Specialised cells and stem cells

measurements of RBC

-7.5 um in diameter -2.0 um thick

muscle

-can shorten in length (to move bones) -skeletal muscle fibres contain myofibrils which contain contractile proteins (allow cells to contract) -muscle fibres separated by connective tissue (work together)

palisade cell labelled

-chloroplasts (absorb large amounts of light for photosynthesis, they can move within the cytoplasm in order to absorb more light) -rectangular (closely packed together to form a continuous layer) -thin cell walls (increasing rate of diffusion of CO2) -large vacuole (maintain turgor pressure)

ciliated epithelium

-ciliated epithelial cells -hair-like structures called cilia that move in a rhythmic manner (sweeps mucus away from lungs) -goblet cells (release mucus to trap unwanted particles and prevents them from reaching the lungs)

cartilage

-connective tissue found in ear, nose, ends of bones -elastin and collagen (firm and flexible -chondrocyte cells embedded in extracellular matrix (maintain the structure -prevents ends of bones from rubbing together and causing damage

how could stem cells be useful in research? 2

-drug trials (new drugs tested on stem cell cultures before animals and humans) -developmental biology (study of the changes that occur as multicellular organisms grow and develop from a single cell, e.g. a fertilized egg, and why things go wrong) used because they divide indefinitely and differentiate into almost any cell within an organism

erythrocyte draw label and annotate to show how it is specialized to its function

-flattened biconcave shape (to increase surface area to volume ratio to transport more oxygen) -no nuclei or many other organelles (to increase available space for haemoglobin) -flexible (they can squeeze through narrow capillaries)

7 diseases that stem cells have the potential to treat, how would stem cells be useful?

-heart disease (muscle tissue in heart caused by a heart attack) -type1 diabetes (insulin-producing cells in the pancreas destroyed by immune system) -Parkinson's disease (dopamine-producing cells in the brain causes shaking and rigidity) -Alzheimer's disease (brain cells destroyed as a result of abnormal proteins) -macular degeneration (causes blindness in elderly and diabetics caused by cell death in eyes) -birth defects (already successfully reversed in mice) -spinal injuries (damaged spinal chords, loss of movement)

neutrophil

-multi-lobed nucleus (squeeze through gaps to get to infections) -granular cytoplasm contains many lysosomes (contain enzymes to attack pathogens)

root hair cell

-root hairs (long extensions that increase the SA, maximizing water and mineral uptake from soil) -vacuole containing cell sap, a solution of ions and sugars (giving a lower water potential so that water moves in by osmosis) -thin cell wall (faster rate of diffusion)

epidermis of plants

-single layer (minimize diffusion distance) -closely packed cells (filter out pathogens) -covered by a waxy waterproof cuticle (reduces water loss) -stomata (to allow CO2 into and out of the plant and water vapour and oxygen in and out)

squamous epithelium link structure to function

-squamous epithelial cells -known as pavement epithelium -very thin (flat cells and only one cell thick) -good for rapid diffusion across a surface -forms lining of lungs and allows rapid diffusion of O2 to blood

guard cell

-stomata (small openings for CO2 to enter for photosynthesis) -they change shape and close when they lose water (prevents further water loss) -cell wall of guard cell is thicker on inner side (changes shape asymmetrically so that it can open and close)

sperm cell labelled

-tail or flagellum (can deliver genetic information to the female gamete) -contain many mitochondria (supplies the energy for swimming movement) -acrosome on head (contains digestive enzymes which are released to digest the protective layers around the ovum and allow the sperm to penetrate, leading to fertilization)

xylem tissue

-vascular tissue responsible for transport of mineral ions and water -elongated dead cells (act as hollow tubes for transport) -lignification (waterproof and provides structural support) -bordered pits (no lignin so water can move through to other cells)

phloem tissue

-vascular tissue that transports sucrose and other organic nutrients from leaves and stems to all parts of the plant -sieve tube cells have little cytoplasm and no nucleus (more space for transport) -sieve plates (let phloem contents through) -companion cells(maintain nucleus and organelles linked by plasmodesmata)

3 types of stem cell and examples of where they occur

1. Totipotent (early embryos) 2. Pluripotent (embryo after 7 days) 3. Multipotent (bone marrow, umbilical cord)

3 examples of organ systems in animals and describe function

1. digestive system (breaks down large insoluble molecules into small soluble ones, absorbs the nutrients into blood, retains water needed and removes undigested material) 2. cardiovascular system (moves blood around the body to provide effective transport system for O2, glucose, hormones ect.) 3. gaseous exchange system (brings air into the body so O2 can be extracted for respiration and CO2 can be expelled)

palisade measurements

25-75 um

for and against use of embryonic stem cells for research and medicine

FOR-can develop into any type of cell (totipotent) -originally donated from those left over from fertility treatment, now they are specifically created in the lab -techniques are being developed to ensure there is no damage to embryos AGAINST-religious objections -moral objections (life begins at conception=murder) -the embryo has rights -who owns the genetic material -results in the destruction of the embryo

how are xylem vessels and phloem sieve tubes produced from meristems?

Meristematic tissue is located between the phloem and xylem tissues (vascular cambium) so stem cells from these regions differentiate into the different cells present in xylem and phloem tissues so the vascular tissue grows as the plant grows

where do stem cells occur in plants? what potency to they have?

Meristems (meristematic tissue) found at the tips of roots and shoots (apical meristems) or between phloem and xylem tissues (vascular cambium) PLURIPOTENT (develop into any tissue but not whole organisms)

plant stem cells useful for medicine?

Paclitaxel from bark of yew trees treats breast and lung cancer It cannot be chemically synthesized and must be obtained from mature trees so supply is limited and the extraction process is difficult and expensive You could use a related plant but still difficult and expensive Recently stem cells form yew tree produce paclitaxel cheaply and in sustainable quantities

tissue (or adult) stem cell

Present throughout life found in bone marrow and other specific areas. They are multipotent but they may be able to be artificially triggered to become pluripotent

Why is it important for erythrocytes and neutrophils to be constantly produced?

RBCs- they are essential for the transport of oxygen but they have a very short lifespan of 120 days (since they do not have a nucleus or organelles) so they need to be replaced constantly WBCs- essential for immune system and need to be replaced as they only live for 6 hours

stem cells and gene therapy to treat SCID

Severe Combined Immunodeficiency, vulnerable to infections (no T cells, without T cells B cells do not function) Treated normally with a bone marrow transplant which depends on finding a matching donor New gene therapy aims to remove stem cells from patient's bone marrow and genetically modify them so they function normally to produce the white blood cells needed put back into the patient and the condition should be corrected

how are erythrocytes and neutrophils produced from stem cells in bone marrow?

The multipotent stem cells in the bone marrow differentiate to become adapted to the specific roles of the white and red blood cells. This is done by the activation of certain genes in the cells.

why do multicellular organisms have specialized cells?

The organism's SA;vol ratio is too low for diffusion to provide enough nutrients or gas to the many cells of the organism. So they need to develop specialized organ systems made up of tissues with specialized cells to carry out these processes (E.g. gas exchange system has a large surface area due to ciliated epithelium and alveoli)

differentiated

The process of cells becoming specialized to carry out a specific function by the selective expression of genes in a cell's genome.

What is the importance of stem cells? why must their activity be carefully controlled?

They are the source of new cells necessary for growth, development and tissue repair. Control is necessary because if they do not divide fast enough then tissues are not effectively replaced, leading to ageing. However, if there is uncontrolled division then they form masses of cells called tumours, which can lead to the development of cancer.

what are the characteristic abilities of stem cells as compared to specialized cells?

They are undifferentiated and can undergo cell division again and again and are the source of new cells necessary for growth, development and tissue repair. Once cells are specialized they lose their ability to divide (they enter G0 phase of cell cycle)

stem cell

Undifferentiated cells that are not adapted to any particular function. They have the potential to differentiate to become any specialized cell in the organism

annotations for sperm

acrosome head (3um wide and 4um long) centriole haploid nucleus microtubules in a 9+2 arrangement tail (40um long) protein fibres to strengthen the tail helical mitochondria

How does a cell become specialized?

all cells begin as undifferentiated cells and originate from mitosis or meiosis they become specialized by differentiation by the activation of certain genes in the cell's genome

induced pluripotent stem cell

artificially changing adult stem cells which are multipotent to become pluripotent stem cells

undifferentiated

cells that are not adapted to any particular function

locations of stem cells

embryos (totipotent or pluripotent after 7 days) bone marrow umbilical cords of nerborn babies (plentiful supply and no invasive surgery)

specialised

having a particular structure to serve a specific function

organ system

made up of different organs which work together to carry out a major function in the body

organ

made up of different tissue types

tissue

made up of only one type of differentiated cell that has specialized for a particular function

levels of organization of a multicellular organism order

molecule organelle cell tissue organ organ system organism

4 main categories of tissue in animals

nervous (transmission of electrical impulses) epithelial (cover body surfaces, internal and external) muscle (adapted to contract) connective (hold other tissues together of as a transport medium)

embryonic stem cell

present at an early stage of embryo development and are totipotent (up until a blastocyst (a mass of cells) is formed, this is pluripotent)

cell

smallest unit of an organism that contains a nucleus and organelles surrounded by a membrane

how could stem cells be used for treating burns?

stem cells grown on biodegradable meshes can produce new skin for patients quicker than normal process of taking a graft from another part of the body

totipotent

stem cells that can differentiate into any type of cell (e.g. a zygote and the first 8 or 16 cells)

pluripotent

stem cells that can form all tissue types but not whole organisms (e.g. present in early embryos and origin of different types of tissue within an organism)

multipotent

stem cells that can only form a range of cells within a certain type of tissue (e.g. Haematopoetic stem cells in bone marrow are multipotent because they give rise to various types of blood cell)

how would induced pluripotent stem cells be useful in research and medicine?

we would not have to use human embryos to get pluripotent cells