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Unit 5: Cell structure and function - PowerPoint PPT Presentation


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Mrs. P Honors Biology. Unit 5: Cell structure and function. Cell Theory. In 1665, Englishman Robert Hooke used an early light microscope to look at a thin slice of cork. Under the microscope, cork seemed to be made of thousands of tiny, empty chambers.

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cell theory
Cell Theory
  • In 1665, Englishman Robert Hooke used an early light microscope to look at a thin slice of cork.
  • Under the microscope, cork seemed to be made of thousands of tiny, empty chambers.
  • Hooke called the chambers “cells”.
cell theory1
Cell Theory
  • By 1855, it was clear that cells were the basic units of life, and the Cell Theory was born. The cell theory states:
  • All living things are made of cells
  • Cells are the basic units of structure and function in living things.
  • New cells are produced from existing cells.
level of organization
LEVEL OF ORGANIZATION
  • The levels of organization in multicellular organisms:
  • Cells g tissues g organs g organ systems g organism
two major types of cells
TWO MAJOR TYPES OF CELLS
  • Cells fall into 2 major categories: prokaryotes and eukaryotes.
prokaryotes
Prokaryotes
  • (pro = before, karyon = nucleus, so literally “before nucleus”
  • Generally smaller than eukaryotes.
  • Lack a nucleus and membrane bound organelles.
prokaryotes1
Prokaryotes
  • Store genetic material in one circular DNA molecule called a nucleoid.
  • Have a cell wall made of peptidoglycan.
eukaryotic
Eukaryotic
  • Eu = true
  • Karyon = nucleus
  • So literally means true nucleus
  • Generally larger than prokaryotes
  • Have a nucleus and cytoplasm.
eukaryotes
Eukaryotes
  • Have membrane bound organelles (literally “little organs”) that carry out different functions.
  • Store genetic material in the nucleus.
parts of the cell
PARTS OF THE CELL
  • A eukaryotic cell is like a microscopic factory. It is filled with organelles, each of which has its own job.
  • Most biologists divide the cell into two major parts: the nucleus and the cytoplasm.
  • The cytoplasm is the part of the cell outside of the nucleus.
eukaryotes1
Eukaryotes
  • eu = true, karyon = nucleus, so literally “true nucleus”
  • Generally bigger than prokaryotes
  • Have a nucleus and cytoplasm (gel like material inside)
cell specialization
Cell Specialization
  • Organisms that are made up of many cells are called multicellular
  • Gene expression is especially important in shaping the way a multicellular organism develops.
slide27

Each of the specialized cell types found in the adult develops from the same fertilized egg cell.

slide28

Cells throughout an organism develop in different ways to perform different tasks. This process is called cell specialization.

  • Different types of cells have different types of shapes and parts so that they can perform different functions.
slide29

Different types of cells have different types of shapes and parts so that they can perform different functions.

slide30

A series of genes called the HOX genes control the differentiation of the cells and tissues in the embryo.

slide31

During the process of differentiation, only specific parts of the DNA are activated. Different parts of the genetic instructions are used in different types of cells (this is influenced by the cell’s environment)

slide32

Because all the cells in an organism contain the same DNA, they initially have the potential to become any type of cell; however, once a cell differentiates, the process cannot be reversed.

specialized cells
SPECIALIZED CELLS
  • Neuron – cells that carry messages throughout the nervous system. Have an axon to send electrical impulses over long distances and dendrites to pass and receive messages from other nerve cells.
slide34

Red Blood cells – have a small disc like shape to increase the surface area for oxygen absorption; hemoglobin binds and carries oxygen; no nucleus to make more space for the hemoglobin

slide35

Muscle cells- A muscle cell is generally elongated and elastic containing mitochondria in large number. The elongated and elastic feature helps muscle tissues to contract; the mitochondria make more ATP for the cell.

slide36

Xylem – have a thick cell wall and hollowed center; used to transport water upward from the roots of a plant

slide37

Phloem – a specialized plant tissue used for transporting nutrients and glucose; made of specialized cells called sieve tube cells and companion cells.

slide38

Stomata – Where transpiration occurs in a plant. Guard cells surround the stoma and open and close to let water in or out.

stem cells
Stem Cells
  • Stem cells – unspecialized cells that continually reproduce. Stem cells can be turned into different specialized cells. Sources of stem cells include:
slide40

Embryonic stem cells – found in an embryo; controversial because have to destroy the embryo; are pluripotent (can turn into almost any type of cell)

slide41

Adult stem cells – found mostly in bone marrow, but also in liver, brain, skin, and some muscle cells; not as useful as embryonic stem cells.

slide42

Umbilical cord/placenta – doctors can now collect an infant’s cord blood; can be used to cure some cancers, blood disorders, and immune disorders.