Unit 1 Flashcards
(87 cards)
1
Q
What do cells contain?
A
Cells contain many cell organelles which perform different functions to keep the cell alive.
2
Q
What is an organism?
A
Living thing.
3
Q
4 main types of cell?
A
- animal
- plant
- fungal
- bacterial
4
Q
What cell organelles does the animal cell contain?
A
- nucleus
- cytoplasm
- cell membrane
- mitochondria
- ribisome
5
Q
What cell organelles does a plant cell contain?
A
Nucleus Cytoplasm Cell membrane Mitochondria Ribosomes
Cell wall
Vacuole
Chloroplasts
6
Q
Fungal cell organelles?
A
Nucleus Mitochondria Cytoplasm Ribosomes Cell membrane Cell wall - (composed of chitin) Vacuole
7
Q
Bacterial cell organelles?
A
Plasmids Cell membrane Cell wall Cytoplasm Ribosomes
8
Q
What is the fungal and bacterial cell walls composed of?
A
Bacterial and fungal cells are not made of cellulose.
Fungal - chitin
9
Q
What is the plant cell wall composed of?
A
Cellulose
10
Q
What is the cell membrane composed of?
A
- phospholipids
- protein
Proteins are involved in the transport of substances across the cell membrane.
11
Q
What is involved in the transport of substances across the cell membrane?
A
- proteins
12
Q
What is the cell membrane described as?
A
Selectively permeable
This means it will allow some molecules to pass through but not other.
13
Q
Explain why the cell membrane is selectively permeable.
A
The cell membrane is described as selectively permeable.
This means it will ALLOW some molecules to pass through but not others.
A substance must be small and soluble to be able to pass through the cell membrane.
14
Q
Diffusion
A
Diffusion is the movement of molecules from a HIGH concentration to a LOW concentration DOWN a concentration gradient.
15
Q
When does a concentration gradient exist?
A
A concentration gradient exists when there is a difference in concentration between two areas.
16
Q
What type of transport is diffusion?
A
Passive - doesn’t require energy
17
Q
Why is diffusion important? (Animal cells)
A
Diffusion is important as it is the process by which useful molecules enter the body cells and waste products are removed.
18
Q
What useful substances enter the cell by diffusion?
A
Glucose
Aminu acids
Oxygen
They all move into the cell because the concentration outside the cell is higher than inside. These molecules enter the cell by diffusion.
19
Q
What waste products leave the cell by diffusion?
A
Carbon dioxide
Urea
They leave the cell because the concentration is higher inside the cell than outside the cell. They leave the cell by diffusion.
20
Q
Definition of osmosis?
A
Osmosis is the movement of water molecules from a high water concentration to a lower water concentration down a concentration gradient through a selectively permeable membrane.
Specific term for DIFFUSION OF WATER.
21
Q
What type of process is osmosis?
A
Passive as it doesn’t require energy.
22
Q
Active transport
A
Active transport moves molecules and ions from an area of low concentration to an area of high concentration, against the concentration gradient.
23
Q
Active transport - Transport proteins in the cell membrane
A
Transport proteins in the cell membrane transport ions and molecules across the cell membrane in active transport.
24
Q
What type of process is active transport?
A
Active - required energy
The energy is in the form of ATP and is obtained through the process of aerobic respiration which takes place in the mitochondria.
25
Where is DNA stored?
Inside the nucleus of the cell are structures called chromosomes.
Chromosomes are made of DNA.
DNA is made of 2 strands twisted together, the shape of DNA is described as a double helix.
26
Why do we need DNA?
DNA carries the genetic information for making PROTEINS.
A section of DNA is a gene.
Genes carry out the instructions to make PROTEINS.
Proteins are important substances in living things that carry out a variety of functions.
Genes are passed from parent to Offspring.
Half of our genes come from our mother and half of our genes come from our father.
27
Due to everyone's DNA being unique, how can the police use it?
To identify criminals.
28
DNA base pairs
There are 4 DNA bases:
Cytosine
Guanine
Adenine
Thymine
These make up the genetic code.
C+G , A+T are complementary base pairs.
29
What are the building blocks of proteins?
Amino acids.
30
1. Messenger RNA (mRNA)
| 2. Role of the ribosome
1) mRNA carries the complementary copy of the DNA base sequence of a specific Gene in the nucleus out to a ribosome.
2) Ribosomes attached to the mRNA. Instructions carried by the mRNA are used to assemble amino acids in the correct order to make a specific protein.
(Instructions for making proteins are stored in DNA in the nucleus but proteins are synthesised is the ribosome).
31
What are the functions of proteins?
The variety of protein shapes and functions arises from the sequence of amino acids.
Proteins have a variety of important functions in the body including:
Functions:
- structural
- enzymes
- hormones
- antibodies
- receptors
32
What are enzymes?
Enzymes are biological catalysts - speed up chemical/ cellular reactions, unchanged after reaction, can be used many times.
Enzymes are made by all living cells.
Enzymes are made of proteins.
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Enzyme action.
A substance an enzyme acts upon as a called its substrate.
Substance made at the end of reaction are the products.
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How do enzymes work?
The shape of an enzyme matches exactly the shape of its substrate.
The part of the enzyme that fits its substrate is called the active site.
The shape of the enzymes active site is complementary to substrate shape. Therefore:
- enzyme can only act on one substrate.
- specific to one substrate.
35
What is a DEGRADATION reaction.
Degradation reactions involves large molecules being broken down into smaller molecules.
Example:
Hydrogen peroxide (substrate) is broken down by catalase (enzyme) to produce oxygen and water (products).
Hydrogen peroxide >((catalase))> Oxygen + water
Substrate enzyme products
36
What is a SYNTHESIS reaction?
Synthesis reactions involve many small molecules joining together to make a large molecule.
Example:
Glucose-6-phosphate > ((catalase)) > Oxygen + water
37
Temperature and enzymes
At very low temperatures, enzymes are inactive but undamaged.
At low temperatures, enzyme and substrate molecules move slowly. They meet rarely, so enzyme activity remains low.
Warmer conditions cause enzyme and substrate molecules to move faster, meet more regularly, so increased rate of reaction.
Enzyme works best at it OPTIMUM TEMPERATURE.
(37°C) (this optimum temp is where the rate of reaction is the fastest.)
38
Enzymes at high temperatures.
If Temp increases above optimum temp, the shape of the enzymes active site changes.
This change affects the reaction rate, slowing it down, eventually the enzyme stops working.
At Very high temp, the shape of an enzymes active site is permanently damaged and will never bind to its substrate again.
The enzyme is denatured. The damage is irreversible.
39
What are all organisms composed of?
Cells
40
What is the basic unit of life?
Cells
41
Function of the nucleus
Controls cells activities/ stores genetic information (DNA)
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Function of the cytoplasm
Site of chemical reactions
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Function of the cell membrane
Controls the movement of substances into and out of the cell.
(It is described as selectively permeable)
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Function of the mitochondrian
Site of aerobic respiration
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Function of the ribosome
Site of protein synthesis
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Function of the cell wall
Supports and strengthens the cell.
Plant - mad eof cellulose
Fungal- chitin
Bacteria - not made of cellulose
47
Function of the vacuole
Contains cell sap.
48
Function of the chloroplasts
Site of photosynthesis (contains chlorophyll)
49
Function of plasmid
Small circular ring of DNA.
50
How are bacterial cells different from animal, plant and fungal cells?
Bacterial cells lack membrane bound organelles (such as a nucleus and a mitochondria).
Bacterial cells have a very different cell wall structure from plant and fungal cells.
51
Osmosis in animal cells - red blood cells
Red blood cells placed in a solution with the HIGHER water concentration compared to the contents (e.g. pure water) will gain water by osmosis, swell up and BURST.
This occurs because water moves from a higher water concentration OUTSIDE the cell to a lower concentration INSIDE the cell.
Red blood cells placed in a solution with a LOWER water concentration compared to their contents (e.g. concentrated solution of salt) will LOSE water by osmosis and SHRINK.
This occurs because water moves from a higher water concentration INSIDE the cell to a lower concentration OUTSIDE the cell.
52
Osmosis in plant cells
Plant cells in a solution with a HIGH water concentration compared to their contents (e.g. pure water) will GAIN water by osmosis and swell up until their cytoplasm and cell membrane are pushing against their cell wall. They are said to be TURGID.
This occurs because water moves from a higher water concentration outside the cell to a lower water concentration inside the cell. The cell wall prevents the plant cell from bursting.
Plant cells placed in a solution with a LOW water concentration compared to their contents (e.g. concentrated salt solution) will LOSE water by osmosis. Their cell membranes will peel away from their cell walls and they are said to be PLASMOLYSED.
This occurs because water moves from a higher water concentration inside the cell to a lower water concentration outside the cell.
53
Active transport example - Sodium/ Potassium pump
For nerve cells to function effectively, they must maintain low levels of sodium inside the cell and a high level of potassium outside the cell.
Via active transport, sodium ions are pumped out of the cell and potassium ions are pumped into the cell. Each type of ion is moving against its own concentration gradient.
54
Gene definition
A gene is a section of DNA that codes for ONE protein.
Genes carry the instructions to make proteins.
55
What is DNA?
DNA is a double stranded helix and carries the genetic information to make proteins.
A gene is a section of DNA that codes for ONE protein.
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What are Amino acids?
Amino acids are the subunits (building blocks) of protein and have to be in a specific sequence to ensure that the protein produced is the correct shape and fully functional.
Each group of 3 bases along a DNA strand represents a code word for one of the amino acids that make up proteins.
Different proteins contain different sequences of amino acids and therefore are coded for by a different base sequence.
57
What do the order of bases in a DNA molecule determine?
The order of bases in DNA determines the order of amino acids in a protein.
Each group of 3 bases along a DNA strand represents a code word for one of the amino acids that make up proteins.
Different proteins contain different sequences of amino acids and therefore are coded for by a different base sequence.
58
Enzyme uses
Biological detergents
Food and drink industry
Waste industry- water treatment
Genetic engineering- produce insulin and human growth hormone.
Production of biofuels
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Genetic engineering
Genetic engineering is the transfer of genetic information from one cell to another. (Artificially)
Genetic information can be transferred within the same species or a different species.
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Genetic engineering- bacteria
Bacteria cells contain circular plasmids composed of DNA.
During genetic engineering, human genes are transferred into a bacterial plasmid and then into a bacterial cell.
Bacteria are useful for genetic engineering because they can be grown quickly, easily and at a low cost.
61
Products of genetic engineering
- Insulin is produced for the treatment of type 1 diabetes.
| - human growth hormone is produced to prevent forms of dwarfism in children.
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Stages of genetic engineering
1) Identify the required gene from the source chromosome (in the source cell)
2) extract the required gene using an enzyme.
3) extract the plasmid from the bacterial cell.
4) insert the required gene into the plasmid and seal it using another enzyme.
5) insert the modified plasmid into the bacterial host cell.
6) the bacterial cell reproduces and produces the required protein.
63
What is the process of respiration
Respiration is the process used to release energy from food for use in cells.
Respiration occurs in all cell types.
Respiration is a series of enzyme controlled reactions.
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Types of respiration (2)
1. Respiration with oxygen (aerobic respiration)
2. Respiration without oxygen (fermentation)
(((Breathing occurs in the lungs. Respiration and breathing are related but they are NOT THE SAME PROCESS.)))
65
Adenosine triphosphate (ATP)
(Food stores energy in the form of chemical energy. Our bodies cannot use energy in this form and therefore must change it into a different form - ATP)
Our bodies use energy in the form of a molecule called ATP.
ATP is composed of adenosine and 3 inorganic phosphate molecules (Pi).
ATP is formed when Adenosine Diphosphate (ADP) and a Pi molecule are joined using energy from the respiration of glucose in our food.
66
Making and breaking ATP
(Diagram in jotter)
The energy from the breakdown of glucose is used to build up ATP from ADP and Pi.
When energy is needed, the reverse happens. ATP is broken down into ADP and Pi releasing energy. This energy is used for a number of cellular processes.
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Cellular processes that use energy examples
| From the breakdown of ATP
Muscle cell contraction
Transmission of nerve impulses
Cell division
Protein synthesis
(Some energy is also lost as heat)
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The role of ATP in the transfer of energy
The energy released from the breakdown of glucose during respiration is used to generate ATP from ADP and a Pi.
The chemical energy stored in ATP can be released by breaking the high energy bond between the final two Pi molecules.
When ATP breaks down, energy is released as well as Adenosine Diphosphate (ADP) and an inorganic phosphate (Pi).
The energy released when ATP is broken down can be used for a variety of cellular activities.
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Glycolysis
Glycolysis takes place in the cytoplasm of the cell.
It is the first stage in both aerobic respiration and fermentation.
Oxygen is therefore NOT required for glycolysis.
Glycolysis is a series of enzyme controlled reactions.
70
Glycolysis process
During glycolysis, glucose is broken down into 2 molecules of pyruvate.
This yields 2 molecules of ATP
(Diagram has better explaination in jotter)
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Aerobic respiration
Aerobic respiration is the breakdown of glucose in the presence of oxygen.
When oxygen is available, aerobic respiration takes place.
The process of aerobic respiration is the same in all cell types.
72
What do proteins do?
Proteins are important substances in living things that carry out a variety of functions.
73
Aerobic respiration stages
The first stage of aerobic respiration is glycolysis.
- glucose is broken down into 2 molecules of pyruvate
- this yields 2 molecules of ATP.
The second stage of aerobic respiration takes place in the mitochondria. Oxygen must be present for this stage to take place.
- pyruvate--> carbon dioxide + water
- this yields a large amount of ATP (36ATP)
- the products are CO2 and H2O
A total of 38 ATP is yielded.
2 from 1st stage, 36 from 2nd stage.
74
Fermentation (animal cells)
Fermentation in animal cells is the breakdown of glucose in the absence of oxygen.
Glucose --> Pyruvate Lactate
When oxygen is not available, Fermentation takes place.
The process of fermentation is different in different cell types.
Fermentation in animal cells takes place entirely in the CYTOPLASM and only yields 2 molecules of ATP. (Stage 1)
When oxygen becomes available to cells again, lactate is converted back into pyruvate. Aerobic respiration can then take place.
75
Fermentation (animal cells) stages
The first stage of fermentation in animal cells is glycolysis.
- glucose --> 2 pyruvate (2 ATP made/ yielded)
During the second stage of fermentation in animal cells, pyruvate is converted into lactate, also no ATP is made.
- glucose -2ATP made-> 2 pyruvate lactate
This reaction is reversible and lactate can be converted back into pyruvate when OXYGEN becomes available.
This reaction is irreversible because when oxygen becomes available to the cells again, lactate is converted back into pyruvate and Aerobic respiration can then take place.
(See diagram in jotter for better explanation)
76
Fermentation (plant and yeast/fungal cells)
Fermentation in plant and fungal cells is the breakdown of glucose in the absence of oxygen.
Fermentation in plant and yeast cells takes place entirely in the cytoplasm.
Both products (ethanol and carbon dioxide) are released from the cells so the reaction is irreversible even if oxygen becomes available.
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Fermentation (plant and fungal cells) stages
Glucose --> ethanol + carbon dioxide
The first stage is glycolysis. (2 ATP is yielded).
Glucose --> 2 pyruvate (--> products)
In the second stage of fermentation in plant and yeast (fungal) cells, pyruvate is broken down into ethanol and carbon dioxide.
Glucose --> 2 pyruvate --> ethanol + carbon dioxide
Both products are released from the cell. This means that if oxygen becomes available, this reaction is not available.
No ATP is yielded in the second stage.
(See diagram in jotter for better explanation)
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Factors affecting the rate of respiration
Respiration is a process controlled by enzymes.
Enzymes are affected by temperature and therefore the process of respiration is also affected by temperature.
Enzymes work at their maximum rate at their optimum temperature (body temp 37°C). The rate of respiration is therefore at its maximum at temps closest to body temps.
The rate of respiration also increases when more oxygen is available.
The higher the oxygen concentration, the greater the rate of respiration.
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Respiration definition
Respiration is the release of chemical energy stored in glucose by all cells through a series of enzyme controlled reactions.
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Active transport facts
Molecules move against a concentration gradient (from low to high)
Active - requires energy
Sodium/ potassium pump moves by active transport
Proteins in the cell membrane are responsible for moving molecules across in active transport.
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DNA structure
Double stranded helix held together by completely base pairs.
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Respiration- how is chemical energy in glucose released?
When glucose is broken down, bonds are broken and this releases energy.
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Passive transport
Passive transport involves the movement of molecules from a HIGH concentration to a LOW concentration DOWN a concentration gradient.
This process does NOT require energy.
Example - diffusion
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Catalyst
A catalyst will:
1) speed up a chemical reaction.
2) remain chemically unchanged after the reaction.
3) lower the activation energy needed for the reaction to take place.
All living cells will produce biological catalysts to speed up cellular reactions.
A biological catalyst is called an ENZYME.
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What are enzymes and other proteins affected by?
Temperature
| pH
86
How are enzymes used in genetic engineering?
Enzymes are used to remove that require gene from the source chromosomes and insert the gene into the plasmid.
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Aerobic Respiration - cytoplasm to mitochondria
Aerobic respiration starts in the cytoplasm and ends in the mitochondria.
Iy initially yields 2 molecules of ATP (stage 1) and further releases a lot of energy to produce a large number of ATP. (Stage 2 - 36 ATP)
Total - 38 ATP
As most energy is produced in the mitochondria, cells requiring a lot of energy will have a lot of mitochondria in comparison to other cells.
