GCSE CCEA Triple Award Biology - Summary Notes

Cells

  • Cells: Basic building units of living organisms.
  • Prokaryotic: Bacterial cells.
  • Eukaryotic: Animal and plant cells.
  • Resolution: Microscope's ability to show fine details.
  • Specimen: The object being viewed.

Cell Structures and Functions

  • Cell Membrane: Controls entry/exit of substances.
  • Cytoplasm: Jelly-like liquid where reactions occur.
  • Mitochondria: Organelles for respiration and energy production.
  • Nucleus: Control center with genetic material (DNA, chromosomes).
  • Vacuole: Fluid-filled sac for storage and support (plants).
  • Cell Wall: Rigid outer layer of plant cells, providing support (cellulose).
  • Chloroplast: Contains chlorophyll for photosynthesis (plants).
  • Plasmids: Small DNA pieces in prokaryotic cells.

Microscopy

  • Start with the lowest power objective lens for a wider view and to prevent damage
  • Coarse and fine focus knobs are required.
  • To prepare a slide, the specimen should be thin and covered with a coverslip, which helps flatten specimen and prevent it from drying out.

Practical Slides

  • Onion Cell: Use tweezers to remove a layer of onion tissue, place on a slide, add iodine, and cover with a coverslip.
  • Cheek Cell: Rub a cotton wool bud on your inner cheek, rub on a slide, add methylene blue, and cover with a coverslip.

Magnification

  • Units: Metre (m), Millimetre (mm), Micrometre (um).
  • Magnification = \frac{\text{Size of image}}{\text{Real size of object}}

Organisation of Living Organisms

  • Multicellular: Animals and plants have many cells that specialise.
  • Tissues: Groups of cells performing a function (e.g., muscle tissue).
  • Organs: Tissues working together (e.g., leaf, stomach).
  • Systems: Groups of organs working together (e.g., digestive system).
  • Circulatory, Digestive, Endocrine, Nervous, Reproductive and Respiratory are examples of organ systems.
  • Exchange with environment, transport substances, and communicate between cells

Diffusion

  • Movement from high to low concentration areas.
  • Factors affecting diffusion rate: concentration gradient, temperature, surface area.
  • Large organisms require specialized exchange surfaces and circulatory systems.

Stem Cells

  • Definition: Undifferentiated cells that can differentiate into various cell types.
  • Adult Stem Cells: Limited differentiation, less plentiful, ethical concerns (consent).
  • Embryonic Stem Cells: Can differentiate into any cell, more plentiful, ethical concerns (embryo destruction).
  • Stem cells originate from meristems at the tips of roots and shoots

Respiration

  • Exothermic process releasing energy from food materials.
  • Diffusion: Movement of molecules from high to low concentration.
  • Concentration Gradient: Difference in solute concentration across a membrane.
  • equation: Glucose + Oxygen \rightarrow Carbon dioxide + Water + Energy
  • C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O + 2890KJ (ATP)
  • Requires oxygen; releases a lot of energy; produces carbon dioxide.

Anaerobic Respiration

  • Definition: Breakdown of glucose in the absence of oxygen.
  • Releases some energy; produces ethanol (micro- organisms, plants) or lactic acid (animals).
  • equation: Glucose \rightarrow Energy + Lactic acid

Gas Exchange

  • Important for O2 and CO2 levels in alveolar air.
  • Air moved by intercostal muscles and diaphragm.
  • Inhalation: Intercostal muscles contract, ribs move up and out, diaphragm contracts and moves down, volume increases, pressure decreases, air flows in.
  • Exhalation: Intercostal muscles relax, ribs move in and down, diaphragm relaxes and moves up, volume decreases, pressure increases, air flows out.
  • Respiration is a complicated chain of chemical breakdowns accelerated by enzymes.

Fermentation

  • Definition: Anaerobic respiration in micro-organisms, used industrially.
  • Brewing: Production of alcoholic drinks.
  • Baking: Production of bread (carbon dioxide expands dough, alcohol evaporates).
  • Limewater turns cloudy white (milky) and hydrogen carbonate indicator changes from orange to yellow in the presence of carbon dioxide.

Investigating

  • Vegetable oil prevents oxygen entering.
  • Number of bubbles collected and the state of the indicator helps to measure rate of respiration.
  • The formula to calculate energy released from food is described.
  • Factors to consider for valid experiment.
  • Breathing rate is measured when exercise is taken increasing the intake and production of carbon dioxide.

Photosynthesis

  • Definition: Process by which plants make carbohydrates
  • Carbon dioxide + Water \rightarrow (using light energy + chlorophyll) Glucose + Oxygen
  • 6CO2 + 6H2O \rightarrow C6H{12}O6 + 6O2

Photosynthesis Practical

  • Destarching: Remove pre-existing starch by keeping plant in the dark for 48 hours.
  • Boil leaf, dissolve chlorophyll in alcohol, soften in hot water, add iodine (blue/black indicates starch).
  • Independent variable – the presence or absence of chlorophyll. Dependent variable – whether starch is present or not.
    Control variables – methods and equipment used.
    *Light is needed.
    *Chlorophyll is needed.
    Photosynthesis comparisons
    There is a compensation point – happens at dawn and dusk.

Leaves and gas exchange

  • Large surface area.
  • Thin.
  • Moist.
  • Permeable.
  • Epidermal cells, waxy cuticle, palisade mesophyll layer.

Factors affecting photosynthesis

  • Light.
  • Carbon dioxide.
  • Temperature.
  • Water availability.

Minerals

  • Magnesium.
  • Calcium.
  • Nitrate.

Nutrients

  • Provide energy.
  • Growth and repair.
  • Maintain health.
  • Test for Starch, Protein, Reducing sugars (eg glucose), Fats and oils.

Energy

  • Fat gives 38 KJ, protein gives 17 KJ and carbohydrates gives 17 KJ.
  • Age, Gender and Activity affects energy requirements.

Digestion

  • The breakdown of large, complex, insoluble molecules into small, simple, soluble ones.
  • Ingestion, absorption, assimilation and egestion.

Assimilation

  • Sugars, fats and amino acids.

Regions

  • Mouth, Stomach and Small intestine.

Enzymes

  • Convert one kind of substrate molecule into one kind of product molecule e.g. starch will only fit into the active site of amylase This is referred to as the “Lock and Key model”
  • Enzymes are proteins and can therefore be denatured or destroyed by temperature or pH.

Nervous System and Hormones

  • Nervous System: Fast, uses nerve impulses.
  • Hormonal System: Slow, uses hormones in blood.
  • **Nervous: Messengers are neurotransmitters, CNS is instantaneously reacting and Hormonal: Messengers are hormones.

Responses

  • Stimuli: Changes in the environment.
  • Receptors: Detect stimuli.
  • Co-ordinator: Brain or spinal cord.
  • Effectors: Muscles or glands.
  • *Coordination - * Impulse generated in a sensory neurone which is transmitted along neurone to CNS.
  • *Reflexes - *Rapid automatic responses

Neurones

  • Carry information in the form of nerve (electrical) impulses.
  • Synapses are junctions between two neurones

Reflexes

  • Voluntary actions use conscious thought and Reflex actions happen quickly

The Eye

  • The eye is a specialised sensory organ that contains receptors sensitive to light.
  • Each segment has a specific role which assists with seeing.
  • Correct intensity of light reaches the retina, adjusting light and focus is a reflex action.

Homeostasis

  • Maintaining a constant internal environment.
  • Helps your cells work as efficiently as possible.

Hormonal System

  • Insulin produced in pancreas in specialised cells in Islets of Langerhans.
  • Glucose is needed constantly for respiration and must always be present in the blood in sufficient concentration.
  • If too much is created in the pancreas a negative feedback is induced.

Diabetes

  • A disease in which a person is unable to produce enough – or any – insulin to control their blood glucose conc
  • Type 1 and type 2 is determined, with symptoms shown.

Excretory

  • Elimination of metabolic waste products and toxic materials taken in from the environment.
  • Each component has a role in the process.

Filtratrion

  • Filters only the blood plasma.

Reabsorption

  • Reabsorb into the blood capillaries .

Osmoregulation

  • Maintaining the water balance at a constant level in the body.
    • A part of the brain called the hypothalamus continuously monitors blood concentration.
    • Excess of water has different effects than the scarce of water.

Sensitivity

  • Tropism is a growth in response to stimulus plants.

  • Positive and negative directions exist.

  • Light inhibits its production.

  • Tropisms of shoots.

Kidney

  • The study of organisms and their environments / habitats, e.g. woodland or river.

Habitat

  • Area where a population lives.

  • Process used to estimate the number of organisms in an area.

Quadrat

  • Square frame - is used to sample plant distribution.

Belt transect

  • Used when sampling organisms along an environmental gradient.

Random sample

  • Used when estimating the number of organisms in an area

Factors

  • Ecological studies often investigate effect of abiotic (non-living) factors on distribution of organisms.
  • Biotic factors are living features of the environment e.g.

Food chains / webs

  • Is a community of organisms interdependent on each other and environment they live in.
    The different stages in feeding sequence known as trophic levels

Energy loss

  • At each trophic level in food chains is due to 3 main reasons
    Not all available food is eaten
    Lots of energy lost in respiration as it provides energy for movement

Pyramids of numbers / biomass

For food web to be sustainable there must be enough food for all organisms – there will usually be more producers than primary consumers.
Main conditions for decay is, Oxygen, moisture, and temperature.
Photosynthesis take carbon compounds to atmosphere as carbon dioxide
Decomposition is when they’re broken down into simpler products.
Combustion in the burning of fossil fuels will revert to carbon dioxide.

Nitrogen

In organisms is in the form of amino acids and proteins.

  • Root hair cells are specialised
  • Agricultural land needs to be fertilised regularly

Pollution

Pollution is the presence of unwanted substances, produced by human activity, which harm ecosystems.

Water pollution is often runoffs from fields being eutrophication.

  • Water courses in NI are affected heavily.

Activity

  • Human activities such as deforestation, fossil fuel burning, and excessive use of fertilisers potentially damage biodiversity.

Reproduction

Is Vital in living organisms otherwise they would no longer exist, and comes in two forms, Sexual(animals) and asexual (plants)
Gametes is a sperm and egg cell Sex cells Haploid cells, that get restored when together.
Male and Female systems have different purposes. Make and receive.

Fertilisation is the fusing of the haploid nuclei.

Placenta is a temporary exchange Surface created in the body. Transferring nutrients to the body
Maternal or baby can result, Large surface area between the uterus wall.
Sex Hormones and the cycle the hormones are all determined, And hormones are given for puberty.

Mechanical chemical is a different example of advantages of treatment.

Fertility

Some have issues with having treatments on treating such as the drugs.

Permeable allowing liquid or gases to pass through it
Impermeable Not allowing liquid or gas to go through
Plasmolysis Shrinking of the cytoplasm of a plant cell.
Xylem Moves water and mineral ions upwards in a plant
Phloem Plant tissue that transports dissolved food materials
Transpiration Evaporation of water from the leaves of a plant

Active transport Selective movement of molecules across living cell. Is a passive process of energy
Has a high high low gradient
If cell is put in pure form it’ll explode(Lysis)
When losing it wilts.
Visking tubing Higher of water outside visking tubing than inside – water moves in via. osmosis and water moves up glass tubing.
Vary mass as the cylinders do, This is a transpiration area for plants need to prevent water loss
These actions prevent water out if closed.
Temperature is an important feature to water uptake.
There is a washing process that goes through that also effects the overall product.
Has an explanation the model and plan experiment to do so also.

Chromosomes

Chromosomes, genes and DNA. Diagram represents the human karyotype – the chromosome map of a human, each a different shape and size.. The father is a decider than and mom. There is hundreds of genes. Each trait has a quality.
sugar phosphate. Each phosphate base, is considered DNA unit
The DNA is a code for cells to reproduce
and have enzyme control. Coding allows cells to exist
Cell Division Mitosis and Miosis for DNA control.
Occurs in normal cells, and happens from growth to to make new cells.

Muiosis can only happen through testys, with the production of more cycles in one generation after division a cycle can occur.

Mendel, had the first idea of serious study but there are also important generalizations for the DNA, with Monohonhybrid.
Has 4 different classes to go through.
There can be 3 different reasons for what the cross is.
1) 2) and 3. Is used to determine the genotype of an individual.
Sex Determination.
There is one side that must have the Y for the son to get what he requires. Some have genetic conditions called health.
Chromosomal structure must be in place.
Amniocentesis is important to see after week 12-14 and there is also ethical implications of the work.
Genetic engineering and DNA transfers often is used to make better and stronger forms.
There is restriction to keep human safe, variation and natural selection must have species quality to keep going so they are there to evolve.
All kinds of bodies are there for the same job.