Unit 2 Biology

Cells PhotosynthesisEnergy and biomass

Nutrient cycling

Enzymes

Homeostasis

Genes and cell division

Genetics

Cells

Animal CellsNucleus: controls everything in the cell, contains the information to make new cellsCytoplasm: A jelly like substance in which chemical reactions in the cell take place, the chemical reactions are controlled by enzymesCell membrane: gives the cell its shape and controls which substances enter and leave the cellRibosomes: Where proteins are madeMitochondria: Releases energy from respiration for the cell to use- found in the cytoplasm, small sausage shaped structures

Plant Cells

Cell wall: outside the cell membrane, made of cellulose and strengthens the cellChloroplasts: found in the cytoplasm. They absorb light energy to make food by photosynthesisVacuole: a large sac in the centre of the cytoplasm. It contains a watery fluid called cell sap

Differences between plant and animal cellsPlant cells Animal cells

Have tough cell walls for support

No cell wall

A large PERMENANT vacuole containing cell sap

Some with small vacuoles, however no cell sap

Chloroplasts, absorb sunlight for photosynthesis

No chloroplasts

Box-like shape SHAPE VAIRES

Specialised cellsLeaf palisade cells- found in the leaf of the plant, contain lots of chloroplasts for photosynthesis:

Xylem cells- small tubes that carry water up the stem

Root hair cells- are long and thin to absorb water from the soil

Nerve cells- are like wires to carry messages around the body

Sperm cells have a tail to swim to the egg

Red blood cells have a substance that carries oxygen

Tissues and organsTissues are groups of cells that all do the same

job

Organs are made up of groups of tissues.

A number of organs working together make a system.

Diffusion and osmosis

Diffusion is the movement of particles from a region of high concentration to a region of lower concentration until they are

evenly spread out.

Osmosis is the diffusion of water molecules from a dilute solution to a more concentrated one through a partially

permeable membrane.

QUIZ!

What is the use of the:

• Nucleus?• Cytoplasm?• Cell membrane?• Ribosomes?• Cell wall?• Chloroplasts?• Vacuole?Also state whether they are in Plant (P) cells/ Animal (A) cells or both

State the differences between animal and plant cells

What is the mitochondria and where is it found?

Name 3 cells found in the plant and their uses

Define: • Tissues• Organs• Diffusion• Osmosis

SLIDES 2 + 3

SLIDE 4

SLIDE 3

SLIDE 4

SLIDES 7 + 8

Describe the role of enzymes inside the cell

Suggest 2 factors that increase the rate of diffusion

Name the substance that moves across a partially permeable membrane during the process of osmosis

Explain what cell specialism means

answersCONTROL CHEMICAL REACTIONSCONCENTRATION, TEMPERATUREWATERCELLS BEING CHANGED TO DO A SPECIFIC JOB; NERVE CELLS, SPERM CELLS, RED BLOOD CELLS

PHOTOSYNTHESIS

What is photosynthesis?

• Photosynthesis is the process where plants make their own food

• The equation =Carbon dioxide + water glucose + oxygen• Sunlight is absorbed by the green chlorophyll

which are found in chloroplasts• Light energy is used to convert carbon dioxide

and water into glucose

Light energy + chlorophyll

Carbon dioxide + water glucose + oxygenLight energy + chlorophyll

Glucose is used through respiration to give plants their own energy

Excess glucose can be stored in the leaves as insoluble starch

Water is absorbed through the roots from the soil and carried up the stem to the leaves in the xylem vessels

Carbon dioxide enters the leaf by diffusion through the stomata

Oxygen is released as a by product of photosynthesis

Limiting factors

• Limiting factors decrease the rate of photosynthesis, they include:

• Shortage of sunlight• Shortage of CO2• Low temperature

• The rate of photosynthesis would increase if these factors increased

The products of photosynthesis• The glucose produced can be used in respiration to release energy.• This energy can be used to build large molecules from small ones:

• Sugars can be converted into insoluble starch, stored in the roots

• Sugars can be changed into cellulose to form new cell walls

• Sugars can combine with nitrates and other nutrients to form amino acids- build proteins for plant growth

• Sugars can be converted into lipids (fat and oils) and stored in seeds

Healthy growth

Nitrate MagnesiumNitrate is needed to produce amino acids, which then form proteins for the plant

Magnesium is needed to produce chlorophyll- to be used in photosynthesis to absorb the sunlight

If Nitrate is lacking the plant’s growth will be stunted and older leaves will urn yellow

Without magnesium the leaves will turn yellow, due to the lack of chlorophyll which is green

Plants need mineral ions and nutrients to stay healthy. They are found in the soil and absorbed through the plant’s roots.Magnesium and nitrate are vital for a plant to remain healthy:

Leaves

• Leaves are well adapted to carry out photosynthesis. They have:

• A large surface area- to absorb light rays• A thin shape- to allow gases to diffuse in and

out of the leaf easily• Chloroplasts- containing chlorophyll that absorb

light energy• Veins- to carry substances to and from all of the

cells of the leaf

Leaf Structure

cuticlePalisade mesophyll: Where photosynthesis takes place, as lots of chloroplastsSpongy mesophyll: Lots of air space between them, for gas exchange to occurVein: contains xylem tubes and phloem tubes

Xylem tubes: brings water and salt to leaf through stemPhloem tubes: takes dissolved foods away

Cuticle: waterproof layer that also cuts water loss by evaporationUpper epidermis: single layer of cells, no chloroplasts present, sunlight goes straight through to palisade cells

QUIZ!

Why do plants need the process photosynthesis?

How is sunlight absorbed?

Light energy is used for what?

Explain the job of chlorophyll during photosynthesis?

Write the equation for photosynthesis and explain each gases’ use

Name 3 limiting factors of photosynthesis

What are the 5 products and uses of photosynthesis?

What do plants need for healthy growth?

Name 2 gases that are needed and what would happen if they were lacking

Why are leaves well adapted for photosynthesis?

What do the following do in the leaf:-Cuticle?Spongy mesophyll?Lower epidermis?Upper epidermis?Palisade layer?Vein?

ENERGY AND BIOMASS

EnergyThe original source of energy for all communities of living

organisms is radiation from the Sun

Green plants capture this solar energy, transferring it into chemical energy and stored in starch and other substances that make up plant cells

Only about 10% of the solar energy reaching the plant is transferred into chemical energy by photosynthesis.

Most of the energy is:• Reflected by the leaf• Passes straight through the leaf• Simply heats the leaf up

Biomass• Biomass is the mass of living material, and as you go along the

food chain it gets less and less.• A pyramid of biomass shows the mass of all the organisms at

each point in a food chain

We can use these biomass figures to draw a pyramid of biomass to scale2500g 400g 20g

grass

snailsbird

Food production

• If there is less biomass at each stage in a food chain then there must also be less material and less energy.

The efficiency of food production can be improved by reducing the number of stages in

food chains• If we want an energy efficient diet we should

eat from low down the food chain- eating the plants rather than the plant eaters.

Energy losses

Energy consumed

30% lost as heat in respiration

10% for growth

60% lost in urine and faeces

The cow is a mammal, and mammals must keep their body temperature constant.This results in a lot of energy being lost as heat to their surroundings.

Only 10% is used for growth90% is used for:• Lost in food that is uneaten• Lost in faeces and urine• Used in respiration

Ways to improve the efficiency of food production

• Intensive animal farming involves taking steps to reduce energy losses from food animals

• Animals such as poultry are kept indoors, in a temperature controlled environment

• Their movement is also restricted to reduce heat loss from respiration, and to ensure they put weight on quickly

• Plants are treated with hormones• These chemicals ensure that they ripen as they appear

on supermarket shelves, rather than on the plant or during transport.

When discussing the positive and negative effects of managing food production there has to be a compromise between :

Maximising food production from the available land, plants and animals and protecting the environment from damage by pollution or over use and treating animals as

humanely as possibly

NUTRIENT CYCLING

Decomposition

• Useful materials like carbon and nitrogen are removed from the environment from living things.

• Eventually they are released when dead organisms are broken down (digested) by microorganisms- we call these microorganisms decomposers

• These decomposers are bacteria and fungi

The ideal conditions for decomposition by microorganisms

are warm and moist

Many bacteria are also more active when there is plenty of oxygen.

Nutrients in environment

producers decomposers

consumers

breakdown

photosynthesis

feeding breakdown

Decomposers• Fungi and bacteria use enzymes to

digest their food• These work in the same way as

enzymes do in your gut• The soluble products are taken up by

the bacteria and fungi• The decomposers absorb the food

and use it for growth and energy• These bacteria and fungi may be

eaten by other organisms and so the nutrients are passed on

• Decomposers food chain:Dead leaves fungus beetle frog

DEAD MATERIALS

BACTERIA AND FUNGI (CARRY OUT

DECOMPOSITION)

GROWTH AND CELL DIVISION

NEW DECOMPOSER MATERIAL

RESPIRATION

RELEASE OF CARBON DIOXIDE

CYCLING

NUTRIENTS RETURNED TO SOIL

The carbon cycle• Carbon dioxide is removed from the atmosphere

by green plants for photosynthesis• The carbon from the carbon dioxide is used to

make carbohydrates , fats and proteins which make up the body of plants

• Some of the carbon dioxide is returned to the atmosphere when green plants respire

• When green plants are eaten by animals and these animals are eaten by other animals , some of the carbon becomes part of the fat and proteins which make up their bodies

• When animals respire some of this carbon becomes carbon dioxide and is released into the atmosphere

• When plants and animals die or release waste, microorganisms feed on their bodies and the waste

• Carbon is released into the atmosphere as carbon dioxide when these microorganisms respire

Photosynthesis and respiration

• Respiration and photosynthesis dominate the carbon cycle

Photosynthesis takes carbon dioxide out of the atmosphere and provides the input for carbon into food chains

Carbon dioxide + water glucose + oxygenLight energy + chlorophyll

Respiration, by animals, plants and microbes releases carbon dioxide back into the atmosphere

ENZYMES

How Enzymes Work

• Enzymes are BIOLOGICAL CATALYSTS

Hotting up

• High temperatures can destroy the shape of an enzyme – DENATURE

• The substrate can then no longer fit and the reaction can no longer take place

Enzymes and respiration

• Enzymes inside living cells catalyse processes such as respiration, photosynthesis and protein synthesis

• Aerobic respiration= Glucose +oxygen carbon dioxide + water + ENERGYThe energy released during respiration is used:• To build larger molecules from small ones• In animals, to make muscles contract• In mammals + birds to maintain a constant body temp• In plants, to build up sugars, nitrates and other nutrients

into amino acids= proteins

OR.. Woman Gone Mad!

WarmthGrowth

Movement

Enzymes and digestionEnzyme Where found Substrate it acts

onProduct

Amylase Mouth Insoluble starch glucose

Protease Stomach, small intestine

Proteins Amino acids

Lipase Small intestine Lipids Fatty acids/ glycerol

In the stomach and small intestine

• Hydrochloric acid is produced in the stomach, gives best pH for protease to work at

• The liver produces bile, which is stored in the gall bladder, before passing down the bile duct into the small intestine.

• Bile neutralises the acid that was added to the food in the stomach- providing alkaline conditions for the enzyme in the small intestine to work best.

• Bile also emulsifies.

Enzymes in industry

• Microorganisms produce enzymes that pass OUT of cells.

• Biological detergents contain proteases and lipases to digest protein and fat stains.

• In industry:• Proteases: pre-digest the protein in baby foods• Carbohydrases: convert starch into glucose• Isomerase: convert glucose syrup into fructose syrup

(fructose is sweeter, therefore less is needed, used in SLIMMING FOODS).

HOMEOSTASIS

What is homeostasis?

• Homeostasis means keeping conditions inside the body constant

• Conditions such as temperature, water level, sugar level, pH of the blood (ion content) and carbon dioxide level.

• These constant conditions are controlled by hormones

• Hormones are produced by glands and are transported to their target organs in the bloodstream

Diabetes• Our blood glucose level is controlled by two hormones: insulin

and glucagon.• Both of these hormones are released by the pancreas.• Diabetics are unable to control their blood sugar level properly.

They can not make enough insulin and so the concentration of glucose in their blood may become dangerously high- ‘hypos’ may occur.

• This can make them tired and thirsty. • Sometimes the blood sugar level can fall too low.• The person can feel weak, irritable and confused- may even faint.• Diabetes can be treated by following a low glucose diet or by

injecting with exactly the right dose of insulin.

Controlling blood sugar• It is the pancreas that monitors and controls blood glucose

level• After a high carbohydrate meal, blood glucose will be too

high.• The pancreas detects this and releases insulin into the blood• Insulin causes the liver to convert glucose to insoluble

glycogen. The liver removes the glycogen from the blood and stores it and so your blood sugar level returns to normal.

• After a lot of exercise your blood sugar will be too low. The pancreas detects this and releases a different hormone, glucagon, into the blood.

• Glucagon causes the liver to convert glycogen into glucose and release it into the blood.

• So your blood sugar returns to normal

Controlling body temperature

• Your body temperature is controlled by receptors in the brain- forming the thermoregulatory centre.

• This part of the brain monitors the temperature of the blood running through it.

• This is your core body temperature• Also temperature receptors in the skin send

impulses to this centre, giving it information about skin temperature

When it’s hot

• Blood vessels supplying the capillaries at your skin surface dilate, so that your blood reaches the surface of your skin and more heat is lost by radiation- so you look flushed

• Sweat glands in your skin release more sweat, which cools the body as it evaporates

Getting colder

• Blood vessels supplying the capillaries at your skin surface constrict, so that less blood reaches the surface of your skin and less heat is lost by radiation- so you look pale

• Sweat glands stop making sweat• Your muscles may start to shiver/ contract.• These contractions need respiration which produces extra heat

energy and these warm your body.

Waste products

• Waste products must be removed from the body because they are toxic.

They include:• Carbon dioxide produced during respiration and

removed from the body by the lungs when we breathe out;

• Urea produced in the liver by the breakdown of excess amino acids – the process deamination.

Urea is filtered out of the blood by the kidney and removed as urine, which is temporarily stored in the bladder.

GENES AND CELL DIVISION

Cell division

• Inside the nucleus are thread like chromosomes• These chromosomes carry genes along their length• A gene codes for a certain characteristic e.g. eye colour• Genes are made up of the chemical DNA• In body cells, chromosomes are found in pairs• Humans have 46 chromosomes which can be separated

into 23 identical pairs• The only human cell that does not have 46 chromosomes

is the gametes (sex cell)• The sperm and the egg each have 23 chromosomes

Mitosis• Mitosis is a type of cell division which makes all the body cells except

the gametes• Before a cell can divide by mitosis, it must make a second set of

chromosomes • Each chromosome makes a copy of itself, so when the cell divides

into two, each cell has a copy of each of the original chromosome set• Each of the new cells will have exactly the same genetic information

• Body cells divide by mitosis:• To produce additional cells during growth• To produce replacement cells if some are damaged• During asexual reproduction to produce clones, that are genetically

identical to the parent

Meiosis

• Is a type of cell division which results in gametes• Cells in reproductive organs divide to form

gametes• Cells in the testes divide by meiosis to form sperm• Cells in the ovaries divide by meiosis to form eggs• When a cell divides by meiosis:• Copies of each of the chromosomes are made• Then the cell divides twice to form four gametes,

each with a single set of chromosomes

Fertilisation

2 gametes fuse togetherA sperm with 23 chromosomes joins with an egg with 23 chromosomes making 46.

Variation in offspring

• The cells of an offspring produced by asexual reproduction are formed by mitosis from parental cells. Identical genes as the parent

• Offspring from sexual reproduction vary:• meiosis= both parental cells mixed• Obtain different alleles• Different characteristics

Stem cells

• Most types of animal cells differentiate at an early stage- specialised cells

• Cell division is usually for repair and replacement

GENETICS

Chromosomes and alleles

• There are 46 chromosomes in human body cells.

• Chromosomes are thread like structures and are made up of long proteins called DNA.

• A gene is a length of DNA that codes for protein, by combining with amino acids.

• Some genes have 2 different forms- alleles.• Dominant alleles and recessive alleles

Hereditary diseases

• Cystic Fibrosis- disorder of the cell membrane- caused by the recessive allele

• Huntington’s Disease- disorder of the nervous system- caused by the dominant allele.

• Embryo Screening= taking cells from embryos and analysing them for diseases/ genetic disorders.

Genetic crosses

• Homozygous= both alleles are the same, e.g. AA/ aa (think homosexual- the SAME sex)

• Heterozygous= different alleles e.g. Aa

DNA

• Is a molecule, containing coded information that determines inherited characteristics.