Topic 1 Key Concepts Flashcards
1
Q
State the two types of cells.
A
Eukaryotic and prokaryotic.
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.
3
Q
List the components of both plant and animal cells. (5)
A
- Nucleus
- Cytoplasm
- Cell membrane
- Mitochondria
- Ribosomes
4
Q
How is genetic information stored in a eukaryotic cell?
A
Within the nucleus, arranged in chromosomes.
5
Q
Other than storing genetic information, what is the function of the nucleus?
A
Controls activities, which are controlled by the genetic material.
6
Q
Describe what the cytoplasm contains.
A
It contains a gel-like substance that contains enzymes.
7
Q
What is the function of the cytoplasm?
A
Site of cellular reactions.
8
Q
What is the function of the cell membrane?
A
Holds the cell together and controls what goes in and out.
9
Q
What is the function of the mitochondria?
A
Site where most reactions of respiration take place.
10
Q
What is the function of the ribosomes?
A
Joins amino acids in a specific order during translation.
11
Q
Which organelles are found in plant cells only? (3)
A
- Large, permanent vacuole
- Cell wall
- Chloroplasts
12
Q
What is the cell wall made of?
A
Cellulose.
13
Q
What is the function of the cell wall?
A
- Provides strength
- Prevents the cell bursting when water enters by osmosis
14
Q
What does the permanent vacuole contain?
A
It contains a cell sap, which is a weak solution of sugars and salts.
15
Q
What is the function of the permanent vacuole?
A
To maintain the internal pressure to support the cell.
16
Q
What is the function of the chloroplasts?
A
Site of photosynthesis.
17
Q
When looking at a cell using a light microscope, why do chloroplasts appear green?
A
Contain chlorophyll, a green pigment.
18
Q
List the organelles found in prokaryotic cells (6)
A
- Chromosomal DNA
- Plasmid DNA
- Cell wall
- Cell membrane
- Ribosomes
- Flagella
19
Q
How is genetic information stored in a prokaryotic cell?
A
Found free within the cytoplasm as:
- Chromosomal DNA, which is a single large loop of circular DNA
- Plasmid DNA, which is small loops of extra DNA
20
Q
What are plasmids?
A
- Small, circular loops of DNA found free in the cytoplasm and separate from the chromosomal DNA
- Carry genes that provide genetic advantages, e.g., drug resistance, which can be passed between bacteria
21
Q
What is a flagellum?
A
- A long, hair-like structure that rotates to make the bacteria move
- It is used to move away from harmful substances like toxins and towards beneficial things like nutrients or oxygen
22
Q
What is a haploid cell?
A
A cell that contains a single copy (half) of each chromosome, e.g., 23 chromosomes in humans.
23
Q
What is a diploid cell?
A
A cell that contains two copies (full) of each chromosome, e.g., 46 chromosomes in humans
24
Q
What are gametes?
A
- Reproductive cells (e.g., egg and sperm cells)
- They are haploid cells
25
Describe sexual reproduction in terms of chromosome number.
Two haploid gametes fuse resulting embryo, which has two chromosomes for each gene and two copies of each allele and is a diploid cell.
26
Describe how egg cells are adapted to their function.
- Haploid nucleus
- Cytoplasm contains nutrients for the developing and feeding embryo
- Cell membrane hardens after fertilisation, preventing the entry of other sperm and ensuring the zygote is diploid with the right amount of DNA
27
Describe how sperm cells are adapted to their function.
- Haploid nucleas
- Long tail enables movement
- Mitochondria in the middle section provides energy for tail movement
- Acrosome at the front of the head contains enzymes that digest through the egg cell membrane
28
Where are ciliated epithelial cells found?
Found lining the surface of structures such as the uterus.
29
Describe the function of ciliated epithelial cells lining the airways.
Move substances in one direction, along the surface of the tissue.
30
What is magnification?
The number of times bigger an image appears compared to the size of the specimen.
31
How can the total magnification of an image be calculated from lens powers?
total mag = eyepiece × objective
32
How can the magnification of an image be calculated?
magnification = image / real
33
What is resolution?
The smallest distance between two objects that can be distinguished.
34
How does a light microscope work?
Passes a beam of light through a specimen that travels through the eyepiece lens, allowing the specimen to be observed.
35
What are the advantages of light microscopes? (4)
- Not expensive
- Easy to use
- Portable
- Observe both dead and living specimens
36
What is the disadvantage of light microscopes?
- Limited resolution
37
How does an electron microscope work?
It uses a beam of electrons that are focused on using magnets. The electrons hit a fluorescent screen, which emits visible light, producing an image.
38
What is the advantage of electron microscopes?
- Greater magnification and resolution
39
Why do electron microscopes have a greater magnification and resolution?
They use a beam of electrons, which has a shorter wavelength than photons of light.
40
How have electron microscopes enabled scientists to develop their understanding of cells?
- Allow small sub-cellular structures (e.g., mitochondria, chloroplasts) to be observed in detail
- Enable scientists to develop more accurate explanations about how cell structure relates to function
41
What are the disadvantages of electron microscopes? (4)
- Expensive
- Large so less portable
- Require training to use
- Only dead specimens can be observed
42
What are enzymes?
Biological catalysts that increase the rate of a chemical reaction in the body.
43
What is an advantage of enzymes in the body?
They enable cellular reactions to take place at lower temperatures and only speed up useful reactions.
44
What is the active site of an enzyme?
The region of an enzyme to which a substrate molecule binds to so the reaction takes place.
45
Why are enzymes described as having a ‘high specificity’ for their substrate?
Only substrates with a specific, complementary shape can fit into an enzyme’s active site.
46
Describe the ‘lock and key’ model.
1. Substrate collides and binds with the active site of an enzyme
2. Substrate converted to products
3. Products released from the active site, which is now free to bind to another substrate
47
What factors affect the rate of an enzyme-controlled reaction?
- Temperature
- pH
- Substrate concentration
48
Explain how increasing temperature affects the rate of reaction.
- A higher temperature increases the rate at first
- But if it gets too hot, some of the bonds holding the enzyme together break.
- This changes the shape of the enzyme's active site, so the substrate won't fit, now the enzyme is said to be denatured.
- The optimum temperature is 37°C
49
Explain how increasing pH affects the rate of reaction.
- If the pH is too high or too low from the optimum, the pH interferes with the bonds holding the enzyme together
- This changes the shape of the active site and denatures the enzyme.
50
Explain how increasing substrate concentration affects the rate reaction.
- The higher the substrate concentration, the faster the reaction
- This is because it's more likely that the enzyme will find a substrate molecule to react with
- However, after a point, there will be so many substrate-molecules that all the active sites will be full
- So adding more makes no difference
51
How can you calculate rate of reaction?
rate = 1 / time
52
What are the units for rate?
s⁻¹ (per second)
53
How are large organic molecules broken down into smaller, simpler molecules in the body?
- Digestive enzymes break them into smaller, soluble molecules.
- They can now easily pass through the walls of the digestive system
- So they can be absorbed into the bloodstream
- To be used by cells to grow and other life processes
54
Give an example of the breakdown of large molecules into smaller molecules in plants.
Starch is broken down by enzymes into smaller molecules (sugars) for respiration.
55
Why are small molecules synthesised into larger organic molecules in the body?
For storage or to build structures.
56
How can the amount of energy contained in food be measured?
Using a calorimetry.
57
What is calorimetry?
A method of measuring heat transfer during a chemical reaction.
58
How can the amount of energy in the food sample be calculated?
Energy in food = Mass of water × Temp change × 4.2
59
How can energy per gram of food be calculated?
Energy per gram = Energy in food / Mass of food
60
What is diffusion?
The net movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient.
61
What molecules can diffuse through a cell membrane?
Small molecules like glucose, amino acids, water, and oxygen. Bigger molecules like starch and proteins can't.
62
What factors affect the rate of diffusion? (3)
- Temperature
- Concentration gradient
- Surface area of cell membrane
63
Define osmosis.
The net movement of water molecules from an area of high water concentration to an area of low water concentration through a partially permeable membrane.
64
What is active transport?
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.
65
What do enzymes called carbohydrases do?
They convert carbohydrates (starch) into simple sugars (maltose and other sugars, e.g, dextrins).
An example of a carbohydrase is amylase.
66
What do enzymes called proteases do?
They convert proteins into amino acids.
67
What do enzymes called lipase do?
They convert lipids into glycerol and fatty acids.
68
What happens to a solutions pH when lipids are broken down?
When lipids are broken down, the fatty acids will lower the pH.
69
What does synthesise mean?
To make something.
Eg carbohydrases sythesise carbohydrates into simple sugars.
70
What is a catalyst?
A catalyst is a substance that increases the speed of a reaction without being changed or used up in the reaction.
71
What are lipids?
Fats and oils.
72
How are carbohydrates synthesised?
By joining together simple sugars.
73
How is glycogen synthesised?
Using an enzyme called glycogen synthase, which joins together lots of chains of glucose molecules.
74
How are proteins synthesised?
By joining amino acids together.
(Can speed up using enzymes)
75
How are lipids synthesised?
By using enzymes with fatty acids and glycerol.
76
How does active transport work in the digestive system?
- When there's a higher concentration of nutrients in the gut than in the blood, the nutrients diffuse naturally.
- However, when the concentration is reversed, active transport allows nutrients to be taken away from the blood, despite the fact it is against the concentration gradient
- This stops us from starving
