gensci t2 l6

the importance of cells in living things

cells

• basic units/building blocks of all living organisms

• every living thing has one or more cells

• carry out functions for survival, growth, reproduction and balance

• tiny, but perform all complex processes that sustain life

nutrient absorption

• cells obtain nutrients needed for growth, repair, and energy production

• ex: intenstinal cells absorb glucose and amino acids from digested food and transfer them into the bloodstream

energy production

• cells convert energy stored in nutrients into atp, which powers cellular activities

• ex: muscle cells use atp to contract when a person walks, runs, or lifts an object

growth and repair

• cells use nutrients to produce new cellular components and replace damaged structures

• ex: skin cells divide and replace damaged or dead skin cells when a wound heals

waste removal

• cells eliminate waste materials produced during metabolic activities

• ex: carbon dioxide produced during cellular respiration moves out of cells and is eventually removed through breathing

maintaining homeostasis

• cells regulate their internal conditions to maintain proper functioning

• ex: cells regulate the movement of water and ions across their membranes to maintain a suitable internal environment

nutrients

are substances that cells obtain and use for growth, repair, and metabolism

energy

is the capacity to perform work, cells obtain energy from chemical reactions involving nutrients or, in photosynthetic organisms, from sunlight

cellular nutrition

• cells obtain, absorb, and use nutrients

• maintain structure, make energy, grow, and repair

• varies by organism type

autotrophic nutrition

• organisms make their own organic food from simple inorganic substances, using an external energy source

• ex: green plants - use sunlight, water, and carbon dioxide to make glucose via photosynthesis

heterotrophic nutrition

• organisms obtain nutrients by consuming other organisms or organic materials

• ex: humans - eat plants and animals, cows - feed on grass, fungi - absorb nutrients from organic materials

ingestion

• food enters the body through the mouth

• ex: eating rice, vegetables, fish or meat

digestion

• food is mechanically and chemically broken down into smaller molecules

• ex: carbohydrates are broken down into simple sugars. proteins are broken down into amino acids, fats are broken down into fatty acids and monoglycerides

absorption

• most nutrient absorption occurs in the small intestine

• the digested nutrients pass through the intestinal lining and enter the blood or lymphatic circulation

transportation

the circulatory system transports absorbed nutrients to different parts of the body

cellular uptake and utilization

• nutrients move from the blood into body cells through the cell membrane using appropriate transport mechanisms. inside cells, nutrients can be used to:

• ex: produce atp, build proteins, repair damaged structures, form new cellular components, support metabolism

carbohydrates

• primary energy source

• digested → glucose → makes atp

• ex: rice, bread, potatoes, corn, fruits

proteins

• build/repair cells, make enzymes, form muscles & membranes

• made of amino acids

• ex: fish, eggs, chicken, milk, beans, tofu

lipids (fats)

• long term energy storage

• make up cell membranes

• cushion organs & support cell functions

• ex: cooking oil, nuts, avocado, butter, fatty fish

vitamins

• regulate metabolism & support enzyme function

• keep cells and body systems working properly

• ex: citrus fruits (vitamin c), carrots & leafy greens (vitamin a)

minerals

• keep cells & body processes functioning well

• help enzymes work & nerves send signals

• ex: calcium: muscles & cell signaling, iron: oxygen transport, potassium: cell membrane balance

water

• solvent for cell reactions; transports nutrients & waste

• participates in chemical processes

• keeps cells shaped and at the right volume

• ex: carries dissolved nutrients in blood and supports reactions within cells

nutrient absorption & the cell membrane

• digested nutrients travel in blood → must enter cells to work

• cell membrane - gatekeeper of the cell

• selectively permeable: allows certain substances in/out, restricts others

simple diffusion

• high → low concentration

• no energy required

• ex: oxygen enters cells from blood

facilitated diffusion

• high → low concentration

• uses transport proteins as helpers

• no energy needed

• ex: glucose enters cells through GLUT transporters

active transport

• low → high concentration (against gradient)

• needs energy from atp

• ex: sodium-potassium pump maintains ion balance in cells

endocytosis

• membrane encloses material → pulls it into the cell

• needs energy

• ex: white blood cells engulf bacteria (phagocytosis)

exocytosis

• vesicle merges with membrane → releases substances out of the cell

• needs energy

• ex: nerve cells release neurotransmitters; waste removal

cellular metabolism

• all chemical reactions happening in cells

• get energy, build and breakdown molecules, keep cells working properly

• anabolism and catabolism

anabolism

• builds big molecules from smaller ones

• requires energy input

• ex: amino acids (proteins), nucleotides (new DNA), CO2 + water → glucose (photosynthesis)

catabolism

• breaks large molecules down into smaller substances

• releases energy that cells capture and use

• ex: glucose (energy released through cellular respiration), stored fats (broken into fatty acids), glycogen (broken into glucose when energy is needed

energy conversion

• changing energy from one form to another

• all living organisms need energy for: movement, growth, reproduction, transport, and maintaining body balance