Biology Revision


Animal, Plant and Bacteria Cells

Cell: The smallest structure and functional unit of an organism

Ribosomes:Protein Synthesis happens here

Cell Wall: Strengthens the cell

Nucleus: contains genetic material which controls the cell.

Mitochondria:Most energy is released by respiration

Chloroplast: Contains chlorphyll which absorbs light for phtosynthesis

Flagellum:Helps bacterium move around

Cytoplasm: Most chemical processes take place here controlled by enzymes.

Cell Membrane: Controls the movement of substances in and out of the cell.

Vacuole: Filled with cell sap to help keep cell turgid.

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Animal Cell Diagram

Image result for animal cell diagram

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Plant Cell Diagram

Image result for plant cell diagram

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Bacteria Cell Diagram

Image result for bacteria diagram (

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Difference between cells

  • Plant:                                               Animal                                                 Bacteria

Has Chloroplasts                          No cell wall                                              DNA in nucleoid

Contains Mitochondria              Contains mitochondria for energy          Surrounded by a                                                                                                                                    membrane

Cell wall made of cellulose        DNA in nucleus                                      Cell wall made of complex                                                                                                                    molecules

DNA in nucleus.                        No chloroplasts                                        No chloroplast

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Leaf Cell and Root Hair Cell


Absorbs Light energy for photosynthesis.


Packed with chlorplasts .

Regular shaped,

Closely packed cells form a continous layer for efficient absorbsion of light .

Root Hair Cell

Functions:Absorbs water and mineral ions from the soil

Adaptions: Long'finger like' process with very thin wall, which gives a large surface area

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Sperm Cell and Red Blood Cell


Fertilise an egg cell. Female Gamete


The head contains genetic information and an enzyme to help perforate the egg cell membrane . The middle section is packed with mitochondria for energy. The tail helps the sperm move towards the egg.

Red Blood Cell:

Function: Contains haemoglobin to carry oxygen to the cell. Biconcave shape.

Adaptions:Thin outer membrane to let oxygen diffuse through easily. Shape increases the surface area to allow more oxygen to be absorbed efficiently. No nucleus so the whole cell is full of haemoglobin.

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Ciliated Epithelial Cell and Xylem


Has cilla to increase the surface area


Cilla are tiny hair like structures on the surface of the cell . The hairs sweep mucus, trapped dust and bacteria up to the back of the throat where it can be swallowed



Transport water up the plant from the roots


It is made from dead cells that lack end walls to make a hollow tube

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Phloem and Nerve Cells


Carries sugars around the cell


It has special sieve platelets in it.

Nerve Cells:


Carry Electrical impulses 


they are long and have connections at each end and they have a myelin sheath to insulate the cell from the electric impulses and make it travel quicker.

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Muscle Cells


Muscle Contraction


Contain a large number of mitochondria to provide energy for muscle contraction . They have special protein fibres to allow the cells to contract

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Plant and Animal Cells

  • Plant and Animal are multicellular
  • Many Different Types Of Cells
  • Each type of Cel is designed to carry out a particular job or function
  • This is known as cell specialism or cell differentiation.
  • Don't all look the same
  • Some cells have a special shape and features to help them do a certain job
  • Animal cells differentiate early in development , but Plant cells differentiate at any stage.
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Redwood Tree- 100m

House- 10m

Human- 1m

Mosquito- 1cm

Flea- 1mm


Cell- 10μm

Bacteria- 1μm

DNA- nm

Aseptic:Free from Contamination caused by harmful Bacteria, Viruses or other microorganisms:Surgially sterile or sterilized

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Chromosomes; Thread like structure of nucleic acid and protein found in the nucleus of most living cells, carrying genetic information in the form of genes..

Haploid:Describes a cell or nucleus of a gamete that has half the number of usual chromosomes(23)

Diploid: Cells that have a full number of chromosomes (46)

Gene: A section of DNA that codes for a charateristic 

DNA: A molecule that contains all the information we need to build you.

Chromosomes: A packet of DNA information. We have 46

Nucleus: A part of a cell that holds all the chromosomes inside.

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Down's Syndrome Causes and Symptoms

Usually cells contain 46 chromosomes. 23 from the mother and 23 from the father.

In people who have Down's Sydrome all or some of the cells in their bodies contain 41 chromosomes instead as theres an extra copy of chromosome 21. This extra gene causes the characteristics of Down's Syndrome.

In most cases , Down's syndrome is not inherited it's just the result of a one off genetic change in the sperm or egg.


Hypotonia (floppiness)                                         Broad Hands with short fingers

Small nose and flat nasal bridge                          Their palm may only have one crease across it

small mouth with a tongue that may stick out       Below average weight and length at birth

eyes that slant upwards and outwards

a flat back of the head

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Down's Syndrome Effects

Thyroid Problems

Hearing Problems

Congenitial Heart Disease

Eye Problems


Bone, Muscle, Joint or Nerve problems

Leukemia or other cancers

Immune system problems

Developmental problems

Alzheimers disease

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Turner's Syndrome Causes and Symptoms


A girl with turner syndrome only has one x sex chromosome rather than the usual two. This happens randomly when the baby is conceived in the mother's womb.


Thick Neck Tissue

Cystic Hydroma (Swelling of the neck)

Being a small baby

Heart Conditions

Kidney Abnormalities

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Turner's Syndrome Effects

Webbed Neck

Low hairline

Drooping of the eyelids(ptosis)

Lower set eyes

Abnormal bone development

Larger number of moles

Edema in the hands and feet (extra fluid)

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Jacobsen Syndrome

Jacobsen syndrome is a condition characteristics by the deletion of sevral genes on chromosome II.


Paris-Trousseau Syndrome-Bleeding disorder

Hypertelorism- Wide set eyes

Ptosis- Droopy eyelids

Micronathia- Small lower jaw

Macrocephaly- Large head

Trigonocephaly- Skull abnormalities.


ADHD :Congenitial Heart disease :Short Stature :Skeletal abnormalities

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Cell Division and Mitosis

Interphase- Prophase-metaphase- anaphase- telophase

Interphase:Chromosomes in the nucleus are copied

Prophase: Chromosomes condense and become fatter and shorter

Metaphase:Chromosomes line up along the centre

Anaphase: Chromosomes now split and move towards poles

Telophase: Two nuclear envelopes form at poles. 2 daughter cells identical to original are created.Image result for mitosis  THERE IS A TO IN MITOSIS AND THERE IS A TOE ON YOUR BODY.

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The Microscope

In 1878 Robert Koch discovered how to grow bacteria in a petri dish named after his assisstant Julius Petri . He was able to discover which Bacteria caused certain diseases, including TB and Cholera. Scientists still grow microorganisms in the lab so that they can be investigated.

Bacteria can be grown in either nutrient rich broth or nutrient rich agar. This acts as a food source for the organisms.This food source contains the carbohydrates, mineral , proteins and vitamins they need to grow.

When grown on'Agar plates' the bacteria will form visable colonies on the surface of the agar or they could spread out and cover the whole plate .

Once you have grown your bacteria you can see how effective they are by calculating the size of the zone of inhibition.The larger the zone of inhibition the more effective the antibiotic is against the bacteria. To calculate the area of an inhibition zone you use the followign formula:

Area= π r2 

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Stem cells

Stem cells ; a cell that has not yet become specialised (this has the potential to become any type of cell)

Embryonic cell: Unused embryos 

Adult cells: Tissue such as bone marrow.

They can repair damged organs, bones,cartlidge. Treat diseases and regrow brain cells. Repair immune cells system.Reverse paralysis, regrow lost limbs

Adult stem cells are limited in what types of cells they can become 

Embryonic stem cells 

they come from the embryo

embryonic stem cells can differentiate into any type of cell

they divide rapidly and can be rejected

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Therapeutic cloning Pros

Clone embryo

embryo can be rejected

used for medical treatment


Will offer a cucre for many diseases such as cancer and diabetes

offers treatment to many incurable diseases

no waiting lists for organ transplants

Less lab animals and money will be wasted testing new drugs

Donated cells are identical so there is no problems with rejection

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Therapeutic cloning Cons

Drugs given to a women to stimulate eggs are dangerous

Embryonic stem cells are unstable and cause tumours

Even at 3 days embryos are considered as living things

Embryos are created purely for research.

use of stem cells could cause the transfer for viral infection

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