Cell Structure and Function

1
Chapter 4

• Cell Structure and Function

2
1. What is a cell?

• A cell is the smallest unit that can carry on
  all of the processes of life.

3
2. Early scientists that led to the cell theory

• Anton van Leeuwenhoek (1600s) given credit for
  developing the 1st mini microscope, looked at
  pond water and made detailed drawings
• Robert Hooke coined the term cell when he
  looked at slices of cork and dead plant cells
• Robert Brown (1833) observed a dark structure
  near the center of the cell (we now know this is
  the nucleus)
• Matthias Schleiden (1838) stated all plants are
  made of cells
• Theodor Schwann (1839) discovered all animals
  are made of cells
• Rudolph Virchow (1855) - stated all cells come
  from the division of preexisting cells

4
3. Cell Theory

• All living things are composed of cells.
• Cells are the basic units of structure and
  function in living things.
• All cells come from preexisting cells.

5
4. 8 Characteristics that all living things share

• Consist of organized parts (cells)
• Obtain energy from their surroundings
• Perform chemical reactions
• Change with time (evolution)
• Respond to their environments
• Reproduce
• Maintain constant internal environment
  (homeostasis)
• Share a common history

6
5. Relationship between a cells shape and its
function
Nerve cells communication

• Diversity of shape reflects diversity of
  functions
• Can be simple or complex depending on its
  function
• Cell shape evolved to allow the cell to perform
  its function effectively

Skin cells protection
Blood cells transport
7

• 6. What factor limits the size that most cells
  are able to obtain?
• Limited by the relationship of the cells outer
  surface area to its volume
• Most cells range from 10 -100µm

8
7. What is the problem with cells getting too
large?

• As a cell grows, its volume increases much
  faster than its surface area
• The surface area (the membrane) would not allow
  materials to enter or leave the cell quickly
  enough to meet the cells needs.
• Therefore, most cells are microscopic in size.

9
8. Three Basic Parts of the Cell

• Plasma Membrane regulates what enters and
  leaves the cell
• Cytoplasm site of many chemical reactions of
  the cell
• Material between the cell membrane and the
  nucleus
• Contains the organelles of the cell
• Control Center controls all of the cells
  activities
• Either free-floating DNA in center of the cell
  (Prokaryotes) OR a membrane bound organelle
  called a nucleus (Eukaryotes)

10
9. Two basic types of cells

• Prokaryotes organisms whose cells lack nuclei
  and other organelles (i.e. bacteria)
• Eukaryotes organism whose cells contain nuclei
  and other organelles

Pro- before Eu- true -karyon kernel/nucleus
11
10. What is an organelle?

• A well-defined, intracellular body that performs
  specific functions for the cell.
• Ex/mitochondrion produces energy (in the form of
  ATP) for the cell

12
Prokaryote vs. Eukaryote
Typical Prokaryote (a bacterium)
13
11. Prokaryote vs. Eukaryote
Characteristic Prokaryotic Eukaryotic
Cell membrane ? ?
Cytoplasm ? ?
Genetic Material ? ?
Nucleus ?
Organelles ?(only ribosomes) ?
Archaea ?
Bacteria ?
Plants, animals, fungi, protists ?
14
11. Units of Organization
CELLS ? TISSUE ? ORGANS ? ORGAN SYSTEM ? ORGANISM
15
12. PROKARYOTIC CELL DIAGRAM
PILI used for attachment to surfaces
CELL MEMBRANE Regulates what enters and leaves

• CELL WALL
• protection

DNA controls all cells activities
FLAGELLA moves the cell
RIBOSOME makes proteins
16
Animal Cell
cytoplasm
Nucleus
Nucleolus
Nuclear envelope
Rough ER
mitochondria
lysosome
ribosomes
Cell (Plasma) membrane
Golgi apparatus
Smooth ER
17
Plant Cell
s organelles only found in plant cells, NOT
animal cells
Rough ER
Nuclear envelope
Smooth ER
Nucleus
Nucleolus
Central Vacuole
Golgi Apparatus
Mitochondria
Cell Wall
Cytoplasm
Cell (Plasma) membrane
Chloroplast
18
Cell Membrane outer boundary

• In plants animals
• Structure
• Phospholipid bilayer
• hydrophilic heads, hydrophobic tails
• Contains lipids (bilayer), proteins (channels),
  and carbohydrate chains (identification cards)
• Function
• Regulates what enters and leaves the cell
• Semi-permeable membrane
• Protection and support

19
Nucleus - control center

• In plants and animals
• Structure
• Genetic material called chromatin (DNA
  proteins)
• Function
• Information center of the cell
• Protects DNA
• Directs/controls cell activities

20
Nucleolus -

• In plants animals
• Structure
• Made of RNA proteins
• Small, darkened region inside of nucleus
• Function
• where ribosomes are made

21
Mitochondria

• In plants animals
• Structure
• Double membrane
• Cristae - inner folds, increase surface area
• Outer membrane for protection of organelle
• Function
• Powerhouse of the cell produces ATPs (cell
  energy)
• Able to self-replicate (? in cells with high
  energy need)
• Releases energy from food for the organism to use
  in the process of cellular respiration

22
Ribosomes

• In plants animals
• Structure
• Little dots
• Small (25 nm) ball-like structures
• Found free-floating in cytoplasm or attached to
  rough endoplasmic reticulum
• Composed of RNA and protein
• Function
• Synthesis of proteins (where proteins are made)

23
Endoplasmic Reticulum

• In plants animals
• Structure
• Network of flattened sacs
• Can be rough (w/ ribosomes) or smooth (w/o
  ribosomes)
• Function
• Transport materials within or out of cell
  intracellular highway
• Synthesis of macromolecules
• Rough - proteins, lipids, carbs
• Smooth - lipids

24
Lysosome

• In animals only
• Structure
• Small, circular structures
• Found only in animal cells
• Contain digestive enzymes
• Function
• Digestion of
• Worn out organelles
• Debris
• Large ingested particles
• Lysosomes are responsible for your hands not
  being webbed!!

25
Golgi Apparatus

• In plants animals
• Structure
• Flattened stacks of membranes that are not
  connected
• Vesicles fuse with Golgi and get released from
  Golgi
• Function
• Collection, modification, packaging of proteins
  and other substances
• Vesicles attach, deposit materials
• Golgi modifies materials based on needs
• Vesicles attach to membrane and distribute
  modified substances

26
Vacuole

• In plants - 1 large, central
• In animals several small
• Function
• Storage of water, salts, proteins, carbohydrates,
  waste products
• Pressure system for plants, prevents wilting
• Special vacuole contractile vacuole - prevents
  excess water intake, leading to cell-bursting
  found in freshwater PROTISTS like a paramecium

27
Cell Wall

• Only in plants, bacteria, fungi
• Structure -
• Lies outside the cell membrane
• Made of fibers of cellulose (plants)
• Very porous
• Function
• Helps to protect and support the cell
• Gives rectangular shape to plant cells

28
Chloroplasts

• Only in plants
• Structure
• Inner membranes (thylakoids) surrounded by an
  outer membrane
• Function
• Conversion of light energy (sun) into chemical
  energy (glucose/food) during the process of
  PHOTOSYNTHESIS
• Other Plastids
• Chromoplasts Store pigments (ex. carrot root
  cells, flower petals)
• Amyloplasts - Store food/starch

29
Cytoskeleton - framework

• In plants microtubules, intermediate filaments,
  microfilaments
• In animals all
• Function maintains cell shape and provides
  internal support
• Microtubules - hollow tubes of proteins, hold
  organelles in place, maintain shape, act as
  tracks that guide organelle movement
• Intermediate filaments rods that anchor
  organelles in place
• Microfilaments long threadlike, used for cell
  movement
• Cilia short, hairlike projections used for cell
  movement
• Flagella long, taillike projections used for
  movement
• Centrioles organize microtubules during cell
  division

30
Who Am I? (quick review)

• I stated all plants are made of cells
• I stated all cells come from the division of
  preexisting cells
• I coined the term cell when I looked at slices
  of cork and dead plant cells
• I am given credit for developing the 1st mini
  microscope and I looked at pond water and made
  detailed drawings
• I discovered all animals are made of cells

31

• List 3 organelles you learned about today.
• Describe the function of each of the organelles
  you listed.
• Yes, you should write your name on the paper?