Animal Cell- Structure and functions

Nucleus: Controls all the activities of the cells and carry instructions to make new cells and organisms.

Cytoplasm: Most of the Chemical reactions needed for life take place here.

Cell membrane: Controls the passage of substances into and out of the cell.

Mitochondria: Transfer of energy by aerobic respiration

Ribosomes: Protiens are made here (protein Synthesis)

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Plant Cell- Structure and functions

All of the ones that Animals have along with:

All have: 

Cell walls: made of cellulose that strengthens the cell and gives it support.

Some not all have:

Chloroplasts: Contains green Chlorophyll that absorbs light energy to make food by photosynthesis. (not found in roots as they dont photosynthesis)

Permanent Vacuole: space in Cytoplasm filled with Cell sap to keep the cells Rigid

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Yeast and Bacteria

Yeast: single celled microorganisms used to make bread and wine.

Contains: Cell membrane, Cytoplasm, Nucleus, Mitochondria, Cell Wall.

Aerobic Respiration = Oxygen + Sugars -> Energy

Anaerobic Respiration (Fermentation) = Sugars -> Ethanol + Carbon Dioxide

Bacteria: Single celled living organisms that are much smaller than Alant and Animal cells used to make yoghurt and cheese.

Contains: Cell Membrane, Cell Wall, Cytoplasm and Circular DNA Molecule.

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Specialised Cells

Fat Cells

-Small amount of Cytoplasm and a large amount of Fat.

-Few Mitochondria (need less Energy)

-Are Expandable

Human Cone Eye Cells

-Outer section: contains special pigment which Chemically changes in coloured light.

-Middle: Full of mitochondria (release the energy needed to reform visual pigment, lets you see colour continually)

-Final part: Specialised Synapse (connects to Optic Nerve.) When coloured light changes your visual pigment, an impulse is triggered which travels alont the optiv nerve to the brain. 

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Specialised Cells (Part 2)

Root Hair Cells

-Hairs increase surface area for water to enter.

-Large vacuole: speeds up osmosis from soil to hair cell.

Sperm Cells

-Long tail helps it swim

- Middle -full of mitochondia (provides energy for tail0

- Acrosome stores digestive enzymes to break down outer layers of Egg

- Large nucleus contains genetic information to be passed on 

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A net movement of  particles from an region of high concentration to a region of low concentration, down a concentration gradient.

- The greater the difference in the concentration, the faster the rate of diffusion 

Diffusion in Living Organisms

Water, Simple Sugars (Glucose), Amino Acids and Oxygen in your lungs. 

Each individual cell is adapted to make difussion easier and more rapid.

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Tissue: A group of cells that all do the same job


- Muscular: Contracts to bring about movement.

- Glandular: Has secretory cells - produce enzymes and hormones.

- Epithelial: Covers  outside of body along + internal organs.


- Epidermal:  cover surface to protect

- Mesophyll: Has Chlorophyll for Photosynthesis

- Xylem + Phloem: carry water and minerals

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Made up of tissues

In the very important Organ, the Stomach:

- Muscular tissue: To churn the food and digestive juices together

- Glandular tissue: To produce the digestive juice

- Gpithelial tissue: Covers the inside and outside of the Organ.

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The Digestive system

- The digestive system is a muscular tube

- Starts and your mouth ends at your Anus

- Contains lots of Organs and Glands

- Glands such as the Pancreas and Salivary Glands produce and release digestive enzymes to break down your food.

- The food you take in and eat is made up of large insoluble molecules that your body can't absorb. Your food needs to be broken into smaller more solube molecules called digestion.

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The process by which plants make their food usig Carbon Dioxide, Water and light energy.

Carbon Dioxide + water -> Glucose + Oxygen (presence of Light)

- Sunlight is absorbed by Chlorophyll in Chloroplast.

- Carbon Dioxide enters the leaf by diffusion through the Stomata.

- Water is absorbed through the roots and is carried to the leaves in the xylem vessels.

- Glucose is used through repiration to give plants their own energy. Excess can be stored in the leaves as insoluble starch.

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Leaf Adaptations

- Broad leaves for larger surface area

- Contains Chlorophyll to absorb light energy

- Air spaces to allow gaseous exchange

- veins to bring plenty of water to the cells

Limiting factors decrease the rate of photosynthesis.

Examples: Low temperature, Shortage of Sunlight and low Carbon Dioxide levels. 

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Glucose in Plants

Used For:

- Starch for storage (insoluble, won't have an effect on the water balance, Energy source for the plant when light levels are low)

- Oil/fat for storage (Provides lots of energy for the seed, used to make cell walls tronger or a source of energy) 

- Amino acids/Proteins/Enzymes (Made by combining sugers with Nitrate ions and other Mineral ions)

- Cellulose for cell walls (strengthen cell walls)

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Healthy plant growth

- Nitrates are needed to produce Amino acids, which then form Proteins for the plant. If Nitrate is lacking the plants growth will be stunted and the older leaves will turn yellow.

- Magnesium is needed to produce Chlorophyll to be used in photosynthesis to absorb the sunlight. Without Magnesium, leaves turn yellow.

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People use Greenhouses in their garden and Farmers use huge plastic Polytunnels to grow plants as fast as possible. They do this by giving the plants a warm environment, plenty of light, plenty of carbon dioxide and plenty of water. 

- Hydroponics: Growing plants in water with a perfect balance of mineral ions instead of soil so nothing slows down their growth.

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Measuring distribution of organisms

Quadrat: Usually a square frame made of wood or metal that you lay on the ground (outlines your sample area)

Sample size is important and it must be chosen at random to reflect the true distrubution of the organisms so that the findings are valid.

Transect: A streched tape between two points that is sampled using quadrats at regular intervals.This shows how ditribution changes along the line. 

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Validation of Data

Reproducible data: When other people can do the same investigation and can get similar results as yours.

Contolling variables ensure that other scientists and carry out the same investigation under the same conditions. 

Sample size is an important factor in both reproducibility and validity of data.

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Proteins and Enzymes

Proteins are:

- Structural components such as muscles and tendons

- hormones such as insulin

- antibodies that destroy pathogens

- catalysts in the form of enzymes 

Enzymes: biological catalysts that speed up reactions. They:

- Build large molecules from small ones

- Change one molecule to another

- Break down large molecules into smaller ones

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Enzymes continued

The substrate of the reaction fits into the active site of the enzyme. The reaction takes place rapidly and the products are released from the surface of the enzyme

Temperature increases the enzyme's reactions but they can become denatured same with PH.

The amino asid chains are folded to form the active site

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Enzyme action factors


The rate of the enzyme-controlled reaction increases as the temperature increases. But if the temperature gets too high the long chain amino acids unravel so the active site changes and the enzyme becomes denatured.


A change in PH affects the forces that hold the folded chains in place and therefore changes the shape of the molecule. The active site is lost, so the enzyme no longer works as a catalyst.

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Digestion Enzymes

- Carbohydrases break down carbohydrates in your mouth and small intestine into sugars. (Made in the salivary glands, pancreas and small intestine)

- Proteases break down proteins in your stomach and small intestine into amino acids. (Made in the stomach, pancreas and salivary glands)

-Lipases break down fats in your small intestine into fatty acids and glycerol. (Made in the pancreas and small intestine) 

Food is not digested in the liver or the pancreas.

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Speeding up Digestion

Hydrochloric acid allows your stomach's protease enzymes to work very effectively and kills most of the bacteria that you take in with the food. Enzyme work best in a acid pH.

As food somes into the small intestine from the stomach, bile is squirted on it. It nuetralises the acid from the stomach and makes the food alkaline. ideal condition for enzymes in the small intestine.

- Bile allows fat to be broken down to smaller droplets to increase the surface area.

- Bile is made in the liver and is stored in the gall bladder

- Bile is not an enzyme, doesnt break down fat

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Enzymes- Advantages and disadvantages


- Increases the rate of reactions

- Low temperatures and normal pressures mean it is cheaper that high temperatures or higher pressures.

-Pure enzymes use the substrate more efficiently


- Expensive equipment needed to keep temperatures constant

- Pure enxymes are expensive to produce

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Aerobic Respiration

Breaking down food using oxygen to release energy for the cells

- Respiration involves a series of many small reactios that are controlled by an enzyme

- Mitochondria- small rod-shaped parts found in cells, have a folded membrane (larger surface area for enzymes involved in aeerobic respiration)

Reasons for respiration

- Living cells need energy for the basic functions of life

- All muscular activities use energy

- Keeping temperature constant

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- Heart rate increases, arteries dilate. Blood flow increases, increasing gaseous exchange and the supply of glucose to the muscles

- Breathing rate increases, more energy is supplied to the muscles and more carbon dioxide is released

- Person 1 is a faster runner than Person 2 because Person 1 sends more blood to their musces, supplies more energy and glucose, faster rate of respiration and less lactic acid is made.  

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Anaerobic Respiration

Breaking down food without oxygen to release energy for the cells.

Glucose -> Lactic acid (+ energy)

Oxygen dept: The extra oxygen that must be taken into the body after exercise has stopped to complete the aerobic respiration of lactic acid.

Anaerobic breakdown of glucose releases less energy than aerobic respiration

If muscles work hard for a long time they become fatigued and don't contract efficiently. If they don't get enough oxygen they will respire anaerobically. 

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Asexual cell division where two identical cells are formed (no genetic vaariation)

New body cells are produced:

- when the animal is growing

- To replace worn out tissues

- To repair damaged tissues

1. The cell has 2 copies copies of DNA all spread out in long strips 

2. The cell duplicates the chromosomes

3. The cell divides into 2 daughter cells that have the same choromsomes as the parent cell

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Animal Cell Differentiation

Specialising for a particular job

- Many have cells that become specialised very eary in life.

- Important genes for the particular jobs are turned on and the others are turned off.

- In mature animals mitosis is restricted (only needed to repair damaged tissueand to replace worn out tissues.) This is because differentiation has already taken place.

- It's difficult to clone animals as specialised cells can't go back to unspecialised as their cells are differentiated permanently

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Plant Cell Differentiation

- Plants through their life, don't fully differentiate until they have reached their final position in the plant.

- Differentiation in a plant isn't permanent as a plant cell can move around the plant and will redifferentiate and become a different type of cells.

- Plants can be cloned using tiny peices of leaf tissue because it can become unspecialised and can undergo mitosis again and again

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The 2 stage process of cell division which reduces the chromosome numbers of a daughter cell. It is involved in making the gametes for sexual reproduction. (variety)

1. The cell is in the reproductive organ looks like a normal cell

2. The chromosomes are copied and divides into two new cells

3. 2 cells divide again leaving 4 new cells that have half the amount of chromosomes the original cell has

- When gametes fuse in fertilisation a new body cell forms with 23 pairs of chromosomes

- The cell then divides by mitosis to form a new individual

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Stem Cells

Stem cells are undifferentiated cells that can form a variety of different cell types.

- Can be found in an embryo, blood, the brain, mucles and the Liver.

- Diseases that can be treated by stem cells: Spinal cord injuries, paralysis, blindness and dementia

- Cons: Ethical and Religious issues, human right violation (if taken from an embryo), Slow process and can cause Cancer

Zygote -> embryo -> foetus -> baby

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Gregor Mendel

- Worked out the main principles of inheritance

- Crossed lots of peas to see predictable patterns being formed through inheritence


- Each individual inherits a set of factors from each parent

- The combination of the characters determines the characteristics of an individual

- DNA chromosomes and genes hadn't been discovered

- People couldn't accept the link between plants and animals

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DNA are material of inheritence they are a double helix structure.

- Our genes are carried on chromosomes found in the nuclei of our cells.

-Chromosomes are made up of long molecules of a chemical known as DNA 

- Genes are a small section of the DNA

- DNA carries instructions to make proteins such as enzymes

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The Genetic Code

- DNA are made up combinations of four different chemical bases that are grouped into groups of three (codes for an amino acids)

- Genes are made up of a lot of thhese bases.

- Amino acids form specific  proteins

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Inheritance in action

Homozygous: 2 identical alleles for characteristics (DD or dd)

Heterozygous: 2 different alleles for charateristics (Dd)

Genotype: Genetic makeup regarding a particular characteristic

Phenotype: Physical appearance regarding a particular characteristic

Dominant: Characteristics that will show up in the offspring even if only one allele is inherited

Recessive: characteristic that will show up in the offspring only if both alleles are inherited

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Inherited Conditions

Polydactyly: When a baby is born with extra digits. Requires  a dominant allele. If one parent has polydactyly and is heterozygous there is a 50% chance that the child will have it too.

Cystic Fibrosis: A genetic disorder that affects many organs in the body, particularly the pancreas and lungs. Requires 2 recessive alleles. Physio and antibiotics can help lungs clear of mucus. Enzymes are used to replace ones that the pancreas can't produce.

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How Fossils form

1. Reptile dies and falls to the groud

2. Flesh rots, sand or soil and clay cover the skeleton before it is damaged

3. Skeleton becomes mineralised and turns to rock which shifts in earth with the fossil trapped inside. (millions of years)

4. Fossil emerges as the rocks move and erodes

Fossil record is incomplete as many fossils haven't been found yet or geological activity destroyed fossils

Fossil: Animal buried in sediment; hard parts don't decay and soft parts do decay

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Extinction: Perma nent loss of all members of a species

Reasons for extinction:

- New predators

- New cdieases

- Too successful competition

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Isolation of different populations of the same species; different environmental conditions; mutations occur because of genetoc variation; survive, breed pass on genes, different populations no longer able to successfully breed with each other

Endemic: When a species evolves and is only found in one place in the world

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