristalsis

A

The circular muscles and the longitudinal muscles work antagonistically. When the circular muscles contract and the longitudinal muscles relax the gut it made narrower and when the opposite happens the gut becomes wider. Waves of muscular contraction like this pass along the the gut pushing food along.

46
Q

What parts of your body break down foods using enzymes?

A

The mouth, the stomach and the duodenum.

47
Q

What are the three classes of enzymes and what do they each break down?

A

Carbohydrases act on carbohydrates. Proteases act on proteins. Lipases break down lipids.

48
Q

What enzyme does saliva contain?

A

Amylase.

49
Q

What are examples of carbohydrases and what digestive action does it have and where?

A

Amylase turns starch to maltose, it is produced by the salivary glands to act in the mouth and in the pancreas to act in the small intestine. Maltase turns maltose into glucose, produced in the small intestine and acts in the small intestine.

50
Q

Examples of proteases and what they do

A

Pepsin turns proteins into peptides. Tripsin turns proteins into peptides. Peptidases turns peptides into amino acids.

51
Q

What does lipase do?

A

Turns lipids into fatty acids and glycerol.

52
Q

How can pepsin work in the stomach?

A

Though the stomach is very acidic pepsin has an optimum pH of about 2.

53
Q

Function of the large intestine?

A

Most of the digested food has been absorbed and the waste products consist of indigestible remains, water and dead bacteria. The function of the colon is to absorb most of the water from the contents, leaving a semi solid waste material called faeces.

54
Q

Describe the cardiac cycle.

A

Blood enters atria, bicuspid and tricuspid valves are closed. The walls of the atria contract raising blood pressure forcing open the bicuspid and tricuspid valves. Blood passes into the ventricles. When they are full they contract, closing the valves. Ventricles continue to contract and pressure continues to increase forcing open the semi lunar valves at the base of the aorta and pulmonary artery. Pulmonary artery takes blood to the lungs and the aorta carries blood to all other parts of the body.

Biology GCSE (18 decks)

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