Flashcards
Biology Topic 4.4
Cards in this deck (30)
- 1Why do some trees grow so tall with massive roots?So they can absorb more light than their competitors and absorb maximum nutrients from the ground.
- 2What are the three principles plants use to build tall structures?1. They produce cell walls out f cellulose.
2. They build columns and tubes from specialised cells.
3. They stiffen some of these special cells with lignin. - 3What are the four organelles in a plant cell that are not present in an animal cell?Vacuole (and the tonoplast)
Chloroplasts
Amyloplasts (these contain starch grains)
Cell wall - 4What are pits, plasmodesma and parenchyma?Pits are places where the cell wall is thinner.
Plasmodesma are channels between cells.
Parenchyma is a tissue which fills spaces between more specialised tissues. - 5What are the two types of glucose and how are they different?
- 6Describe the structure of cellulose.1. β-glucose forms 1,4 glycosidic bonds between adjacent molecules.
2. For this every other molecule must be inverted.
3. The cellulose molecules remain as straight chains.
4. Hydrogen bonds form between the OH groups in neighbouring chains forming bundles called microfibrils. - 7How is a cell wall built?Layers of microfibrils are laid down at angles to each other. They are held together by a natural glue composed of pectins and hemicelluloses.
- 8What is the region between cell walls called and what is it made of?Middle lamella
It's mainly made of pectins - 9What are the three specialised cells found in a vascular bundle and what are their functions?1. Xylem vessels - carry water and minerals up the plant and provide support.
2. Phloem sieve tubes - transport the products of photosynthesis u and down the plant.
3. Sclerenchyma - support the plant. - 10What are the stages in forming xylem vessels?1. Cells arrange themselves in a column
2. Lignin impregnates the cell wall, waterproofing the cell.
3. The tonoplast breaks down.
4. There is autolysis of the cell contents (the organelles, cytoplasm and surface membrane are broken down by enzymes).
5. You're left with a tube of dead cells. - 11Sclerenchyma fibres are also lignified but not all plants are as strong as each other. What do smaller plants rely on instead of lignification?Having turgid cells.
- 12What happens in a leaf to allow water to move though a plant?1. Water vapour diffuses out of the stomata due to the concentration gradient
2. Water evaporates from the cells lining the substomatal cavity
3. Water is replaced by means of capillary action within cell walls
4. Water is drawn out of the xylem vessels
5. A continuous stream of water is drawn up though the xylem by mass flow. - 13What is capillary action and how does it occur in a plant?When a tube is small enough water will continuously move up the tube due to cohesion (intermollecular forces between water molecules) and adhesion (hydrogen bonds between water molecules and the cell wall).
The minute channels between cellulose microfibrils in the cell wall act as capillaries. - 14Xylem vessels transport some inorganic ions as well as water. What ions does it transport and how are these used by the plant.Nitrate ions - to make amino acids
Magnesium ions - to make chlorophyll
Calcium ions - used for growth, structure and permeability of the cell surface membrane.
(these dissolve in the water and are transported by a mass flow system though the xylem vessels) - 15Describe the structure of phloem.1. The cells form a long, narrow column
2. The cells have few organelles because they disintegrate during development
3. The cells are still alive aided by companion cells
4. Most of the cell is liquid filled space called the lumen
5. Each cell is called a sieve tube element and they're separated by sieve plates (perforated walls which allow material to pass though to adjacent cells) - 16What molecules are transported thought phloem vessels and by what process are they transported?Sugars and amino acids are transported by translocation in either direction though the plant.
- 17The products of photosynthesis (solutes) are actively transported into and out of the phloem. Describe the journey.1. The solutes are created at the source (e.g a leaf) and pumped into a transfer cell.
2. They're then pumped into the phloem and water joins them from the xylem moving by osmosis.
3. Pressure builds allowing the material to move though the phloem by mass flow.
4. The solutes are pumped into another transfer cell and the water moves back into the xylem by osmosis again.
5. The solutes are pumped into the sink (e.g. fruit) where they may be used or stored. - 18How are transfer cells adapted to their function?1. Infolds to increase surface area
2. Many mitochondria to provide energy for active transport.
3. Many plasmodesmata so material can move straight between cytoplasms and not undergo active transport. - 19Why are plant fibres useful in manufacturing? How are fibres extracted from plants?They're strong, flexible, long and thin.
By a process called retting. - 20By what process do bacteria divide? What is their growth known as? What is generation time?They divide by binary fission - The circular DNA replicates and new cell content is synthesised before a new cell wall forms and the cell divides into two.
It's known as exponential grown.
The time for bacteria to go though one cycle of binary fission. - 21What are the ideal conditions bacteria grow under?Sufficient nutrients
optimum temperature (often 37°C)
Optimum pH
No build up of toxic waste products
Sufficient oxygen supply (only if the bacteria relies on aerobic respiration) - 22What are the phases of bacterial growth?Lag phase - time the bacteria adjust to the new conditions.
Log phase - time where the bacteria is growing at their optimum rate for the conditions.
Stationary phase - time when growth is limited by conditions (balance between growth rate and death rate)
Death phase - death rate is greater than growth rate. - 23How can plants be used as antibacterials? Give an example.They store toxic compounds on the surfaces of their leaves which can be lethal to microorganisms. This makes plant extracts a popular base in many of today's medicines.
e.g. Garlic contains allicin which is harmful to campylobacter (it interferes with lipid synthesis and RNA production) - 24What is the modern procedure for drug testing?1. Pre-clinical trials - tests on cells and tissue cultures to test the effectiveness of the drug, it must be approved by the MHRA
2. Clinical trials - phase 1 - tests on healthy volunteers to see if the drug is absorbed, metabolised, distributed and excreted.
3. Clinical trials - phase 2 - Drug is tested on a group of ill people to test the effectiveness.
4. Clinical trials - phase 3 - double blind, randomised, controlled trials are done looking a statistically significant improvement.
5. After licencing - data is continued to be collected for safety. - 25What are the two types of plant?Monocotyledons - plants with leaves which are the same on both sides (e.g. grasses). These are more commonly called endospermic.
Dicotyledons - plants with two sided leaves. - 26What are the functions of a seed?1. Protect the embryo
2. Aid dispersal
3. Provide nutrition for the new plant - 27What three places can seeds store food?Monocotyledons store food in the endosperm.
Dicotyledons absorb nutrients from the endosperm and store food in the leaves which swell to fill the seed.
Plants with no apparent cotyledons (leaves) store food in the developing stalk. - 28How does a seed germinate?When conditions are right it will absorb water though a small pore in the seed coat. This triggers metabolic changes in the seed. Enzymes are produced which mobilise stored food reserves. (Maltase, amylase, proteases and lipases)
- 29What are two common uses for seeds?Starch is easy to extract from plants because it's in insoluble granules. When heated with water the granules gelatinise. Therefore, it can be used as super absorbers used in nappies.
Vegetable oils extracted from seeds are often used as fuels nowadays because they cause much less pollution. - 30What are three reasons why oil-based plastics are not sustainable?1. Burning fossil fuels contributes to a net increase in atmospheric CO2 levels which contributes to climate change.
2. Oil reserves will eventually run out.
3. Plastics generate non-biodegradable waste causing massive waste disposal problems.
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- Edexcel new AS level Biology topic 4.4 Making use of biodiversity
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- Amy Tourle
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