CELLS

THE BUILDING BLOCKS OF LIFE

Cell Theory

• All living things are made of one or more cells.• The cell is the basic unit

of life in which the activities of life occur.• All cells are reproduced

from cells that already exist.

Cells!

Discovery Discovered in 1665 by a

British scientist, Robert Hooke, while examining cork under a microscope of his own invention

Types of Cells• Cells are the basic building

blocks of life• There are 2 type of cells:

prokaryotic and eukaryotic• Prokaryotes are primitive,

unicellular organisms• Eukaryotes are much more

complex and can be uni- or multi-cellular organisms

Prokaryotes

Ex: Bacteria, which are the smallest organisms on Earth

pro = before

karyon = nucleus

Animal Cells

Animal Cell Types

• Muscle Cells

• Adipose Cells (fat)

• Nerve Cells (neurons)

• Epithelial Cells (skin)

• Blood Cells (red and white)

Plant Cells

Plant Cell Types

• Plants also have distinct specialized types of cells

• Stem Cells are long and tube-like Root Cells

Leaf Cells

Human Cell Types• There are around 200 distinct

types of eukaryotic cells in the human body each with their own specialized purpose/job

• There are estimated to be 10 trillion cells that make up a human body; that’s 10,000,000,000,000!

Organelles

• Specialized parts of the cell that perform cellular activities that are necessary for life.

• Prokaryotic cells do not have proper organelles.

• There are some organelles that plant cells have that animal cells do not.

Cell Membrane• The cell is held together by a

flexible structure called the cell membrane.• This membrane also controls

what enters and exits the cell.• In plants & fungi there is an

additional layer of protection and support from a cell wall.

•Cytoplasm refers to the jelly-like material surrounding the organelles.

• It is comprised of organelles and cytosol which is mainly water with other substances dissolved in it (like amino acids).

Cytoplasm

• The nucleus is the control center of the cell; the brain!

• It is the largest organelle containing chromosomes of genetic information (DNA), a sort of instruction manual on how the cell should function that includes a recipe for how to reproduce itself.

Nucleus

Cell Reproduction

• Asexual Reproduction – the offspring has only one parent cell and inherits ONLY the genetic material (DNA) of that cell.

• Sexual Reproduction – offspring has genetic material (DNA) combined from 2 parent cells that it receives through a fertilization process.

Asexual ReproductionADVANTAGES:• Simple• Fast• Low energy output• Large number of offspring• Daughter cells are identical to parentsDISADVANTAGES:• No genetic variation

Binary Fission Since they don’t have nuclei,

prokaryotes (i.e. bacteria) simply replicate the DNA & cell components and divide into 2 daughter cells

Budding A copy (clone) of the parent cell

grows attached to the side of the parents cell until it is fully grown at which time it separates and becomes a daughter cell

Ex: unicellular eukaryotes like yeast & hydra

Fragmentation An organism when broken into

pieces (either naturally or as a result of a trauma) regenerates each piece; each piece becoming a new individual

Ex: sea stars, flat worms

Vegetative Propagation

Plants cells (roots & shoots) reproduce in many different ways– Runners (grasses)– Rhizomes (ginger)– Bulbs/corms (onions, tulips)– Tubers (potatos)

Mitosis

• Primary method of asexual cell reproduction in eukaryotic cells for growth and repair

• It is taking place in your body RIGHT NOW!

Lifecycle of a Cell

Interphase

• G1 (growth 1) the cell prepares for DNA replication in…

• S (synthesis) DNA replication occurs

• G2 (growth 2) the cell prepares for mitosis

• Interphase ends when mitosis begins

Deoxyribonucleic Acid

• DNA contains all the information for cells to live, perform their functions and reproduce, and it also determines what traits an organism will have.

• More to come on that; we will be revisiting this topic a lot throughout this unit.

•Vacuoles are larger than vesicles.

• Either structure may store water, waste products, food, and other cellular materials.

• The vacuoles are much larger in plant cells.

Vacuoles & Vesicles

Ribosomes

Ribosomes are the organelles that create proteins from the directions they receive from the DNA in a process called protein synthesis*

Centrioles

• Found ONLY in animal cells.

• Only appear during the reproduction stage of the cell’s life cycle.

• More about their function when we get to cell reproduction.

Mitochondria• Combines nutrients from food

and oxygen and converts them into fuel that the cell can use (ATP) with the byproducts carbon dioxide and water in a process called cellular respiration.

• There are more mitochondria in cells that have to perform lots of work (ex: leg muscle cells, heart muscle cells etc).

Unlike animals who ingest/eat their food; plants get their food from the sun through a process called photosynthesis which takes place in the chloroplasts.

Photosynthesis

Chloroplasts• Chloroplasts capture light energy

and combine it with carbon dioxide from the air and convert it to food and water which is then stored in the vacuoles until it is needed.

• The food/water stores are then distributed by the mitochondria as needed.

Venn Diagram