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Biology Paper 1 > Topic 1 - Key Concepts in Biology > Flashcards

Topic 1 - Key Concepts in Biology Flashcards

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1
Q

How is the structure of an animal cell related to its function?

A

( eukaryotic cell - has a nucleus )

NUCLEUS - holds DNA, controls activity

CYTOPLASM - jelly like substance, reactions take place here

MITOCHONDRIA - respiration, releases energy for cell processes

RIBOSOMES - where proteins are made (protein synthesis)

CELL MEMBRANE - controls what enters and leaves the cell

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2
Q

How is the structure of a plant cell related to its function?

A

( eukaryotic cell - has a nucleus )

CELL MEMBRANE - controls what enters and leaves the cell

NUCLEUS - holds DNA, controls activity

CYTOPLASM - jelly like substance, reactions take place here

MITOCHONDRIA - respiration, releases energy for cell processes

RIBOSOMES - where proteins are made (protein synthesis)

CENTRAL VACUOLE

CHLOROPLASTS

CELL WALL

CELL MEMBRANE - controls what enters and leaves the cell

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3
Q

How is the structure of a bacteria cell related to its function?

A

( prokaryotic cell - has NO nucleus )

Loop of CHROMOSOMAL DNA - carries the majority of the bacterial genes

RIBOSOMES - make proteins

PLASMID DNA - contain additional genes not found in chromosomes

CELL WALL - for protection, made of different substances to plant cell walls

FLAGELLUM - to help them move

CELL MEMBRANE

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4
Q

Name the three structures that are found in most plant cells but not animal cells, and describe their functions (4 marks)

A

Chloroplasts are the structures where photosynthesis takes place to make food for the plant cell. The cell wall is made of cellulose, and it is tough so that it helps support the cell and keep its shape. The large central vacuole contains cell sap, which helps to keep the plant cell rigid.

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5
Q

Muscle cells contain more mitochondria than skin cells, suggest why (3 marks)

A

Muscle cells respire more (1) they need more energy (1) As they carry out aerobic respiration/ produce ATP (1)

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6
Q

Plants don’t have skeletons, explain how they stand upright. (2 marks)

A

The plant is supported by the cell wall around each cell (1) and the vacuole in each cell when it is full.

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7
Q

Explain why not all plant cells have chloroplasts. (2 marks)

A

Not all plant cells photosynthesise, eg root hair cells (1) Cells that do not photosynthesise do not need chloroplasts (1)

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8
Q

How is an egg cell adapted to its function?

A

egg cell - contains nutrients in cytoplasm supplies growing embryo.

HAPLOID nucleus, can fuse with another haploid nucleus from the sperm to form a diploid zygote.

After fertilisation, membrane changes so no more sperm cells can enter.

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9
Q

How is a sperm cell adapted to its function?

A

TAIL for swimming to the egg cell

Many mitochondria around base of the tail, releases energy needed to propel it

HAPLOID nucleus that fuses with the egg nucleus to form a diploid zygote

acrosome contains enzymes to digest a way through the egg cell membrane

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10
Q

How is a ciliates epithelial cell adapted to its function?

A

Epithelial cells line tubes, eg the trachea.

Cilia moves things along tube, such as mucus.

lot of cilia to move mucus away from the lungs.

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11
Q

How has microscope technology developed over time?

A

see more of the structures of cells and organelles, more clarity and detail

increased understanding of the role of sub-cellular structures

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12
Q

How does magnification improve the use of a microscope?

A

enables you to see the cells and the structures inside them

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13
Q

Explain the use of a light microscope

A

uses LIGHT to magnify objects.

The greatest possible magnification is about X2000

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14
Q

Explain the use of an electron microscope

A

uses ELECTRONS to view an object.

makes it possible to magnify objects up to about X10 million.

can see objects in cells more clearly and in far more detail than light

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15
Q

Magnification equation?

A

Magnification (M) = Image Size (I) / Real size (R)

= M = I divided by R

  • Image in millimetres (mm)
  • Multiply by 1000 to get measurement in micrometers ( weird p m)
  • if the image has a scale bar, use that to find the answer
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16
Q

Some cells were viewed by microscope using a X4 eyepiece and a X20 objective. Calculate the magnification of the cells seen through the microscope. (1 marks)

A

Magnification of object

= magnification of eyepiece X magnification of objective

= 4 X 20 = 80

The cells will be magnified 80 times by the microscope

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17
Q

What are the units of measurement to measure small structures

A

milli (10−3)
micro (10−6)
nano (10−9)
pico (10−12)

A micrometer is one millionth of a metre

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18
Q

State how many picograms there are in 1g (1 marks)

A

1 000 000 000 000
Or
10 to the power of 12

(Pico means 10 -12)

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19
Q

A mitochondrion measures 0.000 002m

Write this in standard form (1 mark)

A

2 x 10 -6 m

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20
Q

A mitochondrion measures 0.000 002m

Write this in micrometers (1 mark)

A

2 micrometers or 2 pm (weird p)

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21
Q

Explain how to use a light microscope safely (core practical)

A
  • start with the lowest POWER OBJECTIVE under the eyepiece
  • clip the SLIDE securely on the stage
  • adjust the LIGHT SOURCE (MIRROR) so that the light goes up through the slide
  • use COARSE FOCUSING WHEEL to focus on slide
  • move slide so cell is in middle of the view
  • if needed, move a higher POWER OBJECTIVE into position above the slide
  • use FINE FOCUSING WHEEL to bring cell back into focus
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22
Q

Explain precautions and problems involved in using a light microscope (core practical)

A
  • if you using sun as light source make sure microscope mirror doesnt point directly at the Sun could cause permanent eye damage
  • never use coarse focusing wheel with a higher power objective as could crash
  • if part of slide is not in view with a higher power objective, go back to lower power objective, brings it back into centre view and focuses it before returning to the higher power objective
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23
Q

A student is given a microscope slide of a section through a leaf.

(A) describe how the student should use a light microscope to study xylem cells in the leaf section (4 marks)

(B) the lens closest to the specimen is called the:

A - subjective
B - eyepiece
C - objective
D - stage

A

(A) Place the lowest power objective below the eyepiece (1) then place the slide on the microscope stage (1) and use the coarse focusing wheel to focus the image. (1) If needed, move a higher power objective into place and focus using the fine focusing wheel (1)

(B) C

24
Q

Explain the mechanism of enzyme action including the active site and enzyme specificity

A

biological catalysts that control reactions

enzymes are specific (only works with one substrate) to its substrate and activity of enzymes is affected by temperature, substrate concentration and pH.

25
Q

Explain what is meant by the active site of the enzyme (2 marks)

A

The part of the enzyme molecule where the substrate binds/fits/bonds. (1) this is where reaction takes place. (1)

26
Q

Explain the role of the active site in an enzyme controlled reaction.

(4 marks)

A

shape of the active site matches shape of the substrate molecules, holds them together so bonds can form between to make the product.

product molecule doesn’t fit the active site well so it is released from the enzyme.

27
Q

Explain how enzymes can be denatured due to changes in the shape of the active site

A

If shape of the enzyme changes, its active site may not work.

28
Q

Explain the effects of temperature on enzyme activity

A

At OPTIMUM temperature the enzyme is working at its fastest rate

At LOWER temperatures molecules move slower so substrate molecules take longer to fit react into the active site.

HIGHER temperatures cause active site to change shape so cant hold the substrate tightly and the reaction goes slower

At VERY HIGH temperatures active site breaks up and enzyme denatured

29
Q

Explain the effects of substrate concentration on enzyme activity

A

substrate concentration low - not every active site of each enzyme molecule is busy, + substrate increases the rate of reaction.

highest rate of reaction and substrate concentration - adding more substrate has little effect because active site of every enzyme molecule is busy.

30
Q

Explain the effects of pH on enzyme activity

A

Changing pH - changes active site shape therefore changi got its ability to bond with substrate.

enzyme works fastest at the optimum, pH.

further from optimum pH, slower rate of reaction

31
Q

Explain how to investigate the effects of pH on amylase activity

A
  • add amylase to buffered starch solution in a test tube
  • place tube in water bath, constant temperature
  • take samples of the mixture at regular intervals (eg every 10s) and mix them with a fresh drop of iodine solution on a dimple tile
  • repeat test until iodine solution stops changing colour when starch/amylase mixture is added. Record time taken for this to happen
  • repeat procedure at different pH values
32
Q

Explain what happens during investigating the effects of pH on amylase practical

A

Starch - broken down by amylase to sugars, buffering solution makes sure pH stays same during

bear in mindeffect of temperate on enzyme action. Keep solution at the optimum temperature.

Iodine solution - usually orange/yellow, in the presence of starch it turns black/blue

33
Q

How can the method of investigating the effects of pH on amylase practical be improved

A
  • more accurate measuring apparatus
  • taking mean of several repeats at each pH to help reduce the effects of random variation
  • taking measurements over a narrower range of pH
34
Q

Explain how to calculate the rate of enzyme activity

A

1 / time because the mass of starch used at each pH is the same. You can then compare rates of amylase for different pHs.

Eg:
Starch digested in 20s at pH 6.

1/ 20 = 0.05

35
Q

Explain what enzymes do in a chemical reaction

A

Enzymes are BIOLOGICAL CATALYSTS.

catalyse reactions that synthesise large molecules from smaller ones and break down large into smaller ones.

Enzymes SPEED UP rate of a chemical reaction but aren’t used up. means they can be used again

36
Q

Explain the role of an enzyme in digestion and synthesis

A

Some DIGEST large molecules into smaller ones in gut where large food molecules are broken down so can be absorbed into blood

Some SYNTHESISE larger molecules from smaller molecules. Important for supporting processes and growth.

37
Q

Explain the importance of enzymes as biological catalysts in the synthesis of carbohydrates

A

Carbohydrates DIGESTED by AMYLASE (Eg starch for energy storage in plants) into sugars (Eg glucose for respiration)

These sugars can be SYNTHESISED back into carbohydrates

38
Q

Explain the importance of enzymes as biological catalysts in the synthesis of lipids

A

Lipids (eg for energy storage) DIGESTED by AMYLASE into fatty acids and glycerol (eg for respiration)

fatty acids and glycerol can then be synthesised back -> lipids

39
Q

Explain the importance of enzymes as biological catalysts in the synthesis of proteins

A

Proteins (eg for muscle cells) DIGESTED by PROTEASE into amino acids (eg to make enzymes)

amino acids can then SYNTHESISE back into proteins.

40
Q

State the smaller molecules these large molecules are broken down into:

A) carbohydrates
B) proteins
C) lipids

A

A) carbohydrates —> sugars

B) proteins —> amino acids

C) lipids —> fatty acids and glycerol (need to mention both)

41
Q

People with cystic fibrosis have thick mucus lining their gut. They have to take capsules containing enzymes before meals. Explain why (3 marks)

A

The thick mucus prevents enzymes being secreted into the gut. If they didn’t take enzyme capsules before meals this food wouldn’t be digested into smaller, soluble molecules. As a result they wouldn’t absorb enough nutrients.

42
Q

Explain the method to investigate the use of chemical reagents to identify starch, reducing sugars, proteins and fats

A

TO TEST FOR STARCH: place a few drops of iodine on solid food, or mix with a solution of the food

TO TEST FOR REDUCING SUGARS: add an equal volume of Benedicts solution to a food solution and mix. Heat the mixture in a 95 degree water bath for a few minutes.

TO TEST FOR PROTEINS (Biuret test) : add an equal volume of 0.1 mol dm-3 potassium hydroxide solution to the food solution and mix. Add a few drops of 0.01 mol dm-3 copper sulfate solution and mix

TO TEST FOR FATS: add an equal volume of ethanol to the food solution and shake thoroughly. Add water to the mixture.

43
Q

Explain safety precautions to be taken during the investigation of chemical reagents

A
  • handle iodine solution carefully as it can stain skin and clothing
  • wear suitable eye protection for all tests
  • work safely with hot water to avoid scalding. Use a heat resistant glove or tongs to handle hot equipment
44
Q

Explain the results of the chemical reagents practical

A

IODINE - STARCH = yellow/orange normally, blue/black if food is present

BENEDICTS SOLUTION - REDUCING SUGAR = blue normally, green, orange or red if food is present (depending on how much sugar is present)

BIURET TEST - PROTEIN = pale blue normally, pale purple if food is present

ETHANOL - FAT = clear normally, cloudy if food is present

45
Q

Explain how the energy contained in food can be measured using calorimetry (method)

A
  1. The temperature of the water at the start is measured
  2. The mass of the food sample is measured
  3. The food is set alight (eg in a Bunsen flame), then placed immediately under the tube
  4. The temperature of the water at the end is measured
46
Q

Explain how using calorimetry works

A
  • the calorimeter contains a measured volume of water
  • when all the food is burned, the increase in temperature is related to the energy released from the food
  • the energy released from the food by burning is transferred to the water
  • as the water gains energy, its temperature increases
47
Q

A student used calorimetry to measure the energy in a potato snack, using the apparatus shown (practical). The test tube contained 10cm3 water. Give two reasons why this may not be an accurate measurement. (2 marks)

A

Taking too long to move the burning food to under the tube, or holding the food at different distances from the tube. This would affect how much energy is transferred to the surrounding air and not the tube.

48
Q

Explain how substances are transported into and out of cells by diffusion

A

High concentration of dissolved molecules (concentrated solution) moves through a partially permeable membrane to low concentration of dissolved molecules (dilute solution).

Diffusion is important in the body, eg to move oxygen into cells and to remove carbon dioxide

49
Q

Explain how substances are transported into and out of cells by osmosis

A

Osmosis is the net movement of water molecules across a partially permeable membrane

50
Q

Explain how substances are transported into and out of cells by active transport

A

Low concentration of dissolved molecules (dilute solution) moves to a high concentration of dissolved molecules (concentrated solution) through a partially permeable membrane.

Active transport needs energy from respiration. There is net movement against the concentration gradient.

51
Q

What is active transport used for in the plants and animals

A

Active transport makes it possible for cells to absorb ions from very dilute solutions, eg root cells absorb minerals from soil water, and small intestine cells absorb glucose from digested food in the gut into the body

52
Q

Explain how to investigate osmosis using potatoes (method)

A
  1. Mark the value of one solute concentration on one tube and repeat using a different tube for each concentration. Fill each tube two thirds full of the appropriate solution.
  2. Blot a piece of potato dry on a paper towel, then measure and record its mass. Use the forceps to place it into one of thet tubes, and record the tube. Repeat for all tubes.
  3. After 20 minutes, use the forceps to remove each piece of potato, blot it dry and measure its mass again. Record all final masses.
53
Q

What is the conclusion for the investigation of osmosis in potatoes

A

The results show that when the solution concentration is very dilute, water enters the potato cells. This is due to osmosis because the solute concentration of the potato cells is greater than the surrounding solution. As the solute concentration of the solution increases above that inside the potato cells, osmosis causes water to be lost from the potato.

54
Q

Explain why certain apparatus is needed and improvements that can be made when doing the potato osmosis practical

A

The change in mass may be very small, you should measure to 2 dp.

The solute in the solutions must be something that is too large to diffuse across the cell membrane. Sucrose is often used.

Blotting removes surface water, and can help to increase the accuracy and repeatability of measurements.

Repeating the test at each solute concentration and calculating the mean of the results can help to reduce the effect of random variation

55
Q

Explain how to calculate the percentage change in mass in osmosis

A

% change in mass = final mass - initial mass / initial mass

Biology Paper 1 (4 decks)

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