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GCSE Biology > Key concepts in Biology > Flashcards

Key concepts in Biology Flashcards

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1
Q

State the two types of cell

A

Eukaryotic (animals and plants) and prokaryotic

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2
Q

What is the difference between a eukaryotic and a prokaryotic cell?

A

A eukaryotic cell contains a nucleus and membrane-bound organelles. A prokaryotic cell does not.

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3
Q

List the components of both plant and animal cells (5)

A

● Nucleus
● Cytoplasm
● Cell membrane
● Mitochondria
● Ribosomes

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4
Q

How is genetic information stored in a eukaryotic cell?

A

Within the nucleus, arranged in chromosomes

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5
Q

Other than storing genetic information, what is the function of the nucleus

A

Controls cellular activities

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6
Q

Describe the structure of the cytoplasm

A

● Fluid component of the cell
● Contains organelles, enzymes and
dissolved ions and nutrients

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7
Q

What is the function of the cytoplasm?

A

Site of cellular reactions e.g. first stage of respiration

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8
Q

What is the function of the cell membrane?

A

Controls the entry and exit of materials into and out of the cell

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9
Q

What is the function of the mitochondria?

A

Site of later stages of aerobic respiration in which ATP is produced

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10
Q

What is the function of the ribosomes?

A

Joins amino acids in a specific order during translation

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11
Q

Which organelles are found in plant cells only? (3)

A

● Large, permanent vacuole
● Cell wall
● Chloroplasts

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12
Q

What is the cell wall made of?

A

Cellulose

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13
Q

What is the function of the cell wall?

A

● Provides strength
● Prevents the cell bursting when water enters by osmosis

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14
Q

What does the permanent vacuole contain?

A

A solution of salts, sugars and organic acids

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15
Q

What is the function of the permanent vacuole?

A

Supports the cell, maintaining its turgidity

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16
Q

What is the function of the chloroplasts?

A

Site of photosynthesis

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17
Q

When looking at a cell using a light microscope, why do chloroplasts appear green?

A

Contain chlorophyll, a green pigment

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18
Q

List the organelles found in prokaryotic cells (6)

A

● Chromosomal DNA
● Plasmid DNA
● Cell wall
● Cell membrane
● Ribosomes
● Flagella

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19
Q

How is genetic information stored in a prokaryotic cell?

A

Found free within the cytoplasm as:
● Chromosomal DNA (single large loop
of circular DNA)
● Plasmid DNA

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20
Q

What are plasmids?

A

● Small, circular loops of DNA found free in the cytoplasm and separate from the main DNA
● Carry genes that provide genetic advantages
e.g. antibiotic resistance

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21
Q

What is the prokaryotic cell wall composed of?

A

Peptidoglycan

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22
Q

What is a flagellum?

A

● Long, rotating, ‘whip-like’ protrusion
● Enables bacteria to move

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23
Q

What is a haploid cell?

A

A cell that contains a single copy of each chromosome (half the number of chromosomes)
e.g. 23 chromosomes in humans

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24
Q

What is a diploid cell?

A

A cell that contains two copies of each chromosome (full set of chromosomes)
e.g. 46 chromosomes in humans

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25
Q

What are gametes?

A

● Reproductive cells (e.g. egg and sperm cells)
● They are haploid cells

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26
Q

Describe sexual reproduction in terms of chromosome number

A

● Two haploid gametes fuse
● Resulting embryo has two chromosomes for each gene and two copies of each allele ∴ diploid

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27
Q

Describe how egg cells are adapted to their function

A

● Haploid nucleus contains genetic material
● Mitochondria in cytoplasm produce energy for the developing embryo
● Cytoplasm contains nutrients for the developing embryo
● Cell membrane hardens after fertilisation, preventing the entry of other sperm and ensuring the zygote is diploid

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28
Q

Describe how sperm cells are adapted to their function

A

● Haploid nucleus contains genetic information

● Tail enables movement

● Mitochondria provide energy for tail movement, ATP

● Acrosome contains enzymes that digest the egg cell membrane

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29
Q

Where are ciliated epithelial cells found?

A

Where are ciliated epithelial cells found?

Found lining the surface of structures such as the respiratory tract and uterus.

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30
Q

Describe the function of ciliated epithelial cells lining the airways

A

Move in synchronized waves to beat mucus (containing dirt and pathogens) up to the back of the throat where it can be swallowed.

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31
Q

What is magnification?

A

The number of times bigger an image appears compared to the size of the specimen

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32
Q

How can the total magnification of an image be calculated from lens powers?

A

Total magnification=
eyepiece lense magnification x objective lense magnification

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33
Q

How can the magnification of an image be calculated?

A

magnification= size of image/size of specimen

34
Q

What is resolution?

A

The smallest distance between two objects that can be distinguished

35
Q

How does a light microscope work?

A

Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed.

36
Q

What are the advantages of light microscopes? (4)

A

● Inexpensive
● Easy to use
● Portable
● Observe both dead and living specimens

37
Q

What is the disadvantage of light microscopes?

A

Limited resolution

38
Q

How does an electron microscope work?

A

It uses a beam of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible light, producing an image.

39
Q

Name the two types of electron microscope

A

Transmission electron microscope (TEM) Scanning electron microscope (SEM)

40
Q

What is the advantage of electron microscopes?

A

Greater magnification and resolution

41
Q

Why do electron microscopes have a greater magnification and resolution?

A

They use a beam of electrons which has a shorter wavelength than photons of light

42
Q

How have electron microscopes enabled scientists to develop their understanding of cells?

A

● Allow small sub-cellular structures (e.g. mitochondria, ribosomes) to be observed in detail

● Enable scientists to develop more accurate explanations about how cell structure relates to function

43
Q

What are the disadvantages of electron microscopes? (4)

A

● Expensive
● Large so less portable
● Require training to use
● Only dead specimens can be observed

44
Q

How do you convert from m to mm?

A

× 1000 (× 103)

45
Q

How do you convert from m to µm?

A

× 1 000 000 (× 106)

46
Q

How do you convert from m to nm?

A

× 1 000 000 000 (× 109)

47
Q

How to you convert from nm to m?

A

÷ 1 000 000 000 (× 10-9)

48
Q

How do you convert from m to pm?

A

× 1 000 000 000 000 (× 1012)

49
Q

Convertions to remember:
milli, micro, nano, pico

A

a milli (10−3)
b micro (10−6)
c nano (10−9)
d pico (10−12)

50
Q

What are enzymes?

A

Biological catalysts that increase the rate of a chemical reaction without being permanently altered themselves

51
Q

What is an advantage of enzymes in the body?

A

They enable cellular reactions to take place at lower temperatures

52
Q

What is the active site of an enzyme?

A

The region of an enzyme to which a substrate molecule binds and the reaction takes place

53
Q

Why are enzymes described as having a ‘high specificity’ for their substrate?

A

Only substrates with a specific, complementary shape can fit into an enzyme’s active site.

54
Q

Describe the ‘lock and key’ model

A
  1. Substrate collides with the active site of an enzyme
  2. Substrate binds, enzyme-substrate complex forms
  3. Substrate converted to products
  4. Products released from the active site which is now free to bind to another substrate
55
Q

What factors affect the rate of an enzyme-controlled reaction?

A

● Temperature
● pH
● Substrate concentration

56
Q

Explain how increasing temperature initially affects the rate of an enzyme-controlled reaction

A

● As temperature increases molecules have more KE
● Movement of molecules increases
● Probability of a successful collision increases
● More enzyme-substrate complexes form
● Rate of reaction increases

57
Q

Explain how increasing temperature above the optimum affects the rate of an enzyme-controlled reaction

A

● Temperature increases above the optimum
● Increased vibrations break bonds in enzyme’s structure
● Active site changes shape, enzyme is denatured
● No more enzyme-substrate complexes can form
● Rate of reaction decreases

58
Q

Explain how pH affects the rate of an enzyme-controlled reaction

A

● Enzymes have an optimum pH
● pH shifts from the optimum
● Bonds in the enzyme’s structure are altered
● Active site changes shape, enzyme is denatured
● Rate of reaction decreases

59
Q

Explain how the substrate concentration affects the rate of an enzyme-controlled reaction

A

● Substrate concentration increases
● Number of substrate molecules in the same volume increases
● Probability of a successful collision increases
● More enzyme-substrate complexes form
● Rate of reaction increases
● Once all active sites become full, the rate of reaction plateaus

59
Q

How can the rate of an
enzyme-controlled reaction be calculated when given a value for time?

A

rate= 1/time

60
Q

What are the units for rate?

A

s-1 or 1/s

61
Q

Why must large organic molecules be broken down into smaller, simpler molecules in the body?

A

● Large molecules are too big to be absorbed across the surface of the gut wall
● ∴ large molecules are broken down into smaller molecules for absorption into the bloodstream

62
Q

What type of molecules are proteins and carbohydrates?

A

Polymers

63
Q

Give an example of the breakdown of large molecules into smaller molecules in plants

A

Starch is broken down by enzymes into simpler sugars which are respired to release energy.

64
Q

What are the monomers of carbohydrates?

A

Simple sugars

65
Q

Which group of enzymes catalyses the breakdown of carbohydrates?

A

Carbohydrases

66
Q

Which type of carbohydrase catalyses the breakdown of starch?

A

Amylase

67
Q

What are the monomers of proteins?

A

Amino acids

68
Q

Which type of enzyme catalyses the breakdown of proteins?

A

Proteases

69
Q

What is the function of lipases?

A

Enzymes which catalyse the breakdown of lipids into fatty acids and glycerol

70
Q

Why are small molecules synthesised into larger organic molecules in the body?

A

Large molecules are used for storage (e.g. glycogen) or are used to build structures (e.g. organelles).

71
Q

Which enzyme catalyses the formation of glycogen from glucose?

A

Glycogen synthase

72
Q

How can the amount of energy contained in food be measured?

A

Measured using calorimetry

73
Q

What is calorimetry?

A

A method of measuring the heat transfer during a chemical reaction

74
Q

Describe the method used to measure the amount of energy in a sample of food

A
  1. Add a set volume of water to a boiling tube, record initial temperature
  2. Record the mass of a small sample of food (e.g. bean)
  3. Stick the sample onto a mounted needle
  4. Using a bunsen burner light the food sample
  5. Hold the sample under the boiling tube until it burns up
  6. Record the maximum temperature reached by the water
  7. Record the final mass of the food sample
75
Q

What is simple diffusion?

A

The net movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient

76
Q

What molecules enter and leave cells via simple diffusion through the cell membrane?

A

Small molecules e.g. oxygen, water, glucose, amino acids

77
Q

What factors affect the rate of diffusion? (3)

A

● Temperature
● Concentration gradient
● Surface area of cell membrane

78
Q

Define osmosis

A

Define osmosis

The net movement of water molecules from high water concentration to low water concentration

79
Q

What is active transport?

A

The movement of molecules across a cell membrane from an area of low concentration to an area of high concentration, against the concentration gradient, using energy

80
Q

How is a percentage change in mass calculated?

A

(final mass - initial mass)/initial mass x100

GCSE Biology (1 decks)

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