Cycling of Matter in Living Systems

2.1 The Cell, as an Efficient, Open System

Cells carry on all of the life processes including:

Intake of nutrients Movement Growth Response to stimuli Exchange of gases Waste removal Reproduction

Cell Membrane

Protective barrier Allows transport of materials into and out of

the cell Composed of double layer of lipid (fat)

molecules and embedded proteins Connects the cell to the external environment Semi-permeable layer

Regulates the entry of molecules into and out of the cell

Nucleus

Contains DNA, the genetic material of the cell

Directs cellular activities Surrounded by the nuclear envelope, which

has pores to allow the transport of materials

Cytoplasm

Gel-like substance inside the cell membrane Contains nutrients required by the cell to

carry on the life process Organelles are suspended in the cytoplasm Allows for the movement of organelles and

molecules within the cell, referred to as cytoplasmic streaming

Cell Wall – plants, bacteria and fungi

Rigid frame around the cell that provides strength and support.

Chlrorplasts - plants

Contain chlorophyll that produces a green color, they are the sites of photosynthesis

Photosynthesis uses energy from the sun to convert carbon dioxide and water into sugars for the plant’s use and storage

6H2O(l) + 6CO2(g) C6H12O6(aq) + 6O2(g)

Vacuoles and Vesicles

Membrane bound structures that serve to store nutrients, products of secretion and fats

In plants, the central vacuole stores water for the cell

In plant cells, when fluids enter, the central vacuole swells, increasing the turgor pressure causing the cell to become rigid.

Vesicles transport substances through the cell.

Endoplasmic Reticulum

Series of interconnected small tubes that branch from the nuclear envelope.

Materials can be transported through these tubes

Rough endoplasmic reticulum has ribosomes attached to it and is associated with protein synthesis

Smooth endoplasmic reticulum is associated with fat and oil production

Ribosomes

May be attached to the endoplasmic reticulum or free in the cytoplasm

Sites where amino acids are assembled into proteins in the process of protein synthesis

Lysosomes

Membrane bound sacs in the cell where digestion occurs

Defend against invading bacteria Destroy damaged cell organelles Control digestion of certain tissues during

development

Golgi Apparatus

Flat, disc shaped sacs involved in secretion Receives substances from the endoplasmic

reticulum and packages them for transport out of the cell

Mitochondria

Rod-like structures Convert chemical energy in sugars into

energy the cell can use, cellular respiration

C6H12O6(aq) + 6O2(g) 6H2O(l) + 6CO2(g)

Chemical Composition of Cell Structures

Major elements making up the structure of plant and animal cells are carbon, hydrogen, oxygen and nitrogen

They are organized into four major organic compounds: lipids (fats and oils), carbohydrates (sugars, starches and cellulose), protein (muscle fibre) and nucleic acids (DNA).

Similarities: Plant and Animal

Both have cell membrane and an internal network of fibres, the cytoskeleton, made of lipids and proteins

Both have genetic material (DNA) made up of sugars, nitrogen bases and phosphate

Differences: Plant and Animal

Animal cells have centrioles, involved in cell division

Plant cells have cell walls Plant cells contain chlorophyll, used for

photosynthesis Plant cells have a large central vacuole,

animal cells have small vacuoles and vesicles

HOMEWORK:

BLM 6 & 7