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Presented by: ABIGAIL SLATER
MAB- Maintaining a Balance
Presented by: ABIGAIL SLATER
MAINTAINING A BALANCE
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Enzymes
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Negative feedback systems
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Movement of materials in xylem and phloem
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The KIDNEY!
ENZYMES
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Globular protein molecules
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Long chains of amino acids folded into a specific shape
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Specific shape determines specific function
E.g. Catalase enzyme different physical shape to rennin enzyme
ENZYMES
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Function as a CATALYST- accelerates chemical reactions in cells Not changed in chemical reactions
ENZYMES
Substrates •
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The molecules enzymes act on Fit together with enzymes at the active site
ENZYMES
“use a simple model to describe the specificity of enzymes on substrates”
ENZYMES
‘Lock and Key’ Model
ENZYMES
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Temp and pH can change the shape of the enzyme’s active site E.g. Rennin curdling milk
RESPONDING TO CHANGE
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Maintain homeostasis, optimal functioning.
Homeostasis: the maintenance
of a constant or almost constant internal state, regardless of external environmental change.
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Nearly all responses involuntary
RESPONDING TO CHANGE
Negative feedback: a response which counteracts or cancels out a change. •
Ensures that the organism maintains a constant internal environment.
RESPONDING TO CHANGE
Positive feedback: a response which increases a change. •
Only occurs in rare circumstances –
E.g. During childbirth walls of uterus contracting
RESPONDING TO CHANGE
Negative feedback involves: •
Nervous system –
–
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Central nervous system (CNS): brain and spinal cord Peripheral nervous system (PNS): system of nerves which carry information to and from CNS in form of electrochemical nerve impulses
Endocrine system (hormones)
NEGATIVE FEEDBACK SYSTEMS
Sensory Nerves
Motor Nerves
NEGATIVE FEEDBACK SYSTEMS
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Situation of increased temperature, how does the body respond?
E.g. Q.24 c) 2009 ‘Draw and label a model of a feedback mechanism’
NEGATIVE FEEDBACK SYSTEMS
Sensory Nerves
Increased temp
Thermoregulatory centre of the hypothalamus
Temp sensitive cells in skin Motor Nerves
Sweating
Sweat glands
SESSION 2
Presented by: ABIGAIL SLATER
XYLEM AND P HLOEM
MAB 2.6 “Describe current theories about processes responsible for the movement of materials through plants in xylem and phloem tissue.”
XYLEM AND P HLOEM
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Specialised vascular bundles Transport water and nutrients around plant
XYLEM AND P HLOEM
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Xylem- transports water and mineral ions Phloem- transports organic nutrients E.g. sugar, amino acids, plant hormones
XYLEM- TRANSPIRATION STREAM THEORY
Water and ion transport in xylem:
‘Transpiration stream theory’ Or
‘Cohesion-adhesion-tension theory’
XYLEM- TRANSPIRATION STREAM THEORY
Xylem: •
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Dead cells stacked on top of one another with ends broken away. Spirals of lignin support cell walls and hold vessel open
XYLEM- TRANSPIRATION STREAM THEORY Longitudinal view
XYLEM- TRANSPIRATION STREAM THEORY Transverse view
XYLEM- TRANSPIRATION STREAM THEORY
Step 1: Water and dissolved minerals absorbed into plant’s roots by osmosis through the high surface area of the plant’s root tip hairs.
XYLEM- TRANSPIRATION STREAM THEORY
Step 1: Water and dissolved minerals absorbed into plant’s roots by osmosis through the high surface area of the plant’s root tip hairs.
XYLEM- TRANSPIRATION STREAM THEORY
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Water pressure forces water into xylem vessels.
XYLEM- TRANSPIRATION STREAM THEORY
Photosynthesis:
XYLEM- TRANSPIRATION STREAM THEORY
Transverse view through plant leaf
XYLEM- TRANSPIRATION STREAM THEORY
Step 2: As the sun warms the plant’s leaves, their stomata open and water evaporates through these openings.
XYLEM- TRANSPIRATION STREAM THEORY
Step 3: Osmotic movement of water across plant leaves to replace water just lost by osmosis.
XYLEM- TRANSPIRATION STREAM THEORY
Step 4: As molecules of water leave the xylem and move into the leaf, this creates tension which pulls the water column up the xylem.
XYLEM- TRANSPIRATION STREAM THEORY
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Tension- the upward ‘pull’ of the water column Cohesion- attraction between water molecules to form a continuous stream Adhesion- attraction between water molecules and xylem vessel so water doesn’t fall down with gravity
XYLEM- TRANSPIRATION STREAM THEORY
Step 5: This movement is called a a stream of water moving up the plant from roots to the leaves through the xylem vessel
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Water only moves up the xylem Water also carries mineral ions
XYLEM- TRANSPIRATION STREAM THEORY Arrange in order: a. Meanwhile, as the sun warms the leaves, their stomata open and water evaporates through these openings. b. Overall this movement is a a stream of water moving up the plant from roots to the leaves through the xylem
c.
vessel. Water and dissolved minerals are absorbed into plant’s roots by osmosis through the plant’s root tip hairs.
d. As molecules of water leave the xylem and move into the leaf, this creates tension which pulls the water column up the xylem. (Cohesion- adhesion-tension) e. Water moves by osmosis across plant leaves to replace water just lost by osmosis, this osmotic pressure extending into the xylem.
XYLEM- TRANSPIRATION STREAM THEORY Answer: c. Water and dissolved minerals are absorbed into plant’s roots by osmosis through the plant’s root tip hairs. a. Meanwhile, as the sun warms the leaves, their stomata open and water evaporates through these openings. e. Water moves by osmosis across plant leaves to replace water just lost by osmosis, this osmotic pressure extending into the xylem. d. As molecules of water leave the xylem and move into the leaf, this creates tension which pulls the water column up the xylem. (Cohesionadhesion-tension) b. Overall this movement is a a stream of water moving up the plant from roots to the leaves through the xylem vessel.
PHLOEM- PRESSURE FLOW THEORY
Phloem: •
Banana strings ! phloem bundles
PHLOEM- PRESSURE FLOW THEORY
Phloem: •
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Transports organic nutrients such as sucrose, amino acids and plant hormones Unlike xylem, nutrients are transported both up and down the plant. Active transport- requires energy
PHLOEM- PRESSURE FLOW THEORY
Phloem: •
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Made up of living cells, containing a cytoplasm and cell wall but no nucleus Cells are called sieve tube elements
PHLOEM- PRESSURE FLOW THEORY
Phloem: •
Sieve tube elements are surrounded by companion cells which load the sugars into the sieve elements
