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109 Cards in this Set
- Front
- Back
What is magnification? |
How much bigger an image looks compared with the original object. |
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What is resolution? |
The ability of an optical instrument to see or produce an image that shows detail clearly. |
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Light microscope |
Max mag 2000x Resolution 200nm |
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Light microscope pros and con |
Cheap Easy to use Potable Able to study live specimens Limited resolution |
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Laser scanning microscopes |
Max mag approx 2000x High resolution Displayed on a computer Best for looking at living cells Can focus on structures at different depths |
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Laser scanning microscopes cons |
Low resolution compared to electron microscope Not portable Expensive |
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Transmission election microscopes TEM |
Max mag approx 5,000,000x Very high resolution Best for looking at internal structure of objects |
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Transmission election microscopes TEM cons |
Can’t be used to look at living things Expensive Specimen has to be chemically fixed i.e. dehydrated |
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Scanning electron microscopes SEM |
Max mag approx 500 000x Best for looking at surfaces of objects Able to see objects in 3D |
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Scanning electron microscopes SEM cons |
Resolution often not as high as the transmission electron microscope Electrons do not pass through the specimen Expensive Great skill/training to use |
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Staining samples for use in light microscopy |
A lot of biological material inside a cell isn't coloured, so staining helps distinguish different features. Chemicals bind to other chemicals on, or in the specimen or specific structures. |
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Colouring in electron microscopy |
Starts off black ands white, colour is added by specialised computer programs afterwards |
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Equation for image size |
Image size= Actual size x Magnification |
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Structures of eukaryotic cells (14) |
Nucleus, Nucleolus , nuclear envelope, rough and smooth endoplasmic reticulum, Golgi apparatus, ribosomes, mitochondria, lysosomes, chloroplasts, plasma membrane, centrioles, undulipodia and cilia. |
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Function of Nucleus |
Stores all of the cells genetic material in the form of DNA, which contains the instructions for protein synthesis |
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Function of Nucleolus |
Makes ribosomes and RNA which passes into the cytoplasm and are used in protein synthesis. |
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Function of Nuclear envelope |
A double membrane with nuclear pores |
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Function of rough endoplasmic reticulum (RER) |
Transports proteins made by the attached ribosomes |
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Function of smooth endoplasmic reticulum (SER) |
Involved in making lipids |
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Function of Golgi apparatus |
Modifies proteins received from the RER and then packages them into vesicles so they can be transported
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Function of ribosomes |
Site of protein synthesis |
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Function of mitochondria |
Where ATP is made
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Function of Lysosomes
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Contain digestive enzymes that are used to break down material
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Function of Chloroplasts
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Site of photosynthesis in plant cells
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Function of Plasma membrane
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Controls the entry and exit of substances into and out of the cell. |
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Function of Centrioles |
Form the spindle which moves chromosomes during cell division |
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Function of undulipodia and cilia |
Move by ATP, e.g wave mucus along or make sperm swim |
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Making and secreting a protein |
1. A gene with instructions encoded is copied onto a piece of mRNA. 2. mRNA leaves nucleus through nuclear pore 3. mRNA attaches to a ribosome, reads instructions to assemble the protein 5. Molecules pinched off in vesicles and travel to to Golgi apparatus 6. Vesicle fuses with G.A, that processes and packages the molecules ready for release 7. Pinched off in vesicles from the G.A travel to the plasma membrane 8. Vesicle fuses with it P.M opens and releases molecule outside |
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Cytoskeleton providing- 1. mechanical strength 2. aiding transport with cells 3. enabling cell movement |
Due to protein fibres that keep the cells shape by giving an internal framework- microfilaments and microtubes |
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Functions of microfilaments and microtubes |
supporting organelles strengthening the cell and maintaining cell shape transporting materials within the cell (e.g. spindle during mitosis) cell movement (cilia and flagella) |
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Cells prokaryotic and eukaryotic both have |
plasma memebrane cytoplasm ribosomes for assembling amino acids into proteins DNA and RNA |
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Prokaryotic differences from eukaryotic |
Do not have a nucleus No membrane bound organelles Cell wall made of peptidoglycan not cellulose Smaller ribosomes Naked DNA as a loop floating free in cytoplasm Small loops of DNA called Plasmids |
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Prokaryotic cell division |
Binary fission- before they divide their DNA is copied so that each new cell receives the large loop of DNA and any smaller plasmids |
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Structure and ultrastructure of plant cells |
Cell wall thats outside the cell surface membrane and made of cellulose, its strong and is kept rigid by the pressure of the fluid inside the cell. The vacuole makes the cell stable and turgid which supports the whole cell. |
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Cell cycle- M phase |
Checkpoint chemical triggers condensation of chromatin Halfway through metaphase ensures the cell is ready to complete mitosis Cell growth stops Pro, meta, ana, tele and cytokineses occurs |
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Cell cycle- G0 phase |
Testing phase triggered early during G1 Cells may undergo apoptosis (programmed cell death) differentiation (changes type of cell) or senescence (makes cells divide) Some cells (neurons) remain in this phase for a very long time or indefinitely
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Cell cycle- G1 phase |
Checkpoint- ensures that the cell can enter S phase and begin DNA synthesis Transcription of genes to make RNA occurs Organelles duplicate |
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Cell cycle- S phase |
All DNA molecules are replicated Housekeeping genes duplicated Once cells enter its committed to finishing the cycle DNA replicated The phase is rapid as DNA pairs susceptible to mutagenic agents reducing mutations
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Cell cycle- Cytokine |
Any number of substances which are secreted by certain cells of the immune system and have an effect on the other cells |
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Pre Mitosis, interphase |
DNA prepares to divide, and replicates |
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Mitosis, prophase |
Chromosomes supercoil & become visible under a Light microscope The nuclear envelope breaks down Centriole divide in two and move to opposite ends of the cell to form a spindle |
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Mitosis, metaphase |
Chromosomes line up along the middle of the cell They attach to the spindle thread by their centromere |
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Mitosis, anaphase |
Replicated sister chromotids are separated yen the centromere splits Spindle fibres shorten, pulling the chromotids apart |
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Mitosis, telophase |
Separated sister chromotids reach the poles of the cells A new nuclear envelope forms around each set Spindle breaks down Chromosomes uncoil so they are no longer visible under a light microscope |
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Cytokinesis, post mitosis |
The whole cell splits down to two new cells, each one identical to each other and to the parent cell |
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Meiosis (first division) prophase |
Chromosomes condense then arrange themselves Ito homologous pairs and crossing over occurs Like mitosis- centrioles move opposite end of cell spindle fibres forms Nuclear envelope breaks down |
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Meiosis (first division) Metaphase
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Homologous pairs line up at centre of cell Attach to the spindle fibres by their centromeres |
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Meiosis (first division) Anaphase
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Spindle contracts, separating homologous pairs One chromosome goes to each end of the cell |
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Meiosis (first division) Telophase
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A nuclear envelope forms around each group of chromosomes |
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Meiosis cytokinesis |
Division of cytoplasm, occurs and two haploid daughter cells are produced |
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Meiosis (second division) |
At the end of meiosis 1= two haploid daughter cells The two daughter cells undergo that stages again, PMATC again |
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Meiosis (second division) anaphase |
Sister chromatids are separated, each new daughter cell inherits one chromatid from each chromosome. 4 genetically different- haploid daughter calls are made (the gamete) |
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Chromatids cross over in prophase 1 |
Homologous pairs of chromosomes pair up, bits of chromatids swap over. Chromatids still contain the same gene but have a different combination of alleles |
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How meiosis produces genetic variation |
Crossing over during P1shuffles alleles Independent assortment of chromosomes in A1leads to chromosomes line up randomly Haploid gametes are produced that undergo random fusion with gametes |
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erythrocytes (red blood cells) |
biconclave disc shape to maximise surface area no nucleus = more room for haemoglobin |
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Neutrophils |
Flexible shape to engulf foregoing particles or pathogens Many lysosomes contain digestive enzymes to break down the engulfed particles |
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Epithelial cells |
Some have cilia to move particles They are flattened in shape |
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Sperm cells (spermatozoa) |
Many mitochondria, sperm head contain enzymes Undulipodium to move, small, long and thin Nucleus contains half chromosomes |
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palisade cells |
contains chloroplasts to absorb light thin walls so that CO2 can diffuse in |
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Root hair cells |
Hair like projections to increase surface area to absorb water and minerals from the soil |
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Guard cells |
thin outer wall, thick inner wall in light they absorb water to become turgid and allow gaseous exchange
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tissue |
group of similar cells that perform a particular function |
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Organ |
a collection of tissue that work together to form a specific overall function |
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organ system |
a number of organs working together to form a life function |
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Ciliated epithelial tissue |
Column shaped, exposed surface covered with cilia Move in synchronised waves, e.g. waft mucus/eggs Found on saurface of tubes |
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Cooperation between cells example |
Movement: due to muscular and skeletal system, only if the nervous system 'instructs'. It uses energy so requires supply of nutrients and oxygen from the circulatory system Receiving chemicals from digestive and ventilation systems |
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Cartilage |
Hyaline cartilage- forms the embyonic skeletion Fibrous cartilage- occurs in discs between vertebrae Elastic cartilage makes up the outer ear and the epiglottis |
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Muscle tissue |
Vascularised (many blood vessels) Elongated & contain myofilaments made of protein |
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Types of muscle |
Skeletal- connective tissue sheets Cardiac- walls of the heart Smooth- walls of intestine, blood vessels, propels along these tracts (passages) |
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Epidermial Tissue |
Flatterned cells, form protective covering over leaves, stem and rools Some have walls impregnated with a waxy substances, forming a cuticle |
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Vascular Tissue |
Tissue concerned with transport Xylem & Phloem both present in vascular bundles |
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How Xylem derives from meristem (cambuim cells differentiate into xylem vessels) |
Lignin (woody substances) deposited in their cell walls- reinforce, waterproof them but also kills the cell Ends of cells break down, Xylem forms continuous columns with wide lumens to carry water and dissolved minerals |
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How phloem derives from meristem (cambium cells differentiate into phloem sieve tubes or companion cells) |
Sieve tubes loose most of their organelles and sieveplates develop betweeen them Companion cells retain their organelles and continue metabolic function to provide ATP for active loading of sugar into sieve tubes |
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Stem cells |
Undifferenated cells able to express all of its genes and divide by mitosis |
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Sources of stem cells |
Early embryo- when zygote begins to divide Umbilical cord blood Adult stem cells- bone marrow |
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Bone marrow transplants |
Treats dieases of blood (sickle cell anamia & leukaemia) and immune system |
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Stem cells, development in biology |
Enables a better understanding of how multicellular organism develop cell functions & what goes wrong when diseased |
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Why plants need a transport system |
All living things need to take substances and return waste to their environment |
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Examples parts of the plant can that can do one thing but not another |
Roots can obtain water but not sugars Leaves can produce sugars but cannot obtain water from the air |
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Xylem and phloem tissue in Roots |
Xylem is arranged in an X shape, phloem found between the arm of the xylem |
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Xylem and phloem tissue in Stem |
Vascular bundles found around the outside of the stem in a ring shape Xylem on the inside, phloem on the outside separated by a layer of cambium- meristem cells |
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Xylem and phloem tissue in Leaves |
Xylem on top, phloem in the 'veins' of a leaf |
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Xylem function and structure |
Transports water and mineral ions from the roots up to the leaves- vessels do this Fibers help support the plant Living parenchyma cells which act as packing tissues to separate and support the vessels |
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Xylem Vessels |
Long thick walls impregnated by waterproof lignin- prevents collapsing, creates patterns making the stem or branch flexble Vessels always stay open Lignification is not complete= pits or bordered pits- allow water to leave & pass into living parts of the plant |
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Sieve tube elements |
Little cytoplasm No nucleus Form a tube - sugars are transported Sieve plates- cross walls that are perforated Thin walls
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Companion cells |
Found between sieve tubes Cytoplasm, nucleus, mitochondria ATP loads sucrose into the phloem Plasmodesmata between companion cells allows flow of minerals between the cells |
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Plasmodesmata |
Gaps in the cell wall containing cytoplasm that connect two cells |
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Apoplast pathway |
Water passes through spaces in cell walls By mass flow Dissolved mineral ion & salts carried with water |
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Symplast pathway |
Water passes through plasma membrane Can pass through plasmodesmatas |
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Vacuolar pathway |
Water passes through plasma membrane and vacuoles |
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Water potential |
The tendency of water molecules to move from one place to another |
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Transpiration |
The loss of water vapour from the aerial parts of a plant due to evaporation |
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Transpiration a consequence of gaseous exchange- how plants reduce water loss |
Stomata opens- water can be lost to reduce this: Waxy cuticle- prevents water through epidermis Stomata closes at night Deciduous plants loose leaves in winter- conserve the water that they have got |
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Factors that affect transpiration rate |
Number of leaves Number-size-position of stomata Presence of cuticle Light Temperature Relative humidity Air movement Water available |
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How a potometer is used to estimate transpiration Pt 1 |
Cut healthy shoot underwater to stop air entering xylem Cutting shoot at a slant to increase surface area Ensure apparatus is full of water and that there is only the desired air bubble Insert shoot into apparatus underwater |
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How a potometer is used to estimate transpiration Pt 2 |
Remove potometer form water and ensure it is airtight around the shoot Dry leaves and Keep conditions constant to allow shoot to acclimatize (adjust) Shut screw fixed and record position of air bubble Start timing and measure distance moved per unit of time |
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The movement of water between plant cells |
Water passes from cell with higher water potential (less negative) To the cell, with the lower water potential (more negative) |
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The movement of water between plant cells and their environment |
Water moves down the water gradient If water potential inside the cell is greater than the water potential outside the cell Water moves out of the cell by osmosis Vice versa |
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The pathway water is transported from the root cortex to the air surrounding the leaves Pt 1 |
Water enters the root hair cells by osmosis At the same time, minerals are actively pumped from the root cortex into the xylem Consequentially water moves from root hair cell along symplast pathway to follow the xylem |
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The pathway water is transported from the root cortex to the air surrounding the leaves Pt 2 |
Casparian strip blocks the apoplast pathway between the cortex and the xylem Water must join the symplast pathway to reach the xylem When water reaches the top of the xylem it enters the leaves Leaves the leaves through the stomata |
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How Adhesion transports water from the root cortex to the air surrounding the leaves |
Water molecules form hydrogen bonds with the walls of the xylem As the xylem vessels are narrow H bonds can pull water up the sides of the vessel |
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How cohesion and the transpiration stream transports water from the root cortex to the air surrounding the leaves |
Water molecules attract to each other due to forces of cohesion The forces are strong enough t hold the molecules together in a long chain As molecules are lost from the top the whole column is pulled up ad one chain This is called the transpiration stream |
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How the if some xerophytes are adapted to reduce water loss by transpiration |
Smaller leaves less surafce area Densely packed spongy mesophyll Thicker waxy cuticle Closing stomata, stomata in pits Hairs on surface of leave trap layer of air reduce diffusion of water out of stomata
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Hyrophytes |
Plants that live in water Large air spaces in the leaf Stomata are on the upper epidermis Large air spaces in the stem helps with buoyancy and diffuse quickly |
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Translocation |
The transport of assimilates (substances that have become a part of the plant)throughout a plant |
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Translocation between sources (where the sugars come from eg leaves) and sinks (where they go eg roots) |
Sugars made in leaves and transported to roots in early spring leaves need energy to grow so sugars are transported from the roots (now the source) to the leaves (now the sink) |
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Transport in the phloem involving active loading at the source and removal at the sink Pt 1 |
ATP used by companion cells to actively transport proteins out of their cytoplasm and into the surrounding tissue This sets up a diffusion gradient and the hydrogen inn diffuse back into the cells Done through cotransport proteins which enable H ions to bring sucrose back into the cell with them |
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Transport in the phloem involving active loading at the source and removal at the sink Pt 2 |
Concentration of sucrose molecules builds up, they diffuse into the sieve tube elements through the plasmodesmata The entrance of sucrose into the sieve tube elements reduces the water potential water follows by osmosis and increases the hydrostatic pressure at the source to lower hydrostatic pressure at the sink |
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Transport in the phloem involving active loading at the source and removal at the sink Pt 3 |
Sucrose moves via either diffusion or active transport from sieve tube to the surrounding cells This increases the water potential in the sieve tube elements so water moves into surrounding cells by osmosis this reduces the hydrostatic pressure at the sink |