1
Q
multicellularity
A
- multicellularity means that the functions necessary to maintain life are shared between different specialised cells.
- cells work cooperatively for survival and reproduction
2
Q
what makes organisms multicellular?
A
- cells (except gametes) must have the same DNA.
- cells must be connected, communicate and cooperate to function as a single organism.
-must have specialised cells - cells must be dependant on each other
3
Q
advantages of multicellularity in plants
A
- more energy efficient & longer lifespan
- sexual reproduction
- variation in population
- complex responses to external stimuli
4
Q
disadvantages of multicellularity in plants
A
- more energy required for survival
- cells cannot function independently
- more energy required for sexual reproduction
- populations take longer to evolve
5
Q
levels of organisation in animal cells
A
organisational level of cells:
- specialised cells
- tissues
- organs
- systems
- organism
6
Q
cell specialisation
A
- all multicellular organisms begin as a single cell (zygote) from the fusion of gametes
- the zygote develops into a multicellular embryo via mitosis
- continued cell division, resulting in multicellular organism and trillions of specialised cells
7
Q
define cell differentiation
A
unspecialised cells (stem cells) become specialised cells
8
Q
cell differentiation
A
- stem cells originate in blastula (blastocyst in mammals)
> make up germ layers & differentiate to form specialised cells (tissues & organs)
9
Q
what are the three germ layers
A
- endoderm (internal) > lung, digestive & thyroid cells
- mesoderm (middle) > cardiac & skeletal muscle, RBC’s
- ectoderm (external) > neuron on brain, pigment cells
10
Q
differentiation in animals
A
adult stem cells and only occurs in some tissues
11
Q
differentiation in plants
A
- meristem tissue (at tips of shoots and roots)
- apical meristem (organs and root growth)
12
Q
what is gene expression
A
the process where the information stored in genes is used to build different structures in a cell
13
Q
features of gene expression
A
- determines how cells differentiate & function
- specialised cells:
> some genes are expressed / ‘switched on’
> some are not expressed / ‘switched off’ - eg. specialised pancreatic cells express the genes needed to produce insulin
14
Q
levels organisation in vascular plants
A
- specialised cells
- tissues
-organs - systems
-organism - eg. angiosperms, conifers, cycads, ferns, ginkoes
15
Q
functions of specialised cells in vascular plants
A
- transport of nutrients
- transport of H2O
- acquiring energy via photosynthesis
16
Q
functions of specialised tissues in vascular plants
A
- involved in transport of H2O and nutrients
> xylem (H2O from roots)
> phloem (sugars and other organic compounds)
17
Q
functions of specialised organs in vascular plants: roots
A
- absorb & store H2O and nutrients from soil
- support- anchor the plant to the ground
Stems:
18
Q
functions of specialised organs in vascular plants: stems
A
- support the plant
- transport H2O and nutrients (+ stores)
- grow new plant tissue
> dermal tissue (outer layer)
> ground tissue (inner layer- non-vascular tissue)
> vascular tissue
19
Q
specialised organs in vascular plants: leaves
A
- made up of: upper and lower epidermis and mesophyll
- vascular tissue (xylem and phloem) = veins in leaf structure
- photosynthesis
- epidermis (upper): covers entire leaf, secretes the waxy cuticle, no chloroplasts
- epidermis (lower): regulates gas exchange and H2O loss
20
Q
C3 plants
A
- account for 95>% of plants
- photosynthesis occurs in mesophyll cells
- 3 carbon molecules produced by CO2 molecule
> calvin cycle - follow photosynthetic pathway with stomata open
21
Q
C4 plants
A
- more complex photosynthetic process that C3 plants
- occurs in mesophyll & bundle sheath cells
- no photorespiration
22
Q
specialised organs in vascular plants: flowers & friuts
A
FLOWERS:
- assist with fertilisation of ovules (in ovaries) by sperm (in pollen)
- specialised structures
> attract pollinaters
> create pollen for wind or water dispersal
FRUITS:
- protect the developing seeds
- help seeds disperse away
> attach to fur on animals for dispersal
23
Q
equation for photosynthesis
A
6CO2 + 6H2O –> C6H12O6 + 6O2
24
Q
equation for cellular respiration
A
C6H12O 6 + 6O2 –> 6CO2 + 6H2O + ATP
25
what are specialised cells
specialised cells are cells that have:
- a specific function.
- unique structural adaptations to carry out their functions
26
advantages of multicellularity in animals
- body cells isolated from external enviro by skin
- buffers against changes in external enviro
- allows internal conditions to be maintained
27
disadvantages of multicellularity in animals
- cells don't have direct access to external enviro
- difficult for cells to gain essential substances (H2O and nutrients) and remove unwanted substances (CO2 and wastes)
28
what are specialised tissues (animals)
groups of similar specialised cells working together to carry out a particular function
29
what are the 4 basic types of specialised tissues (animals)
1. muscle tissue- cells that can contract (skeletal & cardiac)
2. nerve tissue- neurons sense stimuli & transmit signals
3. connective tissue- supporting & connecting structures (bone & blood)
4. epithelial tissue- one/more layers of cells: cover internal and external surfaces (skin, intestinal lining)
30
organs
structures made up of 2 or more tissues that perform a similar function
31
carbohydrates
- immediate energy source
- glucose broken down to ATP
> excess stored as glycogen - polysaccaride
> stored in liver and muscles
32
lipids (fats)
- energy storage
- required for creation of cell membrane, hormones and vitamins
33
amino acids (protein)
- required for protein synthesis
- not stored but are found in blood
- animals can't synthesise all the amino acids they need
34
vitamins
- organic compounds made by plants, some animals and microorganisms
- required in small amounts
- 13 required by humans and other mammals
35
minerals
- inorganic
- more than 20 required in our diet
- calcium, phosphorus, magnesium, iron, sodium, potassium, iodine
- found in cytosol of cells, structured components & molecules of many enzymes and vitamins
36
what are vascular plants
plants with specialised vascular tissues and systems for the transport of water and nutrients, including xylem and phloem
37
what are the tissues for transportation in vascular plants
transport occurs inside closed vessels which are organised into vascular bundles, consisting of:
- xylem: transports H2O and dissolved nutrients from the roots to leaves
- phloem: transports sugars from leaves to roots
- lignin: sheath that strengthens and supports the tissue
38
structure and function of vascular tissue
xylem and phloem:
- contain continuous tubular pathways through the roots, stems & leaves
- fluids flow through these tubes to all parts of the plant
39
arrangement of xylem and phloem tissues in roots, stems and leaves
roots:
- central core of the xylem in a star/cross shape, with phloem between the arms of the xylem
stems and leaves:
- xylem and phloem grouped into vascular bundles
40
xylem tissue
composed of xylem vessels and tracheids
- long, water filled tubes made up of dead cells joined end to end
- openings at each end so fluid can flow through
- tracheids: large, pointed, water-filled cells
> not connected end to end
- mature tracheids and xylem tissue:
> made of dead cells
> are strengthened
41
phloem tissue
- transports organic solutes- sugars such as sucrose (glucose and fructose)
- transported from the site of synthesis (leaves) to site of use/storage (stems and roots)
- composed of:
> sieve tubes
> companion cells
> parenchyma cells
> sclerenchyma cells
42
mature phloem sieve tubes
- living cells
- no lignin in their cell walls
- linear rows of elongated cells
- plasmodesmata connects the cells
43
digestion
The breakdown of food to pass across the plasma membrane
> absorbed in the walls of the intestines
44
egestion
food which isn't absorbed that passes through the body
> faeces
45
excretion
removal of metabolic waste
> liver
46
physical digestion
- the physical breakdown of food
- happens before chemical digestion
- increases SA for enzymes to act- speeds up digestive process
47
bile
- digestive juice produced in the liver & stored in the gallbladder
- not an enzyme
- involved in physical breakdown of fats- emulsification
- breaks up large fatty masses into small droplets
48
chemical digestion
- breaking apart of complex molecules into simple molecules using enzymes
> protein based molecules that increase speed of chemical reactions
- split food molecules = hydrolysis (hydro = water, lysis = split)
49
3 major enzymes in chemical digestion
- amylase (saliva): breaks down carbohydrates into sugars
- protease: breaks down proteins in the stomach
- lipases: break down lipids in small intestines
50
extracellular chemical digestion
- digestion = outside the cells
- digested molecules are then absorbed
- occurs in mammals and most other animals
51
intracellular digestion
- food engulfed into food vacuole
- enzymes released for digestion
- nutrients released straight into the cytosol
- type and size of food that can be limits digestion
> Single celled organisms + invertebrates (mussels, jellyfish and flatworms)
52
3 types of diets in animals
- herbivores: consume plants, spend most of the day eating
- carnivores: consume other animals, spend little time eating
- omnivores: consume plants and animals, humans spend 30-90 mins a day eating
53
human digestive system
mouth --> oesophagus --> stomach --> liver --> small intestine --> duodenum --> large intestine
54
mouth
- physical digestion by teeth
- chemical digestion via salivary amylase (break down carbs)
- saliva coats food to protect oesophagus
- food is swallowed and enters oesophagus
55
swallowing
- reflex triggered by back of tongue
- epiglottis prevents food entering trachea (windpipe)
56
oesophagus
- peristalsis- wave of muscular contractions
- mucus produced but no enzymes!
- oesophageal sphincter closes once food enters stomach
> prevents food from moving back up
57
stomach
- mechanical digestion = stomach churns food
- glands (stomach walls) secrete digestive juices that help chemically break down food
- food and juices now called chyme
- glands in the stomach also secrete mucus to protect the stomach lining from acid wear.
58
digestive juices
- hydrochloric acid
- pepsinogen
- gastric lipase
59
liver (digestive function)
- regulating metabolism
- removing toxins
- processing nutrients
- storing excess glucose as glycogen
- producing bile for mechanical breakdown of fats
60
gallbladder/pancreas
gallbladder: stores bile released into small intestine
pancreas: produces digestive enzymes- activated once food enters the duodenum
- hormones = insulin and glucagon (regulates sugar levels in blood)
61
small intestine
- primary nutrient exchange organ = thin & large SA
- lining is one cell thick- rapid nutrient transfer
- villi and microvilli increases SA:V and high blood supply
> helps SI to exchange materials faster across the membrane
62
duodenum
- receives small amounts of chyme from stomach & pancreatic enzymes, intestinal enzymes and bile
> bile: alkaline and neutralises stomach acids = favourable pH for enzyme action
63
enzymes in the small intestine
- complete digestion and allow for absorption
- lipid-soluble molecules diffuse across PM easily
- water-soluble molecules travels across membrane via facilitated diffusion or active transport (depending on conc. gradient)
- most H2O absorbed across the PM osmotically
- blood from intestines goes to liver first to deposit nutrients before the rest of the body
64
large intestine
- lacks enzymes
- 5 parts: appendix, rectum, caecum, colon, anus
- H2O and a few minerals are absorbed here
- undigested waste materials are absorbed
- stools form --> expelled via anus
- thin, easily stretched walls --> movement of digested food not as effective
65
nature of wastes
CO2:
- break down of carbs and lipids = transpiration
- CO2 released via respiratory system
Nitrogenous waste:
- break down of protein - contains amino acids
- nitrogenous part broken off
- ammonia- toxic
- detoxified to urea - low toxicity
66
mammalian kidney
- 2 kidneys at back of abdominal cavity
- filters blood and reabsorbs useful substances --> blood vessels form a filtrate
- blood flow always high (~25% blood flow)
> enters from the aorta via renal artery
> leaves via renal vein
- urine formed in the kidney, drained via ureters into the bladder, released via urethra
URINE = passive filtration, selective reabsorption, secretion
- functions carried out by nephrons
67
nephrons
- ~1000000
- nephron composed of a:
> bowman's capsule
> tubular region
--> proximal convoluted tubule
--> loop of Henle
--> distal convoluted tubule
68
components of kidneys
- 2 components (outer cortex and inner medulla)
- glomerulus = looping capillaries found in the cortex
- contain pores (fenestrae) = filtering of small particles
- podocyte cells line regulate protein filtration
69
filtration
- across glomerulus into bowman's capsule
- high blood pressure in glomerulus blood vessels force fluid through capillaries, into bowman's capsule
- water and small molecules pass
- blood and large blood proteins = glomerular capillaries
- RBC/large proteins in urine = broken filtration system
> blood leaking from glomerulus into Bowman's capsule, result of high blood pressure or damaged glomerular capillary
70
reabsorption
- occurs along the nephron
- amino acids, sodium chloride & glucose reabsorbed
- active transport- lots of energy
- water reabsorbed passively via osmosis
- loop of Henle - production of concentrated urine
71
secretion
- active removal of particular substances by cells in tubule wall
- added to filtrate as it passes through nephron
72
liver (excretory function)
- maintains stable internal enviro
- prepares substances for excretion
> detoxifies harmful chemicals
> breaks down amino acids --> ammonia --> urea
- waste products travel to kidneys for excretion
73
hormones
- specific chemical messengers produced by an organism
- released from glands
74
endocrine system
- made up of glands and organs which synthesise and secrete hormones
- blood transports hormones to target cells
75
pituitary gland
- base of the brain and the 'master gland'
- produces many hormones
- involved in a range of cellular functions
> growth, lactation, kidney function, regulation of thyroid and adrenal glands
- secretes hormones via exocytosis
76
hypothalamus
- above the pituitary gland
- detects internal stimuli and maintains internal optimal conditions
- hormones released regulate specific hormone production in pituitary gland
77
digestion of cellulose
- cellulose =component of cell wall
- too large to be absorbed
- enzyme cellulase needed to digest it (only produced in some herbivores)
- organisms who don't produce cellulase undergo mutualism with bacteria that produce cellulase
- bacteria provided with nutrients & organism provided with cellulase
78
hindgut fermenters
- fermentation in the caecum (where small & large intestine join)
- after small intestine (high SA absorption)
- limitation : cellulose not fully absorbed
79
foregut fermenters
- fermentation is before the stomach in the rumen
1. food regurgitated to mouth = further physical digestion (rumination)
2. moved to the rumen for chemical digestion
- pro = full absorption
- con = takes a long time
