The cell is the basic structural and functional unit of all organisms. The structure of cells is more or less the same in the simplest to the most complicated plants and animals.

ANIMAL

CELL

Hand out pictures

PLANT

CELL

• Cells are made up of proteins, carbohydrates, lipids, water and nucleic acids

• Unicellular (amoeba)

• Mulitcellular (human)

• Very small; average human cell is 20 µm, average plant cell is 40 µm, average bacteria is 5 µm (micrometer)

• Look at your ruler

• Nanometer is a thousandth of a um

PROTOPLASM

• Total contents of the cell are called the

protoplasm

• Consists of nucleus (double membrane) and

cytoplasm (around the nucleus)

• Organelles are membrane-bound and are

suspended in the cytoplasm

List 7 criteria that classify an organism as living:

1. Movement

2. Reproduce

3. React to Stimuli

4. Growth

5. Breathing – Respiration

6. Excrete waste

7. Feed

• It is a translucent, viscous, semi-fluid grey substance

• Consists mainly of water in which dissolved substances (true solution) and other substances are in suspension.

• The elements oxygen, hydrogen, carbon and nitrogen comprise about 95% of the living protoplasm.

• Most of the elements appear in compounds which may be organic; example: carbohydrates, proteins and lipids;

or inorganic example: water, gases, mineral salts and vitamins

Water

• Serves as a solvent of organic and inorganic substances in the cell

• It is the medium biochemical reactions take place in

• It serves as a transport medium which assists in absorption of substances needed for metabolic processes

• It assists to eliminate waste substances from the cell

Proteins

• Serves as building material of cells and cell membranes

• Enzymes are proteins which help in controlling numerous chemical reaction in the protoplasm

• Hormones are proteins

Let’s look at the ultrastructure of the cell

Ultrastructure: detailed structure as can be seen by an electron micrograph

• The cell wall is the non-living structure outside the cell membrane of most plant cells

• Tick and rigid

• The primary cell wall is permeable and made of cellulose fibers that criss-cross one another

• The secondary cell wall is made of lignin

• The middle lamella is made of sticky substances called pectin

• Permeable to water, dissolved salts, ions and gases

• Rigid due to presence of cellulose lignin and pectin

• Is non-living and virtually non-elastic

• Provides support to herbaceous plants

• Provides direct support to the cell and mechanical support to the cell as a whole (strength and rigidity)

• Maintains the shape of the cell

• Protects the contents of the plant cell

• Permeable to water and other substances and contributes to the movement of water on a whole

• Occasionally cell walls acts as food reserves

Membranes enclose cells

• Outer covering,

• protective layer around

ALL cells

• For cells with cell walls, the

cell membrane is inside the

cell wall

• Allows food, oxygen, &

water into the cell & waste

products out of the cell.

• Also called the plasma

membrane or

plasmalemma

• The cell membrane is the outer most layer surrounding the cell

• Very thin – 7 nm, consisting of 3 layers

• It is flexible and composed of an inner and outer layer of protein molecules and between them two layers of phospholipids

Fluid Mosaic Model• Bilayer of phospholipid molecules

• Phospholipid molecules are made up of two parts

– Head which faces the inside and outside (hydrophylic)

– Tail which face inwards (towards each other – hydrophobic)

• Large protein molecules are embedded in the phospholipid bilayer

• Carbohydrates attach to the lipids (glycolipids) or proteins (glycoproteins)

• Membrane is dynamic (not static)

• Proteins form channels for transportation in and out of the cell

1. Give the definition of hydrophilic and hydrophobic.

2. Why is it called the fluid mosaic model?

• The cell membrane serves as the living barrier between the cell and its environment

• Keeps the cell together

• It is differentially/selectively permeable (only certain substances can pass in and out of the cell)

TRANSPORT ACROSS MEMBRANESAtoms and molecules

• Atoms and molecules are always moving due to kinetic energy

• Move differently in solid, liquid and gas

Solutions

• Sugar in water makes a solution

• Sugar molecules dissolve and spread out

• Sugar = solute

• Water = solvent

Diffusion

• Movement of molecules from a region of higher concentration to a region of lower concentration down a concentration gradient until it is evenly spread out

• Gases in plant and animal cells usually move by diffusion

TRANSPORT ACROSS MEMBRANES

Osmosis

• Special type of diffusion

• Movement of water through a selectively permeable membrane from a higher concentration to a lower concentration (concentration gradient)

• Pores in membrane usually only allow water to pass through

Both processes are passive because no external energy is required for the molecules to move

Diffusion Osmosis

• Movement of any molecule

• No membrane needed

• Movement of water molecules

• A selectively permeable membrane has to be present

TRANSPORT ACROSS MEMBRANES

Osmosis in living cells

• Cell membranes are selectively permeable

• Allow water to pass through but not solutes

• Animal cells shrink if you put them in concentrated solutions. Why?

• Plant cells absorb water from the soil with their root cells. How?

TRANSPORT ACROSS MEMBRANES

Active transport

• Opposite of diffusion and osmosis

• Molecules from low to high concentration against the concentration gradient

• Need energy and carrier molecules which are found in the membranes

• Carrier molecules attach to molecules on the lower concentration side of the membrane and carry them across to the high concentration side

• Need energy to do this (cellular respiration)

• E.g. in plant cells: root hair cells absorb mineral irons against a concentration gradient

• E.g. in animal cells: absorption of glucose from the small intestine against a concentration gradient

Draw and label a diagram of the nucleus

• Every true cell has a nucleus

• Largest cell organelle

• Controls all activities of the cell (by controlling protein synthesis)

• It plays a role in hereditary characteristics

• 4 parts

– Nuclear membrane (has pores)• Double membrane

• Outer membrane continuous with endoplasmic reticulum

– Nucleoplasm• Jelly-like

– Chromatin network• DNA (single-stranded)

– Nucleolus• Made up of protein and RNA (plays a role in making proteins)

• During cell division chromatin becomes shorter and thicker: double-stranded chromosomes

• Chromosomes carry the hereditary characteristics

• Chromosome consists of 2 identical strands called chromatids

• Chromatids are held together by a centromere

• Genes are found on the chromatids (section of DNA)

• 46 chromosomes in humans

• Very small (15-20 nm)

• In plant and animal cells

• Make proteins

• Float freely or attached to the endoplasmic reticulum (ER)

• Ribosome's are made in the nucleolus

• 2 parts: small and large subunit

• Consist of proteins and RNA

• On ER or in cytoplasm

• Clusters are called polysomes

• Organelles and cytosol (liquid medium of the cell)

• In plant and animal cells

• About 1 µm long

• Outer smooth membrane and inner membrane

• Inner membrane folded to form cristae

• Cristae increase the surface area

• Cristae covered with granules which consist of enzymes for aerobic respiration

• Matrix

FUNCTION

• Aerobic respiration (food is broken down in the presence of oxygen to release energy)

• Cells store energy in ATP (adenosine triphosphate)

• Energy carriers

• 50 – 2 500 mitochondria per cell

• Double membrane

• Only in plant cells

• 3 types:

– Chloroplasts

– Chromoplasts

– Leucoplasts

Chloroplasts• Oval shaped

• 1-100 per cell

• Only found in plants that are exposed to light and are green in colour

• Inner and outer membrane

• Fluid matrix is called the stroma

• Thylakoids are stacked like coins to form grana

• Grana are connected to other grana by single

thylakoids or lamellae

• Thylakoids contain chlorophyll (absorb sunlight to

convert CO2 and H2O into chemical potential

energy/food = photosynthesis)

• Oil droplets and starch grains may collect in the

stroma

Chromoplasts• Contain carotenoid or coloured pigments

• Mainly found in fruits and flowers

• Chloroplasts can convert into chromoplast (ripening fruit eg. Banana)

Leucoplasts• Colourless

• Mainly found in food storage organs (bulbs and tubers)

• Store starch = amyloplasts

• Can also store proteins and fats

• Can turn into chloroplasts if exposed to sunlight (potatoes)

• Endoplasmic reticulum (ER)- It is a network of membranes throughout the cytoplasm of the cell. There are two types of ER.

• When ribosome's are attached it is called rough ER and smooth ER when there are no ribosome's attached.

• Found in both plant and animal cells• Extensive system of membranes in cytoplasm (canal system)• The rough endoplasmic reticulum is where ribosomes are

transported and where most protein synthesis occurs in the cell. The function of the smooth endoplasmic reticulum is to synthesize lipids in the cell. The smooth ER is also helps in the detoxification of harmful substances in the cell.

• Often continuous with nuclear and plasma membrane

• Golgi complex- It is the organelle in the cell that is responsible for sorting and correctly shipping the proteins produced in the ER to the correct place.

(Just like our postal packages which should have a correct shipping address, the proteins produced in the ER, should be correctly sent to their respective address.)

• In the cell, shipping and sorting done by the Golgi complex. It is a very important step in protein synthesis.

• If the Golgi complex makes a mistake in shipping the proteins to the right address, certain functions in the cell may stop.

• Golgi vesicles are also used to form lysosomes

• Makes and processes secretions (saliva and mucous)

• Same structure as smooth ER

• Stack of flattened sacs called cisternae

• In both plant and animal cells

• What is the difference between the vacuoles in the plant and the animal cell?

• What is a vacuole?

• What is the differentially permeable membrane surrounding a vacuole called?

• In plant cells can occupy 80-90% of the cell

• Fluid-filled cavity bound by the tonoplast

• Fluid is called cell sap and consists of water and solutes (sugars and salts)

Functions• Stores water, ions, pigments and soluble

compounds• Responsible for the uptake of water by

osmosis and assist in intercellular transport• They maintain the turgidity of cells and

provide mechanical support• They perform specialized functions such as

digestion (phagosomes), osmoregulation (contractile vacuoles) and excretion (dictyosomes) – mostly in unicellular organisms

• The word "lysosome" is Latin for "kill body."

• Contain digestive enzymes

• Digest food particles or worn out organelles

• Engulf viruses and bacteria

• The centrosome is a specialized area in the cytoplasm near the nucleus.

• It contains two specialized cylindrical bodies, the centrioles, lying at right angles to one another.

• The centriole is a hollow cylinder consisting of 9 fibrils• The centriole forms the pole of the spindle during cell

division• Centrioles occur on most animal cells but are absent

in most plant cells

Nucleus

Chromosomes

Mitochondria

Ribosomes

Chloroplasts

Vacuoles

ER

Cell Membrane

• The Cell worksheet

• Word zone- CELL worksheet

• Table 2.2 pg 53

• Textbook: activity page 53 and 54