Cells

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Unit : cells – the basic units of life Created BY: Ms Mwelase

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Transcript of Cells

Page 1: Cells

Unit : cells – the basic units of lifeCreated BY: Ms Mwelase

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The study of cells and micro organisms has changed over time with the change in technology.

These were studied in the beginning with hand lenses, single lens microscope, light microscope

Today we have electron microscopes. Two types of electron microscopes are used today:

SEM – Scanning electron microscope and TEM – Transmission electron microscope.

HOW to study cells.

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1632-1723ANTON VAN LEEUWENHOEK

Developed a microscope with one lens.

Discovered - bacteria- blood cells-

spermatozoa- protozoa

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1662 – ROBERT HOOK

Uses the concept cell for the first time.

He used it when he looked at the microscopic structure of cork cells.

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1831 – ROBERT BROWN (Botanist)

Describes the nucleus of a cell

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Developed the cell theory:- Plants and animals are made of groups

of cells.- The cell is the basic unit of living

organisms

1838-1839MATTHIAS SCHLEIDEN (Botanist)THEODOR SCHWANN (Zoologist

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1855 – RUDOLPH VIRCHOW

Expanded the cell theory: He said that new cells formed by

the division of existing cells

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1880 – AUGUST WEISMANN

Expanded the cell theory more:

He said that all cells can be traced to their origin

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All living organisms are made out of cells New cells are formed by the division of

existing cells The cell houses genes, which are the

blueprint for growth, functioning and development of cells

The cell is the functional unit of life because all chemical reactions of life take place inside the cell

Schleiden, Schwann and Virchow compiled the cell theory

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WHAT IS A CELL?

A cell is the basic unit of structure and function in organisms.

Cells differ in size, shape and in function.

A cell consist of smaller structures called organelles.

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Prokaryotic or Eukaryotic cells. Only organisms of the domains Bacteria

and Archaea consist of prokaryotic cells – cells without a membrane bound nucleus.

Protists, fungi, animals and plants all consist of eukaryotic cells – cell with a membrane bound nucleus.

Two types of cells

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General structure of an animal cell as seen under a light microscope

(called a micrograph)

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Line diagram of a general animal cell

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Micrograph of a general plant cell

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Line diagram of a general plant cell

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PLANT CELL ANIMAL CELL

DIFFERENCES BETWEEN PLANT- AND ANIMAL CELL

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STRUCTURE AND FUNCTIONS OF THE

DIFFERENT ORGANELLS OF CELLS

Chapter 6 p. 98 – 131

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Porous Varies in thickness Consist of pectin (elasticity), cellulose fibrils held

together with non-cellulose substances (hardens the cell when mature) and lignin (adds strength to cell especially in woody plants)

Cell wall is permeable and protects the inside of the cell.

Middle lamella (layer of adhesive substances) – holds the cells together

Plasmodesmata (pores) that connects the cytoplasm of the connecting cells – selectively permeable

CELL WALL(ONLY IN PLANT CELLS)

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CELL WALL WITH PLASMODESMATA AND INTERCELLULAR SPACES

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CELL MEMBRANE/PLASMA- (ANIMAL- AND PLANT CELLS)

Consist of 2 phospholipid layers and proteins in between.

The phospholipid layers are part hydrophillic and part hydrophobic

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NUCLEUS

+/- 5µm, largest organelle in cell.

Enclosed by a nucleomembrane with nuclear pores. Function: Protection and add to selective permeability.

Filled with nucleoplasma, a nucleolus and chromatin. Function of chromatin: carries genetic material in the form of chromosomes.

Function of nucleolus: Produce r-RNA

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MITOCHONDRION Consist of 2 membranes:

Outer – and a highly convoluted inner membrane- These folds are called cristae – they increase the surface area.

Filled with matrix called stroma that contains DNA and ribosomes.

Function: Produce energy in the form of ATP by means of cellular respiration

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CHLOROPLAST (PLANT CELL ONLY)

Enclosed by a double membrane

Filled with stroma and thylakoids filled with chlorophyll arranged in groups called grana.

Ribosomes and starch grains in stroma.

Function: Photosynthesis

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VACUOLE(Large in plant-, small in animal-)

Membranous sac Filled with cell sap. Causes turgor pressure in the

vacuole. Function: Stores various

substances, including waste. Helps with osmotic potential

of cell.

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Endoplasmic Reticulum – Transport system in cell

Ribosomes – Protein synthesis Golgi-apparatus – Make lysosomes and

acts as transport system. Lysosomes – Intracellular digestion. Plastids e.g.– Leucoplasts – Stores

starch - Chromoplast – gives colour

to flowers and fruit.* Centrioli – Mitosis in animal cells

OTHER SMALLER ORGANELLES

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The cell membrane has the ability to regulate transport molecules across its structure.

This function is essential to the cell’s existence.

The fluid mosaic model helps to explain how membranes regulate the cell’s molecular traffic.

PERMEABILITY OF THE CELL MEMBRANE

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Hydrocarbons, carbon dioxide and oxygen – non-polar

So they can dissolve in the lipid bilayer of the membrane.

They can cross the membrane without the aid of membrane proteins.

Polar molecules like, water and glucose move slowly across the membrane and need the aid of proteins to get across the membrane.

Permeability of the lipid bilayer

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Hydrophyllic substances can avoid contact with the hydrophobic lipid bilayer by passing through transport proteins that span the membrane.

Channel proteins – tunnel for polar molecules to pass through membrane

Aquaporins – channel proteins for the transport of water

TRANSPORT PROTEINS

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Carrier protein: Hold onto solutes that want to move across the membrane and changes shape as it moves through the membrane.

Each carrier protein is specific to what it transports.

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1. If the Golgi-apparatus of a cell is destroyed, that cell would _____________

stop releasing cellular products. become a dictyosome. release digestive enzymes in the cytoplasm

for self-digestion. behave normally.

2. Which of the following characteristics does not apply to mitochondria?

Double unit membrane. Connected to the ER. Inner membrane is folded. Larger than ribosomes.

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1. Which is not a key point in the cell theory?

All living cells consist of one or more cells. The cell is the basic unit of life. No cell can exist unless at least one other cell is present. New cells arise only from cells that already exist.

2. The main constituent of most cell walls in plants is_____. glucose. glycogen. proteins and phospholipids. Cellulose.

3. Which of the following is found in both plant and animal cells?

Chromosomes Chromoplasts Chondrocytes Leucoplast

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Part of the nucleus that mainly consist of RNA. The inner plasma membrane in the cell

surrounding the vacuole. Organelles in living cells that contain enzymes, Give 2 functions of the plasma membrane. What is Archaea?