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Junior Certificate Science Junior Certificate Science BiologyBiology

Maintenance of lifeMaintenance of life

Theresa Lowry-LehnenTheresa Lowry-LehnenRGN, BSc (Hon’s) Specialist Clinical Practitioner (Nursing), Dip Counselling, RGN, BSc (Hon’s) Specialist Clinical Practitioner (Nursing), Dip Counselling,

Dip Adv Psychotherapy, BSc (Hon’s) Clinical Science, PGCE (QTS), H. Dip. Ed, Dip Adv Psychotherapy, BSc (Hon’s) Clinical Science, PGCE (QTS), H. Dip. Ed, MEd, MEd,

Emotional Intelligence MHS AccreditedEmotional Intelligence MHS Accredited

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A typical plant cell:A typical plant cell:Cell wall – made of cellulose which strengthens the cell

Cell membrane – controls what comes in and out

Nucleus – controls what the cell does and stores information

Large vacuole – contains sap and helps support the cell Cytoplasm –

Chemical reactions happen here

Chloroplasts (containing chlorophyll) – this is needed for photosynthesis

13/04/23Plant cells have three “extra” things than animal Plant cells have three “extra” things than animal

cells:cells:

Both types of cell have these: Only plant cells have these:

Nucleus

Cytoplasm

Cell wall

Large vacuole

Chloroplasts

Cell membrane

1)

2)

3)

5)

4)

6)

13/04/23Some specialised cells we’ll come Some specialised cells we’ll come across…across…

Palisade cells – found near the top of a leaf and are packed with chloroplasts

Guard cells – can open or close to let in CO2 and regulate water content

Xylem – long and cylindrical to help transport water

Root hair cell – big surface area and thin cell wall for absorption of nutrients and water

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PhotosynthesisPhotosynthesis

PHOTOSYNTHESIS is when a plant makes its own food.

Photosynthesis USES:

Carbon dioxide

Water

Energy (from the sun)

Photosynthesis PRODUCES:

Oxygen

Glucose

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Four things are needed for photosynthesis:

Travels up from the roots

WATER

CARBON DIOXIDEEnters the leaf through small holes on the underneath

SUNLIGHTGives the plant energy CHLOROPHY

LL The green stuff where the chemical reactions happen

13/04/23Photosynthesis happens in Photosynthesis happens in the “palisade” cells in the the “palisade” cells in the

leaf:leaf:

Palisade

cells

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Equations for photosynthesis:

Carbon dioxide + _____ glucose + _____

6CO2 + 6H20 C6H12O6 + 6O2

Sunlight

Chlorophyll

Sunlight

Chlorophyll

The GLUCOSE produced by photosynthesis is used by the plant for _______ (through ____________). It is stored in the plant as ___________.

Words – respiration, starch, water, oxygen, energy

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Three factors can affect Three factors can affect photosynthesis:photosynthesis:

1. Temperature – the best temperature is about 300C – anything above 400C will slow photosynthesis right down

2. CO2 – if there is more carbon dioxide photosynthesis will happen quicker

3. Light – if there is more light photosynthesis happens faster

13/04/23Drawing graphs of these Drawing graphs of these factorsfactors

1. Temperature

Photosynthesis is controlled by enzymes – these are destroyed at temperatures above 400C

2. Carbon dioxide

3. Light

Photosynthesis increases at first but is then limited by a lack of increase in temp or CO2

Photosynthesis increases at first but is then limited by a lack of increase in temp or light

13/04/23What is the glucose used What is the glucose used for?for?

1) Glucose (sugar) can be used to make long chains of starch…

Glucose molecules

Starch molecule

2) Glucose can be used to make cellulose for cell walls…

3) Glucose can be combined with nitrates to make proteins (for growth)…

4) Glucose can be converted into lipids (fats or oils) to store in seeds…

Glucose molecules

Glucose molecules

Glucose molecules

Cellulose

Proteins

Lipid structure

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Xylem and phloemXylem and phloem

Xylem vessels transport water from the root to the leaf and stem to replace the water lost through transpiration.

Phloem cells transport nutrients from the leaves to the rest of the plant.

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Plant growthPlant growth

Plants also need three important minerals to keep healthy. They absorb these through their roots.

Plants grow using food they make through photosynthesis. So what else do they need?

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The 3 main nutrients…The 3 main nutrients…

Potassium: Helps the enzymes that are needed for

photosynthesis Lack of it leads to yellow leaves with

dead bits

Nitrates: Used to make proteins Lack of it leads to a small plant,

yellow leaves

Phosphates: Used to provide phosphorus to help

photosynthesis and respiration Lack of it leads to small roots and

purple leaves

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TranspirationTranspiration1) Water evaporates through the stomata

2) Water passes back into the leaf through the XYLEM vessels by osmosis

3) Water is then pulled upwards through the xylem tissue

4) This is replaced by water entering from the root tissue

5) Water enters root hair cells by osmosis to eventually replace the water lost through respiration

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Root hair cells

Plant roots are made of “root hair cells” which have a large surface area and a thin cell membrane to help absorb water and minerals:

Thin cell membrane

Large surface area

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Water lossWater loss

Water loss through the stomata is biggest on a hot, dry, windy day. Plants that live in these conditions often have a thicker waxy layer.

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Controlling water lossControlling water lossCarbon dioxide enters a leaf through the ________. These cells are also responsible for controlling the ______ content of the leaf…

The ______ cells control how wide the stomata opens (if at all). If too much water is being lost through the stomata then the guard cells will _____ to prevent further loss.

Water and carbon dioxide enter here No more water

and carbon dioxide allowed

in

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Turgor pressureTurgor pressureConsider a plant that’s been well watered:

Because there is a _______ concentration of water in the soil than in the ____, water will enter the plant cells through _______ and the cells will become TURGID (“_________”):

In this case the stomata will ______ to allow carbon dioxide in and water ___ and photosynthesis will carry on.

Words: out, swollen, higher,

soil, osmosis, open

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Turgor pressureTurgor pressureConsider a plant that’s been badly watered:

Because there is a lower concentration of water in the soil than in the plant water will leave the plant cells through osmosis and the cells will become FLACCID (“soft”):

In this case the stomata will close to stop water from escaping through transpiration. Because they are closed carbon dioxide cannot get in and so photosynthesis stops.

Turgid = “tense” Flaccid = “floppy”

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DiffusionDiffusionDiffusion is when something travels from an area of high concentration to an area of low concentration. For example, consider the scent from a hamburger…

The “scent particles” from this hamburger are in high

concentration here:

Eventually they will “diffuse” out into this

area of low concentration:

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OsmosisOsmosisOsmosis is a “special kind of diffusion”. It’s when water diffuses from a concentrated area to a less concentrated area through a partially permeable membrane (i.e. one that allows water to move through but not anything else):

Water Sugar solutionIn this example the water molecules will move from left to right (along the concentration gradient) and gradually dilute the sugar solution.

This is how water moves into root hair cells

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Strong sugar

solution

Medium sugar

solution

Weak sugar

solution

Pota

to c

ells

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Active TransportActive TransportActive transport is when substances are absorbed _______ a concentration gradient (like a ball being rolled ___ a hill). This takes place in the opposite direction to normal _______. This is how nitrates are taken in by root hair cells:

Root hair cells “pull” more nitrate ions in

This process needs ________ (just like rolling a ball up a hill would). This energy is provided by __________.

Root hair cell already has a large concentration of nitrate ions

Words – energy, up, respiration, diffusion, against

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Plant hormonesPlant hormones

In the shoot the growth hormones collect on the ____ side, causing it to _____ more there and bend _____ away from the force of ______.

Hormones STIMULATE growth in SHOOTS.

In the root hormone also collects on the lower side, but this time it _____ _____ growth, causing the root to grow _______ towards gravity.

Hormones RETARD growth in ROOTS.

Words: upwards, downwards, slows down, lower, grow, gravity

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Other interesting facts…Other interesting facts…In shoots, light causes hormones to collect in the shaded part of the stem, causing the shoot to grow towards the sunlight.

Artificial hormones can also be used to kill weeds, control when a plant ripens, help many plants grow from one stem and other exciting uses…

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The Nervous SystemThe Nervous SystemThe NERVOUS SYSTEM consists mainly of the brain, the spinal cord, nerve cells (“neurones”) and receptors.

Types of receptor:

1) Light receptors in the eyes

2) Sound receptors in the ears

3) Taste receptors on the tongue

4) Smell receptors in the nose

5) Touch, pressure and temperature receptors in the skin

6) Changes of position receptors in the ears (balance)

Stimulus Receptor Coordinator Effector Response

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Examples of reactionsExamples of reactionsStimulus Receptor

(i.e. the thing that detects the stimulus)

Effector (i.e. the thing that will do

the reaction)

Response (i.e. action

taken)

Bright light

Sour taste

Losing balance

Sit on a drawing pin

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Types of nerve cellTypes of nerve cellNucleus Muscle strands

(effector)Cell body

1) Motor neurone 2) Sensory neurone 3) Relay neurone

Impulse Impulse

Nerve cells (neurones) are elongated with branched endings to connect to many muscles

fibres.

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Conscious actionsConscious actionsA conscious action is one where the brain makes a considered response. Here’s what happens:

Stimulus Receptor Sensory Neurone Coordinator

Motor Neurone Effector Response

1) Receptors in your skin detect a stimulus

3) Here another sensory neurone carries the signal to the brain

4) The brain decides to move away the hand

5) This impulse is sent by MOTOR NEURONES to the hand muscles (the effectors) via the spinal chord…

2) The impulse is carried by SENSORY NEURONES to the spinal chord

6) Which then moves the hand away

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Reflex actionsReflex actionsSometimes conscious action is too slow to prevent harm, e.g…

In situations like this the body bypasses the brain to produce a quicker response. Here’s how it works…

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Reflex actionsReflex actions

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SynapsesSynapses

Neurones never touch each other – there is a small gap between them called a SYNAPSE. A signal is sent from one neurone to the next by a chemical transmitter across the synapse. These transmitters are then destroyed.

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The EyeThe Eye

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Suspensory ligaments

Optic nerve

The EyeThe Eye

Retina

Pupil

Cornea

Ciliary musclesSuspensory ligaments

Optic nerve

Lens

IrisSclera

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Seeing thingsSeeing things

Rays of light are refracted (bent) first by the cornea and then by the lens. They focus on the retina.

13/04/23Seeing things at different Seeing things at different distancesdistances

For distant objects the ciliary muscles

relax and the suspensory ligaments pull tight making the lens pull thin – the

light doesn’t bend as much.

For close objects the ciliary muscles

contract allowing the lens to go fat, thus bending the light

more.

13/04/23HomeostasisHomeostasisHomeostasis means “controlling internal conditions”:

Waste products that need to be removed + how

CO2

Urea

Internal conditions that need controlling + how

Temperature

Ion content

Water content

Blood glucose

Produced by respiration, removed via lungs

Produced by liver breaking down amino acids, removed by kidneys and transferred to bladder

Increased by shivering, lost by sweating

Increased by eating, lost by sweating + urine

Increased by drinking, lost by sweating + urine

Increased and decreased by hormones

13/04/23Controlling body Controlling body temperaturetemperature

Body temperature is controlled by the thermo-regulatory centre in the ________. It is kept at 370C as this is the best temperature for __________ to work in. If the body becomes too hot then blood vessels _________ and sweat glands release ________. If the body is too ______ then blood vessels constrict and muscles start to __________.

Words – sweat, enzymes, cold, dilate, shiver, brain

13/04/23KidneysKidneys

Blood in

Blood out

Ureter (tube that takes urine down to bladder)

Kidneys are made up of two important tissues – BLOOD VESSELS and TUBULES.

Kidneys are responsible for controlling ion, urea and water content.

13/04/23KidneysKidneysKidneys work in 3 stages:

1. ULTRAFILTRATION - Lots of water and products of digestion are squeezed out of the blood and into tubules under pressure.

3. WASTE – excess water, excess ions and any urea are now removed through the ureter

2. SELECTIVE REABSORPTION – the blood takes back the things it wants (e.g. glucose and ions) even though this means going against a concentration gradient.

Blood vessel Tubule

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Kidney structureKidney structure

13/04/23Controlling water contentControlling water contentThe amount of water reabsorbed into the blood vessels in the kidney is controlled by the hormone ADH:

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Controlling GlucoseControlling Glucose

The amount of glucose in our blood (“blood sugar level”) is controlled by the

pancreas…

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Controlling GlucoseControlling GlucoseThe amount of glucose in our blood is controlled by the hormones insulin and

glucagon working with the PANCREAS:

Glucose returns to normal

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DiabetesDiabetesDiabetes is a ________ in which a person’s blood sugar (i.e. glucose) level may rise to a _______ level. This is because the ______ doesn’t produce enough _________.

Diabetes can be treated by __________ carefully or by injecting extra insulin when needed. Diabetics have to test their blood sugar level before they decide how much insulin to _______ themselves with.

Words – insulin, disease, inject, dangerous, eating, pancreas

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Smoking, drugs and alcoholSmoking, drugs and alcohol

Smoking

Drugs

Alcohol

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SmokingSmokingCigarettes contain 3 harmful things:

1. NICOTINE, which is an ___________ drug that raises the heart beat, narrows the arteries and so causes ____ _____ _____. This leads to heart _________.

2. TAR, which coats the lining of the _______ making them less able to take in oxygen. It also contains carcinogens which cause ______________.

3. CARBON MONOXIDE, which is a _______ ____ which joins up with ____ blood cells making them incapable of transporting _____________ around the body.

Words – high blood pressure, oxygen, red, addictive, disease, poisonous gas, lungs, cancer

13/04/23Damaging the alveoli Damaging the alveoli (emphysema)(emphysema)

Before smoking After smoking – less surface area