Cell Structure

Microscopes

Light• Uses a beam of light• Can magnify up to

2000x• Can observe living

specimens

Electron• Uses a beam of electrons• Can magnify up to

500,000x• Can only observe dead

specimens • TEM – looks through a thin

layer of tissue• SEM – Used to observe

external features

Cell Theory

• All living things are made of one or more cells

• Cells are the basic unit of structure and function in living organisms

• All cells arise from existing cells

* Memorize this *

Formation of the Cell Theory• Van Leeuenhoek – created the microscope and

used it to see “animalcules” in pond water• Hooke – looked at bark and saw empty boxes

he named “cells”• Schleiden – looked at plants and determined

they were all made of cells• Schwann – looked at animals and determined

they were all made of cells• Remak, Virchow, Redi – biogenesis – “life

comes from life”

Pasture – finally “proved” the theory of biogenesis

Features of all cells• Cell Membrane – made of phospholipids

– Polar head and non polar tail– Selectively permeable – only some things pass

through– Fluid –Mosaic model

•Cytoplasm – fluid inside the cell

–Organelles “float” in it

•Ribosomes – make proteins•DNA – provides the instructions for the cell

Prokaryotic Cells• Do not have membrane bound structures

inside of them

• Cell wall – a rigid outer structure that helps give shape and provide protection.

• The DNA is a single loop – NOT in a nucleus!

• Flagella – a hair-like projection used for movement

• Smaller than eukaryotic cells

Many Bacteria Live in Extreme Environments

• Halophiles

• Thermophiles

• Aerobic

• Anaerobic– Facultative anaerobes– Obligate Anaerobes

Eukaryotic Cells (Plant and Animal Cells)

• Cells have a nucleus– Nucleus is where the DNA is located– Surrounded by a nuclear envelope

• Membrane-bound organelles – Organelles are structures that carry out specific

jobs in the cell

• May use cilia or flagella for movement or to move substances across the cell surface– Cilia are little hairs

• Cytoskeleton – supports the shape of the cell, helps transport organelles and substances– Microtubules

• Thin, hollow

• Made of proteins

– Microfilaments • Smaller than microtubules

• Solid

• Centrioles – help move chromosomes during cell division– Made of microtubules– Found in animals

Endoplasmic reticulum – (ER)

• Rough (RER) – has ribosomes on it – makes proteins

• Smooth (SER) – makes lipids and breaks down toxins

• Vesicle – a small sac that is used to transport substances

• Golgi apparatus – modifies, packages and distributes proteins

• Lysosomes – small sacs that contain digestive enzymes

• Mitochondria – the cell’s power plant– Endosymbiotic theory – A

prokaryote began to live in a larger cell as the result of a symbiotic relationship.

• Has a double membrane

• Has DNA – circular like prokaryotes

• Reproduces independently of the cell

Plant Cells• Cell wall – made of cellulose

• Chloroplasts – site of photosynthesis– Also thought to be endosymbionts– DNA is very similar a photosynthetic bacteria

• Central Vacuole – takes up most of the plant cell – contains water, food, and wastes– When the vacuole is full, the plant stands

upright– When it is not full the plant wilts and droops