Biology B2
Cells and function
- Created by: Annabel smith
- Created on: 04-05-13 16:23
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
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)
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
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
Diffusion
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
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)
Photosynthesis
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
Plants' use of glucose
- Converted to insoluable starch - storage
- Respiration
- Converted to fats, oils - storage
- Produce cellulose - strengthen cell wall
- Produce proteins
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.
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
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
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
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
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
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
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
Mitosis
- 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
Meiosis
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.
Stem cells
UNSPECIALISED cells
- found in embryos and adult bone marrow
- these cells go on to differentiate
- can be used for paralysis, leukemia
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
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
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
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
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)
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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