aqa knowledge powerpoint unit 2 biology 2 b2.1 cells and ... · aqa knowledge powerpoint unit 2...

AQA Knowledge PowerPointUnit 2 Biology 2 B2.1 Cells and simple cell transport

PiXL AQA Knowledge PowerPoint Unit 2 Biology 2 B2 GCSE Additional Science for certification June 2014 onwards

• All living things are made up of cells. The structures of different types of cells are related to their functions. To get into or out of cells, dissolved substances

have to cross the cell membranes.

• B2.1.1 Cells and cell structure

• B2.1.2 Dissolved substances

No Higher Tier content

B2.1.1 Cells and cell structure

Part Function Plant or animal

NucleusContains genetic material,

which controls the activities of the cell

Both

CytoplasmMost chemical processes

take place here, controlled by enzymes

Both

Cell membrane

Controls the movement of substances into and

out of the cellBoth

Mitochondria Most energy is released by respiration here Both

Ribosomes Protein synthesis happens here Both

Cell wall Strengthens the cell Plant ONLY

ChloroplastsContain chlorophyll,

absorbs light energy for photosynthesis

Plant ONLY

Permanent vacuole

Filled with cell sap to help keep the cell turgid

Plant ONLY

All living things are made up of cells. The structures of different types of cells are related to their functions

Yeast: Yeast is a single‐celled organism. The cells have a nucleus, cytoplasm and a membrane surrounded by a cell wall.

Bacteria: Single‐celled organism.A bacterial cell consists of cytoplasm and a membrane surrounded by a cell wall.The genes are not in a distinct nucleus.

B2.1.1 Cells and cell structure ‐ Specialised cells Cells are specialised for a particular function. Structure helps them to carry this function out.

Cell Diagram Function Adaptations

Leaf cell

Absorbs light for photosynthesis. Lots of chloroplasts.

Root hair cell

Absorbs water and mineral ions from the

soil.

Large finger like shapes to increase surface area.

Sperm cell Fertilises an egg

Head contains an enzyme to help penetrate egg, lots of mitochondria so

egg can swim to sperm.

Red blood cell

Carries oxygen to the cells.

Thin outer membrane so oxygen diffuses easily, no nucleus so more

room for oxygen.

Goblet (mucus) and cilia cells are found in the lining of the gut and the tubes into the lungs. They are

specialised to release and move mucus. Helps food slide down easily in the gut and helps trap dirt and bacteria before they enter the lungs. The cilia cells

help move the mucus especially in the lungs. Cilia cells have lots of mitochondria.

B2.1.2 Dissolved substances

Location Particles move From ToSmall intestine

Digested food products e.g.

glucose

Small intestine

Blood in capillary of

villus

Lungs

Oxygen Alveolar air space

Blood circulating around the

lungs

Diffusion is the spreading of the particles of a gas or liquid,resulting in a movement of particles from a region where they are of a higher concentration to an area of lower concentration.

Diffusion can occur in: Air ‐ smells from perfume etc. Liquids – tea from a tea bag, dyein water etc. Through membranes – small intestines, blood cells etc.

Concentration gradientA difference in

concentration between two areas next to each other. Particles will move downthe concentration gradient

High to Low.The larger the difference in concentration the fasterthe rate of diffusion.

AQA Knowledge PowerPointUnit 2 Biology 2 B2.2 Tissues, organs and organ systems


The cells of multicellular organisms may differentiate and become adapted for specific functions. Tissues are aggregations of similar cells; organs are

aggregations of tissues performing specific physiological functions. Organs are organised into organ systems, which work together to form organisms.

• B2.2.1 Animal organs

• B2.2.2 Plant organs


B2.2.1 Animal organs

Organisation of a multicellular organism

cells tissues organs organ systems

A TISSUE is a group of specialised cells working together to carry out a particular function.

Tissue Function

Muscular tissue

Contracts, bringing about movement

Glandular tissue

Produces substances such as enzymes and

hormones

Epithelial tissue

Covers some parts of the

body

Tissues in the stomach The stomach is an organthat contains:muscular tissue, to churn the contentsglandular tissue, to produce digestive juicesepithelial tissue, to cover the outside and the inside of the stomach.

The digestive systemAn organ system which humans and other mammals have so

they can exchange substances with the environment.

Part(s) FunctionPancreas/ salivary glands

Produce digestive juices

Stomach Digests food

Liver Produces bile

Small intestine

Digest and absorb soluble

food

Large intestine

Absorbs water/ produces faeces

B2.2.2 Plant organs Tissue DefinitionEpidermal Covers the plant, contains stomata.

Mesophyl Where photosynthesis takes place. Contains palisade cells and spongy layer.

Xylem Carries water and mineral ions from roots.

Phloem Carries glucose from the mesophyll to the rest of the plant.

Stomata Pores on the underside of the leaf that allow gases to diffuse in and out.

Plants organsStem support for the leaves and flowers. Water and glucose transported too. Leavesmake the food for

the plant where photosynthesis happens. Roots anchor the plant in the soil, take up water and

mineral ions.Flowers are reproductive organs to attract insects.

AQA Knowledge PowerPointUnit 2 Biology 2 B2.3 Photosynthesis


Green plants and algae use light energy to make their own food. They obtain the raw materials they need to make this food from the air and the soil. The

conditions plants are grown in can be changed to promote growth.

• B2.3.1 Photosynthesis


Photosynthesis Photo = light, Synthesis = making of (glucose) Photosynthesis = making glucose using light

B2.3.1 Photosynthesis

Plants convert glucose into starch and store it.

Cover part of a leaf in black paper then test it for starch

using iodine.

Factors that can limit the rate of photosynthesis • Light intensity – not enough light no photosynthesis • CO2 concentration ‐ not enough light no photosynthesis • Water availability – plants wilt, not enough no

photosynthesis• Temperature – too low temp enzymes don’t work well

Plant cells use some of the glucose produced during

photosynthesis for respiration. Also use the glucose to make: oil for storage, cellulose for cell

walls, proteins (also need nitrates for this from the soil).

GreenhousesFarmers can use greenhouses to increase plant growth. Artificial light ‐ allows photosynthesis to continue beyond

daylight hours. Heating ‐ allows photosynthesis to continue at an increased rate heater can also give off extra carbon dioxide released into the greenhouse this allows photosynthesis to continue at an increased rate.

AQA Knowledge PowerPointUnit 2 Biology 2 B2.4 Organisms and their environment


Living organisms form communities, and we need to understand the relationships within and between these communities. These relationships are affected by

external influences.

• B2.4.1 Distribution of organisms


B2.4.1 Distribution of organisms The distribution of living organisms in a particular habitat may be affected by physical factors (abiotic) e.g.

Temperature, amount of light, availability of water, availability of nutrients, availability of oxygen and carbon

dioxide. They can also be affected by living factors (biotic) availability of prey, disease, predators.

Quadrats: These are square frames, used to mark off specific areas of ground 0.5m X 0.5m

Quadrats:Sample an areaRandom method generate numbers using a calculator. Take several samplesCount number of organisms in each quadrat or count the % cover. Calculate an average from the samplesMultiply the average by the area of the fieldImprove results by taking more samples

Line Transect:Measure out an area, good for investigating changing habitats, place quadrat at regular intervals, record organisms, repeat on different line to

collect average

ValidData collection that is suitable to answer the

investigation hypothesis

ReproducibleAnother group are able

to carry out the investigation and

collect similar results

AQA Knowledge PowerPointUnit 2 Biology 2 B2.5 Proteins – their functions and uses


Proteins have many functions, both inside and outside the cells of living organisms. Proteins, as enzymes, are now used widely in the home and in

industry.

• B2.5.1 Proteins

• B2.5.2 Enzymes


B2.5.1 Proteins ‐ Enzymes

Protein molecules are made up of long chains of amino acids. These long chains are folded to produce a specific shape that enables other molecules to fit into the protein. Proteins: structural components of tissues e.g. muscles, hormones, antibodies, enzymes.

Enzymesmade of proteins they are biological catalysts ‐substances that increase the rate of chemical reactions

without being used up.

Enzymes are also easily affected by pH changes. Need specific conditions to keep them working at their best. OPTIMUM CONDITIONS!

To begin with heat will help increase collisions between the enzymes and substrates BUT too hot and it will denature (remember denature NOT die)

Uses of enzymes: Biological detergents: Contain protease and lipase, break down protein and fats in stains. Baby food: Protease, Pre digest proteins. Diet products:

isomerase is used to convert glucose syrup into fructose syrup, which is much sweeter, can be used in

smaller quantities in slimming foods

DENATURED

B2.5.2 Enzymes –Digestive enzymes Enzymes for respiration, photosynthesis and protein synthesis work inside cells. Other enzymes produced

by specialised cells and released from them e.g. digestive enzymes. Catalyse means to speed up.

Enzyme Reaction catalysed

Where produced

Amylase Starch → sugars Salivary glands, pancreas, small

intestineProtease Proteins → amino

acidsStomach, pancreas, small intestine

Lipase Lipids → fa y acids + glycerol

Pancreas, small intestine

Digestion and pH: The stomach releases acid. The enzymes made in the stomach work best in acidic conditions. The

enzymesmade in the pancreas and small intestinework best in alkaline conditions. The liver produces bile which is released into the small intestine. Bile neutralises the acid that was added to the food in

the stomach.

Digestion and absorption occurs in the gut this goes from the

mouth to the anus.

AQA Knowledge PowerPointUnit 2 Biology 2 B2.6 Aerobic and anaerobic respiration


Respiration in cells can take place aerobically or anaerobically. The energy released is used in a variety of ways. The human body needs to react to the

increased demand for energy during exercise.

• B2.6.1 Aerobic respiration

• B2.6.2 Anaerobic respirationHigher tier content: HT ‐ As the breakdown of glucose is incomplete, much less energy is released than during aerobic respiration. Anaerobic respiration results in an oxygen debt that has to be repaid in order to oxidise lactic acid to carbon dioxide and water.

B2.6.1 Aerobic respiration

Aerobic Respiration The process of releasing energy from food in cells. Aerobic respiration ‐uses oxygen. All chemical reactions inside cells are controlled by enzymes.

RESPIRATION RELEASES ENERGY IT DOES NOT PRODUCE ENERGY.

Glucose reacts with oxygen, producing carbon dioxide and water as waste products. To release energy. This takes place continuously in animals and plants.

Aerobic respiration (with oxygen)glucose + oxygen → carbon dioxide + water (+ energy)

Released energy is used for:To build up larger molecules using smaller ones. In animals, to enable muscles tocontract. In mammals and birds, to

maintain a steady body temperature in colder surroundings. In plants, to build up sugars, nitrates and other nutrients into amino acids which are then built up into

proteins.

Mitochondria: Tiny organelles found in most plant and animal cells. Where the respirationreactions happen. More active cells have moremitochondriae.g. muscle cells, sperm cells.

During exercise changes take place: the heart rate and breathing increases. Blood flow increases so more glucose and O2 to cells. Muscles store glucose as glycogen – the glycogen

gets converted back to glucose during exercise.

B2.6.2 Anaerobic respiration

During exercise, too little oxygen is reaching the muscles they use anaerobic respiration to RELEASE energy. It is the incomplete breakdown of glucose and produces lactic acid.

RESPIRATION RELEASES ENERGY IT DOES NOT PRODUCE ENERGY.

Anaerobic respiration (without oxygen)glucose → lac c acid (+ small amount of energy)

Higher Tier OXYGEN dept: Anaerobic respiration results in an oxygen debt that has to be repaid in order to change lactic acid to carbon dioxide and water. The extra oxygen needed is called the oxygen debt.

In yeast anaerobic respiration produces ethanol and carbon dioxide (which is why we used it to make beer and bread) we call this fermentation.

Lactic AcidIf muscles have long

periods of exercise they get fatigued‐ they stop

contracting properly. One cause is the build‐up of lactic acid in the muscles. Lactic acid is poisonous. We can only tolerate small amounts in our body. Blood flowing through the muscles

removes the lactic acid.

‐The heart continues to pump faster.‐The breathing rate remains high.‐This delivers the extra oxygen to the muscles.‐This pays back the oxygen debt.

AQA Knowledge PowerPointUnit 2 Biology 2 B2.7 Cell division and inheritance


Characteristics are passed on from one generation to the next in both plants and animals. Simple genetic diagrams can be used to show this. There are ethical

considerations in treating genetic disorders.Higher Tier ‐ construct genetic diagrams of monohybrid crosses and predict the outcomes of monohybrid crosses and be able to use the terms homozygous, heterozygous, phenotype and genotype. Foundation Tier ‐ should be able to interpret genetic diagrams of monohybrid inheritance and sex inheritance.• B2.7.1 Cell divisionHigher Tier ‐When a cell divides to form gametes:■ copies of the genetic information are made ■ then the cell divides twice to form four gametes, each with a single set of chromosomes.• B2.7.2 Genetic variationHigher Tier ‐ Each gene codes for a particular combination of amino acids which makes a specific protein.• B2.7.3 Genetic disorders

Genetic information is in the nucleus of cellsInside the nucleus are chromosomesmade up of DNA –BODY CELLS have two sets of chromosomes, SEX CELLS (gametes) have one set of chromosomesin humans body cells 46 chromosomes (23 pairs), sex cells (sperm/egg) 23 single chromosomes. BODY CELLS DIVIDE BY MITOSIS (makes my toes)

SEX CELLS DIVIDE BY MEIOSIS

B2.7.1 Cell division

MITOSIS cell division for growth and repair of cells (produces clones).

1

2

3

4

5

6

Higher Tier MEIOSIS cell division to produce sex cells for reproduction.

Creates 4 daughter cells, genetically unique , makes gametes (sperm, egg), 23 chromosomes only

1. Parent cell2. Chromosomes make identical copies of themselves3. Line up along the centre4. They move apart5. Two daughter cells start to form.6. Two new daughter cells with identical chromosomes to the parent cell.

Fertilisation: where gametes join. New cell divides by mitosis to form baby.

B2.7.1 Cell division – STEM cells STEM CELLS: Cells that can become anything, they are undifferentiated

Embryonic stem cells can be made into any type of cell (curing all sorts of disease) but come from aborted embryos (which can be a problem) We also don't know the

long term effect of their use yet.

Adult bone marrow stem cells can also be used but can’t be made into as many different things but you can give permission to have them taken

the operation can be painful!

Stem cells can be used in new treatments for Parkinson's disease and paralysis. They can be harvested from inside embryos, umbilical cords and bone marrow.

There are social and ethical issues concerning the use of human embryonic stem cells.

Plant Cells: Most plant cells stay unspecialised. They can differentiate all through their lives. Unspecialised cells are made at the stems and roots, where mitosis takes place almost constantly. This makes it very easy to clone plants.

Sexual reproduction leads to variation: Meiosis ensures that all gametes contain the same genes, but have a different selection of alleles. Also, it is random which sperm fertilises which egg.

B2.7.2 Genetic variation

Alleles ‐different forms of the same gene represented by two letters. For example, eye colour

Recessive‐ characteristic onlyexpressed when two of the same alleles are present e.g. bb. Dominant‐ characteristic expressed when one or both

alleles are present e.g. BB or Bb

HIGHER TIER: Homozygous‐ two of the same allele e.g. bb or BB Heterozygous‐ two different alleles e.g. Bb Genotype‐ the genes present e.g. Bb or bb or BB Phenotype‐ the genes that are expressed in the physical characteristics. e.g., brown eyes, blue eye, blond hair, brown hair. Each gene codes for a particular combination of amino acids which makes a specific protein.

Determining sex (gender): Human body cells have 23 pairs of

chromosomes in the nucleus. One of these pairs controls the inheritanceof gender: XX=female XY=male

All individuals (except for identical twins) produced sexually are genetically

different DNA fingerprinting can identify individuals.

HIGHER TIER: You must be able to draw for monohybrid crosses, these and identify genotype and phenotype of offspring. You must work out % of offspring with each characteristic. T – tall t – shortWhat % of the offspring will be short?

Cystic fibrosis (a disorder of cell membranes) inherited from both parents. The

parents can be carriers of CF but not have CF. Caused by a recessive allele so can passed on by parents who don’t have it. Causes thick, sticky mucus to accumulate in the lungs

and the digestive system. This causes: Lung infections, problems with breathing,

problems with digestion and absorption.

B2.7.3 Genetic disorders

Polydactyly: Extra fingers or toes ‐ caused by a dominantallele can be passed on by only one parent who has the disorder.

Some genetic disorders are inherited e.g. polydactyly, cystic fibrosis. Embryos can be screened for the different types of disorders.

Some genetic disorders are inherited e.g. polydactyly, cystic fibrosis. Embryos can be screened for the different types of disorders.

A genetic pedigree or Family trees can also be used to trace how a disease is inherited.

On the right is an example for cystic fibrosis.

B2.7.2 Genetic variation – Gregor Mendel

Gregor Mendel (1822‐1884) studied the inheritance of different characteristics in pea plants. • Found that when he bred red‐flowered

plants with white‐flowered plants, all the offspring had red flowers.

• If he bred these plants with each other, most had red flowers, but some had white.

• This was because the allele for red flowers is dominant, and the allele for white flowers is recessive.

FIRST CROSS:All the offspring have red flowers, even though they

carry the recessive allele for white flowers

SECOND CROSS:Three‐quarters of the offspring have red flowers

and a quarter have white flowers

Called the father of modern genetics. No one took his ideas seriously until after his death.

AQA Knowledge PowerPointUnit 2 Biology 2 B2.8 Speciation


Changes in the environment of plants and animals may cause them to die out. The fossil record shows that new organisms arise, flourish, and after a time become extinct. The record also shows changes that lead to the formation of new species.

• B2.8.1 Old and new speciesHigher Tier ‐ genetic variation – each population has a wide range of alleles that control their characteristics■ natural selection – in each population, the alleles that control the characteristics which help the organism to survive are selected■ speciation – the populations become so different that successful interbreeding is no longer possible.

B2.8.1 Old and new species ‐OLD

FOSSILS – SHOW EVIDENCE OF EARLY LIFE FORMS.Can be formed byMineralisation of the hard parts (shells, bones, teeth etc)Some soft parts do not decay/rot, because they are buried.Traces of the animals (footprints, burrows, faeces, etc)

Fossils can be used to gather evidence for evolution. This is called a fossil record.

ExtinctionPermanent loss of all members of a species.Caused by a change:New predatorsNew diseasesLoss of habitatMore successful competitor

Can’t find evidence of all earlier life forms: Many were soft‐bodied, so left few traces behind as many destroyed by geological activity.

New species arise as because of: Isolation – two populations of a species become separated e.g geographically.

B2.8.1 Old and new species ‐NEW

Higher Tier:Genetic variation – each population has a wide range of alleles that control their characteristics.Natural Selection Variation –populations of organisms have variations.Over‐production –produce more young than will survive to adulthood.Struggle for existence – competition for survival between the organismsSurvival – those with advantageous characteristics are more likely to survive Advantageous characteristics inherited – better adapted organisms are more likely to Reproduce successfully passing on the advantageous characteristics to their offspring in their genes.Gradual change – over a period of time the more individuals with the advantageous characteristics in the population.

Higher Tier: SpeciationTakes place when an isolated

population becomes so different from the original population that a

new species is produced.

Endemic: A species that has evolved to live in only one place in the world.

Species: A group of similar organisms that can breed to produce fertile offspring

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