Biology B2

Cells and function

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Plant and animal cells

Plant and animal cells -

-Nucleus - contains genetic makeup of cell, controls activity

- Cell membrane - Controls movement into and out of the cell

- Cytoplasm - Where chemical reactions take place

- Mitochondria - Aerobic respration happens releasing energy

- Ribosomes - Protein synthesis

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Plants only

- Cell Wall - strenghens cell, made of cellulose

- Choloroplasts - contain chlorophyll to absorb light energy for photosynthesis

- Permamnent vacuole - filled with cell sap to keep it turgid (filled with water)

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Bacteria and yeast

- Bacteria - single celled - has cytopasm, cell membrane, cell wall but NO nucleus

- Yeast - single celled - has cytoplasm, cell membrane, cell wall, nucleus

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Specialized cells

- Muscle/sperm cell - many mitochondria - need lots of energy to move

- Gland cell - many ribosomes - need lots of protein to make enzymes

- Mesophyll cell (leaf) - many chloroplasts - to photosynthesise

- Root hair cell - large surface area - absorb water and mineral ions efficiently

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Spreading out of particles in a gas or substance in solution

- NET MOVEMENT in/out of cells - depends on concentration on particles on each side of cell membrane

- Movement from area of HIGH concentration to LOW concentration

- Difference in concentration - CONCENTRATON GRADIENT - Bigger = faster the rae of diffusion

Example - oxygen into the cells of body from bloodstream

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Tissues and Organs

Tissue - group of cells with similar function and structure e.g. muscular, glandular, epithelial, epidermal, mesophyll, xyloem, phloem

Organ - made of tissues e.g. stomach - made of musclular (to churn food), glandular (to produce digestive juices) and epithelial (to cover outside and inside of stomach)

Organ system - group of organs - Digestive system  - glands (pancreas, salivary produce digestive juices), stomach and small intestine (where digestion occurs), liver (bile), small intestine ((absorbtion of soluable food), large intestine (water is absorbed from unsoluable food = poo)

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Green plants and algae ONLY

Equation - carbon dioxide + water (+ light energy) --> glucose + oxygen

Process - CO2 taken in by leaves, water by roots. Chlorophyll traps light energy. Energy used to convert CO2 and water into glucose (starch + sugar)

- Iodine test - only green areas with chlorophyll turn iodine solution black to show starch

LIMITING FACTORS - lack of light, temeperature (too cold the enzymes don't wor efficiently, too hot enzymes become denatured), lack of CO2

- Independant variable - one being tested e.g. concentration of CO2

- Dependant variable - one tested e.g. volume of oxygen produced

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Plants' use of glucose

- Converted to insoluable starch - storage 

- Respiration

- Converted to fats, oils - storage

- Produce cellulose - strengthen cell wall

- Produce proteins

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Organisms in their environment

Living organisms form communities 

 PHYSICAL factors affecting distribution of organisms - Temperature, nutrients avaliable, light, water, oxygen, CO2

- Measuring distribution of organisms  - RANDOM QUANTATIVE SAMPLING - using quadrat - thrown behind to make it random. Count number of organism in square.

SAMPLING ALONG TRANSECT - not random - quadrat placed every 5 metres or so along line and organisms counted. 

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Proteins, catalysts and enzymes

Protein molecules - made from ong chains of AMINO ACIDS

Proteins can be: structual components of tissues (muscles eg.), hormones, antibodies, CATALYSTS

Chemical rections in cells - controlled by proteins called enzymes <-- These are biological catalysts (speed up reactions without altering the substance)

ACTIVE SITE - special shapes within the enzymes where other molecules can fit - if dentatured, this active site changes and therefore cannot cause chemical reactions.

SUBSTRATE - Can be held in the active site and either be connected to other molecules or broken down

- Enzymes can: 

- build larch molecules from smalled ones e.g. glucose --> starch

- change one molecule into another- break down larger molecules into smaller ones

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Factors affecting enzyme action

- Warmer it is, the faster the reaction - higher temperatures, molecules move around more quickly. colliding with each other quicker producing more energy.

- Too hot- enzymes become denatured - active site changes shape

- different enzymes work best at different PH levels

- Too acidic/alkali - enzyme becomes denatured

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Enzymes in digestion

Digestive enzymes produced by specialised cells in the glands and lining of the gut.

- Digestion - involves the breakdown of large, insoluable molecules, to smaller, soluable ones

AMYLASE - carbohydrase - produced by salivary glands, pancreas, small intestine - cataysed digestion of strarch to sugars - works best in alkali

PROTEASE - produced bt stomach, pancreas, small intestine - catalyses breakdown of proteins to amino acids - works best in acid

LIPASE - produced by pancreas and small intestine - catalyses breakdown of lipids to fatty acids and glycerol - works best in alkali

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Use of enzymes

BIOLOGICAL DETERGENTS - proteases, lipases - digest food stains at low temperatures - saves energy

BABY FOOD - proteases- pre-digest proteins

FRUCTOSE - Isomerase - convert glucose to fructose - dieting products

SUGAR SYRUP - carbohydrases - strach to sugar syrup

INDUSTRY - speed up reactions

Advantages - effective at removing stains, saves energy and money by working at lower temperatures, can be used in diagnosis and treatment for illness

Disadvantages - Can cause allergic reaction if touched, can enter ater systems through sewage, industrial enzymes costly to produce, denature at high temperatures needed to kill bacteria

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Aerobic respiration

Equation - Glucose + oxygen --> CO2 + water (+energy)

Energy produced - used for bulding larger molecules, move muscles, maintain body temperature, convert sugars and nitrates into amino acids and then proteins in plants.

Inestigations - usually look at how much CO2 produced - use limewater (turns cloudy) - quicker turns cloudy, fater CO2 is being produced.

 Also done with temperature - e.g. germinating peas left in flas - temp. measured

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Effects of exercise

Exercise - muscles need more energy to contract

- need to increase rate of oxygen and glucose rech muscle cell - aerobic respiration - also need to remove CO2 <-- produced more quickly

- Heart rate increases - blood vessels dilate (widen - allows more oxygen and glucose through

- Breathing rate and depth of breath increases- allows greater uptake of oxygen and release of CO2

- Glycogen stored in muscles converted back to glucose during exercise

Exercise = more energy needed = more oxygen and glucose needed = CO needs to be removed

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Anaerobic respiration

- When not enough oxygen to your muscles for aerobic resp, cells start respiring anaerobically.

 - Glucose not completely broken down - produces lactic acid

 - Less energy released from the glucose

- Blood flowing through muscles removes lactic acid

What is produced?

 - No CO2 or water, just lactic acid

- After exercise, lactic acid needs to be broken down - need a lot of oxygen for this - called OXYGEN DEBT - eventually oxidises lactic acid into CO2 and water

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 - Need cell division for the growth/repair of damaged tissue

MITOSIS - 2 identical cells produced - chromosomes contain genes (alleles) which are passed on 

PROCESS -  copy of each chromosome made in cell before division - split

Plant and animal embryos - lump of unspecialised cells - STEM CELLS 

ANIMAL - cells differentiate early on, cell division mainly for repair/replacement

PLANT - differentiate throughout the plants life

ASEXUAL REPRODUCTION - by mitosis - offspring contains same alleles as parent

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Cells in reproductive organs - testes, ovaries in animals - divide by meiosis - form GAMETES (sex cells) - humans - gametes are sperm and ova

gamete - only has one chromosome of original pair - cells all different from parent and each other

Sexual reproduction - causes variation - gametes fuse half genetic info. from male, haf from female

- when gametes first form - fertilisation - single body cell with new pairs of chromosomes formed <-- individual formed by cells doing MITOSIS

DIFFERENT FROM OTHER CELLS - sex cells divide, to have 2 sets of chromosomes, then DIVIDE AGAIN to have 1 set.

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Stem cells


 - found in embryos and adult bone marrow

 - these cells go on to differentiate

-  can be used for paralysis, leukemia

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Mendel to DNA

Mendel wored out how characteristics were inherited - suggested seperately inherited factors - now called GENES (found in chromosomes)

- Chromosomes made of DNA - long molecule with double helix structure - GENES are short strands of DNA

 Everyone has unique DNA - fingerprint - EXCEPT twins/clones

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Inheritance in action

Humans have 23 pairs of chromosomes - one pair are the sex chromosomes

- Females - **  - Males - XY

- Genes controlling the same characteristic - called ALLELES - DOMINANT - masks the effect of another. RECESSIVE - where the effect is masked

PHENOTYPE - physical appearance of characteristic - e.g. dimples or not - effect genotype

GENOTYPE - genetic makeup - e.g. the dimples gene

HOMOZYGOUS - both alleles are the same - DD(homozygous dominant), dd(homozygous recessive)

HETROZYGOUS -  alleles are different - D,d

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Polydactyly and Cystic fibrosis

Genetic disorders

 Polydactyly - Dominant - only has to inherit one dominant allele to see the effects

C.F - Reccessive - must inherit two recessive alles to see effects

C.F - affects cell membrane - sticky mucus - affect lungs and pancreas - can be inherited from to carriers

PD - parent with PD - Pp. Parent without - pp. - possibilities - Pp, Pp, pp, pp - 50% chance of child getting it

CF - parents carrying CF allele - Cc, Cc - possibilities, CC, Cc, cc, Cc - 25% being a CF sufferer, 50% being carrier, 25% unaffected

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Origins of life on earth

Earth - 4500 million years old. life formed 3500 million years ago.

FOSSILS - indicator of early life forms - formed from hard parts of animal, nature which couldn't decompose due to lack of conditions e.g. ice, footprints/burrows

- Many eary life forms were soft bodied - couldn't fossilize

- natural disaster such as earthquakes crush fossil evidence

- early life condition were not good for fossilizing - fossil record is incomlete

USES of fossils - find out about extinction/adaptations of earlier life

EXTINCTION - caused by many facotrs - biggest being change in environment e.g. climate change

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Isolation and evolution

New speices can arise if existing species of a group become isolated from the rest of the group - GEOGRAPHICAL ISOLATON - charles darwin - finches - galapogas islands - SPECIATION - diffeent beaks - couldn't interbreed

SPECIATION - result of isolation - natural selection of genetic makeup (alleles) - different predators - only  ones with large legs survive - offspring have long legs...

Equation for speciation - isolation --> genetic variation --> alleles selected --> interbreeding no longer possible --> new species (speciation)

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Structure of a leaf

3 main layers - top - paliside mesophyll. Middle - spongy mesophyll. Bottom - Stomata

- Top - exposed to the most light - contain palisade mesophyll - lots of chlorophyll - darker than bottom - large surface area

- Bottom - pores called stomata - open to let CO2 diffuse into leave, close to stop water getting out - controlled by guard cells

-Middle - spongy mesophyll - airy

Water enters leaf through vascular bundle - through hollow tube called xylem - bundle spreads out as veins to cover the whole leaf

- How leaves stop bacteria getting in - above palisade and below spongy mesophyll - epidermis cells - produce waxy coating (cuticle) - seals leaf - only way in through stomata

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Annabel smith


wow this is great!

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