Definition of cytokenesis
Cytoplasmic division following nuclear division, resulting in two new daughter cells
Definition of interphase
Phase of cell cycle where cell isn't dividing; it's subdivided into growth and synthesis phases
Definition of mitosis
Type of nuclear division that produces daughter cells genetically identical to each other and to the parent cell
What do divisions can eukaryotic cells undergo?
Mitosis
Meiosis
What type of cells can undergo mitosis and meiosis?
Eukaryotic
What's the use of mitosis?
Produce new cells for growth and repair
What's the use of meiosis?
Formation of gametes
Definition of chromatids
Replicates of chromosomes
Definition of haploid
Having only one set of chromosomes (represented by symbol n)
Definition of homologous chromosomes
Matching chromosomes, containing same genes at same places (loci). They may contain different alleles for some of the genes
Definition of meiosis
Type of nuclear division that results in the formation of cells containing half the number of chromosomes of the parent cell
Definition of differentiation
Process by which stem cells become specialised into different types of cells
Definition of epithelial cells
Cells that constitute lining tissue
Definition of erythrocyte
Red blood cell
Definition of neutrophil
Type of white blood cell that's phagocytic (can ingest microbes and small particles)
Definition of stem cell
Unspecialised cell able to express all of its genes and divide by mitosis
Definition of guard cells
Cells that surround stomata in lead epidermis
Definition of palisade cells
Closely packed photosynthetic cells within leaves
Definition of root hair cells
Epidermal cells of young roots with long hair like projections
Definition of tissue
Group of cells working together to perform a specific function
Definition of meristem
Area of unspecialised cells within plant that can divide and differentiate into other types of cells
Definition of organ
Collection of tissues working together to perform a particular function
Definition of phloem
Tissue that carries products of photosynthesis, in solution, in plants
Definition of xylem
Tissue that carries water and mineral ions from roots to all parts of plants
Definition of organ system
Number of organs working together to carry out an overall life function
What organs and tissues are involved in the digestive system?
Oesophagus
Stomach
Intestines
Liver
Glands
Pancreas
What organs and tissues are involved in the circulatory system?
Heart
Blood vessels
What organs and tissues are involved in the respiratory system?
Airways and lungs
Diaphragm
Intercostal muscles
What organs and tissues are involved in the urinary system?
Kidneys
Bladder
Uretes
What organs and tissues are involved in the musco-skeletal system?
Skeleton
Skeleton muscles
What organs and tissues are involved in the integumentary system?
Skin
Hair
Nails
What organs and tissues are involved in the immune system?
Bone marrow
Thymus gland
Blood
Stomach acid
What organs and tissues are involved in the nervous system?
Brain
Spinal cord
Nerves
What organs and tissues are involved in the endocrine system?
Hormone glands e.g thyroid
Testes
Ovaries
Adrenals
What organs and tissues are involved in the reproductive system?
Penis
Uterus
Vagina
What organs and tissues are involved in the lymph system?
Lymph nodes
Vessels
What life processes are carried out by the digestive system?
Nutrition to provide ATP and materials for growth and repair
What life processes are carried out by the circulatory system?
Transport to and from cells
What life processes are carried out by the respiratory system?
Breathing and gaseous exchange excretion
What life processes are carried out by the urinary system?
Excretion and osmoregulation
What life processes are carried out by the musco-skeletal system?
Support, protection and movement
What life processes are carried out by the integumentary system?
Waterproofing, protection and temp regulation
What life processes are carried out by the immune system?
Protection against pathogens
What life processes are carried out by the nervous system?
Communication, control and coordination
What life processes are carried out by the endocrine system?
What life processes are carried out by the reproductive system?
Reproduction
What life processes are carried out by the lymph system?
Transports fluid back to circulatory system and important in resisting infections
What are the 4 characteristics of stem cells?
•undifferentiated cell, capable of becoming any type of cell
•described as pluripotent
•able to express all their genes
•can divide by mitosis and provide more cells that can differentiate into specialised cells for growth and repair
What are the sources of stem cells?
Embryonic stem cells
Stem cells in umbilical cord blood
Adult stem cells
Induced pluripotent stem cells (iPS cells)
Where are embryonic stem cells obtained from?
Present in early embryo formed when zygote begins to divide
Where can adult stem cells be found?
Developed in tissues e.g blood, bones and skin
What do adult stem cells act like and why?
Act like repair systems because they're a renewing source of undifferentiated cells
How are iPS cells developed and how?
In labs by reprogramming differentiated cells to switch on certain key genes and become undifferentiated
What are the potential uses of stem cells?
Bone marrow transplants
Drug research
Developmental biology
Repair of damaged or lost tissues
How can stem cells be used in drug research?
Can be developed into particular tissues
New drugs can be tested on these rather than animal tissue first
How can stem cells be used in bone marrow transplants?
Used to treat diseases of the blood and immune system
Used to restore patients blood system after treatment for specific cancers where patients bone marrow cells can be obtained before treatment, stored, then put back inside after treatment
How can stem cells be used in development biology?
Used to get better understanding of how multicellular organisms develop, grow and mature
How are stem cells used to get better understanding of how multicellular organisms develop, grow and mature?
Can study how these cells develop to make particular cells and can learn how each cell type functions and see what goes wrong when they're diseased
What does pluripotent mean?
Able to make any cell types
What does totipotent mean?
Able to make all and placental cells
How can stem cells be used to repair damaged tissues in mice?
Can treat mice with type 1 diabetes by programming iPS cells to become pancreatic beta cells
How can bone marrow stem cells be used to repair damaged tissues?
Can be developed into liver cells (hepatocytes) and used to treat liver disease
Where can stem cells be directed to repair damaged tissue?
Directed to become nerve cells to treat Alzheimer's and Parkinson's or repair spinal cord damage
How can stem cells be used in regenerative medicine to repair damaged or lost cells?
Used to populate a biscaffold of an organ, then directed to develop and grow into specific organs for transplanting
In regenerative medicine, when would there be no need for immunosuppressants?
If patients cells are the ones obtained, reprogrammed to become iPS cells then make organ
What are the different organs in plants?
Leaf
Roots
Stem
Flower
What's the function of the leaf?
Photosynthesis
What's the functions of the roots?
• anchorage in soil
• absorption of mineral ions and water
• storage
What's the functions of the stem?
• support
• holds leaves up to receive sunlight
• transportation of water and mineral s
• transportation of products of photosynthesis
• storage of products of photosynthesis
What's the function of the flower?
Sexual reproduction
What are the key plant tissues?
Epidermal tissue
Vascular tissue
Meristematic tissue
Xylem and phloem
What does epidermal tissue consist of?
Flattened cells (apart from guard cells)
What does epidermal tissue lack?
Chloroplasts
What does epidermal tissue form?
Productive covering over leaves, stems and roots
What does some epidermal tissue also have? Why is this important?
A wall impregnated with waxy substance forming cuticle
Important in plants in dry areas as reduces water loss
What's the function of vascular tissue?
Transportation
What are the 2 types of vascular tissue?
Xylem
Phloem
__ and __ are both present in vascular bundles
What's the function of the xylem?
Carries water and mineral ions from roots to rest of plant
What's the function of the phloem?
Transfers products of photosynthesis, in solution, from leaves to parts of plants that aren't photosynthetic
What does meristematic tissue contain?
Stem cells
What's the function of meristem tissue?
It derives all other tissues from it by cell differentiation
Where is meristematic ticcue found?
At root and shoot tips and in vascular bundles (meristems)
What are the characteristics of cells in meristems?
Thin walls containing little cellulose
No chloroplasts
No large vacuole
Can divide by mitosis and differentiate into other cell types
___ and ___ derive from meristems
What happens as plant cells mature?
Develop large vacuole and rigid cell wall to prevent cell from dividing
What do some combium cells differentiate into and how?
Xylem vessels
Lining is deposited into cell wall to reinforce and waterproof them and the ends of cells break down so xylem forms continuous columns with wide lumens to carry water and dissolved minerals
Other than xylem vessels what can combium cells differentiate into and how?
Phloem sieve tubes - loose most of their organelles
Companion cells - retain organelles and continue metabolic functions to produce ATP for active loading of sugar into sieve tubes
What is parenchyma?
Packing tissue which fills spaces between other tissues
In roots, they store starch
In leaves, they have chloroplasts and photosynthesise
What's parenchyma in aquatic plants and what does it do?
Aerenchyma and provides air spaces to keep plants bouyant
Describe collenchyma cells
Have thick cells walls and they strengthen vascular bundles whilst allowing some flexibility
Describe sclerenchyma cells
Have lignified walls and strengthen stem and leaf midribs
What are microvilli?
Extensions of plasma membrane to increase surface area
What are cilia?
Hair-like organelles which beat and propel substances along epithelial surfaces
What are the 4 main animal tissues and their uses?
Epithelial tissue
Connective tissue
Muscle tissue
Nervous tissue
What does connective tissue do?
Hold structures together and provide support
What is muscle tissue made of?
Cells that are specialised to contract and cause movement
What's nervous tissue made of?
Cells specialised to conduct electrical impulses
What are the stages of meiosis?
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2
What's reduction division?
Division which reduces the chromosomes number
What happens in prophase 2?
• if nuclear envelopes have reformed, break down
• chromosomes coil and condense, each consisting of 2 chromatids
• chromatids of each chromosome no longer identical due to crossing over in prophase 1
• spindles form
What happens in metaphase 2?
• chromosomes attach by their centromeres bt equator of spindle
• chromatids of each chromosome are randomly arranged
• the way they're arranged will determine how the chromatids separate during anaphase
What happens during anaphase 2?
• centromeres divide
• chromatids of each chromosome are pulled apart by motor proteins that drag them along tubulin threads of spindle, towards opposite poles
• chromatids therefore randomly segregated
What happens during telophase 2?
Nuclear envelopes form around each of the 4 haploid nuclei
Animals - 2 cells divide to give 4 haploid cells
Plants - tetrad of 4 haploid cells is formed
How does meiosis produce generic variation?
• crossing over during P1 shuffles alleles
• independent assortment of chromosomes in A1 leads to random distribution of mat and pat chromosomes in pair
• independent assortment in A2 leads to further random distribution
• haploid gametes are produced which can undergo random fusion with gametes derived from another organism
What happens during telophase 1?
Animal cells - 2 new nuclear envelopes form around each set of chromosomes and cell divides by cytokenesis. Then short interphase when chromosomes uncoil
Each new nucleus contains original number of chromosomes but each chromosome consists of 2 chromatids
Plant cells - straight from A1 to P2
What happens during anaphase 1?
Homologous chromosomes pulled apart by motor proteins that drag them along the tubulin threads of spindle
Centromeres don't divide, each chromosome consists of 2 chromatids
Crossed-over areas separate from each other resulting in allele shuffling and swapped areas of chromosome
What happens during metaphase 1?
Pairs of homologous chromosomes attach along equator of spindle
Attach to spindle thread by it's centromere
Homologous pairs arranged randomly with members of each pair facing opposite poles of cell (independent assortment)
Way line up in metaphase determines how segregate during anaphase
What happens during prophase 1?
Chromatin condenses, chromosomes supercoil (in this state can be seen under light microscope)
Nuclear envelope breaks down, spindle threads of tubulin protein form from centrioles
Chromosomes come together in homologous pairs, each pair consisting of 2 chromatids
Crossing over occurs when non-sister chromatids wrap around each other and may swap sections so alleles are shuffled
What's the significance of meiosis?
Genetic variation
What does sexual reproduction increase and why?
Genetic variation because it involves the combining of genetic material from 2 (usually) unrelated individuals of the same species by process of fertilisation
What does genetic variation within a population increase and why?
It's chance of survival when environment changes as some individuals will have characterised that enable them to be better adapted to change
Meiosis means __
Where does meiosis occur?
In diploid cells to produce haploid gametes
What do cells undergo before meiosis?
Interphase
What are held in the ovaries and tested?
Diploid cells undergoing meiosis
What are gonads?
Specialised organs which hold diploid cells undergoing meiosis
What are the 2 gonads?
Ovaries and testes
What must happen for sexual reproduction to occur and why?
Diploid cells must produce haploid gametes so when 2 gamete nuclei fuse during fertilisation, a diploid zygote is produced and normal chromosome number is maintained through generations
How many chromosomes are in a normal body cell?
46
What happens before meiosis?
S phase of interphase where chromosomes are duplicated as DNA is replicated and each chromosome consists of 2 sister chromatids
How many divisions are there in meiosis?
2
Where does the short interphase before the 2nd division take place if happens?
Takes place in plane at right angle to that of meiosis 1
What occurs at end of 2nd division in meiosis?
Cytokenesis
What happens during the budding of yeast?
Bud is formed at surface of cell
Interphase - DNA and organelles are replicated
Set of duplicated chromosomes - each set contained within a nucleus
One daughter nucleus migrates into the bud
Bud increases in size and eventually separates from parent cell, producing identical yeast cell
Is the cell diving during interphase?
Are chromosomes visible during interphase?
What form is DNA in during interphase?
Chromatin
What's the significance of mitosis?
Asexual reproduction
Growth
Tissue repair
Why is mitosis significant in asexual reproduction?
Single-celled protists divide my mitosis to produce new individuals. Some plants reproduce asexually by forming new plantlets on ends of stolons
Why is mitosis significant in growth?
All cells that grow from the zygote must be genetically identical
Why is mitosis significant in tissue repair?
If cells are damaged, important that new cells produced have identical structure and function to the ones that have been lost
When do chromosomes become visible in mitosis?
During prophase
What are the stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What happens during prophase?
Chromosomes shorten and thicken as DNA supercoils
Nuclear envelop breaks down
Centriole divides and 2 new daughter centrioles move to opposite poles
Tubulin threads form spindles between centrioles
What happens during metaphase?
Pairs of chromatids attach to spindle threads at equator region
Attach by their centromeres
What happens during telophase?
Separated chromosomes reach poles
New nuclear envelope forms around each set of chromosomes
Cell now contains 2 nuclei, each genetically identical to each other and to parent cell in which they arose
What happens during anaphase?
Centromere of each pair of chromatids split
Motor proteins, walking along tubulin threads, pull each sister chromatid of a pair in opposite directions towards opposite poles
As centromere goes first, chromatids, now chromosomes, assume a v-shape
Where does the ATP required for anaphase come from?
Provided my aerobic respiration in mitochondria, which gather around spindle fibres
Nuclear envelope breaks down
Centriole divides and 2 new daughter centrioles move to opposite parts of the cell
Cytoskeleton protein (tubulin) threads form spindle between centrioles.
Spindle has 3D structure
What happens once mitosis is complete?
Cytokenesis - cell splits into 2, each containing a nucleus
What happens during cytokenesis in animal cells?
Plasma membrane folds inwards and 'nips in' the cytoplasm
What happens during cytokenesis in plant cells?
End plate forms where equator of spindle was and new plasma membrane and cellulose cell-wall material are laid down either side along plate
What's the equator of a cell restricted by?
Ring of contractile proteins (actin) in the process of cleavage
What are the specialised plant cells?
Palisade
Guard
Root hair
What do xylem and phloem form?
Vascular tissue of plants
Where are palisade cells found?
Within leaves
What are palisade cells adapted for?
How are palisade cells adapted for their function?
They're long and cylindrical and pack close together
Have large vacuole
Have many chloroplasts
Contain cytoskeleton threads and motor proteins
Palisade cells:
How does they're long, cylindrical shape, packed close together help perform their function?
There's little space for air to diffuse but the CO2 in the air spaces are able to diffuse into these cells
How does a large vacuole help them carry out their function?
Means chloroplasts are closer to periphery of cell reducing diffusion distance for CO2
How does having many chloroplasts help them carry out their function?
Carry out more photosynthesis
How does a having cytoskeleton threads and motor proteins help them carry out their function?
Used to move chloroplasts nearer to upper surface of lead when sunlight intensity is low but further down when it's high
What are guard cells?
Pairs of specialised cells within lower epidermis, containing chloroplasts
What can't guard cells do and why?
Carry out photosynthesis as don't have enzymes needed for 2nd stage of process
What cells are responsible for gaseous exchange in plants?
Decribe gaseous exchange in plants
Light energy used to make ATP
ATP activey transports K+ ions from surrounding epidermal cells into guard cells by osmosis
Water enters guard cells, lowering WP
Guard cells swell, tips bulge and stoma enlarge
As stomata open, air enters spaces within layer of cells beneath pallisade cells
CO2 diffuses into pallisade cells for photosynthesis - maintain steep conc grad
O2 produced diffuses out pallisade cells into air spaces and out through open stomata
What leaves along with O2 when the stomata is open?
Water vapour through transpiration
How do cells reproduce?
By duplicating their contents then splitting into 2 daughter cells
What are the 2 main checkpoints in the cell cycle?
G1/S checkpoint
G2/M checkpoint
What is the purpose of the checkpoints in the cell cycle?
Prevent uncontrolled division that would lead to tumours
Detect and repair damage to DNA
As the molecular events that control the cell cycle happen in a specific sequence, it ensures that …
Cell cycle can't be reversed
DNA is only duplicated once during each cell cycle
How many divisions can cells undergo and what's this quantity known as?
50
Hayflicks constant
How do tumours form?
Cell division becomes uncontrollable
What do proto-oncongenes do and how?
Can help regulate cell division by coding for proteins that help regulate cell growth and differentiation
What happens if proto-oncongenes mutate?
May become oncogenes and causes cells to fail to undergo apoptosis and instead keep on dividing leading to a tumour
What's apoptosis?
Programmed cell death
What does senescence mean?
Cell can no longer divide
What is interphase divided into?
G1, S and G2
What happens during G0?
Cells undergo differentiation or apoptosis of senescence
Why is the P53 gene important?
Triggers the 2 main checkpoints in the regulation of the cell cycle, hence also known as tumour suppressor gene
How do prokaryotic cells replicate?
Binary fission
How do prokaryotic cells undergo binary fission?
Cells grows to its limit of size then splits in 2
Before cell divides, DNA is replicated, 2 new loops of DNA are pulled to opposite ends of cell and cell wall forms which begins to separate the prokaryotic cell
Each new cell contains replicated plasmids and synthesised ribosomes. Mitochondria and chloroplasts divide by binary fission
Why happens during M phase of cell cycle?
Cell growth stops
Nuclear division (mitosis) takes place
What happens during G0 phase?
Cells may undergo apoptosis, differentiation or senescence
Some remain here for long time or indefinitely
What happens during G1 phase?
Cell grows and increases in size
Transcription of genes to make RNA occurs
Organelles duplicate
Biosynthesis, including making enzymes needed for DNA replication
What helps control G1 phase?
P53 gene
What happens during G2 phase?
Cell grows
What happens during S phase?
DNA replicates
Once entered pase, committed to completing cycle
When all chromosomes have been duplicated, each one consists of a pair of identical sister chromatids
Why is the S phase rapid?
The exposed DNA base pairs are more susceptible to mutagenic agents so reduces chances of spontaneous mutations
What does S phase stand for?
Synthesis
What does the G1 checkpoint check for?
Cell size
Nutrients
Growth factors
DNA damage
Ready to enter S phase
What does the G2 checkpoint check for?
DNA replication
What does the spindle assembly checkpoint check for?
Chromosomes attachment to spindle
In M phase, what does the checkpoint chemical trigger?
Condensation of chromatin
What does the M phase checkpoint ensure?
Cell is ready to complete mitosis
What do special chemicals in G2 ensure?
Cell is ready for mitosis by stimulating proteins that are involved in making chromosomes condense to form spindle
What are examples of connective tissue?
Bone cartilage
Tendons
Ligaments
What does connective tissue consist of?
Non-living extracellular matrix containing proteins (collagen and elastin) and polysaccharides (hyaluronic acid which traps water)
What does the matrix in connective tissue do?
Separated living cells within the tissue and enables it to withstand forces such as weight
What's the function of muscle tissue?
Allows movement
What are the 3 types of muscle?
Skeletal muscle
Cardiac muscle
Smooth muscle
What does smooth muscle do and where does it occur?
Propels substances along tracts
Occurs in wall of intestines, blood vessels, uterus and urinary tracts
How can you describe muscle tissue?
As well vascularised
What does well vascularised mean?
Many blood vessels
What does cardiac muscle make up and waht does it do?
Walls of heart
Allows heart to beat and pump blood
What does skeletal muscle do?
When contracts, allows bone to move
What are muscle cells called?
Fibres
How would you describe fibres?
Elongated and contain special organelles called myofilaments made of proteins (actin and myosin)
What do myofilaments allow?
Muscle tissue to contract
What are condroplasts?
Immature cells in cartilage
How can cells in cartilage divide?
What does cartilage do?
Secrete extracellular matrix
What happens in cartilage once the matrix has been synthesised?
Condroplasts become mature to become chondrocytes, maintaining the matrix
What are the 3 types of cartilage?
Hyaline
Fibrous
Elastic
Where does fibrous cartilage occur?
In discs between vertebrae in spine and knee joint
What does elastic cartilage make up?
Pinna (outer ear) and epiglottis (flap that closes over larynx)
What does hyaline do?
Form embryonic skeleton
Covers ends of long bones
Joins ribs to sternum
Where can hyaline be found?
Nose, trachea (forming C shape rings to keep trachea open) and larynx
What does epithelial tissue do?
Covers and lines from surfaces in body
How is epithelial tissue adapted for its function?
Made up almost entirely of cells
No blood vessels
Some smooth, some have projections (cilia or microvilli)
Have short cell cycles
Why is epithelial tissue specialised?
To carry out function of protection, absorption, filtration, excretion and secretion
How many times does epithelial tissue divide daily and why?
2-3x to replace worn out/damaged cells
How does epithelial tissue receive nutrients?
By diffusion from tissue fluid in underlying connective tissue
How are root hair cells adapted?
Hair-like projections
Have special carrier proteins
What do root hair cells produce?
ATP needed for transport
Root hair cells:
What do the carrier protein do and where are they?
In plasma membrane to actively transport mineral ions
What do the hair-like projections do?
Increase S.A for absorption of water and mineral ions
What does the active transport of mineral ions into root hair cells do?
Lower the water potential of the cells, causing water to follow by osmosis down the water potential gradient
What do erythrocytes do?
Carry oxygen from lungs to respiring cells
Where do erythrocytes derive from?
Stem cells in bone marrow
How are erythrocytes adapted?
Very small
Flexible
Most organelles are lost at differentiation. No nucleus, mitochondria or ER and little cytoplasm
Erythrocytes:
How big are they and what does this mean?
7.5 micrometers in diameter so large S.A:V
How does being small help function?
Means O2 can diffuse across their membranes and easily reach all regions inside cell. Biconcave shape also increases S.A:V
How does being flexible help function?
Well developed cytoskeleton allows them to change shape so they can twist and turn through narrow capillaries
How does being having few organelles help function?
Provides more space for haemoglobin molecules
Where is haemoglobin synthesised?
Within immature erythrocytes which still have nucleus, ribosomes and RER
What to neutrophils do?
Ingest invading pathogens
Where do neutrophils derive from?
What do neutrophils make up?
~50% WBC in body
How big are neutrophils?
Twice size of erythrocytes
What do neutrophils each contain?
Multi-lobed nucleus
What's the function of neutrophils?
Ingest bacteria and some fungi by phagocytosis
What are neutrophils attracted to and travel towards?
Infection sites by chemotaxis
How are spermatozoa specialised?
Many mitochondria carry out aerobic respiration
Long and thin so easy to move
Enzymes in acrosome
Head of sperm contains haploid male gamete nucleus and very little cytoplasm
What do the enzymes in a spermazoas acrosome do?
Digest outer protective covering of ovum allowing sperm head to enter ovum
What type of enzymes are in the acrosome?
Specialised lysosomes
What does the ATP provided by a sperm cells mitochodria do?
Provides energy for the undulipodium (tail) to move and propel cell towards ovum
Epithelium is …
Lining tissue
What type of epithelial cells are flattened in shape?
Squamous
How are most epithelial cells specialised?
Have cilia
How do multicellular eukaryotic organisms start life?
Zygote (single undifferentiated cell)
How's a zygote formed?
When ovum is fertilised by speratozoon and the 2 haploid nuclei fuse to give cell with diploid nucleus
Is a zygote specialised?
No
What does it mean since a zygote isn't specialised?
All its gene in its genome are able to be expressed
Able to divide by mitosis
What does genome refer to?
Genetic material within individuals
What does gene pool refer to?
All the genetic material within a population
Individuals have …
Genome
Populations have …
Gene pool
Why are different genes expressed in different eukaryotic cells as they dofferentiate?
Some contents of cell change
Shape of cell changes
Different proportions of organelles within cells
Guard cells:
What's the light energy used for?
Make ATP
What does the ATP do?
Actively transport potassium ions from surrounding epidermal cells to guard cells lowering water potential
How does water enter guard cells?
From neighbouring epidermal cells by osmosis
What happens when stomata opens?
Water vapour leaves through transpiration
O2 diffuses out
How does gaseous exchange occur in plants?
Light energy is used to make ATP
ATP actively transports potassium ions from surrounding epidermal cells into guard cells lowering H2O potential
Guard cells swell opening stomata
Air enters spaces within the layer of cells beneath the palisade cells
Gaseous exchange occurs - O2 diffuses into the palisade cells for use in photosynthesis. Will maintain steep concentration gradient
O2 produced during photosynthesis diffuses out of palisade cells into air spaces and out through open stomata
Zuletzt geändertvor 4 Monaten