adult human tallest trees chicken egg frog embryo most eukaryotic cells mitochondrion most bacteria virus proteins atoms diameter of DNA double helix

Quick Review: Where does most of the cell's work take place? What happen to the proteins once they leave the golgi apparatus and enter the cytoplasm? Cytoplasm become plasma membrane protein, stay in the cytoplasm for use in the cell, stored in vesicles until needed for transport.

What is a Cell? Cell: basic or smallest living unit of life of a living organism. Protoplasm: complex jelly-like substance. 70% is water; rest is mineral salts, proteins, carbohydrates, fats. Made up of 3 main parts: (i)Cytoplasm (ii)Cell surface membrane (iii)Nucleus

Part of the protoplasm between cell membrane & nucleus Jelly-like fluid in which many chemical reactions or cell activities take place. 90% water; enzymes, organelles (specialized structures) (i) Cytoplasm

flagellum cytoplasm rough endoplasmic reticulum ribosome mitochondrion Golgi complex plasma membrane vesicle smooth endoplasmic reticulum free ribosome vesicle nuclear pore chromatin (DNA) nucleolus nuclear envelope nucleus

Partially-permeable membrane Controls movement of substances into and out of the cell. Allows only some substances to cross it. (e.g. small molecules: glucose, water, O 2, CO 2 -prevents larger molecules from crossing: starch, proteins (ii) Cell surface membrane

An electron micrograph of a cell membrane (of a human red blood cell) seen in cross-section. made of proteins and fats double phospholipid layers (fats, proteins, phosphate groups)

Parts of a nucleus: -Nuclear envelope, nucleoplasm, nucleolus Nucleoplasm: dense material inside nucleus Nucleolus(1) or nucleoli (2): Making proteins.’ Control cell activities e.g. cell growth, repair of worn-out parts. Essential for cell division. (iii) Nucleus

nuclear pores chromatin nucleolus nuclear envelope

Chromatin: Network of long, thread-like structures Contains hereditary material (DNA and proteins), instructions for the cell to carry out all chemical reactions Controls cell division Chromosomes: when chromatin threads condense and become highly coiled during cell division (rod- shaped)

Non-living layer Made up of Cellulose (a complex sugar) Surrounds cell membrane of plant cell Fully permeable to water, gases, dissolved substances -Protects the plant cell from injury -Supports and gives a fixed shape to plant cell Plant cells – Cell Wall

Membrane Network – Endoplasmic Reticulum (ER)

0.5 micrometers smooth endoplasmic reticulum vesicles ribosomes rough endoplasmic reticulum 0.5 micrometers

2 types: rough and smooth For synthesis and transport of substances Rough ER (RER): ribosomes are attached on outer surface Continuous with nuclear envelope Transports proteins made by ribosomes to Golgi Apparatus for secretion out of the cell. Endoplasmic reticulum

Smooth ER (SER): no ribosomes attached on outer surface Makes substances – fats, steroids (sex hormones in mammals) Detoxification – converts harmful substances into harmless materials. Endoplasmic reticulum

Small round structures Needed to make proteins in the cell 1. Attached to RER membrane – make proteins that are transported out of the cell 2. Free ribosomes in the cytoplasm – make proteins that are used within cytoplasm of the cell Ribosomes

Stack of flattened spaces surrounded by membranes Vesicles: tiny round structures enclosed by a membrane Fuse on one side and pinch off from opposite side of Golgi apparatus Stores and modifies substances made by ER Packages the substances in vesicles for secretion out of the cell Golgi Apparatus

ORGANELLES MITOCHONDRION (mitochondria): “Power house” of a cell Aerobic respiration: food substances are oxidized to release energy Energy is used for cell activities e.g. growth, reproduction, movement etc.

Oval shaped structures Contain green pigment chlorophyll Absorbs sunlight for photosynthesis, for plants to make food PLANT CELLS - Chloroplasts

VACUOLES Fluid-filled space enclosed by membrane Storage of various substances Animal cells: many small vacuoles; store water, food. Exist temporarily Plant cells: one large, central vacuole, filled with cell sap, contains dissolved substances e.g. sugars, mineral salts, amino acids, helps to maintain shape of plant cell Membrane – tonoplast ORGANELLES

chloroplast central vacuole rough endoplasmic reticulum ribosomes cell wall mitochondrion Golgi complex plasma membrane smooth endoplasmic reticulum free ribosome vesicle nuclear pore chromatin nucleolus nuclear envelope nucleus

CENTRIOLES Small, hollow cylinders. Found as a pair near the nucleus. Play an important part in cell division. Only in animal cells. Absent in plant cells. ORGANELLES

Differences between plant and animal cells

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