Life Science_ Term 1 (2023)

Topics Include : Cells; Mitosis; Animal Tissue

Functions of the cytoplasm

Give cell its shape
Transport medium for dissolved substances
Storage area for water insoluble substances
Storage and circulation of substances within cell

Cell membrane (plasmalemma)

Fluid mosaic model
Phospholipid bilayer
Protein molecules embedded into the two phospholipid layers
Provide support and flexibility

Functions of the cell membrane

Controls the movement of substances in and out of the cell
Respiration (dissolved gases enter) and nutrients enter the cell
Excretion
Secretion

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration until the concentration in both regions are the same
- passive transport

Osmosis

The diffusion of water molecules from an area of high concentration to a low concentration across a selectively permeable membrane

Flaccid

Condition between turgid and plasmolyzed when a cell is placed in an isotonic solution

Turgid

Cell has reached maximum tension

Active transport

Molecules move from an area of low concentration to an area of high concentration, they move against the concentration gradient

Function of Nucleus

Contains chromatin network which contains hereditary information in DNA
Contains information that controls all metabolic processes
Nuclear pores allow certain substances in and out
Makes ribosomes

Chromatin Network

Long threads of chromosomes folded and packed loosely

DNA

Two long strands of genetic information made of sugars, phosphates and nitrogenous bases. Formed in a double helix

Replicated chromosome

Contain the genetic information of the cell

Chromosome

Strand of DNA twisted around a backbone of proteins
Thread like structures found in the nucleus

DNA replication

The process during which a DNA molecule makes an identical replica of itself

Haploid

One full set of chromosomes that includes a single copy of each gene.

Diploid

Two sets of chromosomes that include a double copy of each gene.

Mitosis

The process of cell division where two new identical diploid "daughter" cells are formed from diploid "mother" cell.

Role of mitosis

Development and growth
Asexual reproduction
Cell replacement
Replacement of damaged tissues

Location of mitosis

Any living diploid cell

Stem cells

At growing points at the tip of roots and stems

Specialized tissue called Cambium

Stages in the cell cycle

Interphase - cell grows and replicates its DNA
Mitotic phase - cell divides and transfers one copy of its DNA to two identical cells

Interphase

Period between two consecutive cell divisions
Cell growth and DNA replication takes place
Extra organelles formed

Events in prophase

Nuclear membrane and nucleolus disappear
Chromatin network shortens and thickens to form individual chromosomes
Centrioles separate and move to opposite poles of cell, spindle fibre forms between them

Events in Metaphase

Spindle enlarges
Cytoplasmic threads pull double-threaded chromosomes to the 'equator' of the cell

Events in Anaphase

Centromere of each chromosome divides into two
The two chromatids separate (kyrokinesis)
Spindle fibre contracts and pulls chromatids to opposite poles

Events in Telophase

Chromosomes arrange themselves at the poles
Spindle fibre disappears
Cytoplasm divides (cytokinesis) into two daughter cells
Nuclear membrane forms around each group of chromosomes at each pole and a nucleolus forms

Cancer

Result of uncontrolled cell division in the body

Malignant cancer cells

Able to invade tissues and spread to other parts of the body

Metastasis

The spread of cancer cells to locations distant from their original site.

Carcinoma

Cancer that begins in the skin or in tissues that line or cover internal organs

Sarcoma

Cancer that begins in bone, cartilage, fat, muscle, blood vessels or other connective or supportive tissue

Leukemia

Cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood

Lymphoma and Myeloma

Cancers that begin in the cells of the immune system

Central nervous system cancers

Cancers that begin in the tissues of the brain and spinal cord

Ways to treat cancer

Surgery
Radiotherapy
Chemotherapy

Radiotherapy

The destruction of cancer cells using radiation. Treatment is carefully directed at the site of the tumor.

Chemotherapy

Using chemicals to kill dividing cells. Treatment may be administered by drip or orally.

Centromere

Structure which joins to chromatids when the chromosomes are replicated

Chromatid

One of the two DNA threads which form part of a replicated chromosome

Genes

Sections of DNA located at specific regions on chromosomes
Contain the necessary information responsible for the unique characteristics present in living organisms

Centrioles

Arranged at right angles to each other
Control the formation of spindle involved in the movement of replicated chromosomes away from one another during cell division

Endoplasmic Reticulum

Increases internal surface area of cell
Makes, stores and transports carbohydrates, proteins and lipids

Ribosomes

Small granules found in the cytoplasm of all cells Make new proteins

Those in cytoplasm produce proteins needed by cytoplasm

Those in ER produce proteins that form part of the membranes or are secreted

Golgi Bodies

Consist out of a stack of membranes called cisternae
Membranes pinch off to form vesicles that contain proteins and lipids

Function of Golgi Bodies

Collect molecules from the ER, pack them into vesicles and distribute them to different parts of the cell where they are needed or secreted
Proteins secreted from the cell can be hormones or enzymes needed in the body
Form lysosomes

Vesicles and Vacuoles

Structures filled with fluid and surrounded by a membrane
Control amount of water in the cytoplasm
Vesicles from Golgi Bodies contain proteins and lipids

Lysosomes

Tiny sacs formed from vesicles produced by the Golgi Body
Contain enzymes that can breakdown lipids, proteins and carbohydrates

Function of Lysosomes

Destroy foreign material inside or outside cell
Digest and breakdown food particles
Breakdown dead cells and organelles

Cell wall

Made out of cellulose
Some cells have lignin in the cell walls (extra strength)
Permeable to water and mineral salts
Cell walls of adjacent cells joined by thin layer of lamella

Function of Cell wall

Gives cell its shape
Supports and protects the cell

Plasmodesmata

Cytoplasmic channels that connect adjacent plant cells

Plant vacuoles

Surrounded by tonoplast
Contains cell sap

Function of plant vacuoles

Store sugars, minerals and pigments
Cell sap helps give cell its shape
Plays a role in the digestion and secretion of cellular waste
Osmoregulation

Turgor pressure

The pressure exerted by the swollen vacuole outwards on the cell wall

Chloroplasts

Contain chlorophyll
Made up of stroma
Contains the NB enzymes for photosynthesis
Has a double membrane

Leucoplasts

Colorless
Store starch

Thylakoids

Suspended in stroma
Stacks of membrane like structures
The site of photosynthesis

Chemical Equation for photosynthesis

CO2 + H2O → C6H12O6 + O2

Validity

Refers to the experimental procedures (the method used)
Repeat investigation
Record data over longer period
Increase sample size

Reliability

Refers to the results (amount of data obtained)
Control and Experimental setup
Fixed variables

4 Types of animal tissue

Epithelial
Connective
Muscle
Nervous

Sensory neurons

Send information gathered by receptors from internal and external stimuli to the brain.
- located in the skin, eyes and ears

Motor neurons

Send information from the brain to the effectors (muscles and glands).

* located in the spinal cord, brain and body

Interneurons

Connect sensory neurons to motor neurons
- located in the brain and spinal cord

Nervous tissue

Produces and conducts electrochemical signals between organs of the body and the brain.

Connective tissue

Supports, stablizes and protects the body's many organs. Consists of cells surrounded by fluid or materials.

Dense connective tissue

Connect muscle to bones and bones to bones.
- located in the tendons, around muscles and under the skin

Loose connective tissue

Supports, insulates and nourishes organs.
- located between organs and under the skin

Blood

Transports oxygen, nutrients, water and other chemicals throughout the body. Helps develop immunity.
- located in the circulatory system

Cartilage

Absorbs shock and friction.
- located near the joints and in the ear, nose and trachea

Bone

Provides framework for body and site for muscle attachment

Skeletal muscle tissue

Striated, Multinucleated
Voluntary movement
Attached to bones in the skeleton

Smooth muscle tissue

Non-striated, Spindle shaped, One nucleus per fibre
Involuntary movement
Found in the digestive system and walls of veins and arteries

Cardiac muscle tissue

Striated, One nucleus per fibre

Involuntary movement

Responsible for heartbeat

Squamous epithelium tissue

Thin, irregular cells with large flattened nucleus
Protect underlying tissue from friction and allow for movement of substances
Found in the lining of the mouth, oesophagus, blood vessels and alveoli of the lungs

Columnar epithelium tissue

Elongated cells with oval nucleus, some have microvilli
Support other types of cells, involved in secretion of mucus during digestion
Lines the intestine

Ciliated columnar epithelium tissue

Ciliated columnar epithelium cells
Cilia in lungs help trap dust particles
Lines nasal cavity, trachea, bronchi, female reproductive system

Cuboidal epithelium

Square shaped cells with oval nucleus
Secretory functions
Lines glands

Stratified epithelium

Several layers of cells , cells in outer layers are dead
Reduces friction in areas exposed to heavy friction
Found on the surface of skin and inside lining of mouth

Stratified squemous epithelium

Squamous cells atop of multiple layers of cells varying from cuboidal to columnar
Functions in protection

Stratified cuboidal epithelium

Two layers of cuboidal cells
Functions in absorption and secretion

Stratified columnar epithelium

Single layer of columnar cells on several layers of cuboidal cells.

Functions in protection and secretion

Transitional epithelium

Cells vary depending on stretch, surface cells often large, round and bi-nucleated.
Occurs only in bladder, ureter and urethra

Formation of organisms

Cells → Tissues → Organs → Organ systems → Organisms