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Cambridge IGCSE BiologyExtended Level

Cells

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You should be able to:

• Identify and describe the structure of plant cells and animal cells, and describe the functions of their parts.

• Describe the difference between animal cells and plant cells.

• Explain the structure and function of specialised cells: red blood cell, muscle cells, ciliated cells, xylem vessels and root hair cells.

• Define the terms tissue, organ and organ systems, with examples.

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A section through a liver cell (animal cell):

cell membrane

cytoplasm

nucleus

DNA

controls what enters and leaves the cell

metabolic (chemical) reactions occur here

contains the DNA and so controls the cell

contains the coded instructions to make proteins

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Under a microscope

nucleus

cytoplasm

cell membrane

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In the cytoplasm…

• There are ribosomes– They are found on rough endoplasmic

reticulum (R.E.R) and vesicles.– Very important function in the cell.– The place where proteins are made by joining

amino acids together in a long chain.– The instructions carried by DNA in the

nucleus decides the sequence needed to make a particular protein.

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Making Proteins

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Rough Endoplasmic Reticulum

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Ribosomes are found in…

• ALL TYPES OF CELLS!!!– BACTERIA– PROTOCTISTS– FUNGI– ANIMALS– PLANTS

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Mitochondria

• The place that aerobic respiration occurs.

• Oxygen is used to release energy from glucose.

• Cells that use a lot of energy have many mitochondria

e.g: Sperm – swimmers Neurones – transmit impulses

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MITOCHONDRIA ARE FOUND IN ALL CELLS EXCEPT PROKARYOTES (BACTERIA)

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Section through a palisade cell of a leaf (plant cell)

cell membrane

nucleus

cytoplasm

chloroplast

large sap vacuole

cellulose cell wall

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Under a microscope

large sap vacuole

cellulose cell wall

chloroplast

cytoplasm

nucleus

cell membrane

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Cell wall under the microscope• The Cell wall is made of Cellulose.

• Cellulose belongs to a group of substances called polysaccharides, which we will look at in Unit 4.

• The cellulose fibres help to support and protect the cell.

• If the cell absorbs a lot of water and swells, the cell wall stops it bursting.

• The cell wall is fully permeable, the spaces between the fibres allow even very large molecules to go through.

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Chloroplasts

• Never found in animal cells.• Contain a green colouring pigment called

chlorophyll.• Chlorophyll absorbs energy from sunlight which

is then used for making food (starch grains).• Animal cells never have starch granules.

Instead, they have glycogen.• Starch is found in the cytoplasm NOT inside

chloroplasts.

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You should be able to:

• Identify and describe the structure of plant cells and animal cells, and describe the functions of their parts.

• Describe the difference between animal cells and plant cells.

• Explain the structure and function of specialised cells: red blood cell, muscle cells, ciliated cells, xylem vessels and root hair cells.

• Define the terms tissue, organ and organ systems, with examples.

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Comparing animal and plant cells

Found in both animal and plant cells

Found only in plant cells

cell membrane cellulose cell wall

nucleus large sap vacuole

cytoplasm chloroplast

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Coursebook Page 24Do all questions on page 24

Finish for homework

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You should be able to:

• Identify and describe the structure of plant cells and animal cells, and describe the functions of their parts.

• Describe the difference between animal cells and plant cells.

• Explain the structure and function of specialised cells: red blood cell, muscle cells, ciliated cells, xylem vessels and root hair cells.

• Define the terms tissue, organ and organ systems, with examples.

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Specialised Cells

• Not all cells are the same.

• They have different features that depend on their function within an organism.

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Red blood cells transport oxygen

cell surface membrane cytoplasm contains no nucleus

cytoplasm contains haemoglobin

bi-concave disc shape

allows more room for haemoglobin

increases surface area over which absorption of oxygen can occur

haemoglobin is a protein which carries the oxygen molecules

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Muscle cells contract and enable movement of the body

nucleuscell surface membrane

protein strands

The strands of protein slide over each other making the muscle cell (fibre) shorter and causing the muscle to contract

Muscle cells have many nuclei

muscle

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Ciliated cells move bacteria and dust away from the lungs

cilia

magnification X3000

nucleus

Cilia are small extensions of the cell. They beat rhythmically to sweep mucus, which has trapped bacteria and dust, away from the lungs

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Xylem vessels transport water and minerals up the plant

xylem vessel

lignin

no cytoplasm

longitudinal sectioncross-section

water-proof and strong;helps support the plant

hollow: allows for continuous flow of water and dissolved mineral ions

xylem vessels are continuous tubes

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Root hair cells absorb minerals and water from the soil

cytoplasmcontains no chloroplasts as no photosynthesis is needed

root hairincreases surface area for absorption of water and mineral ions

Cross-section of a root hair cell

cell membrane semi-permeable, so will allow water and mineral ions into the cell

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Nerve cells transmit information in the form of electrical impulses

Direction of information

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You should be able to:

• Identify and describe the structure of plant cells and animal cells, and describe the functions of their parts.

• Describe the difference between animal cells and plant cells.

• Explain the structure and function of specialised cells: red blood cell, muscle cells, ciliated cells, xylem vessels and root hair cells.

• Define the terms tissue, organ and organ systems, with examples.

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A tissue is a group of cells of similar structure that perform a shared function

Animal tissues:muscle tissue

nervous tissue

upper epidermal tissue

palisade mesophyll tissue

spongy mesophyll tissue

lower epidermal tissue

Tissues found in the leaf

Cross-section of a leaf

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An organ is a structure made of a group of tissues working together to

perform specific functions

Plant organs include the stem and the leaves

heart

stomach

lungs liver

brain kidneys

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An organ system is a group of organs that coordinate to perform related functions

In plants the shoot is an organ system consisting of leaves and the stem

lymphaticsystem

respiratorysystem

digestivesystem

excretorysystem

reproductivesystem

muscularsystem

skeletalsystem

nervoussystem

endocrinesystem

circulatorysystem

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Levels of organisation

nerve cell nervous tissue

brain nervoussystem

Homo sapiens

smallest largest

cell tissue organ organsystems

organism

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Now you should be able to:

• Identify and describe the structure of plant cells and animal cells, and describe the functions of their parts.

• Describe the difference between animal cells and plant cells.

• Explain the structure and function of specialised cells: red blood cell, muscle cells, ciliated cells, xylem vessels and root hair cells.

• Define the terms tissue, organ and organ systems, with examples.

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Now write down everything you remember from the presentation

• Don’t refer to your text book straight away, see what information you have retained.

• Check the notes you have made by checking your book.