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Biology 3A - homeostasis. The organism and its environment Organisms have needs and produce wastes They must survive in environments that may be inconstant.

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Presentation on theme: "Biology 3A - homeostasis. The organism and its environment Organisms have needs and produce wastes They must survive in environments that may be inconstant."— Presentation transcript:

1 Biology 3A - homeostasis

2 The organism and its environment Organisms have needs and produce wastes They must survive in environments that may be inconstant and harsh, and thus must have features that allow their survival Some of the most important environmental challenges include dealing with temperature extremes, water salinity and water availability In this section we look at how different organisms meet these challenges in order to survive

3 Cells need matter Nutrients and essential materials include: Organic compounds (contain Carbon) eg glucose, proteins, fats, DNA, RNA, ATP used for body structures, cell components, enzymes, hormones, etc Inorganic elements or compounds eg nitrogen, phosphorus, calcium, iron, sodium, potassium, etc used for making organic compounds (eg proteins, DNA & ATP contain nitrogen and phosphorus), maintaining osmotic balance, and pH balance

4 Cells need to remove wastes Describe the effects of these on the cell: Carbon dioxide toxic waste, decreases pH Ammonia toxic waste, increases pH Excess salts alters osmotic pressure – drags in water Excess water alters osmotic pressure – can burst cells

5 Exchange of material Occurs at the cell membrane The processes involved include osmosis, diffusion and active transport

6 Exchange of material 2 Permeable substances can move through Differentially permeable only some substances can move through Hypotonic lower salt concentration Hypertonic higher salt concentration Isotonic same salt concentration Concentration gradient difference in concentrations across membranes Osmotic pressure force that pulls water across a membrane, due to concentration gradients

7 Size and surface area As size increases what happens to surface area to volume ratio? SA:Vol decreases Why is this important? Exchange occurs at surfaces – the larger the SA:Vol, the more exchange will occur

8 Shape and surface area What happens if cells change shape? – alters surface area 2x 2x2 1x1x8 4x2x1

9 How cells increase their surface area Size Shape Folding Cell extensions pseudopods microvilli

10 Cells need energy Energy in the cell is transported as ATP Cells can get energy by: Respiration (all cells) Photosynthesis (plants)

11 Respiration Glycolysis glucose  pyruvate + 2 ATP Fermentation (plants) pyruvate  alcohol + CO 2 Fermentation (animals) pyruvate  lactic acid These all occur in the cytoplasm Transition reaction pyruvate enters mitochondrion and the Krebs cycle Krebs cycle – series of reactions that generates ATP, H 2 O & CO 2 and uses electron transport chain to generate large amounts of ATP (34 – 36 ATP)

12 Summary of respiration

13 Comparison of aerobic and anaerobic respiration AnaerobicAerobic Site it occurs CytoplasmMitochondria Need for oxygen NoYes Waste products Lactic acid (animals) Alcohol + CO 2 (plants) CO 2 + H 2 O Amount of ATP Reactions involved Glycolysis, fermentation Transition, Krebs, electron transport chain

14 Photosynthesis Light dependent reactions Occurs in grana Photosystems I and II use light to split H 2 O into H + and O 2 Electron transport chain generates ATP Light independent reactions Occurs in stroma ATP & H + from light reactions used with CO 2 in Calvin cycle to make sugars  glucose

15 Summary of photosynthesis

16 Comparison between respiration and photosynthesis RespirationPhotosynthesis Inputs Oxygen and glucoseLight, CO 2 and water Products ATP, CO 2 and waterOxygen and glucose Type of cells AllPlants, some protists & cyanobacteria Location in cells Cytoplasm and mitochondria Chloroplasts Where energy comes from Organic compounds eg glucose Light Role of ATP End productMade in light reactions, used up in dark reactions Names of reactions Glycolysis, fermentation, Krebs cycle Light reactions, Calvin cycle

17 Factors affecting rate of respiration Temperature as temperature increases, respiration increases, until temperature gets too high  enzymes denature Concentration of glucose as glucose increases, respiration increases, until maximum level reached Concentration of oxygen as oxygen increases, respiration increases, until maximum level reached Concentration of wastes (CO 2 or alcohol) as wastes increase, respiration decreases

18 Factors affecting rate of photosynthesis Temperature as temperature increases, photosynthesis increases, until temperature gets too high  enzymes denature Light as light increases, respiration increases, until maximum level reached Concentration of carbon dioxide as carbon dioxide increases, respiration increases, until maximum level reached Humidity if humidity decreases, stomata will close to conserve water, hence reducing carbon dioxide, and slowing photosynthesis

19 Enzyme terminology Active site where substrate attaches Substrate what enters a reaction Product what leaves the reaction Enzyme-substrate complex substrate attached to enzyme Lock and key model enzyme & substrate match like a key into a lock

20 Factors affecting enzyme functions Temperature as temperature increases, reaction rate increases, until temperature gets too high  enzymes denature pH enzymes are pH specific – only work in specific pH range Concentration of substrate as substrate increases, reaction rates increase, until maximum level reached Concentration of product as products increase, reaction rates decrease Concentration of enzyme as enzyme increases, reaction rates increase, until maximum level reached Cofactors as increase, rate increases Inhibitors as increase, rate decreases

21 Homeostasis Maintenance of constant internal environment This involves continually replacing substances as they are used up (eg glucose, oxygen) or continually removing substances as they build up (eg wastes)

22 Negative feedback systems Stimulus change in conditions Receptor detects the change Modulator decides what to do about the change Effector part of the body that carries out the response Response change in activity Negative feedback response alters the stimulus in the opposite direction

23 An example of negative feedback Stimulus Negative feedbackReceptor ResponseModulator Effector Exercise causes increased carbon dioxide & decreased oxygen brain heart Heart rate increases Increased oxygen supplied to muscles


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