Topic 4.2 Flashcards
Cell wall: function and description
Description:
. Rígid structure that surround plant cells
. Mainly made of carbohydrate cellulose
Function:
. Supports plant cells
Middle lamella: function and description
Description:
. Outermost layer of cell
Function:
. Acts as an adhesive, sticking adjacent plant cells together
. It gives plant stability
Plasmodesmata: function and description
Description:
. Channels in cell walls that link adjacent walls together
Function: . Allows transport of substances and communication between cells
Pits: function and description
Description:
. Regions of cell wall where wall is very thin
. Arranged in pairs -> pit in one cell is lined up with pit in adjacent cell
Function:
. Allows transport of substances between cells
Chloroplasts: function and description
Description:
. Small flattened structure
. Surrounded by double membrane
. Membranes on inside called thylakoid membranes, stacked up to form grana which are linked together by lamellae (thin, flat pieces of thylakoid membrane
Function:
. Site of protein synthesis-> some part of photosynthesis takes place in the grana and other parts in the stoma
Amyloplast: function and description
Description:
. Small organelle enclosed by a membrane
. Contain starch granules
Function:
. Storage of starch grains
. Convert starch back to glucose for release when plant requires it
Vacuole and tonoplast: function and description
Description:
. Vacuole is compartment surrounded by a membrane called tonoplast
. Vacuole contains cell sap (made up of water, enzymes, minerals and waste products)
Function:
. Keep cells turgid + stops plants from wilting
. Involved in breakdown and isolation of unwanted chemicals in the cell
. Tonoplast controls what enters and leaves the vacuole
Parts of plant stem -> Xylem vessels: function
Transport water and mineral ions up the plant and provide support
Parts of plant stem -> Xylem vessels: adaptations
. Very long, tube-like structures formed from dead cells joined end to end forming bundles
. Cells are no longer than they’re wide, they have a hollow lumen, contain non cytoplasm and have no end walls forming continuous tube
. Walls are thickened with lignin which provide strength
. Pits in walls where there no lignin allow water and mineral ions to move in and out of vessels
Parts of plant stem -> Sclerenchyma fibres: function
Provide support
Parts of plant stems -> Sclerenchyma fibres: adaptations
. Bundles of dead cells that run vertically up the stem
. Cells are longer than they’re wide, have a hollow lumen, have end walls + have more cellulose than other plant cells
Parts of plant stem -> phloem: function
Transport organic solutes from sources to sinks
-> known as translocation
Parts of plant stem -> phloem: adaptations
. Cells arranged in tubes
. Contain different types of cells including sieve tube elements and companion cells
Parts of plant stem -> phloem: adaptations - sieve tube elements
. Living cells that are joined end to end to form sieve tubes, where the ‘sieve’ parts are end walls that have lots of holes allowing solutes to pass through
. Have no nucleus, few organelles and a very thin layer of cytoplasm which is connected between adjacent cells through holes in sieve plates
Parts of plant stem -> phloem: adaptations - companion cells
. There’s one for every sieve tube element
. Carry out living functions for both themselves and their correspond sieve cell
Vascular bundles
Xylem vessels are grouped together with phloem tissue to form vascular bundles and sclerenchyma fibres are usually associated with the vascular bundles
Starch
Starch is the main energy store in plants
-> cells get energy from glucose and plants store excess glucose as starch
. Starch is a mixture of two polysaccharides and alpha-glucose
. Insoluble in water so it doesn’t cause water to enter cells by osmosis making it good for storage
Starch: amylose
. Long, unbranched chain of a-glucose angles of glycosidic bonds give it a coiled structure making it compact and very good for storage
Starch: amylopectin
Long, branched chain of a-glucose where its side branches allow enzymes that break down the molecule to get the glycosidic bonds easily so glucose can be released quickly
Cellulose
. The major component of cell wall in plants
. Cellulose is made of long, unbranched chains of B-glucose joined by 1-4 glycosidic bonds which are straight making cellulose chains straight
. Between 50 and 80 cellulose chains are linked together by a large number of hydrogen bonds to form strong threads called microfibrils which mean that cellulose provides structural support for cells
Plant fibres
Plant fibres are made up of long tubes of plant cells
-> they’re very strong due to:
. Arrangement of cellulose microfibrils in the cell wall -> cell wall contains strong cellulose microfibrils in a net-like arrangement that give plant fibres strength
. Secondary thickening of cell walls -> secondary cell wall is formed between normal cell wall and cell membrane, and its thicker than the normal cell wall so it has more lignin making plant fibres stronger
Sustainable practices
To make products sustainability you have to use renewable resources
-> renewable resources are resources that can be used indefinitely without running out
Sustainable practices: plant fibres and starch
Making products from plant fibres and starch is more sustainable than making them from oil
. Less fossil fuel is used up and crops can be regrown to maintain supply for future generation
. Plant fibres are biodegradable meaning they can be broken down by microbes unlike most oil-based products
. Plants are easier to grow and process to extract the fibres than extracting and processing oil so its cheaper
Plant minerals
Plants need water and inorganic ions (minerals) for a number of different functions
-> these are absorbed through the roots and travel through the plant in the xylem
Water
Needed for photosynthesis, to transport minerals, to maintain structural rigidity and to regulate temperature
Magnesium ions
Needed for production of chlorophyll
Nitrate ions
Needed for production of DNA, proteins, chlorophyll, fruit and seeds + required for plant growth
Calcium ions
Important components of plant cell walls and required for plant growth
Drugs from plants and drug testing: bacterial growth
To test anti microbial properties, conditions need to be right for bacteria to survive and reproduce:
. Source of nutrients to respire and grow
. Supply of oxygen to respire aerobically
. Temperature and pH of environment controlled for optimum enzyme activity
Historic drug testing
Drugs used to be tested using trial and error
-> example: William Witherings digitalis soup
. Withering discovered that an extract of foxgloves could be used to treat dropsy as it contained the drug digitalis, and so he made a chance observation by testing different versions of the traditional remedy mixed with foxgloves on patients
. Too much digitalis poisoned his patients
. Too little digitalis had no effect
Modern drug testing
Modern drug testing consists of a pre-clinical trial where computers are used to model the potential effects, and tests are carried out on human tissues in lab and then on live animal, before clinical trials are carried out on humans
-> during clinical trials new drugs undergo 3 phases
Modern drug testing: phase 1
Involves testing new drug on small group of healthy individuals to find out safe dosage, if there’s any side effects and how the body responds to drug
Modern drug testing: phase 2
Drug is tested on a larger group of patients to see how well the drug actually works
Modern drug testing: phase 3
Drug is compared to existing treatments by testing drug on hundreds or even thousands of patients which are split into 2 groups where one receives the new treatment and the other group receives the existing treatment
Placebos
In phase 2 of clinical trials, patients are split into two groups where one group is given the new drug and the other is given a placebo which is inactive substance that looks exactly like the drug but doesn’t do anything
-> this prevents the placebo effect allowing researchers to see if drug actually works
Double blind study design
In phase 2 and 3 clinical trials are usually double blind -> meaning neither the patients nor the doctors know who’s been given the new drug and who’s been given the placebo or drug
-> this reduces bias in the results as attitudes of patients and doctors wont affect the results
