biology unit

function of circulatory system

• transport substances around the body

  • nutrients

  • hormones

  • oxygen

  • waste products (e.g carbon dioxide)

• regulation of body temperature

parts of the circulatory system

• blood

  • transports various material

• blood vessels

  • network of tubes where blood moves through

• heart

  • pump that pushes blood through blood vessels

red blood cells

• about ½ of blood

• no nuclei

• contain hemoglobin which carries oxygen

white blood cells

• about 1% of blood

• fight and destroy bacteria and viruses that cause disease

platelets

• small cells

• less than 1% of blood

• help blood clot, seal wounds and stop bleeding

plasma

• protein-rich liquid where blood cells float

• about ½ of blood

• carries blood cells, wastes, nutrients and hormones

function of the heart

pumps blood throughout the body

what are blood vessels

network of tubes that carry blood throughout the body

3 types of blood vessels

1. arteries

2. veins

3. capillaries

arteries

• thick muscular walls

• carries blood away from the heart

• experience high blood pressure

• carries oxygenated blood

veins

• thinner wall

• carries blood towards the heart

• has valves that make sure blood moves in the right direction

• carries deoxygenated blood

capillaries

• tiny blood vessels with very thin walls (one cell thick)

• blood cells travel single file

• capillaries link arteries and veins together

• carry oxygenated and deoxygenated blood

• site of gas exchange

Which parts of the heart carry oxygenated blood?

• Left atrium (receives oxygenated blood from lungs)

• Left ventricle (pumps it to the body)

• Travels through pulmonary veins → heart, then aorta → body

Which parts of the heart carry deoxygenated blood?

• Right atrium (receives blood from body)

• Right ventricle (pumps it to lungs)

• Travels through vena cava → heart, then pulmonary arteries → lungs

Where is oxygenated blood “made” and how?

• Made in the lungs

• Oxygen enters blood in alveoli by diffusion

• Red blood cells pick up O₂

Where is deoxygenated blood “made” and how?

• Formed in body tissues

• Cells use O₂ for cellular respiration

• CO₂ is produced and enters the blood

Functions of the digestive system

1. breakdown of food

2. absorption of nutrients

3. elimination of waste

salivary glands

• chemical digestion

• secrete saliva

• Accessory

tongue function

• mechanical digestion

• tongue rolls food into a bolus

esophagus

• muscular tube that connects the mouth to the stomach

• pushes food down to stomach

peristalsis

rhythmic contractions of smooth muscles that move food through the digestive tract

sphincters

muscles that contract to control the amount of food going in and out of the stomach and anus

stomach

• mechanical and chemical digestion

• J-shaped muscular organ

• secretes gastric juices and mucus

small intestine

• digestion and absorption

• 7m long

• contains enzymes

  • further break down carbohydrates, proteins and fats

• nutrients get absorbed into the bloodstream

villi and microvilli

small finger like projections in small intestine that increase surface area for max absorption of nutrients in the bloodstream

liver

• accessory organ

• produces bile

• detoxifies harmful substances- breaking down into non-harmful (i.e alcohol)

function of bile

breaks down fat (emulsification)

gallbladder

• accessory organ

• stores bile

• attached to small intestine

pancreas

• attached to the small intestine

• secretes

  • basic substances

  • pancreatic enzymes

large intestine/colon

• absorption of H₂O and elimination

• 1.5 m long

• bacteria live in and produce vitamin B and K absorbed

What are accessory organs in the digestive system?

• help digestion but food does NOT pass through them

• Salivary glands, liver, pancreas, and gallbladder

Why are they called “accessory” organs?

they assist digestion by producing or storing substances (like enzymes and bile), but they are not part of the digestive tract itself

What is mechanical digestion?

• physical breakdown of food into smaller pieces

• (e.g., chewing in the mouth, churning in the stomach).

• does not change the chemical structure of food.

What is chemical digestion?

breakdown of food using enzymes and acids into smaller molecules (like sugars, amino acids, fatty acids) that the body can absorb.

Where does the majority of chemical digestion occur?

In the small intestine, especially the duodenum, where enzymes from the pancreas and bile from the liver break down food.

What is absorbed from the digestive tract?

• Nutrients (glucose, amino acids, fatty acids, vitamins, minerals)

• Water

Where does absorption occur in the digestive system?

• Small intestine: Most nutrient absorption (via villi and microvilli)

• Large intestine: Absorbs water and some minerals

Hierarchy of cell organization

Cell → Tissues → Organs → Organ Systems → Organism

Cells

Basic unit of structure and function of living things

Tissues

Group of cells with similar structure and function

Organs

Group of two or more types of tissue that perform a specific task

Organ systems

One or more organs and other structures that work together to perform a vital body function

2 stages of the cell cycle

1. growth- interphase

2. division- mitosis and cytokinesis

the cell spends almost _% of its life growing

90

a cell in interphase

• grows and carries out its normal functions

• makes copies of its organelles and forms new ones

• makes a copy of its DNA

• makes mistakes while copying its DNA and fixes them before cell division starts

DNA during interphase is

chromatin which is thin and stringy in apperance

Stages of interphase

1. G1 (growth)

2. S (synthesis

3. G2 (growth)

G1 phase

• cell is in its first growth phase

• Growing and carrying out metabolic ( e.g producing proteins)

S phase

Cell makes an entire identical copy of its DNA

G2 phase

• Cell moves into its second growth phase

• Approaches its maximum size and produces the structures needed for mitosis

Mitosis

Contents of the nucleus (DNA) separate into 2 identical copies

4 phases of Mitosis

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

Prophase

• pro = before=first

• Chromosomes coil (condense) and thicken

• Nuclear membrane disappears

• Centrioles start to move to opposite poles of the cell

• Spindle fibres start to form, originating from the centrioles

Metaphase

• Meta = middle

• Centrioles are located at the opposite poles

• Spindle fibres attach to the centromere of each double stranded chromosome and along them at the center of the cell

Anaphase

• ana = back/seperate

• Each double stranded chromosome splits

  • Sister chromatids get pulled apart and backwards toward opposite poles

Telophase

• Telo = end

• Nuclear membrane forms around each new set of single-stranded chromosomes

• Chromosomes stretch out (decondense) and become thin (chromatin)

Cytokinesis

• cytoplasm and other organelles are distributed amongst the 2 new identical daughter cells

• Cell membrane forms around each

Cytokinesis in animal cells

cell membrane pinches in the middle and creates a cleavage furrow

Cytokinesis in plant cells

A cell plate is formed that develops into a new cell wall

Checkpoints in a cell cycle

• During the cell cycle activities are controlled at specific points

• At each specialised proteins monitor cell activities and send messages to the nucleus

• Nucleus tells the cell whether to divide

Cell division allows organisms to

1. reproduce

2. grow

3. repair damage

asexual reproduction

• producing offspring from 1 parent

• offspring are genetically identical to the parent

what reproduces asexualy

• single-celled organism: bacteria

• some multicellular: houseleek

sexual reproduction

• producing off spring by the fusion of 2 gametes

• the offspring have genetic information different from each parent

how are gamete cells different from other body cells

they only contain half of the DNA usually found in a cell

what make up most of the cell membrane

proteins and phospholipids

diffusion

• large concentration difference between the inside and outside of a cell

• ions and other substances are passively transported from areas with higher concentration to lower concentration

Cell division for growth

• As multicellular organisms grow, the number of cells increases

• Chemicals used in cell activity and growth enter the cell across the membrane and travel through the cell where they are used through passive and active transport.

• diffusion and osmosis take time

• Important chemicals must be available to all parts of a cell, in the right amount of water, for the cell to function properly

• Waste products (e.g. carbon dioxide) must diffuse out of cell quickly so they don’t poison the cell

Why do cells grow in numbers and not in size

When a cell gets too large, chemicals and water cannot move through the cell fast enough for the cell to use

Cell division for repair

• Every day your body sheds millions of dead skin cells, all of which are replaced by new ones

• Your body replaces each red blood cell about every 120 days

• If you break a bone, cells divide to heal the break

• All organism need to repair themselves to stay alive

Cell theory

1. all living things are composed of one or more cells

2. the cell is the most basic and functional unit of life

3. all cells come from pre-existing cells

Prokaryote

• “before nucleus”

• a cell that does not contain a nucleus or other membrane-bound organelles

Eukaryote

• true nucleus

• cell that contains a nucleus and other organelles, each surrounded by a thin membrane