cells and classification

yay slay

mrs h gren

movement respiration sensitivity homeostasis growth reproduction excretion nutrition

m

movement - move towards food, away from predators

r

respiration - release energy in form atp from glucose in their food

s

sensitivity - respond to changes in environment (external stimuli)

h

homeostasis- control their internal conditions eg water content + temperature

g

growth - grow and develop into adult form e.g. people growing taller

r2

reproduction - produce offspring in order for their species to survive

e

excretion - removal of waste products e.g. co2 + urea

n

nutrition - organisms need nutrients to provide them w energy + raw materials for growth and repair eg fats, proteins, carbohydrates

eukaryotic cells vs prokaryotic

eukaryotic:

• animals/ plants / fungi / protoctists

• contain nucleus + membrane bound organelles eg mitochondria

• DNA contained within nucleus

• have CHROMOSOMES

prokaryotic cells

• have a SINGLE LOOPED CHROMOSOME

• no nucleus or membrane bound organelles

• DNA free in cytoplasm

plant cell

nucleus

cell membrane

cytoplasm

ribosomes

chloroplasts

vacuole

cell wall

mitochondria

animal cell

nucleus

cell membrane

cytoplasm

mitochondria

ribosomes

nucleus

membrane bound organelle, contains genetic material which controls cell’s activities

cell membrane

forms outer surface of cell

controls substances that go in and out of cell

cytoplasm

gel like substance (site of most of cell’s chemical reactions)

contains enzymes which control these reactions

ribosomes

small organelles, site of proteinsynthesis in cell

mitochondria

small organelles, site of aerobic resp in cell

cell wall

rigid structure made of cellulose, surrounds cell membrane and supports + strengthens it

vacuole

large organelle, contains cell sap (weak solution of sugars + salts)

supports and strengthens cell

chloroplasts

site of photosynthesis - converts light energy into chemical energy stored as glucose

organisation- organelle

specialised structures within cell, carry out a specific func e.g. mitochondrion

organisation - cell

basic structural and functional units of all living organisms

tissue

group of similar cells working tg to perform a particular function

e.g. xylem tissue (for transporting water + mineral salts) in plants

e.g. muscle tissue (contracts + relaxes to cause movement) in humans

organ

group of different tissues working together to perform a function

e.g. lungs in mammals

leaves in plants

organ systems

• group of organs working together to form an organ system

• each system does a different job

eg in mammals, digestive system = pancreas, liver, stomach etc

descriptions - plants

• multicellular

• have chloroplasts, can photosynthesise

• cell wall made of cellulose

• store carbohydrates as starch

flowering plants examples include

Cereals e.g. maize

Herbaceous legumes e.g. beans and peas

descriptions - animals

• multicellular

• no chloroplasts, can’t photosynthesise

• no cell wall

• most have nervous coordination, meaning they can respond rapidly to external stimuli

• can move from one place to another

• store carbohydrates as GLYCOGEN

mammals e.g humans

insects e.g mosquitoes

fungi

• some are single celled

• others have a body called a mycelium made up of hyphae (thread like structures) which contain many nuclei

• cannot photosynthesise

• cell wall made of chitin

• most feed by saprotrophic nutrition where they secrete extracellular digestive enzymes into area outside their body to dissolve their food and then absorb nutrients

• store carbs as GLYCOGEN

e.g. yeast (single celled fungus)

e.g. mucor (multicellular - has mycelium and hyphae)

e.g. causes athlete’s foot

protoctists

• single celled, microscopic

• some can photosynthesise

amoeba (animal cell like)

chlorella (plant cell like)

• e.g. plasmodium, causes malaria

bacteria

• single celled, microscopic

• no nucleus → circular chromosome dna + plasmids

• some can photosynthesise

• most feed off of other living and dead organisms

e.g. pneumococcus, causes pneumonia

viruses

• particles, not cells

• smaller than bacteria

• parasites: need living host to reproduce

• infect all types living organisms

• no cellular structure: protein coat surrounding genetic material (dna/rna)

e.g. influenza virus (flu)

e.g. tobacco mosaic viruses- discolours tobacco leaves- no chlorophyll production

specialised cells

are specialised to carry out a specific function, meaning their structures vary e.g. rbcs

red blood cells adaptations

1. biconcave shape

provides large SA:V ratio, faster rate diffusion of oxygen in and out of rbc

2. contains protein called haemoglobin

binds to oxygen to form oxyhaemoglobin, allows efficient transport of oxygen from lungs to rest of body

3. no nucleus

more space inside cell for haemoglobin to be packed in: can bind to cell and transport more oxygen around body

4. thin cell membrane: one cell thick

short diffusion distance for gas exchange (oxygen and co2)

5. flexible cell membrane

can squeeze through narrow capillaries to deliver oxygen to all tissues

stem cells

1. cell differentiation = process by which cell changes to be specialised for its function

• as cells change + develop diff organelles + turn into diff cell types this allows them to carry out specific functions

2. undifferentiated cells (STEM CELLS) can divide to form many more stem cells which can differentiate into diff cells

3. found in human embryos- these have potential to turn into any cell in the body

4. adults also have stem cells but only found in certain places e.g. bone marrow and can only turn into some types of cells eg RBCs

5. stem cells form embryos and bone marrow can be grown in a lab, to produce clones (genetically identical cells), and made to differentiate into specialised cells to use in medicine/ research

stem cells can cure diseases

• medicine already uses adult stem cells to cure disease e.g. stem cells transferred from bone marrow of healthy person can replace faulty RBCs in receiver

• embryonic stem cells could also be used to replace faulty cells in sick ppl e.g. insulin producing cells in ppl w diabetes, nerve cells for ppl paralysed w spinal injuries etc

HOWEVER, risk:

• stem cells grown in a lab may become contaminated with a virus which can become contaminated w a virus which is passed onto patient + will make them lot sicker

stem cells - ethical dilemma

• some people are against stem cell research bc they feel human embryos shouldn’t be used for experiments bc each one has potential to be a human life and scientists should develop other sources of stem cells to help ppl without using embryos

• others think curing patients suffering is more important than embryos rights

• one argument in favour is that embryos used in research are usually unwanted from fertility clinics and would be destroyed if not used.