Chapter 6 Flashcards
When looking at a cell tissue down a microscope, why can we see that some cells are dividing and some that aren’t?
Diff cells r are diff stages in the cell cycle
Lots of cells in multicellular tissue don’t have?
The ability to /
What is the interphase?
Even cells that / can go through a long period of not /
Interphase - inbetween /s
Mitosis (outline)
Chromosomes begin to appear and move to opp parts (poles) of the cell
Cytokinesis?
Cell splits into 2
Cell cycle outline?
Process of interphase, mitosis and cytokinesis repeated again and again
3 stages of interphase?
G₁
S
G₂
G₁ (snp)
Preparations are made to ensure cell is ready to go into S phase
Preps include duplicating organelles, growing in size, making proteins that will be needed in S phase
After S phase, there is no…
Going back, the cell has to complete the cell cycle
Why is the S phase called the Synthesis phase?
This is where DNA synthesis (replication) happens
What is replicated first/last?
More imp sequences of DNA replicated first and bits of DNA that are only required by some cell types are repl last
At the end of S phase, all chromosomes will…
Be replicated
Exiting the cell cycle
Cells that don’t / have at one point left the cell cycle e.g. NERVE TISSUE
This occurs early in the G₁ phase - cells here can either continue in the cell cycle or enter the G₀ phase
Cells in the G₀ phase may?
Die
May differentiate
Enter senescence (where they stop /)
How can we see changes that take place in the cell cycle?
By looking at mass of the DNA and the cell overtime
The mass of the cell?
Grows continually during cell cycle as it makes proteins, DNA, organelles
The mass of the DNA during cell cycle?
Increases for a short part of cell cycle as DNA is only synthesised in S phase
During cytokinesis?
half of DNA goes into 1 cell and half into other
Why is mitosis useful?
Every organism must carry out cell / - mitosis in eukaryotes
Mitosis produces genetically identical daughter cells
Importance of mitosis - growth?
Multicellular organisms begin as 1 cell that /s to become a fully grown organism
This one cell contain ALL OF THE GENETIC MATERIAL required to make up the organism
Importance of mitosis - tissue repair?
Cells can die/ become damaged
Mitosis is used to produce a genetically identical copy of the cell that has died/ damaged
The new cell is able to take over the role of the cell that was lost as contains all of same genes
Imp of mit- Wound repair?
Damage can be done to cells by mechanical forces that cause wounds
When this happens in humans, it stimulates the action of WBCs, platetlets, and growth factors
These cause damaged tissue - like blood vessel endothelium and muscle to undergo mitosis
Ensures a fast recovery
Imp of mit - asexual reproduction?
Some organisms use mitosis to reproduce asexually - includes both simple and complex organisms
Binary fission in bacteria = asexual reproduction
Asexual reproduction results in…
Genetically identical offspring
Used by simple organisms like amoeba and yeast
Cancerous growth?
Too much mitosis can be harmful
Rate of mit is carefully controlled by envir and genes in the cell
If genes controlling rate are mutated, cell / can occur uncontrollably
Lots of these damaged cells will die or be killed by immune system - damaged cells have an incorrect genome
G₁/ S checkpoint makes sure?
Aren’t too many or too little cells undergoing /
G₁/ S checkpoint is also called?
Restriction point
What actually are checkpoints?
Times in the cell cycle where chemical events happen to regulate /
Checkpoints also?
Ensure the cell cycle only proceeds in 1 direction
This is to prevent all of the changes that occur when a cell moves thru the cell cycle from happening 2x
If cells start to multiply controllably?
This leads to cancer &tumours
Checking cell /?
Cell / also has to be replicated in the cell cycle
If cell cycle repeats too quickly, cells start multiplying at faster rate
Mitosis happens over and over again - cells /ing at uncontrolled rate
Checking DNA?
Damage to DNA can happen during DNA rep in interphase
The DNA rep phase (S phase) is kept short since exposed bases are more susceptible to mutation
When mutations happen, damaged DNA is detected and repaired at checkpoints
Checkpoints also make sure that DNA is only replicated once in each cell cycle
What is the purpose of cell cycle checkpoints?
Cell cycle involves DNA rep & cell /
Mistakes can happen in both these processes
The cell cycle is REGULATED by checkpoints to stop these mistakes being carried through
Tumours?
Damaged cells that don’t die or get attacked by immune system can form tumours
Benign or malignant
Cells that don’t / are indefinitely in?
G0 phase
Cancer can happen in?
S phase - mutations in DNA rep
Mitosis - DNA exposed to reactions in cytoplasm - mutations -> cancer
what are stem cells?
cells that are able to express all of their genes and divide by mitosis
what happens as development goes on?
cells start to resemble more specialized cells
how do cells change as they go thru differentiation?
- as stem cells /, they become more & more specialized
- as they become specialized, they start to change the no and type of organelles
- the shape may change to become more specialized to their function
what are fully specialized cells unable to do?
- / by mitosis
differentiation is?
where stem cells become more specialized into different cell types
every single cell in the body contains?
the same genome, with all of the same genes
specialized cells only express (genes)?
- a small subset of the genome
- this means they can only produce a small subset of the proteins that the organism can produce
stem cells can express how many of their genes?
all of the genes in the genome
as differentiation goes on?
cells start to express fewer and fewer genes
at the end of differentiation?
a fully specialized cell just expresses the genes needed to perform its function
Pluripotent stem cells -
stem cells that can turn into any type of cell in the organism
Erythrocyte differentiation?
- during development, immature erythrocytes make haemoglobin using their organelles
- after this, the cell loses its organelles so that haemoglobin can fully occupy the space in the cell to become a mature eryhtocyte
- > means more O2 can be transported in a small cell
Adult stem cells?
- Can be found in many diff tissue types
- They can / and differentiate into a small selection of cell types that can replace damaged cells (e.g epithelial tissue in skin)
Embryonic stem cells?
- Come from early embryos and are able to differentiate into any cell type
Umbilical cord blood?
Stem cells are found in the umbilical cord blood
Multipotent - can only differentiate into diff types of blood cell
Why can embryonic stem cells divide an unlimited amount of times?
Cells are undifferentiated so that when they / they produce another copy of themselves
Sources of stem cells?
In mammals we can find stem cells in a range of diff places and stages in development
where are plant stem cells found?
meristem tissue
meristem definition?
an area of unspecialised cells in a plant which can self renew and differentiate
where is meristem tissue that helps the plant grow in length found?
root & shoot tips
where is meristem tissue that differentiates into xylem an phloem tissue found?
cambium
cambium?
a region between xylem and phloem vessels
xylem?
transport of H2O and ions
phloem?
sugars
adaptations of meristem cells?
- meristem cells have very thin cell walls which allows them to easily divide
- and don’t have cholorplasts - which take up space and energy
- only have a small vacuole - makes room for organelles involved in /ing
when meristem /,
they can differentiate into plat cells with feature mor specialised to their function - like palisade cells
cambium tissue diffrentiates into either ____ or ____ cells
xylem or phloem cells
differentiation into xylem?
- involves laying down lignin (a polysaccharide)
- this kills he cells but makes them strong and waterproof
- the ends of xylem cells also break down so that H2O can travel unobstructed
differentiation into phloem?
- the other cambium tissue differentiate into phloem tissue or companion cells
- Sieve tubes carry the phloem sap, have few organelles and have sieve plates between them
- companion cells have lots of mitochondria so they can actively pump sugars unto the phloem
uses of stem cells in medicine ? (damage and disease)
- damage and disease can cause missing or malfunctioning cells
- bc stem cells can differentiate into diff cell types, they can be used to replace lost or damaged tissue
e.g. use of bone marrow stem cells?
- can treat diff types of blood disease
- this is bc bone marrow cells can differentiate into Red and White blood cells
- which can then be used to treat diseases like leukemia
uses of stem cells: induced pluripotent
- induced pluripotent stem cells can be used to treat a wide range of disorders
- Diabetes can be treated by reprogramming cells to become beta cells in the pancreas
- neurodegenerative diseases like Parkinsons may one day be treated by reprogramming cells to become neurons
uses of sc: regenerative medicine ?
- stem cells are starting to be developed into whole organs - this is called regen med
- as well as differentiating correctly, stem cells need to be grown in a specific shape
- the whole organ can then be transplanted into the patient
uses of sc: regenerative medicine ?
- stem cells are starting to be developed into whole organs - this is called regen med
- as well as differentiating correctly, stem cells need to be grown in a specific shape
- the whole organ can then be transplanted into the patient
using stem cells to test drugs means?
can test a new drug onto a paticular typ of body cell instead of testing it directly onto human
- this allows us to assess the potential effects of drugs w/o having to use any human subjects
stem cells can also be used to study development….
- stem cells can also be used to study how animals & humans develop
- by studying the process of differentiation in stem cells we can understand HOW DIFFERENTIATION occurs in the body
- this might also give us clues as to how we can give adult cells the same ability to / as embryonic stem cells
cells in multicellular organisms are ______ for their function?
specialised
organ e.g. - stomach?
- stomach contains a mixture of tissues that are involved in digesting food
- comtains muscle tissue which contracts - squeezing the stomach, tis churns up food, which makes it easier to digest
- epithelial tissue makes up the lining of the stomach -secretes enzymes and protects the rest of the body from the acidic stomach
- connective tissue makes sure all the diff types of tissue are held togethr
organ system?
- top level of organisation
- e.g. digestive system made up of the oesophagus, stomach, pancreas, ect…
- stomach - produces enzymes that break down proteins
- pancreas - then produces enzymes that break down polysaccharides that weren’t brojen down in the stomach
organ system e.g. respitory system?
made up of lungs bronchi trachea -> involved in gas exchange , which circulatory system - made of heart, arteries, veins
haploid?
half the number of chromosomes
HALF - HAP
n =23
gametes - / by meisois
diploid?
- full set of chromosomes - 2 sets
- 2n = 46
- all body cells except gametes
- 23 pairs of homologous chromosomes
what is a homologous pair of chromosomes?
- SAME genes but DIFFERENT allelles
the order of the cell cycle?
interphase > mitosis > cytokinesis
phases of interphase?
G1 > S > G2
phases of mitosis?
PROPHASE METAPHASE ANAPHASE TELOPHASE PMAT
the mitosis cell cycle - names of checkpoints?
- G1S checkpoint
- G2 checkpoint
- spindle assembly checkpoint
interphase - G1?
1st growth phase
- cellular contents, apart from the chromosomes are duplicated
- proteins from which organelles are synthesised are produced and organelles replicated. the cell increases in size
G1S checkpoint?
check for:
- cell size
- nutrients
- growth factors
- DNA damage
- if does not satisfy requirement, enters G0 - resting state
interphase - S phase?
synthesis phase
- each of the chromosomes are duplicated
- DNA is replicated in nucleus
interphase - G2 phase?
- the 2nd Growth phase
- the cell checks the duplicated chromosomes for errors, making any repairs that are needed
- cell continues to increase in size, energy stores are increased
G2 checkpoint?
- quality/ fidelity of DNA replication checked
- check for: cell size, DNA replication and damage
spindle assembly checkpoint?
check for: chromosome attachment to spindle
Chromosomes in interphase are?
- chromosomes are diffuse/ decondensed - not visible as indiv chromosomes
what happens in prophase?
- nucleolus & nuclear envelope disintegrate
- chromosomes condense and become visible
- spindle fibres start to extend from centrioles
what happens in metaphase?
- spindle fibres attach to centromeres and moves chromosomes to align on metaphase plate/ equator of cell
what happens in anaphase?
- spindle fibres shorten pulling chromosomes to opposite poles of the cell
what happens in telophase?
- division furrow forms
- nuclear envelope and nucleolus reform
Cytokinesis - chromosomes and position in cell cycle?
- chromosomes decondense
- cells now in G1
(bio) what is mitosis for? 1 -Growth?
- when an organism grows, more cells are produced by mitosis
(bio) what is mitosis for? 2- tissue repair & cell replacement?
- if a tissue becomes damaged, the damaged cells are replaced not repaired.
- The new cells are produced by mitosis
- cells r being replaced all the time, espec epithelial tissue (tissue on the surface) e.g. the skin and digestive system. The new cells r produced by mitosis (shocker)
(bio) what is mitosis for? 3 - asexual reproduction?
- many organisms reproduce asexually. This is due to mitosis
- e.g. runners from strawberry plants, reproduction of Hydra
- budding in yeast, a unicellular fungus
- prokaryotic organisms reproduce asexually using a version of mitosis called binary fission
why is cytokinesis different in plant cells?
the cell wall
cytokinesis in animals?
- a cleavage furrow forms around the middle of the cell
- the cell surface membrane is pulled inwards by the cytoskeleton until it’s close enough to fuse around the middle forming 2 cells
cytokinesis in plants?
- / furrows can’t form bc of cell wall
- vesicles from the Golgi Apparatus begin to assemble in the middle
- vesicles fuse w each other
- vesicles then fuse w the plasma membrane, / the cell into 2
- new sections of cell wall then form along the new sections of membrane
the mitotic index?
- the higher the proportion of cells in a recognisable phase of mitosis in a tissue sample, the higher the rate of cell division in that sample
- mitotic index = (no. of cells in a mitotic phase/ total no. of cells in sample) x100
what can the mitotic index indicate?
1- the rate of growth in e.g. root tips
2 - the presence of a tumour can indicate cancer
meiosis - series of steps?
Interphase > Prophase I > Metaphase I > Anaphase I > Telophase I > Cytokinesis > Prophase II > Metaphase II > Anaphase II > Telophase II > Cytokinesis
meiosis - prophase I?
- chromosomes form bivalents, crossing over happens forming chiasmata
meiosis - metaphase I?
- independent assortment
- 2(^23) ways of assorting human chromosomes
meiosis - metaphase II?
- independent assortment again
Meisois - cytokinesis 2 ?
- 4 haploid gametes
- genetically unique
- segregation of alleles
mitosis vs meiosis ?
mitosis vs. meiosis
- cell produced = genetically identical vs genetically unique
- diploid cells - chromosomes in homologous pairs vs. haploid cells - no homologous pairs
- 2n = 46 vs n = 23
- 2 cells produced vs 4 cells produced
meiosis - why are the cells produced genetically different? 1 - Crossing over
- homologous pairs pair up to form bivalents during prophase I
- The arms of the chromosomes swap alleles forming a unique mixture of maternal & paternal DNA
- happens many times in a ‘real, bivalent
What is a chiasma?
point of crossing over
meiosis - why are the cells produced genetically different? 2 - independent assortment?
- random alignment of chromosomes on the metaphase plate / equator during metaphase I and II
no of combinations of chromosomes =?
2 (^no. of pairs of chromosomes)
meiosis - why are the cells produced genetically different? 3 - segregation?
- at the 2nd cytokineses, the random combination of alleles separates into 4 gametes
what is a ‘reduction division’?
- meiosis reduces the chromosome number by half
- Diploid ➡ haploid
- e.g. for human cells
- 2n = 46 ➡ n = 23
- this avoids doubling up of chromosome number at fertilisation maintaining chromosome number down generations
⭐ specialised cells - erythrocytes - biconcave disk shape?
structural feature: biconcave disk shape ➡ increases SA: Vol ratio which ⬆ rate of O2 and CO2 diffusion
⭐ specialised cells - erythrocytes - no nuclei?
structural feature: no nuclei - few organelles ➡ maximises Vol for O2 carrying haemoglobin molecules
⭐ specialised cells - erythrocytes -small and flexible?
structural feature: small and flexible ⭐ specialised cells - erythrocytes - able to squeeze through narrow capillaries
⭐ specialised cells - neutrophil - multilobed nucleus?
structural feature: multilobed nucleus ➡ makes it easier for them to squeeze through small gaps to et through into the site of infection
⭐ specialised cells - neutrophil - granula cytoplasm ?
structural feature: granula cytoplasm ➡ contains many lysosomes that contain enxymes used to attack pathogens
⭐ specialised cells - ciliated epithelial cells - cilia
sf: ‘hair-like’ structures called cilia on one surface ➡ that move in a rhythmic manner
- ciliated epithelium lines the trachea for example cauing mucus to be swept away from the lungs
⭐ specialised cells - ciliated epithelial cells - goblet cells?
sf: goblet cells ➡ release mucus, trap any unwanted particles present in the air. This prevents the particles ,which may be bacteria, from reaching the alveoli once inside the lungs
⭐ specialised cells - squamous epithelial cells - one cell thick?
sf: very then due to the squat or flat eclls hat make it up, only one cell thick ➡ present when rapid diffusion across a surface is essential. forms lungs and allows rapid diffusion of O2 into the blood
⭐ specialised cells - sperm cell - flagellum
sf: flagellum (tail) ➡ movement
⭐ specialised cells - sperm - many mitochondria
sf: many mitochondria ➡ supply energy needed to swim
⭐ specialised cells -sperm - acrosome
sf: acrosome ➡ contains digestive enzymes which r released to digest protective layer around the ovum, and allow sperm to penetrate, leading to fertilisation
⭐ specialised plant cells- palisade mesophyll cells - chloroplasts
;sf: chloroplasts ➡ absorb large amounts of sunlight for photosynthesis
⭐ specialised plant cells- palisade mesophyll cells - chloroplasts - mobile
sf: chloroplasts can move within the cytoplasm ➡ in order to absorb more light
⭐ specialised plant cells - guard cells around stomata
sf: pairs of guard cells on the surfaces form stomata ➡ stomata necessary for CO2 to enter plan for photosynthesis
⭐ specialised plant cells - root hair cells - root hairs
sf: have long extensions called root hairs ➡ increase SA of teh cell ➡ maximises uptake of H2O and minerals from soil
⭐ specialised plant cells- palisade mesophyll cells - cells are rectangular box shaped
sf: cells are rectangular box shaped ➡can be closely packed to form a continuous layer
⭐ specialised plant cells- palisade mesophyll cells - thin cell walls
sf: thin cel walls ➡ increasing rate of CO2 diffusion
⭐ specialised plant cells- palisade mesophyll cells - large vacuole
sf: large vacuole ➡ maintain turgor pressure
⭐ specialised plant cells - guard cells - stoma closes
sf: stoma closes to prevent further water loss ➡ when guard cells lose H2O and become less swollen as a result of osmotic forces, they change shape and stoma closes
⭐ specialised plant cells - guard cells - cell wall is thicker on one side
sf: the cell wall of a guard cell is thicker on one side➡ so cell does not change shape symmetrically as its volume changes
organ ➡ organism?
Organelle ➡ Cell ➡ Tissue ➡ organ ➡ organ system ➡ organism
example of an organelle?
mitochondrian
example of a cell?
cardiac muscle cell
example of a tissue?
cardiac muscle tissue
example of a organ?
heart
example of an organ system?
cardiovascular system
example of an organism?
homo sapiens - humans
TISSUE DEFINITION?
a collection of specialised cells co-ordinating to carry out a specific function
- also includes the basement membrane
- also includes any secretions of clls within the tissue e.g mucus from goblet cells
what is squamous epithelium made from?
made up of specialised squamous epithelial cells + basement membrane
squamous epithelium: structure + how relates to function?
- one cell thick ➡ and very thin as it’s present when rapid diffusion across a surface is essential. e.g. walls of alveoli
ciliated epithelium made from?
- ciliated epithelial cells
- goblet cells
- basement membrane
- mucus
ciliated epithelium - structure + how relates to function
- cilia on 1 surface, ciliated epithelial cells closely packed together, covered in a layer of mucus ➡ goblet cells release mucus to trap unwanted particles, cilia move mucus up airways to keep airways free of particles/ pathogens, many mitochondria to provide ATP for cilia movement
cartilage - what it’s made from
- fibres of elastin and collagen
- chondryte cells
- extracellular matrix
cartilage - description + function
- cartilage is a firm , flexible connective tissue composed of chondrite cells embedded in an extracellular matrix ➡ cartilage prevents te ends of bones rubbing together and causing damage ➡ firm and flexible
muscle tissue - description?
- muscle fibres
- connective tissue
muscle tissue - structure + function?
skeletal muscle has fibres arranged in parallel, joined by connective tissue ➡ , needs to be able to shorten in length in order to move bones, which in turn move the diff parts of te body, contraction of parallel fibres allows this
xylem - what is made from?
- parenchyma cells
- vessel elements
- lignin
xylem - structure + function?
the tissue is composed of vessel elements, which are elongated dead cells. The walls of these are strengthened with a waterproof material called lignin which provides structural support for plants ➡ allows transport of water and dissolved ions up plant along vessels - also sideways between vessels
phloem - description?
- sieve tube
- sieve plate
- companion cells
- parenchyma cells
phloem - structure + function?
it’s composed of columns of sieve tube cells seperated by perforated walls clled sieve plates ➡ sieve plates allow movement of cell sap fro leaves to stem, little cytoplasm increases ease of cell sap movement, companion cells support function of sieve tube elements
Organ definition?
a collection of tissues co-ordination to carry out a specific function
e. .g animal: heart, liver, muscle
plant: leaves, stem, roots
organ system definition?
a collection of organs co-ordinating to carry out a specific set of functions
animal: cardiovascular system, nervous system, endocrine system
plant: vascular system, reproductive system
STEM CELL DEFINITION?
unspecialised cells that can divide and differentiate to form diff types of specialised cells
the 2 main types of stem cell are?
- embryonic
- adult
embryonic stem cells can be either: ?
totipotent or pluripotent
totipotent stem cells ?
can form ANY specialised cell, the whole organism, and extraembryonic cells e.g. placenta, umbilical cord
pluripotent stem cells?
can form any type of cell but not the whole organism
adult stem cells are?
multipotent
multipotent stem cells?
can form a set of specialised cells - e.g. haematopoietic stem cells in bone marrow can form any type of blood cell, but no other type of cell
examples of stem cells - adult hematopoietic ?
adult hematopoietic bone marrow stem cells - these cells can / to form 8 different blood cells - they are multipotent
examples of stem cells - meristematic cells in plants?
- wherever a plant is growing quickly, meristemic tissue will be found / plant stem cells
- e.g. root and shoot tips, buds, between xylem and phloem tissue in vascular bundles
Cells in multi-cellular organisms have?
Evolved to become more specialised to their functions
Erythrocyte specialisations?
- Transport O2 to body cells
- Have a well developed cytoskeleton that allows them to bend
- This allows them to squeeze through narrow capillaries
Neutrophils specialisation?
- Type of WBC
- Travel to sites of infection and engulf bacteria and fungi
- Much larger than erythrocytes bc they don’t need to enter the smallest capillaries
- Travel to sites of infection by moving along a gradient inflammatory chemicals
- This is called CHEMOTAXIS & is possible bc neutrophils have receptors on their CM for inflammatory chemicals
What else do neutrophils have?
A multilobed nucleus which allows them to move around more quickly and engulf materials: more quickly bc can change shape as it moves through narrow passages and engulf materials as can stick out projections of its cytoplasm to engulf pathogens w/o damaging nucleus
Animal cell - Spermatozoa specialisation?
- Specialised for swimming and fertilisation
- Tail (undulipodium) which allows them to swim
- Movement of tail requires ATP so sperm has lots of mitochondria
- They are long and thin which makes them streamlined - which makes it easier to swim
Sperm cell: acrosome?
- Once a sperm cell has swum to an ovum (egg cell) it digests the coating on the outside of the egg cell - does this w an organelle called an acrosome
- This is a special type of lysosome which contains the digestive enzyme lysozyme
Epithelial cells: specialisation?
- Make up lining between body + outside
- Lines digestive, respiratory tract
Xylem and phloem make up the _____ of the plant?
Vessels
Xylem cells?
Are dead, have no organelles to allow H₂O to pass straight through
Phloem cells (sieve tube elements)?
Have a small amount of cytoplasm - means there’s lots of space for phloem sap
Palisade cells?
- Cells in the upper layer of leaves which carry out photosynthesis
- Cylinder shaped and long which allows light to be absorbed along their whole length
- Pack tightly = max photosynthesis - but their shape allows there to be gaps for CO2 to pass through
Palisade cells 2?
- Lots of chloroplasts for photosynthesis
- Large vacuole pushes chloroplasts towards the edge of the cells - means CO2 entering the cell has a short diffusion distance
- Chloroplasts can be moved up and down the cell by the cytoskeleton 7 motor proteins- when sunlight is ↓ they are moved to top & when ↑ they are moved further down to avoid being damaged
Guard cells?
- Thick cell wall in the middle and thein cell wall at their tips
- They have chloroplasts but they only have the enzymes to carry out the 1st stage of photosynthesis - means can produce ATP but not sugars
Opening & Closing stomata?
- When need to be opened, guard cells produce ATP thru 1st stage of Ps
- ATP is used to pump potassium ions into the guard cell - this lowers the water potential of the cell and water rushes in
- The water pushes against the sides of the ell - making it swell and become turgid
- Swelling occurs more when the guard cell is thin - at the tips of the guard cell
- This pushes the 2 guard cells away from each other opening the stoma
- This lets gases travel in and out of the leaf
What is the function of root hair cells?
Absorb water and mineral ions from the soil
How do root hair cells absorb water and mineral ions?
Protein pumps on their CM which transport minerals into the cell - this requires ATP so have lots of mitochondria to provide it
The mineral ions in the cell lower its ψ so H2O follows by Osmosis
What do the protrusions of the root hair cell do?
↑ SA of the cell = more space to absorb H2O + ions + allows RHC to have lots of protein pumps for efficient transport
Xylem cells are dead so?
Form hollow tubes
In order to survive?
Organisms need to exchange substances w the external environment
Exchange can either be?
Can occur passively - diffusion, osmosis, or active transport
SA:V what is the SA of
The surface where exchange occurs
SA:V =?
SA/V
SA =?
Area of all sides added together, cm²
Volume =?
Area of cross section x length cm³
Factors affecting need for specialised gas exchange surface: metabolic activity?
- Organisms w a lower metabolic rate require fewer nutrients and produce less waste
- High metabolic rate = require specialised exchange surface
What do all exchange surfaces attempt to do?
Max the efficiency of exchange
How can exchange surfaces maximise their SA?
Folding = less space but high area Hairs = provide an additional area for exchange to occur
Having a transport system close to the exchange surface helps maintain a ?
Strong diffusion gradient
before replication vs after replication?
before rep, each chromosome exists as a single chromatid
- after, each chromosome is made up of 2 sister chromatids -joined by a centro-mere
the overall process of mitosis involves?
the separation of chromosomes to opposite parts of the cell so the cell can /
When can we first see individual chromosomes in mitosis?
prophase
when DNA supercoils?
it turns into a shorter more condensed structure
What does the nuclear envelope disintegrating mean?
genetic material can move more freely throughout the cell
mitosis - what do plant cells not have?
centrioles - they have spindle apparatus (fibres) that form directly from cytoplasm
What is crossing over?
The exchange of DNA between chromatids on homologous chromosomes in Prophase 1 of meiosis
What happens in meiosis 1 & 2?
1 - homologous chromosomes are separated from each other
2 - sister chromatids from each chromosome are separated
In diploid cells,
One set of chromosomes come from father and one from mother
Homologous pairs of chromosomes?
Are matching chromosomes with the same genes in the same places (same gene loci) although they may have diff alleles
Single mutation?
On 1 chromosome, so only 1 daughter cell affected: cells carry mutation
mitosis - when the chromosome split?
- they’re still attached to the spindle fibres, move to the poles with the help of motor proteins
- this process requires ATP so mitochondria gather around spindle fibres
When the question asks the importance of?
Say WHY something is happening
cytokinesis is not a part of?
mitosis
in telophase (mitosis) chromosomes become _____ under microscope?
Invisible
Plant cells - meiosis?
Go directly into the next stage of meiosis without splitting
Why does epithelial tissue need to be replaced often?
Bc its exposed to the outside of the body
Blood vessels don’t run though ______ _____?
Epithelial tissue - the cells receive O2 and Nutrients from the tissue fluid below
How are epithelial cells joined?
By tight functions & desmosomes - made up of proteins that link between cells
Where is epithelial tissue found?@
Where outside meets inside world
Found in digestive tract, respiratory tract, blood vessels
Lines the skin, airways, gut and walls of organs
Meiosis 2 is the same as mitosis except?
Chromatids on each chromosome are no longer identical due to crossing over
Telophase II in plant cells?
The nuclei aren’t separated by plasma membrane yet so the cell splits 4 ways to make 4 cells
mitosis and cytokinesis key diff?
mitosis - nucleus /
cytoplasm - cytoplasm / and 2 new cells are produced
Why do cells enter G0?
- Differentiation
- DNA of the cell may be damaged
what are alleles?
- genes for a particular characteristic may vary, leading to diffs in the characteristic. diff versions of the same gene are called alleles (a.k.a gene variants)
- diff alleles of a gene will all have the same locus
Meiosis I vs II?
1- The 1st / is the reduction division when the pairs of homologous chromosomes are separated into 2 cells.
2 - similar to mitosis, and the pairs of chromatids present in each daughter cell are separated, forming 2 more cells.
the 4 main categories of tissues in animals?
- nervous tissue, adapted to support the transmission of electrical impulses
- epithelial tissue - adapted to cover body surfaces - internal and external
- muscle tissue - adapted to contract
- connective tissue - adapted either to hold other tissues together or as a transport medium
there are a no. of diff tissue in plants, inclu:
- epidermis tissue, adapted to cover plant surfaces
- vascular tissue - adapted for transport of water and nutrients
embryonic stem cells?
- are present at a very early stage of embryo development & are totipotent. After abt 7 days, a mass of cells called a blastocyst, has formed and the cells are now in pluripotent state. They remain in this state in the fetus until birth
diseases that stem cells can treat? (7)
- Heart disease
- type 1 diabetes
- Parkinson’s disease
- Alzheimer’s disease
- Macular degeneration
- Birth defects
- spinal injuries
how can stem cells be used to treat heart disease?
muscle tissue in the heart is damaged as a result of a heart attack, normally irreparably - this has been tried exp w some success already
how can stem cells be used to treat Type 1 diabetes?
w insulin - dependent diabetes the body’s own immune system destroys the insulin producing cells in the pancreas; patients have to inject insulin for life - this has been tried exp w some success already
how can stem cells be used to treat Parkinson’s?
the symps (shaking and rigidity) are caused by death of dopamine producing cells in the brain, drugs currently only delay the progress of the disease
how can stem cells be used to treat Alzheimer’s?
brain cells r destroyed as a result of the build up of abnormal proteins; drugs currently only alleviate the symptoms
how can stem cells be used to treat macular degeneration?
this condition is responsible for causing blindness in the elderly and diabetics; scientists are currently researching the use of stem cells in its treatment and early results are very encouraging
how can stem cells be used to treat birth defects?
scientists have already successfully reversed previously untreatable birth defects in model organisms such as mice
how can stem cells be used to treat spinal injuries ?
scientists have restored some movements to the hind limbs of rats w damaged spinal cords using stem cell implants
stem cells are already being used in the treatment of burns…
stem cells grown on biodegradable meshes can produce new skin for burn patients, this is quicker than the normal process of taking a graft from another part of the body
+ of stem cell use?
- the embryo’s used originally were donated from those left over after fertility treatment. More recently, the law in the UK has changed so that embryo’s can be spec created in the lab as a source of stem cells
- of stem cell use - destruction?
the removal of embryos from stem cells usually results in the destruction of the embryos, altho techs are being developed that will allow stem cells to b removed w/o damage to embroys
- of stem cell use - moral and religious ?
- religious + moral objections - many ppl believe that life begins at conception and the destruction of embryos is thfr murder
- there is a lack of consensus as to when the embryo itself hs rights and who owns the genetic material that is being used for research
alts to embryonic stem cell use?
- the controversy is holding back progress that could lead to successful treatment of many incurable diseases
- the use of umbilical cord stem cells overcomes these issues to a large extent, but r only multi-potent, restricted usefulness
- adult can be used, but don’t / as well as UBSCs & are more likely to have acquired mutations
- iPSCs
induced pluripotent stem cells ?
are adult stem cells that have been genetically modified to act like embryonic stem cells so are pluripotent
use of ____ stem cells does not raise the same ethical issues as animal cells?
plant
Connective tissue is involved in?
Separating (e.g. organs) and connecting (e.g. joints - connecting bones) cells and withstanding forces
Connective tissue typically has ?
Lots of non-living protein and carbohydrates that form an extracellular matrix as cells of connective tissue secrete proteins and carbs
Elastin in connective tissue?
One polypeptide in CT is elastin - which gives CT its elasticity
E.g. skin needs to stretch
Collagen in CT?
Polypeptide with high tensile strength, provides strength
Hyaluronic acid in CT?
A polysaccharide which traps water
Examples of CT?
Blood - connects body parts together through blood vessels
Bone - provides a structure to withstand forces
Cartilage?
Type of CT
- located in joints and around soft tissue
Developing cartilage?
- Starts out as cells called chondroblasts
- These secrete fibres that make up the extracellular matrix and the cartilage
- Once the matrix has been formed, the chondroblasts develop into chondrocytes
- The mature chondrocytes are less metabolically active than the chondroblasts
Muscle tissue?
- Controls movement - e.g. of limbs
- Is metabolically active so it has a rich supply of blood
- Made up of muscle cells called muscle fibres
- Which have specialised organelles called myofibrils which control muscle contraction
Elastic cartilage?
Found in structure that need to be strong but flexible like ear and the epiglottis
Fibrous cartilage?
- Occurs between vertebrae in the spine where it allows vertebrae to move
- It also occurs in the knee join next to hyaline cartilage where it performs a similar function - lining the ends of the bones allowing joints to be smooth
Hyaline cartilage?
- Surrounds the ends of long bones, forms the early skeleton in the developing human and joins ribs to the sternum
- It provides structure for body parts like the nose, rings around the trachea, and in the voice boc (larynx)
How many types of cartilage?
3, which occupy diff spaces in the body - Hyaline cartilage, fibrous cartilage, elastic cartilage
Types of muscle?
3 types::skeletal, cardiac, smooth
Skeletal muscle?
(think skeleton) allows the body to move around
Attached to bones via tendons
When it contacts, moves bone
Cardiac muscle?
Located in walls of heart
When it contracts, it pumps blood around the heart and then into the rest of the body
Smooth muscle?
Located in the walls of tubes in the body. Tubes - oesophagus, mouth, stomach
In the walls of the intestines, blood vessels and urinary tracts
When contracts, pushes substances along tubes
