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Basic Structure of a Cell

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Introduction to Cells Cells are the basic units of organisms Cells can only be observed under microscope

Basic types of cells:

Animal Cell Plant Cell Bacterial Cell

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Number of Cells

Organisms may be: • Unicellular – composed of one cell • Multicellular- composed of many cells that may organize

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Prokaryotes include bacteria & lack a nucleus or membrane-bound structures called organelles

Eukaryotes include most other cells & have a nucleus and membrane-bound organelles (plants, fungi, & animals)

Cells May be Prokaryotic or Eukaryotic

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Prokaryotes

Nucleoid region contains the DNA

•Cell membrane & cell wall

• Contain ribosomes (no membrane) to make proteins in their cytoplasm

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Eukaryotic Cell

Contain 3 basic cell structures:

• Nucleus

• Cell Membrane

• Cytoplasm with organelles

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Two Main Types of Eukaryotic Cells

Plant Cell Animal Cell

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Organelles

Very small size

Can only be observed under a microscope

Have specific functions

Found throughout cytoplasm

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Protect and support the enclosed substances (protoplasm)

Resist entry of excess water into the cell

Give shape to the cell

Cell wall

CELL WALL

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CELL WALL

Made of cellulose which forms very thin fibers

Strong and rigid Found in plant cells

Cell wall

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Living layer Controls the movement of materials into and out of the cell

Selectively permeable

Cell membrane

Cell or Plasma Membrane

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Lies immediately against the cell wall in plant cells

Made of protein and phospholipids

Selectively permeable

Cell membrane

Surrounding the Cell

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Jelly-like substance enclosed by cell membrane

Provides a medium for chemical reactions to take place

Cytoplasm

Cytoplasm of a Cell

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Contains organelles to carry out specific jobs

Examples: chloroplast & mitochondrion

Cytoplasm

More on Cytoplasm

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Controls the normal activities of the cell

Bounded by a nuclear membrane

Contains chromosomes

NUCLEUS

Nucleus

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Each cell has fixed number of chromosomes that carry genes

Genes control cell characteristics

Nucleus

More on the Nucleus

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Nucleolus

• Cell may have 1 to 3 nucleoli

• Inside nucleus

• Disappears when cell divides

• Makes ribosomes that make proteins

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Smooth & Rough Endoplasmic Reticulum

Smooth ER lacks ribosomes & makes proteins USED In the cell

Rough ER has ribosomes on its surface & makes proteins to EXPORT

RIBOSOMES • Small specks made of RNA.

• Found in cytoplasm or on the

endoplasmic reticulum

• Makes proteins

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Rod shape Site of Cellular respiration

Cell Powerhouse

Mitochondrion ( mitochondria )

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Active cells like muscles have more mitochondria Burn sugars to produce energy ATP

In Animal Cells:

Mitochondria

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Have a large central vacuole

Surrounded by tonoplast Contains cell sap Sugars, proteins,

minerals, wastes, & pigments

Plant Cell Organelles

Vacuole

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Contain the green pigment chlorophyll

Traps sunlight to make sugars (food)

Process called photosynthesis

Plant Cell Organelles

Chloroplast

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Golgi Bodies • Stacks of flattened

sacs

• Have a shipping side & a receiving side

• Receive & modify proteins made by ER

• Transport vesicles with modified proteins pinch off the ends

Transport vesicle

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Lysosome • Contain digestive

enzymes

• Break down food and worn out cell parts for cells

• Programmed for cell death (lyse & release enzymes to break down & recycle cell parts)

LYSOSOME • Small cylindrical

• Used during

mitosis

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Different kinds of plant cells

Onion Epidermal Cells

Root Hair Cell

root hair

Guard Cells

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mitochondrion

nucleus

glycogen

granule

cell

membrane

cytoplasm Animal cell

No cell wall or chloroplast Stores glycogen in the cytoplasm for food energy

vacuole

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Animal Cell Organelles

• Near the nucleus • Paired structures • Help cell divide

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Different kinds of animal cells

white blood cell

red blood cell

cheek cells sperm

nerve cell

muscle cell

Amoeba

Paramecium

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Similarities between plant cells and animal cells

Both have a cell membrane surrounding the cytoplasm

Both have a nucleus

Both contain mitochondria

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Differences between plant cells and animal cells

Animal cells Plant cells

Relatively smaller in size

Irregular shape

No cell wall

Relatively larger in size

Regular shape

Cell wall present

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Animal cells Plant cells

Vacuole small or absent

Glycogen as food storage

Nucleus at the center

Large central vacuole

Starch as food storage

Nucleus near cell wall

Differences between Plant Cells and Animal Cells

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STRUCTURE & FUNCTION

OF CELL MEMBRANE (pp. 59-60)

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Structure & function of cell membranes • Lipids = form foundation of membranes

– Separates inside of cell from outside

– Selectively permeable – how phospholipids

interact with H2O

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CELL MEMBRANE AS BARRIER

• Phospholipids = Phosphate

group + 2 fatty acids

– Polar head – phosphate

group – attracted to water

(hydrophilic)

– 2 Non-polar tails – fatty

acids – repelled by water –

interior of membrane

(hydrophobic)

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• Lipid bilayer = double layer

– Non-polar tails – interior – repels ions, polar

molecules (sugars, proteins)

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PROTEINS EMBEDDED IN LIPID

BILAYER • What keeps proteins within lipid bilayer?

– Some amino acids (remember, amino acids make up

proteins) are polar / non polar

– Non polar part = attracted to the interior of lipid

bilayer, but repelled by H2O on either side

– Polar part = attracted to H2O on either side of lipid

bilayer

– **DUAL ATTRACTION holds protein in lipid bilayer*

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Cell Membranes Contain Different Types

of Proteins 1. MARKER proteins – attached to carbohydrate on cell’s

surface (help other cells recognize their cell type (heart,

liver)

2. RECEPTOR proteins – recognize and bind to specific

substances

3. ENZYMES – involved in important biochemical reactions

4. TRANSPORT proteins – aid in the movement of

substances into and out of the cell