Chapter 8

Cellular energy

Energy

!  The ability to do work

Quick Review:

!  Autotroph – makes its own food from the energy from the sun

!  Heterotroph – must consume food to get energy

Different types of autotrophs:

!  Photoautotrophs – convert light into energy

!  Chemoautotrophs- use inorganic substances for energy (hydrogen sulfide)

Metabolism

!  All of the chemical reactions in a cell

Catabolic pathways

!  Release energy by breaking down larger molecules into smaller molecules

Anabolic metabolic pathways

!  Builds larger molecules !  Ex: photosynthesis

ATP

!  Adenosine triphosphate !  Molecule that provides chemical energy !  When ATP is broken down (removal of

a phosphate group), energy is released

Chloroplasts

!  Contain chlorophyll – allow plants to undergo photosynthesis

!  They capture light energy from the sun to produce energy for plants

!  Leaves have large surfaces that act as light collectors for plants

Parts of the chloroplast

!  Thylakoids - Flattened saclike membranes that are arranged in stacks

!  Grana – stacks of thylakoids !  Stroma – fluid-filled space outside the

grana

Diagram of chloroplast

Photosynthesis

!  The anabolic pathway in which light energy from the Sun is converted to chemical energy to use by the cell

During photosynthesis:

!  According to the second law of thermodynamics, heat is released in this process

Leaves of Trees

!  Yellow, red, and orange pigments also exist in leaves of trees

!  Chlorophyll (green) is most abundant, that’s why leaves are green

!  In autumn, chlorophyll breaks down, making the rest of the pigments visible

Photosynthesis energy

!  Energy for photosynthesis is used to make glucose

!  Glucose is made outside of the chloroplasts

Photosynthesis

!   Made of 2 reactions 1.  Light reactions – require light to take

place 2.  Calvin cycle – does not require light

!   Generally does not occur at night because it depends on the products of light reactions

Cellular respiration

!  Living organisms obtain energy by breaking down organic molecules during cellular respiration

Aerobic

!  Requires oxygen

anaerobic

!  Does not require oxygen

Fermentation

!   Occurs without oxygen !   2 types 1.  Lactic acid

!   Causes muscles to feel sore

2.  Alcoholic !   Occurs in some yeast and bacteria

How are photosynthesis and cellular respiration related?

!  The products of photosynthesis are used in cellular respiration

!  The product of photosynthesis is glucose

!  Glucose is then the substrate used in photosynthesis