Lecture #12 - Unique Plant structures Flashcards
What are the three main differences between plant and animal cells?
- Cell wall
- Chloroplast
- Central vacuole
(this is a TEM image)
The plant cell = ____ + _____
Comment on the plasma membrane and the plasmodesmata
Cell wall + the protoplast (everything but the cell wall)
The plasma membrane is similar to animals but cell wall around = structure + shape. They also have plasmodesmata to communicate because cell wall is hard to communicate through
Vacuoles:
- What is it?
- How many vacuoles?
- What’s ther origin?
- What are their functions?
- A vacuole is an organelle surrounded by a single membrane which is called a tonoplast (phospholipid bilayer)
- Young plant cell has many small vacuoles but they merge into one big vacuole
- Vacuoles are produced by the golgi associated endoplasmic reticulum (bud off and form big structures)
- Functions:
- Storage
- Breakdown of macromolecules
- Regulation of cell turgor (specific to plants - cell wall). Turgoe is the rigidity of plant cells - involved in structure of plant
Vacuum - named after this because they initially it was just empty space
What are the two categories of what vacoles store?
- Primary metabolites (growth-associated)
- Secondary metabolites (not growth-associated) - to make the most of their environment. There are two main types; molecules for defence and molecules for signalling.
What are the primary metabolites in vacuoles? There are 8 of ‘em
- Inorganic ions
- Organic acids
- Sugars
(2 + 3 are like products of photosynthesis and used for primary metabolites)
- Oligosaccharides
- Amino acids
- Proteins
- Lipids (not all cells photosynthesise so some have lipids stored in vacuoles)
What’s the tonoplast?
It’s a selective membrane that controls the movement of substances into and out of the vacuole (has proteins in the membrane eg transport proteins)
Some molecules such as water can pass in and out freely
The two main types of secondary metabolites include:
- Molecules for DEFENCE - molecules to stop other animals eating ‘em. These guys make carbs and shit that’s real appealing to us so like, they need to have some way of protecting themselves eg maybe storing toxic compounds
- Molecules for SIGNALLING - plants can’t move so have to signal eg to pollinators etc
What are three examples of storage for defence in vacuoles?
- RUBBER TREE - specialised cells have many small latex containing vacuoles. Some insects stick their mouth into cells and pull out all the nutrients so plants have some cells with latex which is ew
- RAPHIDES - needle shaped crystals of calcium oxalate which can damage digestive tract so some special plant cells have vacuoles containing them.
- ALKALOIDS - group of nitrogen-containing bases and have a variety of toxic effects on animals (sequestered in sufficient concentrations to be effective). Found in young plant tissue because thas vulnerable af. It has an effect on our nervous system. Eg cocaine, morphine etc
Molecules for signalling - explain
Basically like pigments to attract animals for ripe fruit or other chemicals to give petals colour/attract insects e.g. anthocyanins - purple dots are concentrated areas of anth and light purple is vacuole.
Secondary metabolites can now be produced in ___ ___
Cell cultures - uses biotechnology. Place plant cells in solution and the secondary metabolites just leak out. Use cell cultures because more efficient than extracting from harvedt material and ecologically less damaging
Vacuoles: degradation
- What is it?
- What are vacuoles similar to?
Breakdown of organelles and macromolecues
Digestion of cytoplasmic constituents
Vacuoles are acidic and contain hydrolytic enzymes similar to lysosomal enzymes of animal cells (pre much equivalent organelles but vacuoles have more functions)
Note: since heaps of sunlight bc plant cells - get damage to proteins and other ish so vacuoles also need to be replaced. It’s an unavoidable part of being photosynthesis.
Vacuoles: turgor
- Vacuoles play a role in the regulation of cell turgor because?
- High concentrations of solutes in the vacuoles have a _____ ______ ______, resulting in water up take. The plant cell wall enables water up take without ______. Plant cells build up a large internal pressure, turgor pressure.
- ____ _ ____ from vacuoles decreases turgor pressure and results in ____
- Because they contain water and make up such a large por&on of the protoplast, vacuoles can play a role in the regulation of cell turgor.
- High concentrations of solutes in the vacuoles have a NEGATIVE OSMOTIC POTENTIAL, resulting in water up take (water moves from higher to lower osmotic potential). The plant cell wall enables water up take without BURSTING (plant cell wall limites the amount of water - only until the protoplast pushing against cell wall). Plant cells build up a large internal pressure, turgor pressure.
- LOSS OF WATER from vacuoles decreases turgor pressure and results in WILTING (protecting plant when no water more important than photosynthesising so survival mode turned on i.e. can’t get damaged from sunlight)
If plants deprived of water and given water again, they can come back up but we cant.
What’s a plastid?
Plastids are double membrane bound organelles found inside plants and some algae, which are primarily responsible for activities related to making and storing food. Many plastids are photosynthetic but some are not.
Describe the origin of plastids
- Non-photosynthetic eukaryotes inititally
- Engulfing of photsynthetic prokaryotes and they were maintained in cell (formed a stable relationship)
- Chloroplast becomes a SEMI-AUTONOMOUS organelle (can’t survive without host plant - independence but not fully.)
- Turns into a photosynthetic eukaryote.
Chloroplast DNA
- Chloroplasts contain…….. and the DNA (ctDNA) is _____
- Although ctDNA contains info for the formation of many _____ ______, some proteins found in the chloroplast are encoded by genes present in the ……….
Chloroplast DNA
- Chloroplasts contain genetic info and the DNA (ctDNA) is CIRCULAR
- Although ctDNA contains info for the formation of many CHLOROPLAST PROTEINS, some proteins found in the chloroplast are encoded by genes present in the NUCLEUS of the cell
Appreciate this diagram
Look at this diagram and tell me ish about it
- Convert light energy into chemical in the Light Reactions
- Calvin cycle happens in stroma (like cytosol but of chloro) and makign sugars here - doesnt need light, just ATP from light reactions stage
Tell me about the structure of chloroplasts and what reactions take place where
- The chloroplast has three membranes: inner, outer, and thylakoid.
- It has three compartments: stroma, thylakoid space, and inter-membrane space.
- These compartments and the membranes that separate them serve to isolate different aspects of photosynthesis.
- Dark reactions take place in the stroma.
- Light reactions take place on the thylakoid membranes.
Chromoplasts - what do they do etc
- Attract animals – give colour to many flowers and fruits
- Increased carotenoids (pigments) and decreased thylakoid membranes (signal ripeness of fruit) aka ↓ thyla so ↓ green and ↑ other colours
- As fruit ripens, chloroplasts are converted to these
Leucoplasts - what can they store?
- Leucoplasts can store:
- pigments,
- protein,
- lipids,
- or starch
What are proplastids?
All plastids are derived from proplastids, which are present in the meristematic regions of the plant. Proplastids and young chloroplasts commonly divide by binary fission, but more mature chloroplasts also have this capacity.
