Transcript Document

Chapter 2: How Cells Function
2.1: Chemical reactions take place inside cells
2.2: Cells capture and release energy
2.3: Materials move across the cell’s membranes
Have already learned:
-All living things are made of
cells
-Cells need energy to sustain life
-Plant and animal cells have
similarities and differences
Will learn:
-About the types of elements
found in all cells
-the functions of the large
molecules in the cell
-Why water is important to the
activities of the cell
Warm-up Questions
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True for animal cells, plant cells, or both?
They need energy to sustain life
They have organelles
They have cell walls
All cells are made of the same
elements
• The matter that makes up the cell itself is too small
for a light microscope
• All matter broken down into elements, each with own
characteristics
• Example:
– Oxygen, on Earth, found as colorless odorless gas
• 25 elements (of ~100 on Earth ) are essential for life
– 6 elements account for about 99% of the mass of our
bodies!
• Oxygen: 65%, Carbon: 18.5%, Hydrogen: 9.5%, Calcium: 1.5%,
Phosphorus: 1.0%, all other 19: 1.2%
Elements
RANK- simple to complex:
cell, atom, molecule
• Smallest unit of an element: atom
• In our body:
– mostly in the form of compounds – atoms of two or
more elements chemically bonded
– O + O = O2
C + O + O = CO2
• Most cellular activities: atoms and molecules
interacting via chemical reactions (bonds broken
and formed to make new molecules)
• Need and release energy! Chemical energy!
Large molecules for cell function
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1) Carbohydrates
2) Lipids
3) Proteins
4) Nucleic Acids
ALL have carbon atoms
Work together in a cell
Carbohydrates
• Provide the cell with energy
– Also structure
• Breaking the bonds within the cell releases energy
• Simple carbohydrates – carbon, oxygen, hydrogen
• Complex carbohydrates – simple linked into
chains: starch, cellulose, glycogen
• Plants: energy not used makes starches and
cellulose (cell wall)
• Animals eat plants and get energy
http://www.npr.org/templates/story/
story.php?storyId=130731888
Lipids
• Fats, oils, and waxes
• Similar to carbohydrates, also made of carbon,
oxygen, and hydrogen
• Cells use lipids for energy and making structures
• Atoms arranged differently than carbohydrates
• Do not dissolve in water!
– Cannot mix with water
– (important for cell membranes…)
Proteins
• Made of amino acids
• Carbon, oxygen, hydrogen, nitrogen, and sometimes
phosphorus and sulfur
• Linked into long chains, folded into 3-D shapes
• Structure and function determined by type, number, and
order of the amino acids
• We get amino acids from food:
– meats, eggs, cheese, beans, or created by body
• Different types: enzymes (control chemical reactions in
cells), others support growth and repair, muscle
movement, fight infections, deliver oxygen, form part of
the cell membranes
Nucleic Acids
• Hold instructions for the maintenance,
growth , and reproduction of a cell
• DNA – Deoxyribonucleic acid
• RNA – Ribonucleic acid
• Both made of carbon, oxygen, hydrogen,
nitrogen, and phosphorus.
• Subunits called nucleotides
• DNA: information used by the cell for
making all the protein the cell needs
• Nucleotide pattern in DNA is copied to
RNA, which delivers information into the
cytoplasm…where it controls chemical
reactions and form structures.
Two thirds of all cells is water
• All chemical reactions inside the
cell take place in water
• Water makes up:
– 46% of body’s mass inside cells
– 23% outside cells in body fluids
• Polar: slight positive charge near
hydrogen atoms, slight negative
near oxygen
• Attract opposite charges, repel like
• Many substances dissolve in water
Water & Cells
• Most lipids do NOT dissolve in water
• Cell membrane is made of a double layer of lipids
– Head is polar, tail is not polar
– Cell membrane is a boundary, keeping the inside of a
cell separate from the outside
• Water-hating tails repel water