Cell Structure and Organisation Key Question: What is life made of? Life generally consists of : ability to move, ability to reproduce and ability to take in use nutrients for its growth

Learning Outcomes Identify the main organelles and membranes in the cell (nucleus, mitochondria, cell surface membrane, cytoplasm, Golgi Apparatus, endoplasmic reticulum, cell wall, chloroplast, vacuole) Explain the various functions of different organelles

Learning Outcomes Compare the structure of plant and animal cells Describe the relationship between structure and function as seen in xylem vessels, root hair cells and red blood cells Differentiate between the levels of organisation in an organism

The term “cell” was first introduced by Robert Hooke in 1667 who examined thin slices of cork under a microscope Cork cells (dead plant cells) as seen by Robert Hooke What is a cell?

Cell is the basic unit of structure and function in an organism It is the basic block of life All organisms are composed of one (unicellular) or more cell (multicellular) What is a cell? A cell is like a factory. What do you think are the parts or functions of a factory that may be similar to the cell?

How do we study the parts of a cell? Use of microscopes -> light microscope (magnifies objects up to 1000x) -> electron microscope (magnifies objects to >200,000x)

Structure of the cell Protoplasm: Each living cell consists of living material called protoplasm which is contained within the cell membrane. The protoplasm is made up of 70% water and 30% of other substances, most of which are proteins, carbohydrates and fats. The composition of protoplasm varies greatly from cell to cell.

Diagram of animal cell

Diagrams of plant cell

Both Cells Cell surface Membrane (plasma membrane) Thin partially permeable membrane that surrounds the cytoplasm Controls substances entering or leaving cell Keeps cell content in place PPM is like a door that allows only some substances to cross it.

Cytoplasm: Is the part of the protoplasm between the cell surface membrane and the nucleus Contains enzymes and a suspension of specialised structures called organelles Site within cell in which most cell activities occur Both Cells (cytoplasm) Organelles carry out various functions in the cell.

Nucleus: Small spherical structure consisting of nucleoplasm surrounded by a nuclear envelope Contains one or more nucleoli and chromatin Both Cells Nucleoplasm

Functions of the nucleus: Controls cell activities such as growth and repair of worn-out parts Involved in cell division Functions of the nucleolus Nucleolus: needed to make ribosomes Both Cells

Chromatin: Network of long thread-like structures that control cell division Each chromatin thread is made up of proteins and deoxyribonucleic acid (DNA) Chromatin threads condense to become chromosomes (highly coiled structures) during cell division Both Cells

Organelles- Endoplasmic reticulum (ER) There are 2 types of ER – rough ER and smooth ER. Both Cells

Rough Endoplasmic reticulum (RER) Outer surface appears rough and is continuous with nuclear envelope Ribosomes attached to outer surface RER transports proteins made by ribosomes to Golgi apparatus for secretion out of cell Both Cells

Smooth Endoplasmic reticulum (SER) More tubular and may or may not be connected to RER synthesises substances such as lipids and steroids (sex hormones) converts harmful substances into harmless materials (detoxification) Both Cells

Golgi apparatus (Golgi body) Shaped like a disc Consists of stack of flattened spaces surrounded by membrane Vesicles can be seen fusing with one side of Golgi apparatus and pinching off on opposite side Golgi apparatus -> stores and modifies substances made by ER (both SER and RER) -> packages these substances in vesicles for secretion out of cell Both Cells

Are vesicles the same as vacuoles?

Vesicles or vacuoles a vesicle is a relatively small intracellular, membrane-enclosed sac that stores or transports substances. Vacuoles store food and other materials needed by a cell.

Mitochondrion Sausage-shaped like organelles; double membrane with inner membrane thrown into deep folds called cristae Both Cells inner compartment outer membrane matrix cristae

Mitochondrion… Site of aerobic respiration to release energy from food used by cell for growth and reproduction Site of aerobic respiration to release energy from food used by cell for growth and reproduction During aerobic respiration, food substances are broken down to their molecules to release energy. This energy may be used by the cell to perform cell activities such as growth and reproduction.

Vacuoles Fluid filled spaced enclosed by membrane Store substances with cell Animal cell: many small vacuoles that contain water, food substances and enzymes- (digestive enzymes to digest invading bacteria); usually exist temporarily vacuoles

Vacuoles Plant cell: large central vacuole containing cell sap (nutrients- sugars, amino acids, mineral salts, wastes, poisonous substances that deter animals from feeding on plant parts) enclosed by a tonoplast (partially permeable)

Cell Wall: Rigid wall made of cellulose Cell wall is fully permeable Protects the cell from injury and gives plant cell a fixed shape Plant Cell lysosome plasma membrane cell wall nucleolus nucleus mitochondrion sap vacuole chloroplast cell wall of adjacent cell

Chloroplasts: Oval structures Contain a green pigment called chlorophyll Carry out photosynthesis Plant Cell

Centrioles Cylindrical structures that exist as a pair Plays a role in cell division

Differences between plant and animal cells FeaturePlant CellAnimal Cell Cell WallPresentAbsent VacuolesA single, large central vacuole Vacuoles are small and many (temporary) ChloroplastsPresent in photosynthetic cells Absent CentriolesAbsentPresent

Specialized Cells, Tissues, Organs and Systems There are many different groups of cells which have different structure, shapes and sizes They are adapted to perform specific roles Differentiation: - A process by which a cell becomes specialised for a specific function Examples: Root hair cells Red blood cells Xylem vessels

Relating structure to function Red blood cell Root hair cell Xylem vessel

Red Blood Cell – oxygen transport No nucleus: - can carry more haemoglobin and thus more oxygen Circular biconcave shape: - Increase surface area to volume ratio of cell for diffusion of oxygen into and out at a faster rate Contains haemoglobin: -Combines with oxygen to form oxy-haemoglobin which transport oxygen from lungs to all parts of body

Root Hair Cell - absorption Long and narrow protrusion of epidermal cell (root hair): - increases surface area to volume ratio of cell so that water and mineral salts can be efficiently absorbed from the soil

The Xylem Vessel xylem epidermis phloem cambium xylem thickened band lumen hollow vessel long vessel Transverse section through a dicotyledon stem to show the xylem vessels Xylem vessel Dead Plant cells laid end to end (without nucleus and cytoplasm) with thickening cell walls  Xylem vessels

Absence of cross walls or protoplasm - enables water to move easily through the lumen Long, hollow tubes formed from xylem cells laid end to end - Allows water and mineral salts to be conducted from roots to stem and leaves Lignin deposited on walls of xylem vessels - strengthens wall and prevents vessels from collapsing Xylem Vessels – conduction and support xylem vessels bundled together - provides mechanical support to plant

Cell is the basic unit of structure and function in an organism It is the basic block of life From cells to tissues to organs to systems!

Tissues Defined as a group of similar cells working together to perform a specific function There are simple tissues and complex tissues Example of tissues: - Epithelial tissues - Connective tissue - Muscles tissue - Nervous tissue

Simple tissues (cells of the same type) Animal tissues Plant tissues Epithelial tissues These are sheets of cells which cover the external surface or line the cavities of the body Muscle tissues These are concerned with body movements by contracting epithelium lining blood vessels epithelium covering the ovary epithelium lining the trachea muscles in the walls of the intestine muscles of the heart Epidermis Covering tissues of leaves and stems

Animal tissues Plant tissues Complex tissues (several types of cells) Connective tissues These join together body structures, providing protection and support Nervous tissues These are concerned with the conduction of nerve impulses throughout the body blood nerve tissue of the brain Vascular tissues -xylem and phloem tissue

Organs A structure made of different types of tissues working together to perform specific functions There is division of labour among the organs

Organs in animals Stomach (store food, digest and churn) glandular tissues secrete digestive juices Muscular tissues causes stomach to contract and mix food with digestive juices Nervous tissue coordinates actions of stomach

Plant organs Leaves - Make food Stem -transports water with dissolved mineral salts from roots to leaves and food from leaves to other plant parts - gives support to plant above ground

Systems Several organs working together for a common purpose make up an organ system Examples: - Digestive system - Respiratory system - Nervous system - Circulatory system Digestive system

From systems to organisms The different systems in the body make up the whole organism

Division of labour in cells In each cell, there are organelles specially designed to perform a specific job. For example: chloroplasts allow plant to make food, mitochondria enables respiration to take place... Division of labour (breakdown of workload to smaller and more specific tasks) helps individual cells function more efficiently

Division of Labour Unicellular organism one cell carry out all the jobs of the organism Multicellular organism Each type of cell specialises in performing one particular function– DIVISION OF LABOUR different cells have special features to carry out particular jobs Different organs and systems also perform different jobs. However, they work with one another to ensure that the whole organism functions effectively.

Summary FeaturesPlant CellsAnimal Cells Nucleus√√ Cell membrane√√ Cytoplasm√√ Mitochondria√√ Endoplasmic Reticulum√√ Golgi Apparatus√√ Cell Wall√X Chloroplasts√X Vacuole1 large vacuoleNumerous small vacuoles Tonoplast√X

Summary Specialized Cells Root hairsRed Blood CellsXylem Vessels Absorption of water & mineral salts Transport oxygen Transport of water & mineral salts Example Function * How are they adapted for their functions?

Summary Cells Tissues Organs Systems form Organisms form Cell Heart Organ Cartilage Tissues Organism