Cells and Tissues

Cytoplasm

A jelly like substance that suspends the organelles. Cytosol is the liquid part.

Cytoskeleton

Microfilaments (thin threads) and microtubules (hollow tubes) within the cytoplasm, give cell shape, assist in movement of materials, organelles + whole cell.

Nucleus

Controls all activities within the cell. Contains DNA. DNA + nucleolus is suspended in the nucleoplasm.

Nucleolus

Produces cell's ribosomes.

Ribosomes

In cytoplasm
Forms rough endoplasmic reticulum
Joins amino acids together to make proteins
Free ribosomes produce proteins, used by cell. Ribosomes on membrane produce proteins to export for use outside of cell.

Rough Endoplasmic Reticulum (rER)

Ribosomes on surface produce proteins, which are then sent to the Golgi Apparatus.

Endoplasmic Reticulum

Pairs of parallel membranes. Provide the surface for chemical reactions, channels to transport molecules and proteins.

Smooth Endoplasmic Reticulum (sER)

No ribosomes. Produces lipids and steroids.

Golgi Apparatus

Flattened, stacked membranous sacs, cisternae. Modifies and packages proteins in vesicles for exit from cell.

Lysomes

Vesicles produced by the Golgi Apparatus that contain digestive enzymes.
=> break down worn-out organelles.
=> break down materials brought into the cell.

Mitochondria

Powerhouse of the cell. Produces and releases energy (ATP) via aerobic cellular respiration.

Centrioles

Pair of cylindrical structures located near the nucleus. Used in mitosis/ meiosis. Produces spindle fibre.

Cilia (cell projections)

Numerous short projections resembling tiny hairs. Waft back and forth to push mucus out of trachea, bronchi.

Flagella (cell projections)

Long projection(s) from a cell to help it move. E.g. the tail of sperm.

Smallest functioning unit in the human body.

Cells

Hierarchal Organisation

Cells => Tissues => Organs => Systems

Plasma (cell) membrane

A differentially/ semi permeable membrane, allowing certain chemicals to pass through but restricts the movement of others.

Phospholipid Bilayer

Phosphide - hydrophilic (water loving)
2 x Fatty Acid Tails - hydrophobic (water repelling)

Channel Protein

- transport certain molecules
- allows substance into cell, moves with concentration gradient.

Carrier Protein

- large + charged molecules, against the concentration gradient.
- form a hydrophilic pore
- requires energy

Receptor Protein

- provide binding sites for substances such as hormones and neurotransmitters.

Recognition Proteins

- important in cell - cell recognition.
- knows your cell belongs to you
- bacteria is attacked + starts an immune response.
hexagon line going off = carbohydrates

Cholesterol

Also found within lipid centre of plasma membrane. It disturbs close packing of phospholipid molecules, keeping membrane fluid.

Aquaporin

Movement of water

Proteins

Embedded in phospholipid bilayer. They regulate the processes inside the cell.

with the concentration gradient/ down concentration gradient

from high to low concentration

against the concentration gradient/ up concentration gradient

from low to high concentration

What can also travel through the membrane?

Some small uncharged molecules can travel through the membrane
E.g. O2

Fluid Mosaic Model

Fluid - as the molecules that compose it are constantly changing position.
Mosaic - as it is composed of various different kinds of molecules.

Function of Plasma Membrane 1

Regulates passage of materials
= controls what moves in and out of cell

Function of Plasma Membrane 2

Physical Barrier
= membrane separates cell cytoplasm from extracellular fluid.

Function of Plasma Membrane 3

Sensitivity
= it has receptors that are sensitive to particular molecules in its immediate environment.

Function of Plasma Membrane 4

Support
= the internal part of the membrane is attached to the microfilaments of cells cytoskeleton, thus giving support to whole cell.

Passive Processes

No energy is required. Down a concentration gradient.
e.g. simple/ facilitated diffusion & osmosis.

Active Processes

Requires energy (ATP) for transfer to occur. Up a concentration gradient.
or
Moving large molecules into the cell.
e.g. active & vesicular transport

What does ATP stand for?

Adenosine Triphosphate

Simple Diffusion (passive transport)

The movement of particles from an area of high concentration to an area of low concentration (down a concentration gradient)
Equilibrium is reached when concentration of particles on either side of membrane are equal. (net movement stops)
e.g Alcohol

Factor affecting rate of diffusion across membrane: Steepness of concentration gradient

The diffusion rate will be higher when there is a greater difference in concentration between the two regions

Factor affecting rate of diffusion across membrane: Temperature

Molecules with a higher temperature will have more kinetic energy.

Factor affecting rate of diffusion across membrane: Surface Area

Larger surface where diffusion can occur

Factor affecting rate of diffusion across membrane: Particle Mass

Light particles move faster than heavier particles (at a given temperature).

Factor affecting rate of diffusion across membrane: Physical Barriers

Barries, such as membranes, slow the rate of diffusion. Pores in a barrier may enhance diffusion. Thicker barriers reduce rate.

What is another passive process of diffusion that uses a protein in the plasma membrane?

Channel Protein
Transport molecules that cannot move through the phospholipid bilayer/ across the membrane.

Facilitated Diffusion (passive transport)

Carrier Mediated Diffusion (Carrier Protein)
Transfers large, hydrophilic molecules (e.g. amino acids) that cannot pass through the hydrophobic centre.
It doesn't require energy (particles are still moving down concentration gradient)

Facilitated Diffusion Process

1. Molecule attaches to binding site on specific carrier protein.
2. Carrier protein changes shape, moving molecule through membrane.
3. Molecule released from carrier protein on other side of membrane.

Binding Site
(facilitated diffusion - carrier meditated)

shape of a particular molecule they carry

Microtubules

Spiral strands of protein molecules that form a tubelike structure

Microfilaments

Long, thin fibres that function in the movement and support of the cell

As a cell gets larger what does it require?

It requires more resources to be imported and it produces more waste to be exported.

What does a larger volume require

More exchange of resources and wastes across the membrane.
The exchange processes become less efficient with increasing size.

Smaller Cells

- shorter diffusion pathways
- larger surface area to volume ratio

What does a larger SA:V ratio mean?

The cell can act more efficiently.

Osmosis (passive transport)

Movement of water molecules from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration) across a partially permeable membrane.

High/ Low Solute Concentration =

= High/ Low Osmotic Pressure

What do water molecules cross the hydrophobic centre of the membrane through?

Aquaporins (channel proteins)

Isotonic

Same osmotic pressure as another solution

Hypotonic

Lower osmotic pressure (lower solute concentration) relative to another solution

Hypertonic

Higher osmotic pressure (higher solute concentration) relative to another solution.

Active Transport

- movement of particles from an area of low concentration to an area of high concentration (up/ against gradient)
- requires energy (ATP)

Carrier Meditated Transport
(Active Transport)

- harness ATP energy
- low to high concentration
- transfers a phosphate group to the carrier protein
- protein changes shape so that the bound particle can move across membrane.

Endocytosis (Vesicular Transport)

- transport of substances to inside the cell
- inside a membrane-bound vesicle/ vacuole

Invagination (endocytosis)

Infolding of plasma membrane

Pinocytosis (endocytosis)

- intake of liquids
- fluid within vesicle transferred to cytosol

Phagocytosis (endocytosis)

- intake of solids
- contained within membrane enclosed sac (vacuole)
- digestion = vacuole fuses with lysomes (enzyme)
- used by white blood cells to clean up bacteria

Exocytosis

- releases substances out of cell
- fusion of vesicle membrane with plasma membrane
e.g. secretes enzymes and hormones

How many basic tissue types are there?

4 basic tissue types
1. Epithelial
2. Connective Tissue
3. Muscle
4. Nervous

Epithelial Tissue

- covers surfaces, lines cavities, forms glands
e.g. - skin, lining of air passages, blood vessels
(they are named according to their arrangement and shape)

Simple Squamous Epithelium Tissue

- Single layer of flat cells
- forms capillaries (smallest blood vessels)
- forms alveoli (air sacs in lungs)
- good surface for exchange
- very thin = allows rapid diffusion of substances across the epithelium

Simple Cuboidal Epithelium

- single layer of cube shaped cells
- forms kidney tubules
- forms salivary glands and thyroid glands

Simple Ciliated Columnar Epithelium

- single layer of rectangular cells with cilia
- lines the fallopian tubes
- cilia push egg along the fallopian tube

Stratified Squamous Epithelium

- many cell layers thick
- cells become progressively thinner as they move up layers (flat up top)
- forms skin, lining of mouth and vagina)
- thickness provides protection from abrasion

Stratified Cuboidal Epithelium

- few layers of cuboidal cells
- forms sweat and mammary glands

Connective Tissue

- cells rarely touch
- large amount of non-cellular material surrounding them (matrix)
- protect, insulate, connect, support
e.g. cartilage, bone, adipose (fat) or blood

Matrix

Fibres/ ground substances secreted by connective tissue cells

Cartilage (Collective Tissue)

- cells (chondrocytes) embedded in matrix composed of collagen/ elastin
- repair is slow (no blood vessels/ nerves)
- found covering end of bones, in ear, nose, airway walls and vertebrae

Collagen/ Elastin

Support, flexibility and bounce back

Compact Bone (Collective Tissue)

- cells (osteocytes) embedded in concentric rings of matrix
- composed of collagen/ elastin and minerals = e.g. calcium
- forms shaft of long bones

Blood (Collective Tissue)

- liquid matrix plasma
- cells found floating in matrix (erythrocytes, leukocytes and platelets)
- forms part of circulatory system

Muscle Tissue

cells that are able to shorten in length (contract)

Smooth Tissue (Muscle)

Location: organs, uterus, digestive system
One nuclei
Not Striated
Involuntary

Skeletal Tissue (Muscle)

Location: attached to bones, biceps
many nucleus
Striated
Voluntary

Cardiac Tissue (muscle)

Location: wall of heart
One nuclei
Striated
Involuntary

Nerve/ Nervous Tissue

- cells are called neutrons
- carry messages from one part of the body to another - in form of electrical impulses

Cancer Definition

An abnormal mass of cells, a tumour that arises from uncontrolled cell division

Mutation of gene (cancer) ~ PROTO - ONCOGENES

Code for proteins which stimulate cell cycle and promote cell growth.
When mutated it turns into an oncogene, which causes cancer.

Mutation of gene (cancer) ~ TUMOUR SUPPRESSOR GENES

Code for proteins that stop cell cycle progression and promote cell death.

Cause of Cancer - CARCINOGENS

Cancer causing agent
Environmental factors that cause cancer
e.g. UV radiation, viruses, x-rays, chemicals - alcohol and tobacco

Cause of Cancer - RANDOM MUTATIONS

Uncontrolled division of the cell with daughter cells inheriting the mutated gene.
- some mutations can be passed from parent to child
e.g. breast/ colon cancer
- cell must acquire several mutations must occur before they become cancerous

Benign Tumours

Contained within a capital, don't spread to other parts of the body, cells held together by a capsule

Malignant Tumours

Tumour cells that spread to other parts of the body. Known as metastasis
Few cells break off, enter the blood/ lymph vessels and get carried to another place where they can form secondary tumours surrounding them.

Metastasis

Process of spreading cancerous cells spreading to other parts of the body

What are Cancers categorised depending on?

Based on the type of cells which they arise, impacting/ infecting

Cancer Category: Carcinomas

Arise from epithelial cells
e.g. skin, lung, bowel cancer

Cancer Category: Sarcomas

Arise from non- epithelial tissue
e.g. muscle, cartilage and bone

Cancer Category: Lymphomas/ Leukemias

Arise from cells of blood/ lymphatic tissues
Leukemias, cancer of white blood cells

Prevention of Cancer

- education
- legislation
- avoid smoking
- diet adequate in fibre
- wear protective clothing and face masks when handling dangerous chemicals.
- use sunscreens, sunglasses, protective clothing, stay out of direct sunlight e.t.c
- avoid being overweight/ obese
- limit alcohol intake

Early Prevention of Cervical Cancer

Regular Pap smear

Early Prevention of Breast Cancer

Checking for lumps and regular mammograms

Early Prevention of Bowel Cancer

Faecal occult blood test (FOBT)

Early Prevention of Prostate Cancer

Digital rectal exam, prostate specific antigen blood test, biopsy